Synthesis, characterization, and reactivity of new alkynyl complexes of rhodium and iridium: Preparation of neutral (M-M′: M = Rh, Ir; M′ = Pt, Pd) hetero-alkynyl-bridged dinuclear complexes

4578

Organometallics 1998, 17, 4578-4596

Syn th esis, Ch a r a cter iza tion , a n d Rea ctivity of New

Alk yn yl Com p lexes of Rh od iu m a n d Ir id iu m :

P r ep a r a tion of Neu tr a l (M-M′: M ) Rh , Ir ; M′ ) P t, P d )

Heter o-Alk yn yl-Br id ged Din u clea r Com p lexes

Irene Ara,^†J esu´s R. Berenguer,^‡Eduardo Eguiza´bal,^‡J uan Fornie´s,*^,†

Elena Lalinde,*^,‡Antonio Mart´ın,^†and Francisco Mart´ınez^†

Departamento de Quı´mica Inorga´nica, Instituto de Ciencia de Materiales de Arago´n,

Universidad de Zaragoza-Consejo Superior de Investigaciones Cientı´ficas,

50009 Zaragoza, Spain, and Departamento de Qu´ımica,

Universidad de La Rioja, 26001 Logron˜o, Spain

Received May 4, 1998

The alkynylation of [Cp*MX₂(PEt₃)] (Cp* ) η⁵-C₅Me₅; X ) Cl, M ) Rh; X ) I, M ) Ir)

t

with an excess of LiCtCR (R ) Ph (a ), Bu (b), SiMe₃(c)) in thf leads to novel bis(alkynyl)

[Cp*M(CtCR)₂(PEt₃)] (M ) Rh, 3a -c; M ) Ir, 4a ,c) or mono(alkynyl) [Cp*M(CtCR)X(PEt₃)]

(M ) Rh, X ) Cl, 1a -c; M ) Ir, X ) I, 2c′) complexes depending on the reaction time.

Complex 4a and the related (phenylethynyl)iridium derivatives [Cp*Ir(CtCPh)X(PEt₃)] (X

) Cl, 2a ; X ) I, 2a ′) can be prepared by reacting [Cp*IrX₂(PEt₃)] with [AgCtCPh]_n.

Complexes 1-4 undergo facile reaction with [cis-M′(C₆F₅)₂(thf)₂] (M′ ) Pt, Pd; thf )

tetrahydrofuran), affording homobridged bis(µ-alkynyl) [(PEt₃)Cp*M(µ-CtCR)₂M′(C₆F₅)₂] (M

) Rh, M′ ) Pt (5a ,c), Pd (6a ,c); M ) Ir, M′ ) Pt (7a ,c), Pd (8a ,c)) or heterobridged µ-alkynyl-

µ-halide [(PEt₃)Cp*M(µ-CtCR)(µ-X)M′(C₆F₅)₂] (M ) Rh, X ) Cl, M′ ) Pt (9a -c), Pd (10a ,b);

M ) Ir, X ) Cl, I, M′ ) Pt (11a ,a ′,c′), Pd (12a ,a ′,c′)) heterodinuclear compounds. Complexes

5a ,c and 7a ,c can, alternatively, be obtained through a neutralization reaction between the

dianionic complexes Q₂[cis-Pt(C₆F₅)₂(CtCR)₂] (R ) Ph, Q ) PMePh₃; R dSiMe₃, Q ) NBu₄)

and solvento species [Cp*M(PEt₃)(acetone)₂](ClO₄)₂(M ) Rh, Ir) (prepared in situ). The

molecular structures of the heterobridged Rh-Pt (9b) and Ir-Pd (12a ) and homobridged

Rh-Pt (5c), Ir-Pt (7a ,c), and Ir-Pd (8a ) complexes have been determined by X-ray analyses.

In the iridium mixed complexes 7a ,c, 8a , and 12a the alkynyl ligands are σ-bonded to iridium

and π-bonded to Pt (7a ,c) or Pd (8a , 12a ) centers. In contrast, the crystal structure of 5c

shows a dinuclear zwitterionic complex formed by two different alkynyl organometallic

termini, [Cp*Rh⁺(CtCSiMe₃)(PEt₃)] and [cis-Pt^-(C₆F₅)₂(CtCSiMe₃)], held together through

η²-bonding of the alkynyl groups.

In tr od u ction

of interesting ligand-based coupling and cycloaddition

reactions,⁴and (iv) their involvement in catalysis and

in the preparation of new materials.^2a,5In this area,

particular attention has been paid to homo- and het-

erodinuclear complexes stabilized by a double-alkynyl

bridging system, M(µ-CtCR)₂M′,⁶because of their

relevance in C-C coupling alkynide processes,⁷as well

as C-C bond cleavage on butadiynes⁸induced by metal

centers. Considerable experimental work^6-8and recent

theoretical calculations by J emmis et al.⁹on homodi-

nuclear Ti and Zr complexes seem to indicate the

existence of a delicate thermodynamic balance between

coupled and uncoupled structures. The different factors

(metal and substituents) that affect these processes

could be related to the factors that govern the prefer-

ential geometry of the alkynyl ligands on these double-

alkynide-bridged compounds L_nM(µ-CtCR)₂M′L′_n.⁶The

preferential formation of symmetrical (µ-σ-M₂C₂cores,

Ia ,b),¹⁰unsymmetrical (σ/π planar (IIa ) or hinged (IIb)

(M₂C₄cores),^7b,8b-e,h,11chelating (tweezer-like (IIIa ) or

V-shaped (IIIb)),^2c,6,8g,12or intermediate arrangements

The chemistry of transition-metal alkynyl and related

complexes has been studied extensively and continues

to be the focus of considerable attention.¹The interest

in such complexes is due to different factors, including

(i) the ability of alkynide ligands to adopt various

coordination modes,^1a-e,2(ii) their relationship with

vinylidene complexes,³(iii) the possibility of a variety

^†Universidad de Zaragoza-Consejo Superior de Investigaciones

Cient´ıficas.

^‡Universidad de La Rioja.

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Publication on Web 09/17/1998

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4579

Ch a r t 1

(IV)^11d(Chart 1) is still a matter of speculation, although

it is clear that the final structures are governed by

electronic and steric factors both on the metal centers

(ML_n) and on the alkynyl ligands (R substituents).

Several years ago we observed that the tetrahydro-

furan molecules on [cis-Pt(C₆F₅)₂(thf)₂] are easily dis-

placed by diphenylacetylene^13aor by the alkyne frag-

ments of neutral cis-bis(alkynyl)platinum building blocks.

In the latter, dinuclear {cis,cis-[L₂Pt(CtCR)₂]Pt(C₆F₅)₂}

complexes containing a bent chelating type (V-shaped,

type IIIb; Chart 1) double-alkynyl bridging system were

obtained.^13bHowever, treatment of [cis-Pt(C₆F₅)₂(thf)₂]

with anionic Q₂[cis-Pt(C₆F₅)₂(CtCR)₂] leads to σ/π-

alkynide-bridged complexes Q₂[Pt(µ-σ:η²-CtCR)(C₆F₅)₂]₂

(type II; Chart 1) formed via a formal migration of one

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4580 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

σ-alkynyl group between the two Pt centers.^13bWe also

showed that when using [Pt(CtCR)₄]^2-as metal build-

ing blocks, the monoalkynylation process only takes

place with one “Pt(C₆F₅)₂” unit, whereas the reaction

with 2 equiv of [cis-Pt(C₆F₅)₂(thf)₂] gives the trimetallic

compounds {[(C₆F₅)₂Pt(µ-σ:η²-CtCR)(µ-η²:σ-CtCR)]Pt(µ-

σ:η²-CtCR)₂Pt(C₆F₅)₂} with a simultaneous presence of

both chelating (V-shaped) and σ/π types of double-

alkynyl bridging systems.^13cIn view of these results,

it could be speculated that the alkynylation process is

possibly due to the difference in the formal charges of

the metal centers involved. This would not, however,

seem to be the only factor, as it was later found that

not only neutral [cis-Pt(CtCR)₂(PPh₃)₂] but also [cis-

Pt(CtCR)₂(C₆F₅)₂]^2-act only as chelating alkyne ligands

when they react with [Pd(η³-C₃H₅)]⁺. Despite the

presence of a very electrophilic cationic Pd center, no

alkynylation processes were observed and highly polar

species {[Pt(µ-σ:η²-CtCR)₂(C₆F₅)₂]Pd(η³-C₃H₅)}^2-(for-

mally zwitterionic) were formed, clearly showing that

the Pt(II) center has, in these species, a greater prefer-

ence for the electron density associated with the sp

R-carbon of both alkynyl groups than Pd does.^13d,eLotz,

van Eldik, et al. have recently observed related σ,π-

bridging thiophene ligand exchange processes, suggest-

ing a new concept dealing with preferred coordination

sites for metal fragments in σ,π dimetallic complexes.^13f

In an attempt to gain a better understanding of the

factors that determine this σ-alkynyl migration and that

also have an influence on the final arrangement of the

µ-CtCR ligands in these systems, we were interested

in studying the reactivity of [cis-Pt(CtCR)₂(C₆F₅)₂]^2-(R

) Ph (a ), ^tBu (b), SiMe₃(c)) toward the solvento Rh(III)

and Ir(III) [(η⁵-C₅Me₅)M(PEt₃)(acetone)₂](ClO₄)₂species.

Preliminary studies¹⁴revealed that the highly acidic

metal center in [Cp*Ir(PEt₃)(acetone)₂]²⁺is not stabi-

lized by complexation of the metalate [cis-Pt(CtCPh)₂-

(C₆F₅)₂]^2-but rather that the Ir(III) center prefers the

electron density associated with the sp C_Ratoms of the

alkynyl groups, giving the neutral {[(PEt₃)Cp*Ir(µ-σ:η²-

CtCPh)₂]Pt(C₆F₅)₂} (7a ). This result is surprising for

several reasons. First, the formation of 7a implies an

unprecedented double intramolecular alkynyl migration

from Pt to Ir. Second, this process provides a neutral

[Cp*Ir(CtCPh)₂(PEt₃)] fragment which is stabilized in

the final dimer. To the best of our knowledge, this

complex is the first example of a bis(alkynyl)iridium-

(III) derivative containing a “(η⁵-ring)IrL” fragment.

Although extensive studies of mononuclear alkynyl-

rhodium or -iridium (in oxidative states I and III)

complexes have been carried out,^3c,d,15in sharp contrast

reports on related η⁵-cyclopentadienyl or substituted

derivatives are exceedingly rare. The derivatives of this

previously reported type are the chiral or racemic

compounds [CpRh(CtCR)H(PⁱPr₃)] (R ) SiMe₃, Me,

Ph),^15l,16a[Cp*M(L-prolinate)(CtCR)] (R ) Ph (Rh, Ir);

^tBu (Ir)),^16b,cand [Cp*Ir(PMe₃)Ph(CtCR)] (R ) CO₂Et)¹⁷

and, as far as we are aware, analogous bis(alkynyl)

complexes are presently unknown, although bis(alky-

nyl)rhodium species have been proposed as intermedi-

ates in oligomerization reactions.^16b,18

In this paper we report further results of the neu-

tralization reactions between the platinate substrates

[cis-Pt(CtCR)₂(C₆F₅)₂]^2-and the solvento species [Cp*M-

(PEt₃)(acetone)₂]²⁺which allow only the synthesis of the

corresponding dinuclear neutral complexes 5a ,c (M )

Rh) and 7a ,c (M ) Ir), respectively. X-ray studies

reveal that complexes 5c and 7c display a different

bonding arrangement of the alkynyl groups which could

be attributed to a change in the R substituent or to the

stronger σ-alkynyl preference of Pt relative to Rh (5c

type IIb, 7c type IIIb; Chart 1). To clarify the reasons

for this different arrangement, we have carried out the

synthesis and characterization of the novel bis(alkynyl)

mononuclear complexes [Cp*M(CtCR)₂(PEt₃)] (3, M )

Rh; 4, M ) Ir) and that of monoalkynyl [Cp*M(CtCR)X-

(PEt₃)] (1, M ) Rh, X ) Cl; 2, M ) Ir, X ) Cl, I)

derivatives, which have been found as intermediates in

their formation, and examined the reactions of 1-4

toward [cis-M′(C₆F₅)₂(thf)₂] (M′ ) Pt, Pd). The synthesis

of both homobridged M(µ-CtCR)₂M′ (5-8) and hetero-

bridged M(µ-X)(µ-CtCR)M′ (9-12) heteromixed Rh,Ir-

Pt,Pd complexes and solid-state studies of 5c, 7a ,c, 8a ,

9b, and 12a are presented.

Resu lts

Mon on u clear Der ivatives. The synthesis and main

reactions of the mononuclear complexes presented in

this work are summarized in Scheme 1. The starting

materials [Cp*MCl₂(PEt₃)] (M ) Rh, Ir), which have not

been previously reported, have been prepared from

[Cp*MCl₂]₂and PEt₃using a procedure similar to that

described by Maitlis and co-workers.¹⁹

The formation of alkynylrhodium(III) derivatives was

accomplished by the displacement of chloride ligands

from [Cp*RhCl₂(PEt₃)] with alkynyllithium reagents.

t

Thus, when treated with LiCtCR (R ) Ph (a ), Bu (b),

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(13) (a) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B.; Fortun˜o, C.;

Welch, A. J .; Smith, D. E. J . Chem. Soc., Dalton Trans. 1993, 275. (b)

Fornie´s, J .; Go´mez-Saso, M. A.; Lalinde, E.; Mart´ınez, F.; Moreno, M.

T. Organometallics 1992, 11, 2873. (c) Fornie´s, J .; Lalinde, E.; Mart´ın,

A.; Moreno, M. T. J . Chem. Soc., Dalton Trans. 1994, 135. (d)

Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Mart´ınez, F. J . Organomet.

Chem. 1994, 470, C15. (e) Organometallics 1996, 15, 4537. (f) Wald-

bach, T. A.; van Eldik, R.; van Rooyen, P. H.; Lotz, S. Organometallics

1997, 16, 4056.

(14) Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Mart´ınez, F. J . Chem.

Soc., Chem. Commun. 1995, 1227.

(19) Kang, J . W.; Moseley, K.; Maitlis, P. M. J . Am. Chem. Soc. 1969,

91, 5970.

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4581

Sch em e 1

SiMe₃(c)) the dichlororhodium complex [Cp*RhCl₂-

(PEt₃)] afforded the monoalkynyl derivatives [Cp*Rh-

(CtCR)Cl(PEt₃)] (1a -c) (Scheme 1). Optimal reaction

conditions require the use of an excess of LiCtCR (Rh/

Li ) 1/4 (Ph), 1/6 (^tBu)), a low temperature (-20 °C),

and short reaction times. After the reaction mixture

obtained for which the ¹H, ³¹P and ¹³C NMR spectra

reveal that the ratio 1c:3c is 2:1. The formation of a

mixture of 1c and 3c (and also 1a and 3a ) is well-

rationalized in terms of competing chloride-alkynyl

exchange between the formed 1c and [Cp*RhCl₂(PEt₃)].

Complex 3c is prepared pure as a red oil in high yield

(87%) after workup of the reaction mixture of [Cp*RhCl₂-

(PEt₃)] with LiCtCSiMe₃(6.5 equiv) stirred for 30 min

at room temperature. In contrast, the bis(alkynyl)

derivatives 3a (R ) Ph) and 3b (R ) ^tBu) are obtained

(see Experimental Section) as brown air-stable solids

in moderate yield (69%, 3a ; 47%, 3b). Analyses, mass

spectra (FAB+), and NMR (¹H, ³¹P{¹H}, and ¹³C{¹H})

spectral data are reported in the Experimental Section

and selected IR data in Table 1. The most noticeable

absorptions in the IR spectra of 1 and 3 are those

corresponding to the ν(CtC) vibrations which appear

in the range 2033 (3c)-2110 cm^-1(3b), confirming

terminal coordination of these ligands. As expected, the

³¹P NMR spectra show a doublet due to ¹⁰³Rh-³¹P

coupling. Interestingly, the gradual substitution of the

chlorides by CtCR ligands causes a gradual shift of the

signals to lower field (δ 37.2 (3a ), 37.3 (3b), 36.6 (3c)

vs 32.9 (1a ), 32.6 (1b,c); δ 28.0 [Cp*RhCl₂(PEt₃)])). In

the ¹³C NMR spectra, the signals of the alkynyl carbons

are found in the typical chemical shift ranges, split into

a doublet of doublets due to rhodium and phosphorus

coupling. Assignment is based on the stronger cou-

plings that are assumed to occur with the σ-bond

t

for R ) Bu is quenched for 10 min, the monoalkynyl

complex 1b is isolated as a pure orange solid, although

in low yield (33%) due to its high solubility in the usual

solvents, even in hexane. However, despite many

attempts with different reaction times complex 1a can

only be obtained as an oily sample containing small

amounts of 3a (∼14%) and [Cp*RhCl₂(PEt₃)] (∼12%) by

quenching the reaction for 2 min. This impure sample

was further employed to prepare the heterobridged

derivatives 9a and 10a . It should be noted that, in

general, when the reactions occur at room temperature

and/or with prolonged reaction times the monoalkynyl

compounds are rapidly consumed and the bis(alkynyl)

species [Cp*Rh(CtCR)₂(PEt₃)] (3a -c) are easily formed.

On the other hand, when [Cp*RhCl₂(PEt₃)] is treated

with stoichiometric amounts of LiCtCR (1 or 2 equiv),

the reactions do not go to completion and variable

mixtures (depending on the reaction times) of 1 and 3

along with the dichloride precursor are invariably

formed.

In the reaction of [Cp*RhCl₂(PEt₃)] with LiCtCSiMe₃

the displacement of the second chloride on 1c is so fast

that, despite many attempts, we have not succeeded in

obtaining pure 1c. Thus, when [Cp*RhCl₂(PEt₃)] is

stirred at low temperature (-20 °C) with 4 equiv of

LiCtCSiMe₃for only 2 min, the bis(alkynyl) species

[Cp*Rh(CtCSiMe₃)₂(PEt₃)] (3c) is formed along with

the mono(alkynyl)rhodium complex [Cp*Rh(CtCSiMe₃)-

Cl(PEt₃)] (1c). Following workup, an orange oil is

R-carbon (¹J

) 49-54 Hz, ²J

) 28-38.1 Hz

) 2.7-3 Hz).

¹⁰³Rh-C_R

³¹P-C_R

) 7.8-10.3 Hz and ³J

³¹P-C_â

vs ²J

¹⁰³Rh-C_â

The reactions between [Cp*IrCl₂(PEt₃)] or [Cp*IrI₂-

(PEt₃)] and LiCtCR have also been investigated. De-

pending on the reaction time, treatment of [Cp*IrX₂-

(PEt₃)] (X ) Cl, I) with an excess of LiCtCSiMe₃(10

4582 Organometallics, Vol. 17, No. 21, 1998

Ta ble 1. IR Da ta (cm ^-1) for Com p lexes 1-12

dinuclear

[M](µ-X)(µ-CtCR)[M′]^b

Ara et al.

mononuclear

[M]X(CtCR)^a

ν(CtC)

2105 (s)

ν(CtC)

2039 (m)

∆ν(CtC) (cm^-1

)

[Rh]Cl(CtCPh) (1a )

[Rh]Cl(CtC^tBu) (1b)

[Rh](µ-Cl)(µ-η¹:η²-CtCPh)[Pt] (9a )

[Rh](µ-Cl)(µ-η¹:η²-CtCPh)[Pd] (10a )

[Rh](µ-Cl)(µ-η¹:η²-CtC^tBu)[Pt] (9b)

[Rh](µ-Cl)(µ-η¹:η²-CtC^tBu)[Pd] (10b)

[Rh](µ-Cl)(µ-η¹:η²-CtCSiMe₃)[Pt] (9c)

[Ir](µ-Cl)(µ-η¹:η²-CtCPh)[Pt] (11a )

[Ir](µ-Cl)(µ-η¹:η²-CtCPh)[Pd] (12a )

[Ir](µ-I)(µ-η¹:η²-CtCPh)[Pt] (11a ′)

[Ir](µ-I)(µ-η¹:η²-CtCPh)[Pd] (12a ′)

[Ir](µ-I)(µ-η¹:η²-CtCSiMe₃)[Pt] (11c′)

[Ir](µ-I)(µ-η¹:η²-CtCSiMe₃)[Pd] (12c′)

[Rh](µ-η¹:η²-C₂Ph)(µ-η²:η¹C₂Ph)[Pt] (5a )^c

[Rh](µ-η¹:η²-CtCPh)₂[Pd] (6a )

66

46

116

82

95

60

40

2059 (m)

1992 (w)

2026 (m)

1940 (s)

2042 (s)

2062 (s)

2108 (vs)

[Rh]Cl(CtCSiMe₃) (1c) 2035 (vs)

[Ir]Cl(CtCPh) (2a )

[Ir]I(CtCPh) (2a ′)

[Ir]I(CtCSiMe₃) (2c′)

[Rh](CtCPh)₂(3a )

2102 (s)

2105 (vs)

2038 (vs)

2107 (vs)

2021 (m), 1985 (w) 84, 120 (average 102)

2046 (s)

1921 (s)

1940 (vs)

1900 (s)

2065 (s)

59

117

98

207

42

[Rh](CtC^tBu)₂(3b)

[Rh](CtCSiMe₃)₂(3c)

2155 (sh), 2110 (s)

2033 (s br)

[Rh](µ-η¹:η²-C₂SiMe₃)(µ-η²:η¹C₂SiMe₃)[Pt] (5c) 1905, 1867 (vs)

128, 166 (average 147)

70

[Rh](µ-η¹:η²-CtCSiMe₃)₂[Pd] (6c)

[Ir](µ-η¹:η²-CtCPh)₂[Pt] (7a )

[Ir](µ-η¹:η²-CtCPh)₂[Pd] (8a )

[Ir](µ-η¹:η²-CtCSiMe₃)₂[Pt] (7c)

[Ir](µ-η¹:η²-CtCSiMe₃)₂[Pd] (8c)

1963 (s br)

[Ir](CtCPh)₂(4a )

2118, 2108 (vs)

2035 (s)^d

2031 (s), 1971 (m) 87, 137 (average 112)

2068 (s)

1927, 1905 (s)

1963, 1943 (s)

50, 40 (average 45)

108, 130 (average 119)

72, 92 (average 82)

[Ir](CtCSiMe₃)₂(4c)

a

b

d

[M] ) [MCp*(PEt₃)]. [M′] ) [M′(C₆F₅)₂]. ^cTwo very weak bands at 2018 and 1988 cm^-1are also observed. Two shoulders at 2049

and 2026 cm^-1are also observed.

equiv for X ) Cl or 15 equiv for X ) I) in thf results in

the formation of [Cp*Ir(CtCSiMe₃)X(PEt₃)] (X ) Cl, 2c;

X ) I, 2c′) or the corresponding bis(alkynyl) derivative

[Cp*Ir(CtCSiMe₃)₂(PEt₃)] (4c). The reaction was moni-

tored by ³¹P NMR, showing that, as expected, the

formation of 2c,c′ precedes that of 4c. Over a period of

1 h for X ) Cl or 4 h for X ) I the conversion of [Cp*IrX₂-

(PEt₃)] to 4c is nearly complete and after workup (see

Experimental Section) 4c can be isolated as a solid in

high yield, 85-90%. The monoalkynyl derivative 2c′

is obtained in 94% yield by quenching the reaction

mixture for no more than 50 min. However, although

the mono(alkynyl) chloro derivative 2c was clearly

observed by ³¹P NMR spectroscopy (δ -7.8), in the

course of the final formation of 4c, this complex could

not be separated pure from the reaction mixture, which

always contains variable amounts of the dichloride

precursor and 4c. All attempts to prepare the analogous

tert-butyl derivatives 2b and 4b by this synthetic route

failed. In addition, in the reaction of [Cp*IrCl₂(PEt₃)]

with LiCtCPh under different conditions (excess of

LiCtCPh and/or short or prolonged reaction times; see

Experimental Section) inseparable mixtures of 2a and

4a are invariably obtained.

The synthesis of [Cp*Ir(CtCPh)Cl(PEt₃)] (2a ) is,

however, possible by the reaction of [Cp*IrCl₂(PEt₃)]

with an excess of [AgCtCPh]_n(2 equiv) in CH₂Cl₂. This

reaction occurs in a straightforward manner within 3-4

h at room temperature. At this stage of the reaction

the transformation of [Cp*IrCl₂(PEt₃)] into 2a is nearly

complete and only traces of 4a can be detected (³¹P

NMR) (see Experimental Section). Longer reaction

times cause a slow conversion of 2a into 4a , but

concomitant formation of a heteropolynuclear iridium-

silver complex is also observed (δ ³¹P -5.9), probably

due to the partial redissolution of the AgCl formed. The

interaction of AgCl with bis(alkynyl) derivatives^2c,20and

the formation of heteropolynuclear alkynyl-containing

silver compounds by treatment of transition-metal

derivatives with the polymeric [AgCtCR]_nsubstrates

have been previously reported.²¹In our system, the only

signal observed (δ -5.9, s) in the final ³¹P NMR

spectrum together with that corresponding to complex

4a (δ -8.5) (signal ratio ∼1:2) is also observed by

monitoring a CDCl₃solution of 4a treated with an

excess of AgCl(s) (Ir:Ag ) 1:3). In both cases the system

seems to reach the same ratio between both signals,

thus indicating that a possible equilibrium between 4a ,

AgCl(s), and the heteropolynuclear Ir-Ag complex is

probably occurring. Further attempts to separate this

equilibrium mixture were unsuccessful. However, the

formation of pure 4a was achieved by using the corre-

sponding diiodide derivative [Cp*IrI₂(PEt₃)] as the

starting material and either of the alkynylation agents

(LiCtCPh or AgCtCPh). Thus, the reaction of [Cp*IrI₂-

(PEt₃)] with a considerable excess of LiCtCPh (molar

ratio Ir:Li ) 1:15) produces, after ca. 6.5 h of stirring,

the bis(alkynyl) complex 4a in very high yield (∼90%).

The mono(alkynyl) iodide derivative 2a ′ is observed

during the course of the reaction, but it is always

present along with notable amounts of 4a and the

diiodide starting material, which prevents its isolation

in a pure form. Complex 4a can also be obtained by

stirring [Cp*IrI₂(PEt₃)] with an excess of [AgCtCPh]_n

(3.8 equiv) for 4 days. In this way, the expected bis-

(alkynyl) compound is easily obtained as a beige solid

in high yield (78%). As expected, the complex is also

formed through the corresponding mono(alkynyl) iodide

derivative [Cp*Ir(CtCPh)I(PEt₃)] (2a ′) as an intermedi-

ate, which is easily identified (³¹P NMR) in the course

of the reaction. However, using this alternative route

compound 2a ′ can also be isolated as an orange solid in

(21) (a) Abu Salah, D. M.; Bruce, M. I. J . Chem. Soc., Chem.

Commun. 1974, 688; Aust. J . Chem. 1977, 30, 2639. (b) Churchill, M.

R.; De Boer, B. G. Inorg. Chem. 1975, 14, 2630. (c) Espinet, P.; Fornie´s,

J .; Mart´ınez, F.; Toma´s, M.; Lalinde, E.; Moreno, M. T.; Ruiz, A.; Welch,

A. J . J . Chem. Soc., Dalton Trans. 1990, 791. (d) Espinet, P.; Fornie´s,

J .; Mart´ınez, F.; Sote´s, M.; Lalinde, E.; Moreno, M. T.; Ruiz, A.; Welch,

A. J . J . Organomet. Chem. 1991, 403, 253. (e) Fornie´s, J .; Go´mez-Saso,

M. A.; Mart´ınez, F.; Lalinde, E.; Moreno, M. T.; Welch, A. J . New J .

Chem. 1992, 16, 483. (f) Sladkov, A. M.; Gold’ing, I. R. Russ. Chem.

Rev. (Engl. Transl.) 1979, 48, 869.

(20) Fornie´s, J .; Lalinde, E.; Mart´ın, A.; Moreno, M. T. J . Organomet.

Chem. 1995, 490, 179.

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4583

moderate yield (56%) from the resulting final reaction

mixture obtained by refluxing [Cp*IrI₂(PEt₃)] with an

excess of [AgCtCPh]_n(3 equiv) in CH₂Cl₂over ca. 90

min (see Experimental Section for details). Unfortu-

nately, all attempts to prepare the tert-butyl derivatives

2b and 4b using this alternative synthetic route were

fruitless. The reaction of [AgCtC^tBu]_nwith [Cp*IrX₂-

(PEt₃)] (X ) Cl, I) only yields heteropolynuclear iri-

dium-silver complexes, and a mixture of compounds,

which we have not been able to separate, were also

obtained by using an excess of the (3,3-dimethylbuty-

nyl)lithium derivative. These iridium complexes 2a ,a ′,c′

and 4a ,c have been characterized by analytical and

spectroscopic means (see Table 1 and Experimental

Section for details). The most striking spectroscopic

feature is that the ³¹P{¹H} NMR spectra of 2 and 4,

unlike the Rh analogues 1 and 3, show a singlet

resonance at fields higher than that shown by the

corresponding dichloride precursor; in addition, the

gradual substitution of the chloride by alkynyl ligands

also produces a gradual phosphorus shift displacement

to lower frequency (δ -8.5 (4a ) -9.2 (4c) vs -7.3 (2a ),

-7.8 (2c); δ -6.3 for [Cp*IrCl₂(PEt₃)]). The opposite

situation is found in the mono(alkynyl) iodide deriva-

tives 2a ′,c′, which show a singlet (δ -12.7 (2a ′), -13.2

(2c′)) at frequency higher than that observed for [Cp*IrI₂-

(PEt₃)] (δ -19.7).

the usual workup rapidly becomes brown, from which

no definite product could be obtained.

As shown in Scheme 1, there is a second route to

obtaining the heterodimetallic platinum derivatives

with a double-alkynyl bridging system. Thus, com-

plexes 5 and 7 can be prepared by reacting the anionic

Q₂[cis-Pt(C₆F₅)₂(CtCR)₂] (R ) Ph, Q ) PMePh₃; R )

SiMe₃, Q ) NBu₄) and the dicationic bis(solvento)

species [Cp*M(PEt₃)(acetone)₂](ClO₄)₂, prepared in situ

from [Cp*MCl₂(PEt₃)] and 2 equiv of AgClO₄in acetone.

Although yields do not vary very much using either of

the two routes, the first synthetic route is preferred due

to the absence of QClO₄in the reaction mixtures.

Unfortunately, when using the second route the reac-

tions between (NBu₄)₂[cis-Pt(C₆F₅)₂(CtC^tBu)₂] and the

solvento species [Cp*M(PEt₃)(acetone)₂](ClO₄)₂also pro-

duce intractable solution mixtures (NMR spectroscopy)

from which the expected dimers could not be obtained.

These heterodimetallic complexes have different prop-

erties. Thus, heteronuclear Ir-Pt (7a ,c, 11a ,a ′,c′) and

Ir-Pd (8a ,c, 12a ,a ′,c′) complexes are yellow, whereas

the corresponding rhodium derivatives Rh-Pt (5a ,c,

9a ,b) or Rh-Pd (6a ,c, 10a ,b) are orange. Moreover,

although all compounds are air-stable in the solid state,

the phenylethynyl derivatives slowly decompose in

solution. In particular, the decomposition of the (phe-

nylethynyl)rhodium-containing complexes 5a , 6a , 9a ,

and 10a in solution is very fast even at low temperature

(-50 °C). Finally, the double-alkynyl-bridged complexes

(5-8) are considerably more soluble than the hetero-

bridged µ-CtCR-µ-X compounds 9-12.

Heter od in u clea r Der iva tives. The preparation of

either bis(alkynyl)- or halide-alkynyl-bridged dinuclear

complexes was easily accomplished using the bridge-

assisted synthetic methodology.

All of the complexes have been fully characterized by

analytical (except 9c) and spectral means, and the

molecular structures of 5c, 7a ,c, 8a , 9b, and 12a have

been unambiguously confirmed by X-ray diffraction (see

Experimental Section for details).

Thus, the reaction of mono(alkynyl) mononuclear

complexes 1a ,b and 2a ,a ′,c′ with an equimolar amount

of [cis-Pt(C₆F₅)₂(thf)₂] in CH₂Cl₂at room temperature

results in the formation of neutral heterobridged plati-

num complexes [(PEt₃)Cp*M(µ-CtCR)(µ-X)Pt(C₆F₅)₂]

(9a ,b, M ) Rh, X ) Cl; 11a , M ) Ir, X ) Cl; 11a ′,c′, M

) Ir, X ) I) (Scheme 1). The analogous reaction of 1a ,b

and 2a ,a ′,c′ with [cis-Pd(C₆F₅)₂(thf)₂] (molar ratio 1:1)

in CH₂Cl₂, but at lower temperature (-20 °C), gives the

corresponding hetero (µ-CtCR)(µ-X) Rh-Pd (10a ,b, X

) Cl) and Ir-Pd (12a , X ) Cl; 12a ′,c′, X ) I) compounds,

respectively. Similarly, the reaction of the bis(alkynyl)

derivatives [Cp*M(CtCR)₂(PEt₃)] (3a ,c, M ) Rh; 4a ,c,

M ) Ir) with [cis-M′(C₆F₅)₂(thf)₂] (M′ ) Pt, Pd) (1:1) in

CH₂Cl₂, at room (M′ ) Pt) or low (-20 °C, M′ ) Pd)

temperature (diethyl ether for 6a ) results in the forma-

tion of the heterodinuclear homobridged [(PEt₃)Cp*M-

(µ-CtCR)₂M′(C₆F₅)₂] (5a ,c (Rh-Pt), 6a ,c (Rh-Pd), 7a ,c

(Ir-Pt), and 8a ,c (Ir-Pd)) complexes.

As expected, when the inseparable 1c + 3c mixture

(ratio 2:1) is treated with 1 equiv of [cis-Pt(C₆F₅)₂(thf)₂]

in CH₂Cl₂at room temperature, a similar mixture of

the corresponding hetero- (9c) and homobridged (5c)

dinuclear complexes is produced. Due to similar solu-

bilities, all attempts (see Experimental Section) to

obtain 9c as a pure complex from the mixture (9c:5c )

4:1) obtained after the usual workup were unsuccessful;

it is, however, easily characterized by spectroscopic

means in solution (see below and Experimental Section).

The reaction between the bis(tert-butyl) derivative

[Cp*Rh(CtC^tBu)₂(PEt₃)] (1b) and [cis-Pt(C₆F₅)₂(thf)₂] in

CH₂Cl₂produces a very dark green solution that with

Evidence of the formation of these heterodimetallic

complexes with alkynyl bridging ligands is obtained

from the IR spectra, which show, in each case, that the

alkyne ν(CtC) is shifted to smaller wavenumbers. As

can be seen in Table 1, the observed shift, ∆ν(CtC)

(cm^-1), in the heterometallic platinum complexes is

always larger than in related palladium compounds

both for doubly alkynyl bridging derivatives (5-8) and

for heterobridged species (9-12). This spectroscopic fact

indicates that, in line with previous observations,^12dthe

η²-alkyne-metal interaction is stronger in platinum

than in palladium complexes.

The ¹H NMR spectra of the homobridged [Cp*M(µ-

CtCSiMe₃)₂M′(C₆F₅)₂] (5c-8c), both at low tempera-

ture (-50 °C) and at room temperature, only show one

type of alkynyl environment. As in its solid state

complex 5c exhibits an unsymmetrical formal zwitte-

rionic structure, [(PEt₃)Cp*Rh⁺(µ-σ:η²-CtCSiMe₃)(µ-η²:

σ-CtCSiMe₃)Pt^-(C₆F₅)₂)], (see below), for this complex,

the spectra can only be explained by assuming a rapid

exchange between 5c and 5c′ enantiomers even at a

very low (-90 °C) temperature (Scheme 2). Fast migra-

tion of the alkynyl ligands between the metal centers

may take place involving the formation of symmetrical

chelating B type intermediates which, in turn, are easily

accessible through asymmetric A type species with

double-alkynyl bridging systems (Scheme 2). Similar

observations have been previously observed in the case

4584 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

Sch em e 2

t

of related homonuclear [(C₅H₄Bu)₂Zr(µ-σ:η²-CtCR)(µ-

98.0 (7a ) and 51.29/100.52 (8a ) vs 80.2/98.7 (4a )).

Similar upfield shifts of the C_Ratoms have been previ-

ously observed upon complexation of a d⁸metal center

(Pt, Pd, Rh(I), Ir(I)) by a bis(alkynyl) [M](CtCR)₂

fragment.^13e,22The C_âresonances seem to be less

affected, and in general, they do not show such a clear

trend.

η²:σ-CtCR)Zr(C₅H₄Bu)₂]^11aand heteronuclear [Cp₂Ti-

t

(µ-σ:η²-CtCSiMe₃)(µ-η²:σ-CtCSiMe₃)Ni(PPh₃)]^8dcom-

pounds, which had been found in equilibrium at low

temperature with the corresponding symmetrical B type

species. We also noted that the formation of a very

asymmetric double-alkynyl A type bridging system,

approximately halfway between 5c and B (IV; Chart

1), has been recently found in the mixed complex [Cp₂-

Ti(µ-σ-CtC^tBu)(µ-σ:η²-XtC^tBu)Pt(PPh₃)].^11dNotwith-

standing, the change could occur directly through the

µ-σ:σ-CtCSiMe₃intermediate C. In fact, we have also

demonstrated that this type of species can also be stable.

The X-ray study of [Cp₂Ti(µ-CtC^tBu)₂Pt(C₆F₅)₂] reveals

that, although the alkynyl ligands were initially σ-bond-

ed to the Ti center, the µ,σ-CtC^tBu groups are tilted in

this dimer in such a way that the σ-bonding orbitals

point more to the Pt atom.^10b

The asymmetry of the heterobridged compounds 9-12

is clearly reflected in the ¹⁹F NMR spectra, which, in

each case, show the expected two sets of five signals

confirming the presence of two nonequivalent rigid C₆F₅

rings (two AFMRX systems). The room-temperature

NMR data (¹H, ³¹P, and ¹⁹F) reveal no evidence of

possible conformers and, unfortunately, they are not

soluble enough (except 11c′, 12c′) for low-temperature

1

studies. For 11c′ and 12c′ similar patterns of H, ³¹P,

and ¹⁹F NMR were found at -50 °C. Complexes 9b and

12a crystallize adopting a bent disposition, and the

conformer found (see below) is that which places the

“M′(C₆F₅)₂” unit endo to the Cp* ligand. However,

although it is unlikely, a rapid interconversion of

conformers in solution cannot be excluded.

Heterobridged [(PEt₃)Cp*M(µ-CtCR)(µ-X)M′(C₆F₅)₂]

complexes 9-12 proved not to be soluble enough for ¹³C

NMR analysis and the spectra of (phenylethynyl)-

rhodium derivatives 5a and 6a and those of the pal-

ladium complexes 6c and 8c could not be obtained due

to their very low stability in solution. The platinum

derivatives 5c and 7c (R ) SiMe₃) exhibit, in the low-

temperature ¹³C NMR spectra, the expected signals due

to Cp* and PEt₃ligands, while SiMe₃units appear as a

singlet at δ 1.53 for 5c and δ 0.92 for 7c, respectively,

once again indicating that both CtCR units are equiva-

lent. However, despite prolonged accumulation and

probably due to their limited solubility at low temper-

ature, the alkynyl carbon signals could not be located

for 5c and only an ill-defined resonance at 93.77 ppm

(C_Ror C_â) is seen for 7c. Complexes 7a and 8a are

considerably more soluble and, in line with the struc-

tures found in the solid state, complexation of the “Pt-

(C₆F₅)₂” and “Pd(C₆F₅)₂” units by the bis(phenylethynyl)-

iridium fragment is clearly shown by the upfield ¹³C

chemical shift of the C_Rcarbon atoms (δ(C_R/C_â) 55.3/

As we will see later, solid-state structures of Ph-

substituted complexes 7a and 8a show that the iridium

fragment [Cp*Ir(CtCPh)₂(PEt₃)] is chelating the “cis-

M′(C₆F₅)₂” unit with the chelated metal center (Pt, 7a ;

Pd, 8a ) located in both complexes out of the 3-irida-1,4-

diyne plane (IrC₄), thus giving bent IrC₄M cores.

Consequently, two conformers with either the PEt₃or

the Cp* ring toward the M′(C₆F₅)₂unit are possible but

the ³¹P NMR spectra of 7a and 8a (and also of 5-8)

display only one singlet (see above) at all temperatures,

thus suggesting the presence, in solution, of only one

isomer or a rapid interconversion of isomers even at low

temperature. In 7a and 8a (and also in 7c, 9b, 12a ,

and even 5c) the formation of the conformer with the

(22) Ara, I.; Berenguer, J . R.; Fornie´s, J .; Lalinde, E. Organometal-

lics 1997, 16, 3921.

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4585

M′(C₆F₅)₂fragment oriented toward the Cp* ring (see

Figures 1-6) is observed in the solid state. Therefore,

in 7a and 8a both C₆F₅groups are equivalent but the

halves on each ring must be inequivalent. It should be

also noted that a possible rapid interconversion of

isomers (fast inversion of the central IrC₄M core), which

cannot be excluded, does not exchange the halves of the

C₆F₅ring. Accordingly, both complexes exhibit the

expected five signals of equal intensity in the ¹⁹F NMR

spectra at low temperature (-50 °C), thus confirming

a restricted rotation of the C₆F₅groups along the M-C

(M ) Pt, Pd) bond. Increasing the monitoring temper-

ature resulted in a broadening of the two ortho (coales-

cence up to 45 °C) and two meta fluorine resonances in

complex 7a . In contrast, no noticeable change was

observed in the Pd complex 8a , which is rigid up to room

temperature (its low stability in solution precluded

observation at higher temperatures). In 7a the most

simple dynamic process that would produce the ex-

change of the halves of the C₆F₅rings is, of course, their

free rotation along the Pt-C bond with or without

alkyne-Pt breaking. Another less likely possibility

would be dissociation of the Pt(C₆F₅)₂unit. The influ-

ence of different factors on the rotation of C₆F₅rings in

(pentafluorophenyl)palladium and -platinum complexes

has been recently discussed.²³If our assumption is

correct, our results seem to indicate a relatively faster

rotation of C₆F₅rings in 7a compared to that in

compound 8a .

Similar behavior was observed in the phenylethynyl

Rh-Pt derivative 5a , which displayed one broad o-F

(nearly coalesces) and one m-F resonance at room

temperature that split into two different ones (1:1) at

low temperature (-50 °C), as expected. The analogous

Rh-Pd complex 6a decomposes rapidly in solution at

room temperature, and hence, the ¹⁹F NMR spectrum

was only recorded at -50 °C, showing one set of five

C₆F₅fluorine signals. Since no suitable crystals of 5a

and 6a could be obtained due to their rapid decomposi-

tion, their structural assignment has been carried out

on the basis of available spectroscopic data and is not

unequivocal.

F igu r e 1. Molecular structure of complex 9b, showing the

atom-numbering scheme. Hydrogen atoms have been omit-

ted for clarity.

146 (Ph), 1986/143 (^tBu), 1915/125 (SiMe₃)).^11bSmaller

shifts are always seen upon simple complexation of

coordinatively unsaturated ML_nunits by 3-metalla-1,4-

diyne fragments.^{2c,6,8g,12,13d,e,14}Thus, bearing this in

mind, although the formulation is not unambiguous, we

favor a σ/π doubly alkynyl bridging system for 5a

similar to that found by X-ray analysis in 5c.

According to this formulation for 5a the formal

equivalence of both C₆F₅rings observed (only one p-F

resonance) and that of the halves on each C₆F₅at room

temperature could be accounted for by assuming that

the alkynyl ligands rapidly change places between Rh

and Pt (Scheme 2) and that there is a free rotation

around the Pt-C_ipsobonds. Below room temperature

this latter process slows down and only an AFMRX

system is seen in the ¹⁹F NMR spectrum of 5a at -50

°C. The dimer 5c shows only one set of nonrotating

C₆F₅signals evidencing a alkynyl migration between the

metal centers, which seems to be fast even at low

temperature. Thus, on cooling the broadening of the

room-temperature signals is observed, and this is clearly

greater for the low-frequency o-F signal (δ -116.3),

which disappears in the baseline at -90 °C.

The chelating type structure of the remaining trim-

ethylsilyl derivatives 6c, 7c, and 8c was supported by

a variety of data, including an X-ray diffraction study

on 7c. In particular, the ∆ν(CtC) shift (see Table 1) in

For complex 6a (Rh-Pd), the similarity of its ¹⁹F

NMR spectrum with that of 8a (Ir-Pd) and, especially,

the fact that the ∆ν(CtC) shift observed in their IR

spectra are comparable (42 cm^-1in 6a vs average 45

cm^-1in 8a ; Table 1) led us to assume a similar chelating

type arrangement of the bis(alkynyl) bridging system.

In contrast to this, 5a (Rh-Pt) exhibits a medium ν-

(CtC) bond at lower wavenumbers (1900 cm^-1) with a

shift of 207 cm^-1relative to the precursor 3a (2107

cm^-1), which is considerably higher than that observed

(average 112 cm^-1) in the analogous 7a (Ir-Pt ν(CtC)

2031, 1971 cm^-1). This shift (3a f 5a 207 cm^-1) is even

larger than that observed in 5c (average 147 cm^-1), in

which an asymmetrical σ/π doubly alkynyl bridging type

A (Scheme 2) occurs (X-ray see below). Comparable

shifts have been previously observed in related species

with similar bonding arrangements of the alkynyl

the IR spectra (70 cm^-1, 6c, Rh-Pd; average 119 cm^-1

,

7c, Ir-Pt; average 82 cm^-1, 8c, Ir-Pd) is comparable

to those seen in the phenyl-substituted derivatives 7a

(average 112 cm^-1Ir-Pt) and 8a (average 45 cm^-1Ir-

Pd) and considerably smaller than that observed in the

σ/π asymmetrical dimers 5a (207 cm^-1) and 5c (average

147 cm^-1), respectively. Accordingly, in these deriva-

tives 6c-8c the two C₆F₅groups are also seen as

equivalent (only one p-F signal) even at low temperature

(see Experimental Section). The Ir-Pt derivative 7c

exhibits a ¹⁹F NMR pattern similar to that of 7a ,

displaying two o-F (and also m-F) broad resonances at

room temperature that were well-resolved at -50 °C

and coalesced at ca. 40 °C. In contrast, for the Pd mixed

complexes 6c and 8c the rotation of C₆F₅rings is again

restricted at room temperature. No significant changes

were observed at low temperature (only sharper o-F

signals), and the very low stability of these complexes

in solution precluded further experiments.

ligands: [Pt(µ-CtCR)(C₆F₅)₂]₂^2-(ν(CtC)/∆ν(CtC) (cm^-1

)

1956/average 133.5 (Ph), 1923/average 165 (^tBu));^13b[Pt-

(µ-CtCR)(C₆F₅)(PPh₃)]₂(ν(CtC)/∆ν(CtC) (cm^-1) 1963/

(23) Casares, J . A.; Espinet, P.; Mart´ınez-Ilarduya, J . M.; Lin, Y.-

S. Organometallics 1997, 16, 770 and references therein.

4586 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

F igu r e 4. Drawing of the molecular structure of complex

7a , showing the atom-numbering scheme. Hydrogen atoms

have been omitted for clarity.

F igu r e 2. View of the molecular structure of complex 12a ,

showing the atom-numbering scheme. Hydrogen atoms

have been omitted for clarity.

F igu r e 5. Molecular structure of complex 7c, showing the

atom-numbering scheme. Hydrogen atoms have been omit-

ted for clarity.

F igu r e 3. Molecular structure of complex 5c, showing the

atom-numbering scheme. Hydrogen atoms have been omit-

ted for clarity.

Solid -Sta te Str u ctu r es of Din u clea r Com p lexes.

X-ray structural studies were carried out on 5c, 7a ,c,

8a , 9b, and 12a as summarized in Table 2. Refinement,

described in the Experimental Section, yielded the

structures shown in Figures 1-6. Relevant bond lengths

and angles are listed in Table 3. These compounds are

new members of the small family of heterometallic

M-M′ (Rh,Ir-Pt,Pd) complexes which have been struc-

turally characterized to date.²⁴Figures 1 and 2 show

the heterobridged Rh-Pt (9b) and Ir-Pd (12a ) com-

plexes, which consist of (PEt₃)(η⁵-C₅Me₅)M and M′-

(C₆F₅)₂moieties held together by the CtCR bridge and

the chloride group. Considering the Cp* ring to be a

single coordination center represented by its centroid,

in both molecules (9b and 12a ) the Rh and Ir coordina-

F igu r e 6. View of the molecular structure of complex 8a ,

showing the atom-numbering scheme. Hydrogen atoms

have been omitted for clarity.

(24) (a) Markham, D. P.; Shaw, B. L.; Thornton-Pett, M. J . Chem.

Soc., Chem. Commun. 1987, 1005. (b) Hutton, A. T.; Shebanzadeh, B.;

Shaw, B. L. J . Chem. Soc., Chem. Commun. 1984, 549. (c) Albinati,

A.; Emge, T. J .; Koetzle, T. F.; Meille, S. V.; Musco, A.; Venanzi, L. M.

Inorg. Chem. 1986, 25, 4821. (d) Lo Schiavo, S.; Rotondo, E.; Bruno,

G.; Faraone, F. Organometallics 1991, 10, 1613 and references therein.

(e) Stang, P. J .; Huang, Y. H.; Arif, A. M. Organometallics 1992, 11,

845; J . Am. Chem. Soc. 1990, 112, 5648. (f) Stang, P. J .; Huang, Y.-H.;

Arif, A. M. Organometallics 1992, 11, 231. (g) Lu, S.-j.; Wei, F. P.;

Wang, X.-d.; Wang, H.-q.; Huang, L.-r. J . Organomet. Chem. 1996, 510,

7. (h) Tang, Z.; Nomura, Y.; Ishii, Y.; Mizobe, Y.; Hidai, M. Organo-

metallics 1997, 16, 151. (i) Sipavak, G. J .; Yap, G. P. A.; Puddephatt,

R. J . Polyhedron 1997, 16, 3861 and references therein. (j) Tejel, C.;

Shi, Y.-M.; Ciriano, M. A.; Edwards, A. J .; Lahoz, F. J .; Modrego, J .;

Oro, L. A. J . Am. Chem. Soc. 1997, 119, 6679.

tion environment can be described as distorted tetra-

hedral. The deformation from the regular arrangement

can be attributed to the bulkiness of the cyclopentadi-

enyl moiety, which forces the other three coordination

atoms (phosphorus, carbon, and chlorine) to narrow

their interligand angles to less than 90.5° (80.67(12)-

90.23(13)°, 9b; 84.4(3)-89.13(10)°, 12a ), while the cor-

responding angles with the Cp* centroid are enlarged

Ta ble 2. Cr ysta l Da ta a n d Str u ctu r e Refin em en t P a r a m eter s for Com p lexes 5c, 7a ,c, 8a ‚0.5CHCl₃, 9b, a n d 12a ^a

5c

7a

7c

8a ‚0.5CHCl₃

9b

12a

empirical formula

fw

C

₃₈H₄₈F₁₀PPtRhSi₂

C₄₄H₄₀F₁₀PPtIr

1177.0

C₃₈H₄₈F₁₀IrPPtSi₂

1169.20

C_44.5H_40.5Cl_1.5F₁₀PPdIr

1148.01

C₃₄H₃₉ClF₁₀PPtRh

1002.07

C₃₆H₃₅ClF₁₀IrPPd

1022.66

1280.97

unit cell dimens

a (Å)

b (Å)

12.121(2)

19.138(3)

17.940(30

90

90.55(1)

90

4161.4(12)

0.71073

200

19.649(1)

10.482(1)

20.101(2)

90

4041(2), 4

0.71073

298

18.555(3)

12.514(2)

18.372(3)

90

4265.9(12)

0.71073

200

19.788(4)

13.962(3)

17.471(3)

90

4827(2), 4

0.71073

210

19.806(6)

10.319(6)

19.506(6)

90

118.40(3)

90

3506.8(15), 4

0.71073

150(1)

11.472(2)

11.528(2)

15.392(2)

102.79(1)

104.26(1)

104.41(1)

1822.1(5)

0.71073

200

c (Å)

R (deg)

â (deg)

γ (deg)

V,(Å³), Z

wavelength (Å)

temp (K)

radiation

graphite monochromated, graphite monochromated, graphite monochromated, graphite monochromated, graphite monochromated, graphite monochromated,

Mo KR

monoclinic

P2₁/n

Mo KR

orthorhombic

Pna2₁

Mo KR

orthorhombic

Pna2₁

Mo KR

orthorhombic

Pnam

Mo KR

monoclinic

P2₁/c

Mo KR

triclinic

P1h

cryst syst

space group

cryst dimens (mm)

0.36 × 0.24 × 0.12

0.2 × 0.5 × 0.5

0.38 × 0.26 × 0.24

0.5 × 0.4 × 0.3

0.35 × 0.30 × 0.30

0.38 × 0.24 × 0.06

abs coeff (mm^-1

)

4.899

6.700

6.555

3.31

4.655

4.336

transmission factors

abs cor

diffractometer

2θ range for data collection (deg) 4-48

no. of rflns collected

no. of indep rflns

0.978, 0.602

ψ scans

0.119, 0.053

ψ scans

Siemens Stoe AED2

4-47

4082

3738 (R(int) ) 0)

full-matrix least

squares on F²

0.7429

0.813, 0.644

ψ scans

Siemens P4

4-51

5303

4093 (R(int) ) 0.0526)

full-matrix least

squares on F²

1.018

0.309, 0.196

ψ scans

Siemens Stoe AED2

4-50

4748

4408 (R(int) ) 0)

full-matrix least

squares on F²

1.166

0.840, 0.613

ψ scans

Enraf-Nonius CAD4

4-50

6342

6139 (R(int) ) 0.0218)

full-matrix least

squares on F²

1.062

1.000, 0.659

ψ scans

Siemens P4

4-40

4038

3357 (R(int) ) 0.0894)

full-matrix least

squares on F²

1.022

Siemens P4

6840

6496 (R(int) ) 0.0301)

full-matrix least

squares on F²

1.078

refinement method

goodness of fit on F²

final R indices (I > 2σ(I))

R1 ) 0.0645,

wR2 ) 0.1599

R1 ) 0.1073,

wR2 ) 0.1893

R1 ) 0.0473,

R_w) 0.0633

R1 ) 0.0394,

wR2 ) 0.0655

R1 ) 0.0639,

wR2 ) 0.0743

R1 ) 0.0698,

wR2 ) 0.1893

R1 ) 0.0883,

wR2 ) 0.2061

R1 ) 0.0268,

wR2 ) 0.0560

R1 ) 0.0371,

wR2 ) 0.0598

R1 ) 0.0436,

wR2 ) 0.1127

R1 ) 0.0558,

wR2 ) 0.1203

R indices (all data)

R1 ) ∑(|F_o| - |F_c|)/∑|F_o|. wR2 ) [∑w(F_o- F_c)²/∑w(F_o²)²]^1/2. R_w) [∑w(|F_o| - |F_c|)²/∑w(|F_o|)²]^1/2. Goodness of fit ) [∑w(F_o- F_c²)²/(n_obs- n_param)]^1/2. w ) [σ²(F_o) + (g₁P)²+ g₂P]^-1; P )

a

2

[max(F_o²;0) + 2F_c²]/3.

4588 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

Ta ble 3. Selected Bon d Len gth s (Å) a n d An gles (d eg) for Com p lexes 5c, 7a ,c, 8a , 9b, a n d 12a ^a

Complex 5c

Pt(1)-C(7)

1.92(2) Pt(1)-C(13) 2.00(2) Pt(1)-C(19) 2.29(2) Rh(1)-cent(Cp*) 1.873(17) Rh(1)-C(13,14) 2.249(15) C(13)-C(14) 1.25(2)

Pt(1)-C(18,19) 2.255(15) Pt(1)-C(18) 2.379(14) Rh(1)-C(18) 1.96(2) C(18)-C(19)

1.21(2) Pt(1)‚‚‚Rh(1)

3.554(1)

Rh(1)-C(13) 2.374(14) Rh(1)-C(14) 2.29(2) Rh(1)-P(1) 2.302(4)

C(7)-Pt(1)-C(13)

C(1)-Pt(1)-C(19)

86.8(6) C(7)-Pt(1)-C(1)

88.7(6) C(13)-Pt(1)-C(18)

88.5(6) C(18)-Rh(1)-C(13,14) 82.3(6) cent(Cp*)-Rh(1)-C(18) 119.7(7)

67.5(6) cent(Cp*)-Rh(1)-C(13,14) 127.1(6)

cent(Cp*)-Rh(1)-P(1)

178.9(13) Pt(1)-C(13)-Rh(1)

141.7(13) C(19)-C(18)-Rh(1)

131.2(5)

108.4(7)

176.4(14)

151.2(13)

C(1)-Pt(1)-C(18,19) 103.2(6) C(13)-Pt(1)-C(18,19) 81.5(6) C(14)-C(13)-Pt(1)

C(14)-Rh(1)-P(1)

C(18)-Rh(1)-C(13)

89.1(4) C(18)-Rh(1)-P(1)

68.1(6) P(1)-Rh(1)-C(13,14) 93.9(4) Rh(1)-C(18)-Pt(1)

87.2(4) C(13)-C(14)-Si(1)

109.6(6)

C(18)-C(19)-Si(2)

Complex 7a

Pt(1)-C(13) 2.41(2) Pt(1)-C(14) 2.38(2) Pt(1)-C(21) 2.46(2) Pt(1)-C(13,14) 2.312(5) Pt(1)-C(21,22) 2.31(5) Ir(1)-cent(Cp*) 1.88(3)

Pt(1)-C(22) 2.30(2) C(13)-C(14) 1.21(3) C(21)-C(22) 1.21(3) Ir(1)‚‚‚Pt(1) 3.506(1)

P(1)-Ir(1)-C(13)

C(13)-Ir(1)-C(21)

Ir(1)-C(13)-Pt(1)

86.3(6)

79.9(8)

106.0(9)

P(1)-Ir(1)-C(21)

C(1)-Pt(1)-C(7)

87.7(6)

88.3(9)

Ir(1)-C(21)-C(22)

C(1)-Pt(1)-C(13,14)

160.9(18) C(21)-C(22)-C(23)

92.2(17) C(7)-Pt(1)-C(21,22)

86.8(11) C(13)-Ir(1)-cent(Cp*) 128.4(13)

126.6(12) P(1)-Ir(1)-cent(Cp*) 131.4(8)

154.2(21)

92.7(16)

Ir(1)-C(13)-C(14) 176.9(17) C(13,14)-Pt(1)-C(21,22)

C(13)-C(14)-C(15) 156.8(22) Ir(1)-C(21)-Pt(1)

103.3(8)

C(21)-Ir(1)-cent(Cp*)

Complex 7c

Pt(1)-C(1)

2.037(13) Pt(1)-C(7)

2.38(2) Pt(1)-C(13)

Pt(1)-C(18,19) 2.316(1) Ir(1)-C(13) 1.981(13)

2.037(13) Pt(1)-C(19) 2.324(14) Ir(1)-C(18) 1.98(2) Ir(1)-P(1) 2.297(4) Ir(1)-cent(Cp*) 1.886(1)

Pt(1)-C(14)

2.442(13) Pt(1)-C(18) 2.47(2)

C(13)-C(14) 1.25(2) C(18)-C(19) 1.25(2) Ir(1)‚‚‚Pt(1)

3.5624(9)

Pt(1)-C(13,14) 2.31(1)

C(1)-Pt(1)-C(7)

C(7)-Pt(1)-C(14)

82.3(5) C(1)-Pt(1)-C(19)

82.6(6)

96.2(5)

86.6(5)

90.1(4)

176.5(12)

Ir(1)-C(13)-Pt(1)

106.8(5)

172.6(13) C(18)-C(19)-Si(2)

C(13)-C(14)-Si(1)

142.4(13)

145.9(13)

82.9(5) C(7)-Pt(1)-C(13,14)

C(19)-C(18)-Ir(1)

C(1)-Pt(1)-C(18,19) 94.6(5) C(13,14)-Pt(1)-C(18,19)

cent(Cp*)-Ir(1)-C(13) 125.0(4)

cent(Cp*)-Ir(1)-P(1)

cent(Cp*)-Ir(1)-C(18) 127.9(4)

C(13)-Ir(1)-C(18)

C(18)-Ir(1)-P(1)

76.9(6) C(13)-Ir(1)-P(1)

90.5(4) C(14)-C(13)-Ir(1)

130.2(1)

Complex 8a ^a

1.994(13) Ir(1)-cent(Cp*) 1.895(1) Ir(1)‚‚‚Pd(1) 3.435(1) C(7)-C(8) 1.18(2)

Pd(1)-C(7) 2.383(12) Pd(1)-C(8) 2.458(14) Pd(1)-C(7,8) 2.348(1)

Ir(1)-C(7) 1.990(13) Ir(1)-P(1) 2.283(5) Pd(1)-C(1)

C(7)-Ir(1)-C(7a)

C(1)-Pd(1)-C(1a)

Ir(1)-C(7)-Pd(1)

81.0(7)

82.8(7)

103.1(5)

C(7)-Ir(1)-P(1)

C(8)-C(7)-Ir(1)

C(7)-C(8)-C(9)

88.7(4)

177.2(12)

154(2)

C(7)-C(8)-C(9′)

C(7,8)-Pd(1)-C(7a,8a)

P(1)-Ir(1)-cent(Cp*)

159(2)

92.62(2)

130.42(2)

C(1)-Pd(1)-C(7,8)

C(7)-Ir(1)-cent(Cp*)

92.29(2)

126.38(3)

Complex 9b

Pt-C(7)

1.995(5) Pt-C(1) 2.002(4) Pt-C(13) 2.307(4) Rh-P

2.3034(14) Rh-Cl

2.435(1) C(13)-C(14) 1.218(6)

Pt-C(14) 2.345(4) Pt-Cl

2.429(2) Rh-C(13) 2.029(4) Pt-C(13,14) 2.429(5)

Rh-cent(Cp*) 1.843(5) Rh‚‚‚Pt

3.371(1)

C(7)-Pt-C(1)

C(7)-Pt-Cl

C(13)-Pt-Cl

Cl-Pt-C(13,14)

C(13)-Rh-Cl

85.7(2)

171.33(13)

75.65(12)

87.9(2)

C(7)-Pt-C(14)

C(1)-Pt-Cl

C(7)-Pt-C(13,14)

C(13)-Rh-P

P-Rh-Cl

88.5(2)

86.01(13)

100.4(2)

90.23(13)

88.89(5)

Pt-Cl-Rh

87.73(4)

101.9(2)

129.9(6)

127.8(7)

C(14)-C(13)-Rh

C(13)-C(14)-C(15)

Cl-Rh-cent(Cp*)

173.0(4)

158.1(5)

124.3(6)

Rh-C(13)-Pt

P-Rh-cent(Cp*)

C(13)-Rh-cent(Cp*)

80.67(12)

Complex 12a

2.299(3) Ir(1)-Cl(1) 2.445(3) Pd(1)-C(1) 2.341(10) Pd(1)-Cl(1) 2.455(3) Pd(1)-C(2) 2.457(10)

Ir(1)-cent(Cp*) 1.856(13) Pd(1)-C(15) 1.993(11) Pd(1)-C(9) 2.001(10) Pd(1)-C(1,2) 2.325(10) C(1)-C(2) 1.19(2) Ir(1)‚‚‚Pd(1) 3.362(1)

Ir(1)-C(1)

2.025(13) Ir(1)-P(1)

C(1)-Ir(1)-P(1)

88.6(3)

89.13(10)

132.4(4)

84.6(4)

C(1)-Ir(1)-Cl(1)

84.4(3)

123.1(4)

125.0(6)

87.8(3)

C(1)-Pd(1)-Cl(1)

Cl(1)-Pd(1)-C(1,2)

Ir(1)-Cl(1)-Pd(1)

C(2)-C(1)-Ir(1)

78.0(3)

91.6(3)

86.65(9)

175.6(10)

C(15)-Pd(1)-C(2)

C(15)-Pd(1)-C(1,2)

Ir(1)-C(1)-Pd(1)

C(1)-C(2)-C(3)

83.2(4)

96.0(4)

100.4(5)

167.4(11)

P(1)-Ir(1)-Cl(1)

cent(Cp*)-Ir(1)-P(1)

C(15)-Pd(1)-C(9)

cent(Cp*)-Ir(1)-Cl(1)

cent(Cp*)-Ir(1)-C(1)

C(9)-Pd(1)-Cl(1)

a

Symmetry transformation used to generate equivalent primed atoms: x, y, -z + ¹/₂.

more than 123° (124.3(6)-129.9(6)° in 9b; 123.1(4)-

132.4(4)° in 12a ). This structural fact, which is also

apparent in the homobridged 5c, 7a ,c, and 8a com-

pounds, has been previously observed in other mono-

or dimetallic rhodium or iridium cyclopentadienyl

systems.^16b,24d,fIn both complexes, the metal-carbon

distances M(d⁶)-C(centroid of ring) and M′(d⁸)-ipso-

C(C₆F₅), respectively (see Table 3), and the M(d⁶)-P

bond lengths are unexceptional. The structural param-

eters associated with the M(µ-Cl)M′ unit are comparable

in both complexes; the bridging chloride is nearly

symmetrically bonded to both metal centers with M-Cl

distances (2.429(2), 2.435(1) Å, 9b; 2.445(3), 2.455(3) Å,

12a ) and angles at chlorine (87.73(4)°, 9b; 86.65(9)°,

12a ) comparable to related distances and angles found

in doubly chloride bridged d⁶or d⁸homodimetallic

compounds.^24f,25The alkynyl ligand bridges in the more

commonly observed σ,π mode in which the R-C atom is

σ-bound to rhodium (Rh-C(13) ) 2.029(4) Å, 9b) or

iridium (Ir(1)-C(1) ) 2.025(13) Å, 12a ) and the unsat-

urated CtC bond is asymmetrically η²-bonded to Pt (9b)

or Pd (12a ) with the M-C_Rdistances (Pt-C(13) ) 2.307-

(4) Å, Pd-C(1) ) 2.341(10) Å) being slightly shorter

than the corresponding M-C_â(Pt-C(14) ) 2.345(4) Å,

Pd-C(2) ) 2.457(10) Å) distances. The bend-back

observed angles at C_Rand C_â(C_R/C_â: 173.0(4)/158.1-

(5)°, 9b; 175.6(10)/167.4(11)°, 12a ) and CtC bond

distances (1.218(6) Å, 9b; 1.19(2) Å, 12a ) are similar to

those observed for the related systems [(PPh₃)₂Pt(µ-H)-

(µ-σ:η²CtCPh)RhCp*(PMe₃)]²⁺(16a ; 173.9(9)/171(1)°,

1.21(1) Å)^26aand trans-[Pt₂(µ-H)(µ-σ:η²CtCPh)(C₆F₅)₂-

(25) (a) Kukushkin, V. Y.; Belski, V. K.; Konovalov, V. E.; Shifrina,

R. R.; Moiseev, A. I.; Vlasova, R. A. Inorg. Chim. Acta 1991, 183, 57

and references therein. (b) Hartley, F. R. The Chemistry of Platinum

and Palladium; Applied Science Publishers: London, 1973. (c) Churchill,

M. R.; J ulis, S. A. Inorg. Chem. 1977, 16, 1488. (d) Elder, R. C.; Cruea,

R. D.; Morrison, R. F. Inorg. Chem. 1976, 15, 1623. (e) Clark, H. C.;

Ferguson, G.; J ain, V. K.; Parvez, M. Inorg. Chem. 1985, 24, 1477. (f)

Churchill, M. R.; J ulis, S. A.; Rotella, F. J . Inorg. Chem. 1977, 16, 1137.

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4589

(PPh₃)₂] (∼163°, 1.23(2) Å).²⁷The distortion of the

alkyne fragment is significantly less pronounced than

that reported recently in the alkynyl-chloride-bridged

[Cp₂Zr(µ-Cl)(µ-CtCCH₃)ZrCp₂] (168.2(3)/141.2(3)°, 1.286-

(4) Å).²⁸The central M-Cl-C_R-C_â-M′ cores are not

planar. In both compounds, the M′(C₆F₅)₂unit is

directed toward the same side as the Cp* ring, and the

dihedral angle between the M-Cl-C_Rplane and the d⁸

(Pt or Pd) metal coordination plane (M′-Cl-ipso-

C(C₆F₅) atoms and midpoint of C_R-C_â) is 43.5° in 9b

and 36.3° in 12a . This puckering does not, however,

cause any bonding between the metal centers (M‚‚‚M′

) 3.371(1) Å (9b), 3.362(1) Å (12a )).

chelating type structure (V-shape, IIIb; Chart 1). For

complex 8a , although disorder within crystallization

solvent molecules and on one phenyl group (C(9)-C(14))

limited the accuracy of the determination, the presence

of a connectivity similar to that found for 7a and 7c

(Figures 4 and 5) is reflected in the view given in Figure

6.

In all complexes, the chelated metal center (Pt, 7a ,

7c; Pd, 8a ) is located outside (1.0321(7) Å, 7a ; 1.0124-

(7) Å, 7c; 0.8383(4) Å, 8a ) the corresponding starting

3-irida-1,4-diyne plane Ir(CtC)₂. As in complexes 9b

and 12a , in all of the cases the conformer found is that

which places the Pt(C₆F₅)₂unit on the same side as the

Cp* ring. The resulting dihedral angles between the

fragment IrC_RC_Rplane and the corresponding platinum

(7a ,c) or Pd (8a ) coordination planes are 38.3(6)° for 7a ,

37.1(4)° for 7c, and 31.7(4)° for 8a . The M′(d⁸)-C(η²)

alkyne distances in 7c and 8a (2.31(4)-2.47(2) Å) are

similar to those previously observed for 7a (2.30(2)-

2.46(2) Å). The structural parameters of the Ir-Ct

C-E (E ) C, Si) entities (see Table 3) are similar to

those observed for related systems.^{12d,e,13b-e,14}In these

complexes, the most remarkable feature is that the

resulting bite angle C_R-Ir-C_R′(79.9(8)°, 7a ; 76.9(6)°,

7c; 81.0(7)°, 8a ) is notably smaller than those observed

in related tweezer-like titanocene dinuclear derivatives

{[L₂Ti(CtCR)₂]ML_n} (L ) η⁵-C₅H₄SiMe₃) studied (87.4-

(2)-102.8(2)°)^2c,12eand have a greater similarity to those

found in dinuclear chelating type double-alkynyl-

bridged complexes (V-shape, IIIb; Chart 1) formed with

square-planar 3-platina-1,4-diyne species as building

blocks:^12d,13b-de.g. {[L₂Pt(µ-σ:η²-CtCPh)₂]Pt(C₆F₅)₂} (L

) ¹/₂dppe, 79.3(4)°^13b). The Ir‚‚‚M′ nonbonded distances

(3.506(1) Å in 7a , 3.5624(9) Å in 7c, and 3.435(1) Å in

8a ) are comparable to the Ir-Pt separation reported in

the doubly chloride bridged cation [(PMe₃)Cp*Ir(µ-Cl)₂-

Pt(dppp)]²⁺(3.638 Å).^24f

In 5c (Figure 3) the double-alkynyl bridging system

displays an unsymmetrical σ/π disposition (type IIb,

Chart 1) with both alkynyl ligands σ-bonded to different

metals and η²-bonded on π-coordination to the other

metal. This structural disposition has been previously

found in several early (d¹-d¹)^{7b,8c,e,h,11a,29}and late (d⁸-

d⁸)^11b,c,13bhomodimetallic systems but only in a few

heterodimetallic compounds: [Cp₂M(µ-σ:η²-CtCR)(µ-η²:

σ-CtCR)M′Cp₂],^8b[Cp₂M(µ-σ:η²-CtCSiMe₃)(µ-η²:σ-Ct

CSiMe₃)Ni(PPh₃)] (M ) Ti, Zr),^8dand [Cp₂Ti(µ-Ct

C^tBu)₂Pt(PPh₃)].^11dThe latter complexes are formally

M(III)/M′(I) (M ) Ti, Zr; M′ ) Ni, Pt) species and exhibit

very short M-M′ distances (2.728(1)-2.830(1) Å). In

5c the Rh‚‚‚Pt separation (3.554(1) Å) is considerably

longer than that found in the hydride-alkynyl deriva-

tive 16a (2.8265(8) Å)^26aor the separation found in the

A-frame cation [ClPt(µ-σ:η²CtCMe)(µ-dppm)₂RhCO]⁺

(3.066(2), 3.086(2) Å),^24bruling out any significant

metal-metal interaction. Complex 5c can hence be

formally considered as the neutral zwitterionic Rh(III)/

Pt(II) derivative [(PEt₃)Cp*Rh⁺(µ-σ:η²-CtCSiMe₃)(µ-η²:

σ-CtCSiMe₃)Pt^-(C₆F₅)₂]. Significantly, there is little

or no influence of the metal centers on the M-C bond

lengths of the central RhPtC₄framework. Thus, both

the M-C σ-bonds (2.00(2), 1.96(2) Å) and the complexed

η²-bond distances (2.379(14), 2.29(2) Å for Pt and 2.374-

(14), 2.29(2) Å for Rh) are identical, within experimental

error, and are in the range usually found for these

bonds.^{11b-d,13b,c,15b,d,g,22,24b,26,30}Both alkynyl fragments

are only slightly bent at the inner C_Ratoms (178.9(13),

176.4(14)°), while they deviate significantly from 180°

at the outer atoms (141.7(13), 151.2(13)°). Again the

central dimetallacycle core is not planar and the dihe-

dral angle between the two planes defined by Rh(1)-

C(18)-M(1) (M(1) midpoint C(13)-C(14)) and Pt(1)-

C(1)-C(7)-C(13)-M(2) (M₂midpoint C(18)-C(19)) is

28.7(5)°.

Discu ssion

While cyclopentadienyl rings are typical metal aux-

iliaries widely used for the stabilization of alkynyl or

related (vinylidenes, allenylidenes, etc.) groups in ru-

thenium(II) or iron(II) chemistry,^3b,31reported examples

on Rh(III) and Ir(III) are extremely rare.^16,17The

present study has shown that not only mono(alkynyl)

cyclopentadienyl [Cp*M(CtCR)X(PEt₃)] (M ) Rh (1),

Ir (2)) but also bis(σ-alkynyl) [Cp*M(CtCR)₂(PEt₃)] (M

(31) (a) Comprehensive Organometallic Chemistry II; Shriver, D. F.,

Bruce, M. I., Vol. Eds.; Wilkinson, G., Stone, F. G. A., Abel, E. W.,

Eds.; Elsevier: Oxford, U.K., 1995; Vol. 7. For recent work see: (b) Yi,

C. S.: Liu, N.; Rheingold, A. L.; Liable-Sands, L. M.; Guzei, I. A.

Organometallics 1997, 16, 3729. (c) de los Rios, I.; J ime´nez-Tenorio,

M.; Puerta, M. C.; Valerga, P. J . Am. Chem. Soc. 1997, 119, 6529. (d)

Akita, M.; Kato, S.-I.; Terada, M.; Masaki, Y.; Tanaka, M.; Moro-Oka,

Y. Organometallics 1997, 16, 2392. (e) Whittall, I. R.; Humphrey, M.

G. Organometallics 1996, 15, 1935. (f) Coat, F.; Lapinte, C. Organo-

metallics 1996, 15, 478. (g) J ia, G.; Xia, H. P.; Wu, W. F.; Ng, W. S.

Organometallics 1996, 15, 3634. (h) Bruce, M. I.; Hall, B. C.; Zaitseva,

N. N.; Skelton, B. W.; White, A. H. J . Organomet. Chem. 1996, 522,

307. (i) Peron, D.; Romero, A.; Dixneuf, P. H. Organometallics 1995,

14, 3319. (j) Nombel, P.; Lugan, N.; Mathieu, R. J . Organomet. Chem.

1995, 503, C22. (k) Sato, M.; Hayashi, Y.; Kumakura, S.; Shimizu, N.;

Katada, M.; Kawata, S. Organometallics 1996, 15, 721. (l) Whittall, I.

R.; Humphrey, M. G.; Hockless, D. C. R.; Skelton, B. W.; White, A. H.

Organometallics 1995, 14, 3970. (m) Lang, H.; Blau, S.; Rheinwald,

G. J . Organomet. Chem. 1995, 492, 81. (n) Ting, P.-C.; Lin, Y.-C.; Lee,

G.-H.; Cheng, M.-C.; Wang, Y. J . Am. Chem. Soc. 1996, 118, 6433. (o)

Lichtenberger, D. L.; Renshaw, S. K.; Bullow, R. M. J . Am. Chem. Soc.

1993, 115, 3276.

In contrast, as is shown in Figures 4-6, the structures

of the mixed iridium compounds 7a ,¹⁴7c (Ir-Pt), and

8a (Ir-Pd) reveal that all these complexes possess a

(26) (a) Cao, D. H.; Stang, P. J .; Arif, A. M. Organometallics 1995,

14, 2733. (b) Stang, P. J .; Cao, D. Organometallics 1993, 12, 996.

(27) Ara, I.; Falvello, L.; Fornie´s, J .; Mart´ın, A.; Mart´ınez, F.;

Lalinde, E.; Moreno, M. T. Organometallics 1997, 16, 5392.

(28) Takahashi, T.; Nishihara, Y.; Sun, W.-H.; Fischer, R.; Nakajima,

K. Organometallics 1997, 16, 2216.

(29) (a) Wood, G. L.; Knobler, C. B.; Hawthorne, M. F. Inorg. Chem.

1989, 28, 382. (b) Metzler, N.; No¨th, H. J . Organomet. Chem. 1993,

454, C5. (c) Erker, G.; Fro¨mberg, W.; Mynott, R.; Gabor, B.; Kru¨ger,

C. Angew. Chem., Int. Ed. Engl. 1986, 25, 463.

(30) (a) Antwi-Nsiah, F. H.; Oke, O.; Cowie, M. Organometallics

1996, 15, 506. (b) Esteruelas, M. A.; Lahuerta, O.; Modrego, J .;

Nu¨rberg, O.; Oro, L. A.; Rodr´ıguez, L.; Sola, E.; Werner, H. Organo-

metallics 1993, 12, 266. (c) Osakada, K.; Matsumoto, K.; Yamamoto,

T.; Yamamoto, A. Organometallics 1985, 4, 857.

4590 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

) Rh (3), Ir (4)) derivatives of Rh(III) and Ir(III) are

accessible. Complexes 1 and 2 increase the very small

list of the mono(alkynyl) cyclopentadienyl rhodium(III)

and iridium(III) derivatives presently known.^15l,16,17

Compounds 3 and 4 are very unusual. As far as we

know, they are the first reported examples in which a

Cp*ML (M ) Rh, Ir) fragment is stabilized by two

σ-alkynyl ligands. In particular, Maitlis et al. reported

in 1982 that the preparation of complexes [Rh(C₅-

Me₅)(C₄Ph₂HCPh)C₅Ph₂H₂)] (13) and [Rh(C₅Me₅)(C₈-

Ph₄H₂)] (14) could be carried out via bis(alkynyl)

intermediate species such as [Cp*Rh(CtCPh)₂(NCMe)]

and [Cp*Rh(CtCPh)₂(HCtCPh)];¹⁸more recently, re-

lated neutral species [Cp*Rh(CtCR)₂(R-alanine)] (R )

Ph, tol) have been also suggested by Carmona et al.^16b

in the course of the trimerization process that affords

[Cp*Rh(η⁴-C₄HR₂CtCR)] (15) by treatment of [Cp*Rh-

(L-alaninate)(Cl)] with HCtCPh and NEt₃. In this

context, the synthesis of complexes 3 provide a strong

indication that such species could exist. The stability

of these complexes containing two alkynyl ligands

mutually cis is surprising, since C-C alkynyl coupling

reactions on Rh(III) to butadiynes have been observed

previously.³²

Heterobridged mixed dinuclear neutral complexes

[(PEt₃)Cp*M(µ-CtCR)(µ-X)M′(C₆F₅)₂] (Rh,Ir-Pt,Pd,

9-12) have been synthesized using mono(σ-alkynyl)

complexes 1 and 2 as precursors. Several µ-Cl-µ-

alkynyl-bridged homodinuclear (Zr-Zr)^11a,28and het-

erodinuclear (Ti-Cu,³³Zr-Hf^11a) neutral compounds

are known, and it should be mentioned that Stang has

recently prepared, via an unusual C-H alkyne bond

activation, two cationic heterodinuclear Rh-Pt (16a )

and Ir-Pt (16b) derivatives [Cp*(PMe₃)M(µ-H)(µ-η²:σ-

CtCPh)Pt(PPh₃)₂](OTf)₂containing a mixed µ-H-µ-Ct

CR bridging system.²⁶The X-ray crystal structure of

complexes 9b (Rh-Pt, CtC^tBu) and 12a (Ir-Pd, Ct

CPh) revealed that the geometries at the metal centers

and the σ-coordination of the alkynyl ligands to Rh or

Ir have been preserved throughout the reaction, sug-

gesting that the reactions of 1 and 2 with [cis-M′(C₆F₅)₂-

(thf)₂] (M′ ) Pt, Pd) complexes occur, via displacement

of the thf ligands, by simple coordination of chloride and

alkynyl (η²-side) groups to the Pd or Pt centers. At first

sight this result is in contrast to the bonding charac-

teristic found in the formal Rh(III)-Pt(II) cation [Cp*-

(PMe₃)Rh(µ-H)(µ-η²:σ-CtCPh)Pt(PPh₃)₂]²⁺(16a ),^26ain

which the phenylethynyl group is σ-bonded to Pt and

η²-bonded to Rh, but clearly there are notable electronic

and also steric differences on the organometallic frag-

ments in 9-12 compared to 16.

at least in these cases, the iridium center exhibits a

stronger σ-alkynyl preference than the platinum or

palladium. It is remarkable that complexes 7a ,c are

also obtained using [cis-Pt(C₆F₅)₂(CtCR)₂]^2-as unusual

double alkynyl transfer reagents (Scheme 1). Monoalky-

nylation processes between transition-metal centers

yielding dinuclear final compounds with one^4n,34or

two^{11a,d,13b,c,29c}alkynyl ligands connecting the metal

centers have been previously observed, but as far as we

know, these are the first reported examples of double

alkynylation. In contrast, the crystal structure of 5c

(Rh-Pt, CtCSiMe₃) indicates that, in this system, the

Pt atom seems to have a greater preference for the σ

electronic density of the alkynyl groups than does the

Rh center. This was of some surprise to us since, as

mentioned in the Introduction, we had initially assumed

that the alkynylation processes could be caused by the

difference in the formal charge of the metal centers

involved, but clearly this idea is not the determining

factor since complex 5c is obtained not only through the

neutralization route but also by an unexpected σ-alkynyl

ligand migration from Rh to Pt between the neutral

mononuclear species 3c and cis-Pt(C₆F₅)₂.

According to these results and on the basis of their

spectroscopic data, particularly their IR spectra, while

for the Rh-Pt complex 5a we also favor a zwitterionic

formulation with a σ/π double-alkynyl-bridged system,

for 6a (Rh-Pd) a chelating type is assumed. This latter

formulation (6a ) clearly shows that the preference for

a σ-alkynyl bond should be higher in Pt than in Pd, and

this reinforces other previous observations.^13d,eFor

instance, the preparation of (σ-alkynyl)platinum com-

plexes by transmetalation of alkynyl groups using (σ-

alkynyl)palladium complexes has been also recently

reported.³⁵It is reasonable to expect the greater σ-alky-

nyl preference of Ir and Pt over Rh and Pd and the easy

alkynyl migration from Rh or Pd to Pt and from Pt to

Ir on the basis of stronger M-C bonds with a third-row

metal and greater kinetic lability of second-row metals.

There have been previous observations^6-9of the

influence not only of the metal but also of the alkynyl

substituents on the final structures of related double-

alkynyl bridging systems. Changes in the alkynyl

substituents also seem to have a pronounced effect on

the systems reported here. In fact, all our attempts to

prepare the corresponding heterometallic bis(µ-CtC^t-

Bu) derivatives have failed. However, the observation

of σ/π-alkynide zwitterionic type structures for 5a (Rh-

Pt, Ph) and 5c (Rh-Pt, SiMe₃) and chelating type

structures for the related Ir-Pt derivatives 7a (Ph) and

7c (SiMe₃) clearly indicates that a change of R (Ph by

SiMe₃) causes minor changes in the final disposition of

the alkynyl ligands, which can be attributed principally

to the influence of electronic effects of metal centers.

This result is in contrast to previous observations on

early-late [Cp₂Ti(CtCR)₂ML_n] (M ) Ni, Pt) heterodi-

Different conclusions can be drawn from the struc-

tural data of some of the doubly alkynyl bridged

complexes 5-8 formed by starting from 3 and 4 and [cis-

M′(C₆F₅)₂(thf)₂]. The crystal structures of the heterodi-

nuclear iridium derivatives 7a (Ir-Pt, CtCPh), 7c (Ir-

Pt, CtCSiMe₃), and 8a (Ir-Pd, CtCPh) show that once

again both alkynyl ligands remain σ-bonded to iridium,

while the platinum (7a ,c) and palladium (8a ) centers

are stabilized by η²-alkyne interactions, indicating that,

(34) (a) Berenguer, J . R.; Fornie´s, J .; Lalinde, E.; Mart´ınez, F.;

Urriolabeitia, E.; Welch, A. J . J . Chem. Soc., Dalton Trans. 1994, 1291.

(b) Ipaktschi, J .; Mirzaei, F.; Mu¨ller, B. G.; Beck, J .; Serafin, M. J .

Organomet. Chem. 1996, 526, 363. (c) Akita, M.; Ishii, N.; Takabuchi,

A.; Tanaka, M.; Moro-Oka, Y. Organometallics 1994, 13, 258. (d) Fritz,

P. M.; Polborn, K.; Steinman, M.; Beck, W. Chem. Ber. 1989, 122, 889.

(e) Bruce, M. I.; Abu-Salah, O. M.; Davis, P. E.; Raghavan, N. V. J .

Organomet. Chem. 1974, 64, C48. (f) Lai, N.-S.; Tu, W.-C.; Peng, S.-

M.; Lee, G.-H. Organometallics 1994, 13, 4652.

(32) Bedford, R. B.; Hill, A. F.; Thompsett, A. R.; White, A. J . P.;

Williams, D. J . J . Chem. Soc., Chem. Commun. 1996, 1059.

(33) (a) Lang, H.; Frosch, W.; Wu, I. Y.; Blau, S.; Nuber, B. Inorg.

Chem. 1996, 35, 6266. (b) Lang. H.; Blau, S.; Pritzkuw, H.; Zsolnai, L.

Organometallics 1995, 14, 1850.

(35) Osakada, K.; Sakata, R.; Yamamoto, T. Organometallics 1997,

16, 5354.

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4591

[Cp*MCl₂(PEt₃)] (M ) Rh, Ir) were prepared by a procedure

similar to that previously described for related derivatives by

Maitlis et al.¹⁹[Cp*IrI₂(PEt₃)] was prepared from [Cp*IrCl₂-

(PEt₃)] and excess NaI in acetone.

metallic systems, which have essentially flat TiC₄M

cores. In these planar dimers, the final tweezer-like or

σ/π structures could be rationalized as the result of

reducing steric congestion at the central core as a

consequence of notable interactions between bulky

ancillary ligands on Ni or Pt and alkyne substituents.

Thus, whereas for bulky R ) ^tBu (ML_n) PtPPh₃)^11dor

SiMe₃(ML_n) NiPPh₃)^8da σ/π bonding situation is

formed, for R ) SiMe₃and ML_n) Ni(CO)³⁶or [Cp₂Ti-

(µ-σ:η²-CtCPh)(µ-σ:η²-CtCSiMe₃)Ni(PPh₃)]^8da tweezer-

like structure is favored. In the d⁶-d⁸heterodimetallic

systems presented here the dimers exhibit nonplanar

structures which would seem to allow substantial

control of steric factors.

Data for [Cp*RhCl₂(PEt₃)]: Anal. Calcd for C₁₆H₃₀Cl₂PRh:

C, 44.95; H, 7.07. Found: C, 44.89; H, 6.90. MS: m/z 426

[M]⁺8%; 391 [M - Cl]⁺100%. ¹H NMR (CDCl₃, δ): at 15 °C,

4

2.06 (m, PCH₂CH₃, 6H); 1.64 (d, J _P-H3.01, Cp*, 15 H); 1.13

(dt, ³J _P-H15.2, ³J _H-H7.6, P-CH₂-CH₃, 9H). ¹³C NMR (CDCl₃,

1

2

δ): at 15 °C, 99.11 (dd, J _Rh-C6.7, J _P-C2.9, C₅Me₅); 16.92 (d,

¹J _P-C27.2, PCH₂CH₃); 9.38 (d, J _Rh-C1.3, C₅(CH₃)₅); 8.08 (d,

2

²J _P-C4.6, PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, 28.0 (d,

¹J _P-Rh137.8).

Data for [Cp*IrCl₂(PEt₃)]: Anal. Calcd for C₁₆H₃₀Cl₂IrP: C,

37.21; H, 5.85. Found: C, 36.73; H, 6.23. MS: m/z ) 516 [M]⁺

27%; 481 [M - Cl]⁺100%; 363 [IrCp*Cl]⁺30%. ¹H NMR

4

(CDCl₃, δ): at 15 °C, 2.10 (m, PCH₂CH₃, 6H); 1.66 (d, J _P-H

Con clu sion

3

1.7, Cp*, 15 H); 1.1 (dt, J _P-H15.5, J _H-H7.7, PCH₂CH₃, 9H).

¹³C NMR (CDCl₃, δ): at 15 °C, 90.9 (d, ²J _P-C2.7, C₅Me₅); 15.77

(d, ¹J _P-C34.1, PCH₂CH₃); 8.68 (s, C₅(CH₃)₅); 7.19 (d, ²J _P-C3.9,

PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, -6.3 (s).

In summary, mono- and bis(alkynyl) rhodium and

iridium complexes 1-4 have been prepared from

[Cp*MX₂(PEt₃)] (X ) Cl, I) using classical metal-

halogen exchange reactions with LiCtCR or AgCtCR

and their reactivity toward [cis-M′(C₆F₅)₂(thf)₂] (M′ )

Pt, Pd) has been studied. Several hetero-bridged µ-Cl-

µ-CtCR (9-12) and homobridged (µ-CtCR)₂(5-8)

heterodinuclear Rh,Ir/Pt,Pd complexes have been syn-

thesized, and interestingly, the final mixed platinum

complexes 5a ,c and 7a ,c are obtained by starting from

either terminal σ-alkynyl Rh and Ir or platinum precur-

sors. The influence of the alkynyl substituents seems

to be decisive on the final stability of the bis(µ-alkynide)

heterometallic complexes, and only when the substitu-

ents are Ph or SiMe₃are the final dimers easily formed.

The reactions with tert-butylalkynyl groups lead to the

formation of undefined products. X-ray diffraction and

spectroscopic data on the final heterodinuclear products

indicate that the observed metal site preference for σ

coordination to alkynyl bridging ligands in these homo-

bridged dimers follows the order Ir > Pt > Rh > Pd.

These observations are consistent with the expected

stronger M-C bonds with a third-row metal than with

a second-row metal and with the greater kinetic lability

of the second-row metals.

Data for [Cp*IrI₂(PEt₃)]: Anal. Calcd for C₁₆H₃₀I₂IrP: C,

27.48; H, 4.32. Found: C, 27.66; H, 4.15. MS: m/z ) 699 [M]⁺

5%; 573 [M - I]⁺100%, 455 [IrCp*I]⁺27%. ¹H NMR (CDCl₃,

4

δ): at 15 °C, 2.26 (m, PCH₂CH₃, 6H); 1.93 (d, J _P-H1.6, Cp*,

15 H); 1.12 (dt, ³J _P-H15.2, ³J _H-H7.7, PCH₂CH₃, 9H). ¹³C NMR

(CDCl₃, δ): at 15 °C, 92.61 (d, ²J _P-C2.5, C₅Me₅); 21.41 (d, ¹J _P-C

3

2

35.94, PCH₂CH₃); 10.57 (d, J _P-C0.8, C₅(CH₃)₅); 9.92 (d, J _P-C

4.8, PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, -19.7 (s).

Rea ction of [Cp *Rh Cl₂(P Et₃)] w ith LiCtCP h (Com -

p lex 1a ). [Cp*RhCl₂(PEt₃)] (0.3 g, 0.7 mmol) was added, at

low temperature (-20 °C), to a freshly prepared solution of

LiCtCPh (2.81 mmol, molar ratio Rh/Li ) 1/4) in thf (20 mL),

prepared from HCtCPh (0.32 mL, 2.81 mmol) and LiⁿBu (1.75

mL, 2.81 mmol, hexane solution 1.6 M), and the mixture was

stirred for ca. 2 min. The resulting red solution was rapidly

hydrolyzed with moist thf (3 mL) and evaporated to dryness.

The oily residue was treated with toluene/hexane (30 mL, 2/1)

and filtered. Evaporation of the filtrate yielded an oily residue.

The NMR data of this oil (∼90% yield based on Rh) shows it

to be [Cp*Rh(CtCPh)Cl(PEt₃)] (1a ) along with small amounts

of [Cp*RhCl₂(PEt₃)] (∼12%) and [Cp*Rh(CtCPh)₂(PEt₃)] (3a ;

∼14%). As all attempts to purify 1a were unsuccessful, this

complex, 1a , was spectroscopically characterized from this

mixture.

Data for 1a : MS: m/z ) 457 [M - Cl]⁺62%; 391 [M - C₂-

Ph]⁺36%; 372 [M - (PEt₃) - 2H]⁺28%, 356 [Cp*Rh(PEt₃)]⁺

79%, 237 [Cp*Rh]⁺91%. ¹H NMR (CDCl₃, δ): at 15 °C, 7.29,

Exp er im en ta l Section

4

7.16, 7.05 (m, Ph, 5H); 2.04 (m, PCH₂CH₃, 6H); 1.75 (d, J _P-H

All manipulations were carried out under a nitrogen atmo-

sphere. Solvents (hexane, alkanes mixture) were dried by

standard procedures and distilled under dry N₂before use.

Moist thf employed for quenching alkynylation reactions was

RPE grade, used as received.

2.6, Cp*, 15 H); 1.16 (m, PCH₂CH₃, 9H). ³¹P NMR (CDCl₃, δ):

1

at 15 °C, 32.9 (d, J _P-Rh131).

We have also attempted to synthesize 1a , by treating

[Cp*RhCl₂(PEt₃)] with an excess (1:3) of [AgCtCPh]_n, but

NMR (³¹P) only detected mixtures of 1a , 3a , and [Cp*RhCl₂-

(PEt₃)] with undefined products.

The instruments and procedures used have been previously

reported.²²All coupling constants are given in Hz. Mass

spectra were obtained in a VG Autospec double-focusing mass

spectrometer operating in the FAB⁺mode, except for complex

11a ′ (HP-5989B mass spectrometer using the ES(-) tech-

nique).

P r ep a r a tion of [Cp *Rh (CtC^tBu )Cl(P Et₃)] (1b). A solu-

tion of LiⁿBu in hexane (1.6 N, 3.49 mL, 5.58 mmol) was added

dropwise for 5 min to a thf solution (30 mL) of HCtC^tBu (0.76

mL, 5.62 mmol) at -20 °C. After 20 min of stirring [Cp*RhCl₂-

(PEt₃)] (0.4 g, 0.94 mmol) was added and the mixture was

stirred for 10 min. The resulting red solution was hydrolyzed

with moist thf (3 mL) and evaporated to dryness. The oily

residue was treated with toluene/hexane (30 mL, 1/1) and

filtered. Evaporation of the filtrate and treatment of the final

residue with cold hexane afforded 1b as an orange solid. Yield

33%.

Q₂[cis-Pt(C₆F₅)₂(CtCR)₂] (Q ) PMePh₃, R ) Ph;^21dQ )

NBu₄, R ) ^tBu,^21dSiMe₃^13d), [cis-M′(C₆F₅)₂(thf)₂] (M′ ) Pd, Pt),³⁷

38

and AgClO₄were prepared by published methods; [AgCt

39

CPh]_nwas prepared by treating an aqueous ammoniacal

solution of AgNO₃with HCtCPh.

(36) Lang, H.; Imhof, W. Chem. Ber. 1992, 125, 1307.

(37) Uso´n, R.; Fornie´s, J .; Toma´s, M.; Menjo´n, B. Organometallics

1985, 4, 1912.

(38) Smith, G. F.; Ring, F. J . Am. Chem. Soc. 1937, 59, 1889.

(39) van Koten, G.; Noltes, J . G. In Comprehensive Organometallic

Chemistry; Wilkinson, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon

Press: Oxford, U.K., 1982; Vol. 2, p 721.

Data for 1b: Anal. Calcd for C₂₂H₃₉ClPRh: C, 55.90; H, 8.3.

Found: C, 56.00; H, 7.91. MS: m/z ) 471 [M + H]⁺7%; 437

[M - Cl]⁺54%; 391 [M - C₂Bu]⁺29%; 355 [M - Cl - C₂Bu]⁺

25%. ¹H NMR (CDCl₃, δ): at 15 °C, 1.99 (m, PCH₂CH₃, 6H);

t

1.68 (d, J _P-H2.5, Cp*, 15 H); 1.16 (s, ^tBu, 9H); 1.12 (m,

4

4592 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ): at 15 °C, 111.35 (dd,

²J _Rh-C9.14, ³J _P-C2.32, C_â, -CtCR); 98.85 (dd, ¹J _Rh-C5.2, ²J _P-C

mixture of 2a and 4a . Small amounts of unidentified decom-

position products (δ -11.99, -12.6, and -16.25) were also

observed. Longer reaction times only produced an slight

increase of the proportion of 4a , 40:60 being the final ratio of

2a to 4a after 3 days.

P r ep a r a tion of [Cp *Ir (CtCP h )I(P Et₃)] (2a ′). An orange

solution of [Cp*IrI₂(PEt₃)] (0.15 g, 0.214 mmol) in CH₂Cl₂(30

mL) was treated with an excess of [AgCtCPh]_n(0.135 g, 0.64

mmol) and the mixture refluxed for 90 min. Control by ³¹P

NMR of the reaction mixture showed the presence of 4a , 2a ′,

and the precursor [Cp*IrI₂(PEt₃)] (ratio ca. 12:70:18). The

mixture was refluxed for another 30 min and then filtered.

Evaporation of the resulting pale orange solution and addition

of 20 mL of diethyl ether gave 2a ′ as an orange solid. Yield:

56%.

1

2

2.9, C₅Me₅); 82.7 (dd, J _Rh-C52.8, J _P-C38.1, C_R, -CtCR);

4

3

32.56 (d, J _Rh-C0.63, -C(CH₃)₃, CtCR); 28.83 (d, J _Rh-C2.2,

-CMe₃, CtCR); 17.53 (d, ¹J _P-C29.6, PCH₂CH₃); 9.20 (d, ²J _Rh-C

1.3, C₅(CH₃)₅); 8.0 (d, J _P-C4.1, PCH₂CH₃). ³¹P NMR (CDCl₃,

2

1

δ): at 15 °C, 32.6 (d, J _P-Rh133).

P r ep a r a tion of a Mixtu r e of [Cp *Rh (CtCSiMe₃)Cl-

(P Et₃)] (1c) a n d 3c. [Cp*RhCl₂(PEt₃)] (0.4 g, 0.94 mmol) was

added to a cold (-20 °C) solution of LiCtCSiMe₃(3.7 mmol)

in thf (30 mL). The mixture was stirred for 2 min, hydrolyzed,

and evaporated to dryness; the residue was then extracted

with toluene/hexane (30 mL, 1/1) and the extracts were

filtered. Evaporation of the filtrate under reduced pressure

yielded an oily residue which was identified by NMR spec-

1

troscopy (³¹P and H) as a mixture of complexes 1c and 3c in

Data for 2a ′: Anal. Calcd for C₂₄H₃₅IIrP: C, 42.79; H, 5.24.

Found: C, 42.56; H, 5.10. MS: m/z ) 674 [M]⁺25%; 648

[Cp*Ir(C₂Ph)(PEt₃)]⁺26%; 573 [M - C₂Ph]⁺55%, 547 [M -

I]⁺100%. ¹H NMR (CDCl₃, δ): at 15 °C, 7.17, 7.00 (m, Ph, 5

H); 2.15 (m, PCH₂CH₃, 6H); 1.94 (s, Cp*, 15 H); 1.13 (m,

PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ): at 15 °C, 131.6 (s, o-C,

Ph); 129.3 (s, i-C, Ph); 127.45 (s, m-C, Ph); 124.2 (s, p-C, Ph);

a 2:1 ratio. Complex 1c was spectroscopically characterized

from this mixture. Using a shorter reaction time, lower

temperature, or less excess of LiCtCSiMe₃(1:1 or 1:2)

mixtures of [Cp*RhCl₂(PEt₃)] and 3c, sometimes with 1c also,

were always obtained.

Data for 1c: ¹H NMR (CDCl₃, δ): at 15 °C, 1.97 (m, PCH₂-

4

2

CH₃, 6H); 1.70 (d, J _P-H2.5, Cp*, 15 H); 1.12 (m, PCH₂CH₃,

103.13 (s, C_â, -CtCR); 94.14 (d, J _P-C2.5, C₅Me₅); 19.32 (d,

2

9H); 0.04 (s, SiMe₃, 9 H). ¹³C NMR (CDCl₃, δ): at 15 °C, 126.9

(dd, ¹J _Rh-C50.2, ²J _P-C34.6, C_R, -CtCR); 109.0 (dd, ²J _Rh-C7.8,

¹J _P-C36.4, PCH₂CH₃); 9.89 (s, C₅(CH₃)₅); 8.7 (d, J _P-C4,

PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, -12.7 (s).

P r ep a r a tion of [Cp *Ir (CtCSiMe₃)I(P Et₃)] (2c′). To a

cooled (-20 °C) freshly prepared solution of LiCtCSiMe₃(6.43

mmol) in thf (30 mL) was added [Cp*IrI₂(PEt₃)] (0.3 g, 0.43

mmol). The mixture was stirred for 50 min, hydrolyzed with

moist thf (∼3 mL), and evaporated to dryness. The oily residue

was extracted with toluene/hexane (30 mL, 2/1), and the

extracts were filtered. Evaporation of the filtrate yielded an

orange oil, characterized as complex 2c′ by NMR spectroscopy

(¹H and ³¹P). Yield: 94%.

1

2

³J _P-C2.3, C_â, -CtCR); 99.6 (dd, J _Rh-C5.1, J _P-C2.8, C₅Me₅);

1

2

17.5 (d, J _P-C29.4, PCH₂CH₃); 9.28 (d, J _Rh-C1.3, C₅(CH₃)₅);

7.93 (d, ²J _P-C4.2, PCH₂CH₃); 1.17 (s, SiMe₃). ³¹P NMR (CDCl₃,

1

δ): at 15 °C 32.6 (d, J _P-Rh132).

P r ep a r a tion of [Cp *Ir (CtCP h )Cl(P Et₃)] (2a ). A mix-

ture of 0.25 g (0.48 mmol) of [Cp*IrCl₂(PEt₃)] and [AgCtCPh]_n

(0.2 g, 0.96 mmol) in CH₂Cl₂(30 mL) was stirred with exclusion

of light and monitored by ³¹P NMR. After 1 h a 1:1 mixture

of [Cp*IrCl₂(PEt₃)] and 2a is observed. After 4 h, the iridium

dichloride had been converted into 2a . Traces of 4a and of a

new unidentified species (δ -5.9) were also observed. The

excess of [AgCtCPh]_nand AgCl formed was then filtered and

the resulting pale yellow solution evaporated to dryness.

Addition of cold hexane (5 mL) to the residue afforded 2a as a

yellow solid. Yield: 45%.

Data for 2c′: MS: m/z ) 669 [M]⁺22%; 573 [M - C₂SiMe₃

+ H]⁺100%, 543 [M - I + H]⁺75%; 455 [Cp*IrI + H]⁺(98%).

¹H NMR (CDCl₃, δ): at 15 °C, 2.09 (m, PCH₂CH₃, 6H); 1.87

4

(d, J _P-H1.6, Cp*, 15 H); 1.08 (m, PCH₂CH₃, 9H); 0.02 (s,

3

SiMe₃, 9H). ¹³C NMR (CDCl₃, δ): at 15 °C, 105.32 (d, J _P-C

2

0.83, C_â, -CtCR); 103.48 (d, J _P-C21.31, C_R, CtCPh); 94.10

2

1

(d, J _P-C2.75, C₅Me₅); 19.39 (d, J _P-C36.48, PCH₂CH₃); 9.81

(d, ³J _P-C0.88, C₅(CH₃)₅); 8.83 (d, ²J _P-C4.2, PCH₂CH₃); 1.84 (s,

SiMe₃). ³¹P NMR (CDCl₃, δ): at 15 °C, -13.2 (s).

Data for 2a : Anal. Calcd for C₂₄H₃₅ClIrP: C, 49.50; H, 6.05.

Found: C, 49.10; H, 6.38. MS: m/z ) 582 [M]⁺66%; 547 [M -

Cl]⁺100%; 481 [M - C₂Ph]⁺56%. ¹H NMR (CDCl₃, δ): at 15

°C, 7.24, 7.16, 7.03 (m, Ph, 5 H); 2.09 (m, PCH₂CH₃, 6H); 1.80

P r ep a r a tion of [Cp *Rh (CtCR)₂(P Et₃)] (R ) P h (3a ),

^tBu (3b), SiMe₃(3c)). A typical preparation for complex 3a

was as follows:

4

(d, J _P-H1.4, Cp*, 15 H); 1.11 (m, PCH₂CH₃, 9H). ¹³C NMR

(CDCl₃, δ): at 15 °C, 131.55 (s, o-C, Ph); 127.5 (s, m-C, Ph);

124.38 (s, Ph); 102.09 (s, C_â, -CtCR); 93.73 (s, C₅Me₅); 16.8

(d, ¹J _P-C35.5, PCH₂CH₃); 9.12 (s, C₅(CH₃)₅); 7.62 (d, ²J _P-C3.8,

PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, -7.3 (s).

[Cp*RhCl₂(PEt₃)] (0.4 g, 0.94 mmol) was added at low

temperature (-20 °C) to a solution of LiCtCPh (molar ratio

Rh:Li ) 1:5) in thf (20 mL), and the mixture was stirred for

30 min. The resulting red solution was evaporated to dryness,

the resulting red solid was extracted with toluene/hexane

(∼100 mL, 2/1), and the extract was filtered and evaporated

to dryness. Treatment of the solid residue with cold hexane

afforded 3a as a brown solid. Yield: 69%.

Data for 3a : Anal. Calcd for C₃₂H₄₀PRh: C, 68.81; H, 7.21.

Found: C, 68.61; H, 6.91. MS: m/z ) 558 [M]⁺27%; 441 [M

- (PEt₃)]⁺17%; 356 [Cp*Rh(PEt₃)]⁺100%. ¹H NMR (CDCl₃,

δ): at 15 °C, 7.28, 7.16, 7.04 (m, Ph, 10H); 2.03 (m, PCH₂CH₃,

6H); 1.90 (d, ⁴J _P-H2.27, Cp*, 15 H); 1.17 (dt, ³J _P-H15.7, ³J _H-H

7.8, PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ): at -50 °C, 130.9 (s,

o-C, Ph); 129.0 (s, i-C, Ph); 127.5 (s, m-C, Ph); 124.0 (s, p-C,

Rea ction of [Cp *Ir Cl₂(P Et₃)] w ith LiCtCP h . [Cp*IrCl₂-

(PEt₃)] (0.35 g, 0.678 mmol) was added at low temperature to

a freshly prepared solution of LiCtCPh in thf (molar ratio Ir:

Li ) 1:6), and the mixture was stirred at room temperature

overnight. The resulting orange solution was evaporated to

dryness and the residue extracted with toluene/hexane (1/9),

and the extracts were filtered. Evaporation of the filtrate to

dryness and treatment of the residue with hexane yielded a

beige solid (0.2 g). NMR analyses of this solid revealed that

it was an approximately equimolecular mixture of the mono-

and bis(alkynyl) iridium derivatives 2a and 4a .

By using a lower excess of LiCtCPh (Ir/LiCtCPh 1/3) and

a shorter reaction time (1 h), a pale orange solid (57% yield)

was obtained and identified as [Cp*IrCl₂(PEt₃)] with a small

amount of 2a (less than 10%).

The reaction of [Cp*IrCl₂(PEt₃)] with a large excess of LiCt

CPh (Ir/LiCtCPh 1/10) in thf was monitored by ³¹P NMR

spectroscopy. After 1 h of reaction the dichloride precursor

had not been yet consumed and a mixture of this and 2a in a

ca. 2:1 ratio, plus a small amount of 4a (less than 5%), was

clearly observed. After the mixture was stirred for 12 h, all

the dichloride precursor reacted, giving an equimolecular

1

2

Ph); 103.7 (dd, J _Rh-C53, J _P-C30.8, C_R, -CtCR); 102.9 (dd,

²J _Rh-C10.3, J _P-C2.7, C_â, -CtCR); 99.8 (dd, J _Rh-C3.7, J _P-C

3

1

2

1

2

2.8, C₅Me₅); 17.6 (d, J _P-C31, PCH₂CH₃); 9.8 (d, J _Rh-C1, C₅-

2

(CH₃)₅); 7.9 (d, J _P-C3.4, PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at

1

15 °C, 37.2 (d, J _P-Rh122).

Complexes 3b and 3c were obtained similarly by starting

from [Cp*RhCl₂(PEt₃)] (0.4 g, 0.94 mmol) and LiCtCR (R )

^tBu, 5.6 mmol, 3b; R ) SiMe₃, 6.18 mmol, 3c). The reaction

times were 75 min for 3b and 30 min for 3c. The final residues

were extracted with 30 mL of a toluene/hexane (1/1) mixture

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4593

and the extracts filtered. The resulting filtrates were evapo-

rated again, yielding 3b as a gummy brown solid (47% yield)

and 3c as a red oil (87% yield), which were characterized by

spectroscopic methods in solution.

Data for 3b: Satisfactory analyses of this complex could not

be obtained. Anal. Calcd for C₂₈H₄₈PRh: C, 64.85; H, 9.32.

Found: C, 62.96; H, 7.63. MS: m/z ) 519 [M + H]⁺18%; 437

[M - C₂C^tBu]⁺12%; 401 [M - (PEt₃)]⁺92%; 356 [Cp*Rh-

(PEt₃)]⁺100%. ¹H NMR (CDCl₃, δ): at 15 °C, 1.90 (m, PCH₂-

°C, 2.00 (m, PCH₂CH₃, 6H); 1.83 (d, ⁴J _P-H1.1, Cp*, 15 H); 1.06

(dt, ³J _P-H15.7, ³J _H-H7.9, PCH₂CH₃, 9H); 0.01 (s, SiMe₃, 18H).

2

¹³C NMR (CDCl₃, δ): at -50 °C, 104.35 (d, J _P-C18.37, C_R,

-CtCR); 100.30 (d, ³J _P-C0.7, C_â, -CtCR); 94.79 (d, ²J _P-C2.4,

1

3

C₅Me₅); 16.86 (d, J _P-C37.1, PCH₂CH₃); 9.12 (d, J _P-C0.6, C₅-

(CH₃)₅); 7.59 (d, ²J _P-C3.5, PCH₂CH₃); 1.56 (s, SiMe₃). ³¹P NMR

(CDCl₃, δ): at 15 °C, -9.2 (s); at -50 °C, -8.2 (s).

P r epar ation of [(P Et₃)Cp*Rh (µ-CtCP h )₂P t(C₆F₅)₂] (5a).

Meth od A. A solution of [Cp*RhCl₂(PEt₃)] (0.073 g, 0.17

mmol) in acetone (10 mL) was treated with AgClO₄(0.0705 g,

0.34 mmol), and the mixture was stirred at room temperature

for 1 h. The AgCl was filtered and the filtrate treated with

[PMePh₃]₂[cis-Pt(C₆F₅)₂(CtCPh)₂] (0.2 g, 0.16 mmol). The

mixture was stirred for 15 min and evaporated to dryness, and

then treatment of the residue with EtOH afforded complex 5a

as an orange solid. Yield: 28%.

Meth od B. [cis-Pt(C₆F₅)₂(thf)₂] (0.11 g, 0.17 mmol) was

added to a solution of [Cp*Rh(CtCPh)₂(PEt₃)] (3a ; 0.095 g,

0.17 mmol) in CH₂Cl₂(15 mL). The mixture was stirred for 3

min, and the resulting red solution was evaporated to dryness.

Addition of 5 mL of Et₂O rendered 5a as an orange solid.

Yield: 41%.

4

t

CH₃, 6H); 1.75 (d, J _P-H2.4, Cp*, 15 H); 1.14 (s, Bu, 18H);

1.09 (m, PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ): at -50 °C, 108.7

2

3

1

2

(dd, J _Rh-C9.7, J _P-C3, C_â, -CtCR); 98.7 (t, J _Rh-C≈ J _P-C

1

2

3.5, C₅Me₅); 81.46 (dd, J _Rh-C53.9, J _P-C33.6, C_R, -CtCR);

32.5 (s, -C(CH₃)₃, CtCR); 28.9 (s, -CMe₃, CtCR); 18.4 (d, ¹J _P-C

2

31.5, PCH₂CH₃); 9.6 (d, J _Rh-C1, C₅(CH₃)₅); 8.4 (d, J _P-C3,

PCH₂CH₃). ³¹P NMR (CDCl₃, δ): at 15 °C, 37.3 (d, ¹J _P-Rh124).

Data for 3c: MS: m/z ) 551 [M + H]⁺19%; 453 [M - C₂-

SiMe₃]⁺14%; 433 [M - (PEt₃) + H]⁺50%; 356 [Cp*Rh(PEt₃)]⁺

100%. ¹H NMR (CDCl₃, δ): at 15 °C, 1.93 (m, PCH₂CH₃, 6H);

4

3

1.78 (d, J _P-H2.4, Cp*, 15 H); 1.09 (dt, J _P-H16, J _H-H7.6,

PCH₂CH₃, 9H); 0.02 (s, SiMe₃, 18H). ¹³C NMR (CDCl₃, δ): at

-50 °C, 125.9 (dd, ¹J _Rh-C49, ²J _P-C28, C_R, -CtCR); 106.2 (dd,

²J _Rh-C8.4, J _P-C2.6, C_â, -CtCR); 99.5 (t, J _Rh-C≈ J _P-C3.1,

3

1

2

Data for 5a : Anal. Calcd for C₄₄H₄₀F₁₀PPtRh: C, 48.59; H,

1

C₅Me₅); 17.7 (d, J _P-C31, PCH₂CH₃); 9.6 (s, C₅(CH₃)₅); 7.9 (d,

3.71. Found: C, 48.44; H, 3.76. MS: m/z ) 919 [M - C₆F₅

-

²J _P-C3.3, PCH₂CH₃); 1.4 (s, SiMe₃, CtCR). ³¹P NMR (CDCl₃,

H]⁺8%; 558 [Cp*Rh(C₂Ph)(PEt₃)]⁺20%; 457 [Cp*Rh(C₂Ph)-

(PEt₃)]⁺10%; 441 [Cp*Rh(C₂Ph) - H]⁺21%; 356 [Cp*Rh-

(PEt₃)]⁺100%. ¹H NMR (CDCl₃, δ): at 15 °C, 7.22, 6.88 (m,

1

δ): at 15 °C, 36.6 (d, J _P-Rh124).

P r ep a r a tion of [Cp *Ir (CtCP h )₂(P Et₃)] (4a ). Meth od

A. This complex was prepared by following a procedure

similar to that for complexes 3 by treating [Cp*IrI₂(PEt₃)] (0.25

g, 0.36 mmol) with an excess of LiCtCPh (5.36 mmol, molar

ratio 1:15). The reaction time was 6.5 h, the final residue was

extracted with 30 mL of CH₂Cl₂, and the extracts were filtered.

The filtrate was evaporated to dryness, yielding 4a as a beige

solid. Yield: 90%. Control by ³¹P NMR revealed the following

ratios (%) for 4a , 2a , and [Cp*IrI₂(PEt₃)] during the course of

the reaction: (i) at 40 min ∼3:26:71; (ii) at 2 h, 21:54:25; (iii)

at 5 h, 76:18:6; (iv) at 6 h, 92:8:-.

Meth od B. A mixture of 0.15 g (0.22 mmol) of [Cp*IrI₂-

(PEt₃)] and [AgCtCPh]_n(0.17 g, 0.84 mmol) in CH₂Cl₂(30 mL)

was stirred at room temperature protected from the light for

4 days. The excess of [AgCtCPh]_nand AgI formed was then

filtered and the resulting pale yellow solution evaporated to

dryness. Addition of cold hexane (5 mL) to the residue afforded

4a . Yield: 78%.

4

Ph, 10H); 1.99 (d, J _P-H2.68, Cp*, 15 H); 1.87 (m, PCH₂CH₃,

6H); 1.03 (m, PCH₂CH₃, 9H). The ¹³C NMR spectrum could

not be obtained due to decomposition. ¹⁹F NMR (CDCl₃, δ):

at 15 °C, -118 (v br, 4 o-F); - 165.0 (t, 2 p-F); -166.3 (m, 4

3

m-F); at -50 °C, -117.4 (d, J _Pt-o-F441, 2 o-F); -119.63 (d,

³J _Pt-o-F353, 2 o-F); -164.3 (t, 2 p-F); -165.5 (m, 2 m-F);

-165.9 (m, 2 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, 32.1 (d,

¹J _P-Rh128).

P r ep a r a tion of [(P Et ₃)Cp *Rh (µ-CtCSiMe₃)₂P t(C₆F ₅)₂]

(5c). Meth od A. [NBu₄][cis-Pt(C₆F₅)₂(CtCSiMe₃)₂] (0.2 g,

0.16 mmol) was added to a filtered solution of [Cp*Rh(PEt₃)-

(acetone)_x](ClO₄)₂(0.17 mmol) in 20 mL of acetone, prepared

from 72 mg (0.17 mmol) of [Cp*RhCl₂(PEt₃)] and 70 mg (0.34

mmol) of AgClO₄, and the resulting deep orange solution was

stirred for 5 min. The solution was partially evaporated,

causing the precipitation of complex 5c as an orange microc-

rystalline solid. Yield: 62%.

Data for 4a : Anal. Calcd for C₃₂H₄₀IrP: C, 59.33; H, 6.22.

Found: C, 57.47; H, 5.58. The analyses do not fit well,

probably due to small amounts of crystallized CH₂Cl₂

(4a ‚0.25CH₂Cl₂: C, 57.89; H, 6.10). MS: m/z ) 648 [M + H]⁺

100%; 547 [M - C₂Ph - H]⁺56%. ¹H NMR (CDCl₃, δ): at 15

°C, 7.23, 7.14, 7.00 (m, Ph, 10H); 2.07 (m, PCH₂CH₃, 6H); 1.95

(s, Cp*, 15 H); 1.18 (m, PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ):

at 15 °C, 131.4 (s, o-C, Ph); 130.0 (s, i-C, Ph); 127.5 (s, m-C,

Ph); 123.9 (s, p-C, Ph); 98.7 (s br, C_â, -CtCR); 95.3 (s br, C₅-

Meth od B. A solution of [Cp*Rh(CtCSiMe₃)₂(PEt₃)] (3c;

0.23 g, 0.41 mmol) in 15 mL of CH₂Cl₂was treated with [cis-

Pt(C₆F₅)₂(thf)₂] (0.2 g, 0.3 mmol). After 3 min of stirring the

resulting solution was concentrated to ca. 3 mL and complex

5c was separated as an orange solid, which was filtered off

and washed with EtOH. Yield: 41%.

Data for 5c: Anal. Calcd for C₃₈H₄₈F₁₀PPtRhSi₂: C, 42.26;

H, 4.47. Found: C, 42.24; H, 4.91. MS: m/z ) 1081 [M +

H]⁺3%; 551 [Cp*Rh(C₂SiMe₃)₂(PEt₃)]⁺27%; 431 [Cp*Rh(C₂-

SiMe₃)₂- H]⁺100%; 356 [Cp*Rh(PEt₃)]⁺62%. FAB(-): m/z

961 [M - (PEt₃)]^-30%; 926 [Pt(C₆F₅)₂(C₂SiMe₃)]^-100%. ¹H

NMR (acetone-d₆, δ): at 15 °C, 2.10 (m, PCH₂CH₃, 6H); 1.95

2

1

Me₅); 80.2 (d br, J _P-C14.6, C_R, -CtCR); 17.5 (d, J _P-C36.7,

2

PCH₂CH₃); 9.4 (s, C₅(CH₃)₅); 7.8 (d, J _P-C3.5, PCH₂CH₃). ³¹P

NMR (CDCl₃, δ): at 15 °C, -8.5 (s).

4

P r ep a r a tion of [Cp *Ir (CtCSiMe₃)₂(P Et₃)] (4c). This

complex was prepared by following a procedure similar to that

for complexes 3 by treating [Cp*IrI₂(PEt₃)] (0.25 g, 0.36 mmol)

with an excess of LiCtCSiMe₃(5.36 mmol, molar ratio 1:15).

The reaction time was 4 h. The final residue was extracted

with 30 mL of a toluene/hexane (1/1) mixture, and the extracts

were filtered. The filtrate was evaporated to dryness, yielding

4c as a cream-colored solid. Yield: 90%.

This complex can also be prepared, by a similar workup,

starting from [Cp*IrCl₂(PEt₃)] (0.2 g, 0.39 mmol) and LiCt

CSiMe₃(3.87 mmol, molar ratio 1:10) with a reaction time of

1 h. Yield: 85%.

(d, J _P-H2.3, Cp*, 15 H); 1.23 (m, PCH₂CH₃, 9H); 0.00 (s,

SiMe₃, 18H); at -50 °C, 2.06 (m, PCH₂CH₃, 6H); 1.92 (d, ⁴J _P-H

1.3, Cp*, 15 H); 1.20 (m, PCH₂CH₃, 9H); -0.04 (s, SiMe₃, 18H);

at -90 °C the signals are broad, 1.9 (d, Cp*), 1.16 (m,

PCH₂CH₃), -0.06 (br, SiMe₃). ¹³C NMR (acetone-d₆, δ): at -50

°C, due to the low solubility of this complex, the C_Rand C_â

signals are not seen; 149.5, 146.6, 137.9, 134.7 (br, C₆F₅);

104.80 (dd, ¹J _Rh-C4.74, ²J _P-C2.41, C₅Me₅); 19.52 (d, ¹J _P-C29.2,

2

PCH₂CH₃); 10.17 (s, C₅(CH₃)₅); 9.12 (d, J _P-C6.3, PCH₂CH₃);

1.53 (s, SiMe₃, CtCR). ¹⁹F NMR (acetone-d₆, δ): at 15 °C,

3

-114.0 (d, J _Pt-o-F454, 2 o-F); -116.3 (d, J _Pt-o-F410, 2 o-F);

-166.1 (t, 2 p-F); -166.8 (m, 4 m-F); at -50 °C, -113.9 (d,

3

Anal. Calcd for C₂₆H₄₈IrPSi₂: C, 48.79; H, 7.56. Found: C,

48.56; H, 7.65. MS: m/z ) 640 [M]⁺100%; 543 [M - C₂SiMe₃]⁺

60%; 521 [M - 2C₂SiMe₃]⁺45%. ¹H NMR (CDCl₃, δ): at 15

³J _Pt-o-F460, 2 o-F); -116.3 (s br, J _Pt-o-F394, 2 o-F); -165.3

(t, 2 p-F); -166.0 (m, 4 m-F); at -90 °C, -113.8 (br, ³J _Pt-o-F

≈

480, 2 o-F); -117.5 (coalesces, 2 o-F); -164.7 (t, 2 p-F); -165.6

4594 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

2

(br, 4 m-F). ³¹P NMR (acetone-d₆, δ): at 15 °C, 31.7 (d, ¹J _P-Rh

130); at -90 °C, 31.8 (d, J _P-Rh129).

Ph); 125.5 (s, i-C, Ph); 98.0 (s, C_â, -CtCR); 97.8 (d, J _C-P2.6,

C₅Me₅); 55.3 (d, ²J _P-C17, C_R, -CtCR); 14.7 (d, ¹J _P-C36, PCH₂-

CH₃); 9.3 (s, C₅(CH₃)₅); 6.7 (d, ²J _P-C2.8, PCH₂CH₃). ¹⁹F NMR

(CDCl₃, δ): at 20 °C, -114.9 (s br, 2 o-F), -119.3 (s br, 2 o-F)

1

P r ep a r a tion of [(P Et₃)Cp *Rh (µ-CtCR)₂P d (C₆F ₅)₂] (R

) P h (6a ), SiMe₃(6c)). [cis-Pd(C₆F₅)₂(thf)₂] (0.12 g, 0.205

mmol) was added to a solution of [Cp*Rh(CtCPh)₂(PEt₃)] (3a ;

0.115 g, 0.205 mmol) in diethyl ether (20 mL) at -20 °C. The

resulting solution was immediately concentrated to a small

volume (ca. 5 mL), causing the precipitation of 6a as a dark

orange solid, which was filtered off and washed with Et₂O (ca.

2 mL). Yield: 70%.

3

(platinum satellites due to J _Pt-o-Fare observed but are not

well-resolved); - 164.9 (t, 2 p-F); -165.9, -166.5 (s br, 4 m-F,

3

overlapped); at -50 °C, -113.2 (d br, J _Pt-o-F389, 2 o-F);

-117.81 (dd, ³J _Pt-o-F425, 2 o-F); -165.1 (t, 2 p-F); -165.7 (m,

2 m-F); -166.3 (m, 2 m-F); in acetone-d₆, at -90 °C, -113.3 (s

3

br, J _Pt-o-F387, 2 o-F); -117.7 (d, J _Pt-o-F391, 2 o-F); -164.4

(t, 2 p-F); -165.3 (m, 2 m-F); -165.7 (m, 2 m-F). ³¹P NMR

(acetone-d₆, δ): at 20 °C, 5.8 (s); at -90 °C, 2.3 (s).

Data for 7c: Anal. Calcd for C₃₈H₄₈F₁₀IrPPtSi₂: C, 39.03;

H, 4.14. Found: C, 38.81; H, 3.95. MS: m/z ) 1169 [M]⁺7%;

640 [Cp*Ir(C₂SiMe₃)₂(PEt₃)]⁺100%; 626 [Pt(C₆F₅)₂(C₂SiMe₃)]⁺

47%; 543 [Cp*Ir(C₂SiMe₃)(PEt₃)]⁺62%. ¹H NMR (CDCl₃, δ):

Complex 6c was prepared in a way similar to that for 6a ,

starting from 3c (0.45 g, 0.81 mmol) and [cis-Pd(C₆F₅)₂(thf)₂]

(0.74 mmol). Reaction time: 5 min. Yield: 36%.

Data for 6a : Anal. Calcd for C₄₄H₄₀F₁₀PPdRh: C, 52.9; H,

4.03. Due to its instability in solution 6a is probably impure,

due to the presence of traces of Pd. The best analyses found:

C, 51.88; H, 3.72. MS: m/z ) 1082 [Pd₂(C₆F₅)₄(C₂Ph)₂]⁺10%;

998 [M]⁺24%, 880 [M - (PEt₃)]⁺80%; 642 [Pd(C₆F₅)₂(C₂Ph)₂]⁺

92%; 356 [Cp*Rh(PEt₃)]⁺100%, 325 [Rh(C₂Ph)(PEt₃) + 3H]⁺

90%. This complex is very unstable and was characterized

only at -50 °C. ¹H NMR (CDCl₃, δ): at -50 °C, 7.09, 7.02,

6.93 (m, Ph, 10H); 2.03 (s br, Cp*, PCH₂CH₃, 21H); 1.04 (m,

PCH₂CH₃, 9H). ¹⁹F NMR (CDCl₃, δ): at -50 °C, -114.0 (d, 2

o-F); -116.4 (d, 2 o-F); - 163.4 (t, 2 p-F); -163.6 (m, 2 m-F);

-165.1 (m, 2 m-F). ³¹P NMR (CDCl₃, δ): at -50 °C, 35.6 (d,

¹J _P-Rh123). Due to the very low stability of this complex in

solution, its ¹³C NMR spectrum could not be registered.

Data for 6c: Anal. Calcd for C₃₈H₄₈F₁₀PPdRhSi₂: C, 46.00;

H, 4.90. Found: C, 45.65; H, 5.30. MS: m/z ) 657 [Cp*Rh-

(C₂SiMe₃)₂(PEt₃)Pd]⁺21%; 539 [Pd(C₆F₅)₂(C₂SiMe₃) + 2H]⁺

21%; 433 [Cp*Rh(CCSiMe₃)₂+ H]⁺63%; 356 [Cp*Rh(PEt₃)]⁺

73%. ¹H NMR (acetone-d₆, δ): at 15 °C, 2.09 (m, PCH₂CH₃,

4

at 15 °C, 2.06 (d, J _P-H1.7, Cp*, 15 H); 1.98 (m, PCH₂CH₃,

6H); 1.10 (m, PCH₂CH₃, 9H); - 0.18 (s, SiMe₃, 18H); a similar

pattern was observed at -50 °C with only a singlet at δ -0.24

due to SiMe₃; an identical pattern was seen in acetone-d₆even

at -85 °C (δ SiMe₃-0.2). ¹³C NMR (acetone-d₆, δ): at -50

2

°C, 148.4, 145.1, 137.5, 134.4 (br, C₆F₅); 98.09 (d, J _P-C2.3,

C₅Me₅); 93.77 (ill-defined signal C_Ror C_â); 16.86 (d, ¹J _P-C35.12,

2

PCH₂CH₃); 9.5 (s, C₅(CH₃)₅); 8.25 (d, J _P-C4.05, PCH₂CH₃);

0.92 (s, SiMe₃, CtCR). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -113.3

(m br, 2 o-F); -117.5 (m br, 2 o-F); -164.7 (t, 2 p-F); -166.1

3

(m, 4 m-F); at -50 °C, -113.6 (d, J _Pt-o-F462, 2 o-F); -117.9

(d, J _Pt-o-F432, 2 o-F); -164.1 (t, 2 p-F); -165.3 (m, 2 m-F);

3

-165.8 (m, 2 m-F); a similar pattern was observed in acetone-

d₆, but in this solvent the m-F resonances did not resolve into

separate signals even at -85 °C, -112.0, -116.4 (o-F); -164.6

(t, p-F); -165.5 (m-F); on heating, only the 2 o-F resonances

broadened at ca. 0 °C, they still were broad at 16 °C, and they

finally coalesced at 40 °C. ³¹P NMR (CDCl₃, δ): at 15 °C, -5.1

(s); at -50 °C, -4.3(5).

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCR)₂P d (C₆F ₅)₂] (R )

P h (8a ), SiMe₃(8c)). 8a . [cis-Pd(C₆F₅)₂(thf)₂] (0.14 g, 0.25

mmol) was added to a cooled (-20 °C) solution of [Cp*Ir(Ct

CPh)₂(PEt₃)] (4a ; 0.16 g, 0.25 mmol) in CH₂Cl₂(10 mL). The

solution was immediately treated with charcoal and filtered

through Celite and the filtrate evaporated to dryness. Addi-

tion of cold Et₂O to the residue gave 8a as a yellow solid.

Yield: 62%.

8c. Complex 8c was obtained as a beige solid in a way

similar to that for complex 8a , starting from 4c (0.1 g, 0.16

mmol) and [cis-Pd(C₆F₅)₂(thf)₂] (0.097 g, 0.16 mmol). Yield:

38%.

Data for 8a : Anal. Calcd for C₄₄H₄₀F₁₀IrPPd: C, 48.56; H,

3.70. Found: C, 48.35; H, 3.98. MS: m/z ) 1088 [M]⁺13%;

754 [Cp*Ir(C₂Ph)₂(PEt₃)Pd]⁺100%; 649 [Cp*Ir(C₂Ph)₂(PEt₃)]⁺

26%; 548 [Cp*Ir(C₂Ph)(PEt₃)]⁺24%. ¹H NMR (CDCl₃, δ): at

16 °C, 7.03, 6.91 (m, Ph, 10H); 2.14 (s, Cp*, 15H); 2.10 (m,

4

6H); 2.05 (d, J _P-H2.1, 15 H, Cp*); 1.23 (m, PCH₂CH₃, 9H);

-0.18 (s, SiMe₃, 18H); at -50 °C, 2.06 (m, Cp*, PCH₂CH₃,

21H); 1.16 (m, PCH₂CH₃, 9H); -0.23 (s, SiMe₃, 18H); at -90

°C, 2.06 (m, PCH₂CH₃, 6H); 2.02 (s, 15 H, Cp*); 1.11 (m,

PCH₂CH₃, 9H); -0.27 (s, SiMe₃, 18H). ¹⁹F NMR (acetone-d₆,

δ): at 15 °C, -109.9 (m, 2 o-F); -113.3 (m, 2 o-F); -164.3 (t,

2 p-F); -165.6 (m, 4 m-F); at -50 °C, -109.5 (d, 2 o-F); -113.2

(d, 2 o-F); -163.5 (t, 2 p-F); -164.9 (m, 4 m-F); the same

pattern was observed at -90 °C, -109.3 (d, 2 o-F); -113.0 (d,

2 o-F); -162.9 (t, 2 p-F); -164.4 (m, 4 m-F). ³¹P NMR (acetone-

d₆, δ): at 15 °C, 33.2 (d, ¹J _P-Rh125); at -50 °C, 34.1 (d, ¹J _P-Rh

125); at -90 °C, 34.8 (d, ¹J _P-Rh125.5). Due to the low solubility

and stability in solution the ¹³C NMR spectrum could not be

registred.

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCR)₂P t(C₆F ₅)₂] (R )

P h (7a ), SiMe₃(7c)). Meth od A. The preparation of 7a

starting from [PMePh₃][cis-Pt(C₆F₅)₂(CtCPh)₂] and [Cp*Ir-

(PEt₃)(acetone)_x](ClO₄)₂(prepared from [Cp*IrCl₂(PEt₃)] and

AgClO₄) has been previously described.¹⁴Yield: 62%.

Complex 7c was prepared by following the synthesis de-

scribed in method A for complex 5c, but starting from an

acetone solution which contains 0.16 mmol of [Cp*Ir(PEt₃)-

(acetone)_x](ClO₄)₂and 0.2 g (0.16 mmol) of [NBu₄][cis-Pt(C₆F₅)₂-

(CtCSiMe₃)₂]. Yield: 32%.

3

PCH₂CH₃, 6 H); 1.04 (dt, J _H-P16.1, J _H-H8.19, PCH₂CH₃,

9H); at -50 °C, a similar spectrum was observed but with

broader signals. ¹³C NMR (CDCl₃, δ): at -50 °C, 146.6, 143.5,

136.8, 133.23 (br, C₆F₅); 131.41 (s, o-C, Ph); 127.1 (s, m-C, Ph);

126.57 (s), 125.13 (s) (p-C and i-C, Ph); 100.52 (s, probably due

to C_â, -CtCR); 96.98 (s, C₅Me₅); 51.29 (d, ²J _P-C≈ 18, C_R, -Ct

Meth od B. Both yellow complexes can also be prepared

as described in method B for complex 5a , but starting from

[Cp*Ir(CtCR)₂(PEt₃)] (R ) Ph (4a ), 0.094 g, 0.14 mmol; R )

SiMe₃(4c), 0.090 g, 0.14 mmol) and [cis-Pt(C₆F₅)₂(thf)₂] (0.097

g, 0.14 mmol) and stirring for 5 min. Yield: 64.5% for 7a and

35% for 7c.

1

CR); 15.07 (d, J _P-C≈ 40, PCH₂CH₃); 9.55 (s, C₅(CH₃)₅); 7.14

2

(d, J _P-C3.0, PCH₂CH₃); signals at 15.3 and 66.08 due to

diethyl ether are also observed. ¹⁹F NMR (CDCl₃, δ): at 15

°C, -113.7 (d, 2 o-F); -116.3 (d, 2 o-F); -163.9 (m, 2 m-F, 2

p-F); -165.7 (m, 2 m-F); at -50 °C, -113.9 (d, 2 o-F); -116.2

(d, 2 o-F); -163.3 (t, 2 p-F); -163.7 (m, 2 m-F); -165.1 (m, 2

m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, -6.2 (s); at -50 °C, 4.7

(s).

Data for 7a : Anal. Calcd for C₄₄H₄₀F₁₀IrPPt: C, 44.9; H,

3.42. Found: C, 44.55; H, 3.22. MS: m/z ) 1176 [M]⁺10%,

648 [Cp*Ir(C₂Ph)₂(PEt₃)]⁺12%; 547 [Cp*Ir(C₂Ph)(PEt₃)]⁺14%;

310 [Ir(PEt₃)]⁺100%. ¹H NMR (CDCl₃, δ): at 20 °C, 7.06 (m,

4

Ph, 10 H); 2.16 (d, J _P-H1.9, Cp*, 15 H); 1.95 (m, PCH₂CH₃,

Data for 8c: Anal. Calcd for C₃₈H₄₈F₁₀IrPPdSi₂: C, 42.24;

H, 4.48. Found: C, 41.88; H, 3.96. MS: m/z ) 640 [Cp*Ir-

(C₂SiMe₃)₂(PEt₃) + H]⁺100%; 543 [Cp*Ir(C₂SiMe₃)(PEt₃) + H]⁺

53%; 446 [Cp*Ir(PEt₃) + H]⁺59%; 385 [Ir(C₂SiMe₃) - H]⁺68%.

¹H NMR (CDCl₃, δ): at 15 °C, 2.05 (s, Cp*, 15H); ∼2.01 (m,

6H); 0.96 (m, PCH₂CH₃, 9H); in acetone-d₆, at -90 °C, 7.13,

7.05 (m, Ph, 10 H); 2.07 (m, Cp*, PCH₂CH₃, 21 H); 0.88 (m,

PCH₂CH₃, 9H). ¹³C NMR (CDCl₃, δ): at 20 °C, 147.8, 144.75,

137.4, 134.2 (m br, C₆F₅): 130.9, 126.9 (s, Ph); 126.5 (s br, p-C,

New Alkynyl Complexes of Rh and Ir

Organometallics, Vol. 17, No. 21, 1998 4595

PCH₂CH₃, 6 H); 1.12 (m, PCH₂CH₃, 9H); -0.23 (s, SiMe₃, 18H).

¹⁹F NMR (CDCl₃, δ): at -50 °C, -111.1 (d, 2 o-F); -114.6 (d,

2 o-F); -162.6 (t, 2 p-F); -164.2 (m, 2 m-F), -164.8 (m, 2 m-F);

at 16 °C, -111.1 (br, 2 o-F); -114.5 (br, 2 o-F); -163.2 (t, 2

p-F); -165.0 (br, 4 m-F). The o-F signals coalesce at ∼30 °C.

³¹P NMR (CDCl₃, δ): at 15 °C, -8.6 (s). The ¹³C NMR

spectrum could not be obtained due to the low stability of

complex 8c in solution even at low temperature.

impure sample) and 0.19 g (0.35 mmol) of [cis-Pd(C₆F₅)₂(thf)₂]

at -20 °C. Yield: 23%.

Data for 10a ‚¹/₂CH₂Cl₂: Anal. Calcd for C_36.5H₃₆Cl₂F₁₀

-

PPdRh: C, 44.92; H, 3.70. Found: C, 44.93; H, 3.50. MS: m/z

) 765 [M - C₆F₅]⁺8%; 701 [M - Cp* - (PEt₃) + 2H]⁺12%;

457 [Cp*Rh(C₂Ph)(PEt₃)]⁺36%; 391 [Cp*RhCl(PEt₃)]⁺100%;

356 [Cp*Rh(PEt₃)]⁺40%. ¹H NMR (CDCl₃, δ): at 15 °C, 7.25,

7.05 (m, Ph, 5 H); 5.29 (s, CH₂Cl₂, 1 H); 1.96 (m, PCH₂CH₃,

4

6H); 1.90 (d, J _P-H2.7, Cp*, 15 H); 1.12 (m, PCH₂CH₃, 9H).

P r ep a r a tion of [(P Et₃)Cp *Rh (µ-CtCR)(µ-Cl)P t(C₆F ₅)₂]

(R ) P h (9a ), ^tBu (9b)). 9a . [cis-Pt(C₆F₅)₂(thf)₂] (0.21 g, 0.32

mmol) was added to a solution of [Cp*Rh(CtCPh)Cl(PEt₃)]

(1a ) with 3a (∼14%) and [Cp*RhCl₂(PEt₃)] (∼12%) (0.16 g,

∼0.32 mmol) as impurities in 10 mL of CH₂Cl₂, and the

mixture was stirred for 5 min. The resulting solution was

evaporated to dryness and the solid residue treated with cold

Et₂O (ca. 5 mL), affording an orange solid which was identified

as 9a ‚CH₂Cl₂. Yield: 36%.

9b. Complex 9b can be obtained as described for complex

9a , but starting from 0.13 g (0.28 mmol) of [Cp*Rh(CtC^tBu)-

Cl(PEt₃)] (1b) and 0.19 g (0.28 mmol) of [cis-Pt(C₆F₅)₂(thf)₂].

Yield: 61%.

¹⁹F NMR (CDCl₃, δ): at 15 °C, -114.6 (d, 1 o-F); -116.2 (d, 1

o-F); -116.7 (m, overlapping of 2 o-F); -162.2 (t, 1 p-F); -163.7

(t, 1 p-F); -164.2 (m, 1 m-F); -164.8 (m, overlapping of 2 m-F);

-165.6 (m, 1 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, 31.9 (d,

¹J _P-Rh132). Due to its very low solubility and stability in

solution, the ¹³C NMR spectrum could not be registered.

P r epar ation of [(P Et₃)Cp*Rh (µ-CtC^tBu )(µ-Cl)P d(C₆F₅)₂]

(10b). A 0.198 g (0.338 mmol) portion of [cis-Pd(C₆F₅)₂(thf)₂]

was added to a cooled (-20 °C) dichloromethane solution of

1b (0.16 g, 0.338 mmol). The resulting brown solution was

treated with C_activeand, immediately, filtered through Celite.

Evaporation to dryness of the filtrate, followed by addition of

cold diethyl ether, yielded 10b as an orange solid. Yield: 58%.

Data for 10b: Anal. Calcd for C₃₄H₃₉ClF₁₀PPdRh: C, 44.71;

H, 4.30. Found: C, 44.62; H, 4.38. MS: m/z ) 699 [M - Cp*

Data for 9a : Anal. Calcd for C₃₇H₃₇Cl₃F₁₀PPtRh: C, 38.71;

H, 3.34. Found: C, 39.06; H, 3.47. MS: m/z ) 985 [M - Cl

- 2H]⁺9%; 665 [Pt(C₆F₅)₂Cl(C₂Ph)]⁺45%; 391 [Cp*RhCl-

(PEt₃)]⁺82%; 355 [Cp*Rh(PEt₃) - H]⁺71%. ¹H NMR (CDCl₃,

δ): at 15 °C, 7.13, 7.04 (m, Ph, 5 H); 5.29 (s, CH₂Cl₂, 2H); 2.01

t

- C₂Bu + H]⁺19%; 519 [Pd(C₆F₅)₂(C₂Bu) - 2H]⁺26%; 437

t

[Cp*Rh(C₂Bu)(PEt₃)]⁺76%; 391 [Cp*RhCl(PEt₃)]⁺46%; 356

[Cp*Rh(PEt₃)]⁺42%. ¹H NMR (CDCl₃, δ): at 15 °C, 2.08 (m,

4

(m, PCH₂CH₃, 6H); 1.89 (d, J _P-H2.7, Cp*, 15 H); 1.05 (m,

4

PCH₂CH₃, 6H); 1.85 (d, J _P-H2.8, Cp*, 15 H); 1.17 (m,

PCH₂CH₃, 9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -117.2 (d,

PCH₂CH₃, 9H); 0.85 (s, Bu, 9 H). ¹⁹F NMR (CDCl₃, δ): at 15

t

³J _Pt-o-F512, 1 o-F); -119.6 (overlapping of two o-F); -120.4

°C, -112.6 (d, 1 o-F); -113.6 (d, 1 o-F); -116.4 (d, 1 o-F);

-118.2 (d, 1 o-F); -162.3 (m, overlapping of two p-F); -164.4

(m, 1 m-F); -164.6 (m, 1 m-F); -164.9 (m, 1 m-F); -165.5 (m,

3

(d, J _Pt-o-F466, 1 o-F); -162.9 (t, 1 p-F); -165.2 (t, 1 p-F);

-165.8 (m, 1 m-F); -166.0 (m, 1 m-F); -166.6 (m, 1 m-F);

-167.0 (m, 1 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, 33.5 (d,

¹J _P-Rh134). The ¹³C NMR spectrum could not be registered

due to its very low solubility.

1

1 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, 29.5 (d, J _P-Rh133).

The complex is not soluble enough for ¹³C NMR.

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCP h )(µ-Cl)P t(C₆F ₅)₂]

(11a ). A suspension of [Cp*Ir(CtCPh)Cl(PEt₃)] (4a ; 0.09 g,

0.15 mmol) in 10 mL of CH₂Cl₂was treated with [cis-Pt(C₆F₅)₂-

(thf)₂] (0.09 g, 0.14 mmol), immediately giving a dark orange

solution, which was evaporated to ca. 2 mL. Addition of 3 mL

of cold EtOH caused the precipitation of complex 11a as a

yellow solid. Yield: 86%.

Data for 9b: Anal. Calcd for C₃₄H₃₉ClF₁₀PPtRh: C, 40.75;

H, 3.92. Found: C, 40.64; H, 3.44. MS: m/z 835 [M - C₆F₅

+ H]⁺8%; 437 [Cp*Rh(C₂Bu)(PEt₃)]⁺65%; 391 [Cp*RhCl-

t

(PEt₃)]⁺73%; 356 [Cp*Rh(PEt₃)]⁺52%. ¹H NMR (CDCl₃, δ):

4

at 15 °C, 2.04 (m, PCH₂CH₃, 6H); 1.84 (d, J _P-H2.9, Cp*, 15

H); 1.16 (m, PCH₂CH₃, 9H); 0.90 (s, ^tBu, 9 H). ¹⁹F NMR

3

(CDCl₃, δ): at 15 °C, -116.0 (d, J _Pt-o-F535, 1 o-F); -117.9

Data for 11a : Anal. Calcd for C₃₆H₃₅ClF₁₀IrPPt: C, 38.9;

H, 3.17. Found: C, 38.5; H, 2.90. MS: m/z ) 1111 [M]⁺6%;

1075 [M - Cl]⁺12%; 943 [M - C₆F₅- H]⁺9%; 580 [Cp*Ir(C₂-

Ph)Cl(PEt₃) - H]⁺26%; 547 [Cp*Ir(C₂Ph)(PEt₃)]⁺39%; 481

[Cp*IrCl(PEt₃) + H]⁺56%; 411 [Ir(C₂Ph)(PEt₃)]⁺50%; 327

[Cp*Ir]⁺100%. ¹H NMR (CDCl₃, δ): at 15 °C, 7.12, 7.03 (m,

Ph, 5 H); 2.06 (m, PCH₂CH₃, 6H); 1.96 (s br, Cp*, 15 H); 1.01

3

(d, J _Pt-o-F≈ 500, 1 o-F); -119.6 (d, J _Pt-o-F≈ 430, 1 o-F);

3

-121.3 (d, J _Pt-o-F≈ 440, 1 o-F); -163.2 (t, 1 p-F); -164.3 (t,

1 p-F); -165.15 (m, 1 m-F); -165.8 (m, overlapping of two

m-F); -166.9 (m, 1 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, 30.7

(d, ¹J _P-Rh136). The ¹³C NMR spectrum could not be obtained

due to the low solubility of the complex.

3

(dt, J _P-H16.4, J _H-H8.3, PCH₂CH₃, 9H). ¹⁹F NMR (CDCl₃,

δ): at 15 °C, -117.6 (d, ³J _Pt-o-F520, 1 o-F); -119.97, -120.07

(overlapping of two doublets, 2 o-F); -120.7 (d, ³J _Pt-o-F≈ 470,

1 o-F); -163.0 (t, 1 p-F); -165.2 (m, 1 m-F); -165.3 (t, 1 p-F);

-165.9 (m, 1 m-F); -166.9 (m, 1 m-F); -167.2 (m, 1 m-F). ³¹P

NMR (CDCl₃, δ): at 15 °C, 1.3 (s). Due to the low solubility,

the ¹³C NMR spectrum could not be registered.

P r ep a r a t ion of

a Mixt u r e of [(P E t₃)Cp *R h (µ-Ct

CSiMe₃)(µ-Cl)P t(C₆F ₅)₂] (9c) a n d (5c). Starting from a

mixture of 0.25 g of complexes 1c and 3c in a 2:1 ratio (0.327

mmol for 1c and 0.163 mmol for 3c) and 0.33 g (0.49 mmol) of

[cis-Pt(C₆F₅)₂(thf)₂] and following the procedure described for

the synthesis of compound 9a , a mixture of complexes 9c and

5c in a ca. 4:1 ratio was obtained as an orange microcrystalline

solid (0.23 g). All attempts to obtain pure 9c from this mixture

were unsuccessful; therefore, complex 9c was only spectro-

scopically characterized from the mixture.

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCR)(µ-I)P t(C₆F ₅)₂] (R

) P h (11a ′), SiMe₃(11c′)). 11a ′. A suspension of 2a ′ (0.1 g,

0.15 mmol) in 10 mL of CH₂Cl₂was treated with [cis-Pt(C₆F₅)₂-

(thf)₂] (0.1 g, 0.15 mmol) at low temperature and the mixture

was stirred for 5 min. Evaporation of the resulting solution

and addition of cold diethyl ether give 11a ′ as a yellow

microcrystalline solid. Yield: 66%.

11c′. Complex 11c′ was prepared as a yellow solid by

following a procedure identical with that described for 11a ′:

0.16 g (0.24 mmol) of 2c′ and 0.16 g (0.24 mmol) of [cis-Pt-

(C₆F₅)₂(thf)₂] were used. Yield: 35%.

Data for 9c: ¹H NMR (CDCl₃, δ): at 15 °C, 2.04 (m, PCH₂-

4

CH₃, 6H); 1.84 (d, J _P-H2.8, Cp*, 15 H); 1.13 (m, PCH₂CH₃,

9H); -0.17 (s, SiMe₃, 9 H). ¹⁹F NMR (CDCl₃, δ): at 15 °C,

3

-115.7 (d, J _Pt-o-F≈ 545, 1 o-F); -118.3 (d, J _Pt-o-F≈ 470, 1

3

o-F); -119.5 (d, J _Pt-o-F≈ 450, 1 o-F); -121.0 (d, J _Pt-o-F

≈

460, 1 o-F); -163.2 (t, 1 p-F); -164.5 (t, 1 p-F); -165.2 (m, 1

m-F); -165.8 (m, 1 m-F); -166.2 (m, 1 m-F); -166.7 (m, 1 m-F).

³¹P NMR (CDCl₃, δ): at 15 °C, 32.1 (d, J _P-Rh135).

1

P r epar ation of [(P Et₃)Cp*Rh (µ-CtCP h )(µ-Cl)P d(C₆F₅)₂]‚

¹/₂CH₂Cl₂(10a ‚¹/₂CH₂Cl₂). Complex 10a , which crystallizes

with a half molecule of CH₂Cl₂(¹H NMR), can be prepared by

following the same procedure as for complex 9a but starting

from 0.16 g (∼0.3 mmol) of [Cp*Rh(CtCPh)Cl(PEt₃)] (1a ;

Data for 11a ′: Anal. Calcd for C₃₆H₃₅F₁₀IIrPPt: C, 35.95;

H, 2.93. Found: C, 35.79; H, 3.08. ES(-): m/z 1202 [M - H]^-

17%; 1067 [M - Cp*]^-39%; 657 [Pt(C₆F₅)₂I]^-100%. ¹H NMR

(CDCl₃, δ): at 15 °C, 7.08 (2 H), 7.00 (3H) (m, Ph); 2.1 (m,

4

3

PCH₂CH₃, 6H); 2.098 (d, J _P-H1.5, Cp*, 15 H); 0.97 (dt, J _P-H

4596 Organometallics, Vol. 17, No. 21, 1998

Ara et al.

3

16, J _H-H8.2, PCH₂CH₃, 9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C,

SiMe₃)(PEt₃)]⁺43%; 455 [Cp*IrI + H]⁺30%; 445 [Cp*Ir(PEt₃)]⁺

21%. ¹H NMR (CDCl₃, δ): at 15 °C, 2.14 (m, PCH₂CH₃, 6H);

2.02 (s, Cp*, 15 H); 1.09 (m, PCH₂CH₃, 9H), -0.20 (s, SiMe₃,

9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -112.5 (dm, 1 o-F); -113.4

(dm, 1 o-F); -113.9 (dm, 1 o-F); -116.8 (dm, 1 o-F); -162.5 (t,

1 p-F); -162.6 (t, 1 p-F); -164.7 (m, 3 m-F); -165.3 (m, 1 m-F).

³¹P NMR (CDCl₃, δ): at 15 °C, -10.6 (s). Similar NMR

patterns were observed at -50 °C. Due to the low solubility

the ¹³C NMR spectrum could not be registered.

3

-116.8 (dd, J _Pt-o-F456, 1 o-F); -117.5 (dd, J _Pt-o-F≈ 495, 1

o-F); -118.8 (dd, ³J _Pt-o-F430, 1 o-F); -120.7 (dd, ³J _Pt-o-F435,

1 o-F); -163.2 (t, 1 p-F); -165.0 (t, 1 p-F); -165.1 (m, 1 m-F);

-165.6 (m, 1 m-F); -166.3 (m, 1 m-F); -166.8 (m, 1 m-F). ³¹P

NMR (CDCl₃, δ): at 15 °C, -5.7 (s). The complex is not soluble

enough for ¹³C NMR.

Data for 11c′. Anal. Calcd for C₃₃H₃₉F₁₀IIrPPtSi: C, 33.06;

H, 3.28. Found: C, 33.28; H, 2.98. MS: m/z ) 669 [Cp*Ir-

(C₂SiMe₃)I(PEt₃)]⁺18%; 573 [Cp*IrI(PEt₃)]⁺72%; 543 [Cp*Ir(C₂-

SiMe₃)(PEt₃)]⁺100%; 455 [Cp*IrI + H]⁺59%; 443 [Cp*Ir(PEt₃)

- 2H]⁺55%. ¹H NMR (CDCl₃, δ): at 15 °C, 2.12 (m, PCH₂-

CH₃, 6H); 2.05 (s, Cp*, 15 H); 1.09 (m, PCH₂CH₃, 9H); -0.17

(s, SiMe₃, 9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -116.0 (d,

X-r a y Cr ysta l Str u ctu r e Deter m in a tion of Com p lexes

5c, 7a , 7c, 8a ‚0.5CHCl₃, 9b, a n d 12a . Suitable crystals were

obtained at low temperature (-30 °C) by cooling a concentrated

solution of the complex in acetone/ethanol (1/2) (5c) or in

acetone (7a ) or by slow diffusion of Et₂O over chloroform (7c,

8a ) or dichloromethane (9b, 12a ) solutions of the complexes.

Crystal data and other details of the structure analyses are

presented in Table 2. Crystals were fixed on top of quartz

fibers and mounted on the diffractometers. Data were col-

lected by ω/2θ scans (5c, 7c, 12a ), ω/θ scans (7a , 8a ), or ω

scans (9b). Three check reflections remeasured at regular

intervals showed no decay of the crystals over the period of

data collection. The structures were solved by Patterson and

Fourier methods. All non-hydrogen atoms were assigned

anisotropic displacement parameters (except for Cp* in 7a and

for the disordered solvent and C(11′), of a disordered phenyl

group, in 8a ) and refined without positional constraints (except

for the phenyl group (C(9)-C(14) and C(9′)-C(14′)) and solvent

for 8a ). In complex 8a the phenyl ring was refined as a rigid

group. The disorder of this group arises because it is inclined

but not perpendicular to the crystallographic mirror plane.

Also, the anisotropically refined C(4) and F(3) have high

displacement parameters, and disorder was observed in the

phenyl group of the alkynyl ligands. A model in which two

orientations of the arylic group were given equal weight

allowed proper refinement of the structure. Solution in Pna2₁

for 8a could not be carried out successfully. The hydrogen

atoms in all complexes were constrained to idealized geom-

etries and assigned isotropic displacement parameters 1.2

times the U_isovalue of their attached atom, 1.5 times for the

hydrogen methyl atoms. Final difference electron density map

showed some peaks above 1 e Å^-3in the case of 5c, 7a , 8a ,

and 12a . They are probably due to a deficient absorption

correction which may happen in the presence of heavy atoms.

All calculations were carried out using the programs SHELXL-

93⁴⁰and SHELXTL-PLUS.⁴¹

³J _Pt-o-F524, 1 o-F); -116.6 (d, J _Pt-o-F470, 1 o-F); -118.2 (d,

3

³J _Pt-o-F454, 1 o-F); -120.1 (d, J _Pt-o-F453, 1 o-F); -163.6 (t,

3

1 p-F); -164.3 (t, 1 p-F); -165.4 (m, 1 m-F); -165.8 (m, 2 m-F);

-166.6 (m, 1 m-F). ³¹P NMR (CDCl₃, δ): at 15 °C, -8.1 (s). A

similar NMR pattern was observed at -50 °C. Due to the low

solubility, its ¹³C NMR spectrum could not be registered.

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCP h )(µ-Cl)P d (C₆F ₅)₂]

(12a ). [cis-Pd(C₆F₅)₂(thf)₂] (0.12 g, 0.2 mmol) was added to a

suspension of 0.12 g (0.2 mmol) of [Cp*Ir(CtCPh)Cl(PEt₃)] (4a )

in 10 mL of CH₂Cl₂at low temperature (-20 °C), and the

mixture was stirred for 5 min. Evaporation of the mixture to

ca. 2 mL caused the precipitation of a dark yellow-green solid

which was recrystallized from CH₂Cl₂/Et₂O, giving 12a as a

yellow microcrystalline solid. Yield: 70%.

Data for 12a . Anal. Calcd for C₃₆H₃₅ClF₁₀IrPPd: C, 42.28;

H, 3.45. Found: C, 42.56; H, 3.62. MS: m/z ) 921 [M - C₂-

Ph]⁺5%; 855 [M - C₆F₅]⁺5%; 754 [M - C₆F₅- C₂Ph]⁺12%,

582 [Cp*Ir(C₂Ph)Cl(PEt₃)]⁺7%; 547 [Cp*Ir(C₂Ph)(PEt₃)]⁺29%.

¹H NMR (CD₂Cl₂, δ): at 15 °C, 7.00, 6.90 (m, Ph, 5 H); 2.10

4

(m, PCH₂CH₃, 6H); 1.94 (d, J _P-H1.7, Cp*, 15 H); 1.02 (m,

PCH₂CH₃, 9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -114.7 (d, 1

o-F); -116.6 (m, 3 o-F); -162.0 (t, 1 p-F); -163.6 (t, 1 p-F);

-164.2 (m, 1 m-F); -164.8 (m, 2 m-F); -165.7 (m, 1 m-F). ³¹P

NMR (CDCl₃, δ): at 15 °C, -2.4 (s). Due to the low solubility,

the ¹³C NMR spectrum could not be registered.

P r ep a r a tion of [(P Et₃)Cp *Ir (µ-CtCR)(µ-I)P d (C₆F ₅)₂]

(R ) P h (12a ′), SiMe₃(12c′)). These compounds were

prepared as yellow solids in a way similar to that for complexes

11a ′,c′. A 0.12 g (0.18 mmol) portion of 2a ′ and [cis-Pd(C₆F₅)₂-

(thf)₂] (0.104 g, 0.18 mmol) were used to prepare 12a ′ (71%

yield), and 0.11 g (0.16 mmol) of 2c′ with 0.096 g (0.16 mmol)

of [cis-Pd(C₆F₅)₂(thf)₂] were used for the synthesis of 12c′ (yield

40%).

Data for 12a ′: Anal. Calcd for C₃₆H₃₅F₁₀IIrPPd: C, 38.81;

H, 3.17. Found: C, 39.07; H, 3.28. MS: m/z ) 947 [M - C₆F₅

+ H]⁺10%; 829 [M - C₆F₅- (PEt₃)+H]⁺12%; 573 [Cp*IrI-

(PEt₃)]⁺60%; 547 [Cp*Ir(C₂SiMe₃)(PEt₃)]⁺100%; 455 [Cp*IrI

+ H]⁺54%. ¹H NMR (CDCl₃, δ): at 15 °C, 6.99 (m, Ph, 5 H);

2.1 (m, PCH₂CH₃, 6H); 2.13 (d, ⁴J _P-H1.1, Cp*, 15 H); 1.00 (m,

P - CH₂- CH₃, 9H). ¹⁹F NMR (CDCl₃, δ): at 15 °C, -113.5

(dm, 1 o-F); -114.5 (dm, 1 o-F); -115.6 (dm, 1 o-F); -116.9

(dm, 1 o-F); -162.3 (t, 1 p-F); -163.5 (t, 1 p-F); -164.3 (m, 1

m-F); -164.6 (m, 1 m-F); -164.8 (m, 1 m-F); -165.5 (m, 1 m-F).

³¹P NMR (CDCl₃, δ): at 15 °C, -8.7 (s). The complex is not

sufficiently soluble for ¹³C NMR.

Ack n ow led gm en t. We wish to thank the Comisio´n

Interministerial de Ciencia y Tecnolog´ıa (Spain, Project

PB 95-0003-CO2-01,02) and the Universidad de La Rioja

(Project API-98/B16) for their financial support.

Su p p or tin g In for m a tion Ava ila ble: Tables giving posi-

tional and thermal parameters, bond distances, and bond

angles for 5c, 7a ,c, 8a , 9b, and 12a (41 pages). Ordering

information is given on any current masthead page.

OM980344M

(40) Sheldrick, G. M. SHELXL-93, a Program for Crystal Structure

Determination; University of Go¨ttingen, Go¨ttingen, Germany, 1993.

(41) SHELXTL-PLUS, Software Package for the Determination of

Crystal Structures, Release 4.0; Siemens Analytical X-ray Instruments

Inc., Madison, WI, 1990.

Data for 12c′: Anal. Calcd for C₃₃H₃₉F₁₀IIrPPdSi: C, 35.70;

H, 3.54. Found: C, 36.04; H, 2.98. MS: m/z ) 1015 [M -

C₂SiMe₃+ 2H]⁺8%; 573 [Cp*IrI(PEt₃)]⁺100%; 543 [Cp*Ir(C₂-

Article Doi

Synthesis, characterization, and reactivity of new alkynyl complexes of rhodium and iridium: Preparation of neutral (M-M′: M = Rh, Ir; M′ = Pt, Pd) hetero-alkynyl-bridged dinuclear complexes

DOI: 10.1021/om980344m

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Full text of DOI:10.1021/om980344m

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