Novel ruthenium(II) carbene complexes: Products of the reactions of 1-alkynes with (η6-C6Me6)Cl2Ru(PR3)

4740

Organometallics 2000, 19, 4740-4755

Novel Ru th en iu m (II) Ca r ben e Com p lexes: P r od u cts of

th e Rea ction s of 1-Alk yn es w ith (η⁶-C₆Me₆)Cl₂Ru (P R₃)

Heather D. Hansen and J ohn H. Nelson*

Department of Chemistry/ 216, University of NevadasReno, Reno, Nevada 89557-0020

Received J une 13, 2000

The complexes (η⁶-C₆Me₆)Cl₂Ru(PR₃) (1; PR₃) DPVP (diphenylvinylphosphine) (a ), PMe₃

(b), PPh₃(c)) react with NaPF₆in acetonitrile solutions to give the cationic complexes [(η⁶-

C₆Me₆)ClRu(PR₃)(NCCH₃)]PF₆(2a -c) by loss of NaCl. Complexes 1a and 2a react with HCt

CSiMe₃and HCtCPh (and NaPF₆for 1a ) in MeOH to give the carbene complexes [(η⁶-

C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₃]PF₆(3a) and [(η⁶-C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₂Ph]PF₆

(4a ), respectively. The known analogues 3b,c and 4b and the new complex 4c have been

synthesized from 2b,c and HCtCR. The solid-state structures of these complexes show a

wide variation in the orientation of the carbene plane with respect to the plane of the η⁶-

arene ring (dihedral angles of 37.9-59.6°). The solution dynamic behavior of 3a -c and 4a -c

is discussed. Complex 2a also reacts with HCtCCH₂CH₂OH in MeOH to give the oxacyclic

carbene complex [(η⁶-C₆Me₆)Cl(DPVP)RudC(CH₂CH₂CH₂)O]PF₆(5). 1a (and NaPF₆) and 2a

react with HCtCC(OH)Ph₂in MeOH to give the novel phosphorus ylide complex [(η⁶-C₆-

Me₆)ClRuC(dCdCPh₂)PPh₂CHdCH₂]PF₆(6) and with dimethylpropargylamine in CH₂Cl₂

or dichloroethane to give the amino cyclic carbene complex [(η⁶-C₆Me₆)Cl(DPVP)RudCCH₂-

CMe₂NH]PF₆(7) and the metallacyclic complex [(η⁶-C₆Me₆)ClRuCHdC(DPVP)CMe₂NH₂]-

PF₆(8). In the absence of MeOH, reaction of 2a with HCtCC(OH)Ph₂gives the dimeric

complex [(η⁶-C₆Me₆)Ru(µ-Cl)₃Ru(η⁶-C₆Me₆)]PF₆. Complex 2a plus HCtCPh in the absence

of MeOH gives the carbonyl complex [(η⁶-C₆Me₆)Cl(DPVP)Ru(CO)]PF₆(9). Reaction of 2c

with HCtCPh in MeOH for extended time periods (>1 day) gives an analogous carbonyl

complex of PPh₃, [(η⁶-C₆Me₆)Cl(PPh₃)Ru(CO)]PF₆. All complexes have been characterized

1

by H, ¹³C{¹H}, and ³¹P{¹H} NMR and IR spectroscopies and electrochemistry and in most

cases by X-ray crystallography. Complex 1a is an efficient catalyst for the regioselective

addition of H₂O to HCtCPh, producing exclusively acetophenone in 70% isolated yield.

Sch em e 1. Rea ction s of th e P h osp h a a llyl Com p lex

B

In tr od u ction

Previous investigations in our laboratory with the

hybrid hemilabile ligand diphenylvinylphosphine (DPVP)

resulted in the synthesis of the phosphaallyl complexes

[(η⁵-C₅H₅)Ru(η³-DPVP)(η¹-DPVP)]PF₆(A)¹and [(η⁵-C₅-

Me₅)Ru(η³-DPVP)(η¹-DPVP)]PF₆(B).²The η³-DPVP

ligand is a neutral, monometallic phosphaallyl ligand

coordinated to ruthenium through its phosphorus atom

and its vinyl group. The hemilabile nature of the η³-

DPVP ligand in complex B was demonstrated by the

reactions illustrated in Scheme 1. Similar reactions

showed the hemilabile nature of the phosphaallyl ligand

in complex A.¹

As an extension of the chemistry of ruthenium-DPVP

complexes and of the chemistry of (η⁶-arene)ruthenium

complexes, we attempted to synthesize [(η⁶-C₆Me₆)ClRu-

(η³-DPVP)]PF₆(C). Though we have been unable to

confirm the formation of C, its acetonitrile precursor

terminal alkynes to form traditional and novel carbene

complexes.

[(η⁶-C₆Me₆)ClRu(η¹-DPVP)(NCCH₃)]PF₆reacts with

3

We report here (1) the synthesis and characterization

of two new η⁶-C₆Me₆-phosphine-ruthenium-acetoni-

(1) J i, H.-L.; Nelson, J . H.; DeCian, A.; Fischer, J .; Solujic´, L.;

Milosavljevic´, E. B. Organometallics 1992, 11, 401.

(2) Barthel-Rosa, L. P.; Maitra, K.; Fischer, J .; Nelson, J . H.

Organometallics 1997, 16, 1714.

(3) Redwine, K. D.; Hansen, H. D.; Bowley, S.; Isbell, J .; Vodak, D.;

Nelson, J . H. Synth. React. Inorg. Met.-Org. Chem. 2000, 30, 409.

Publication on Web 10/14/2000

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4741

F igu r e 1. Structural drawings of (η⁶-C₆Me₆)Cl₂Ru(PMe₃) (1b) and (η⁶-C₆Me₆)Cl₂Ru(PPh₃) (1c) showing the atom-numbering

schemes (30% probability ellipsoids). Hydrogen atoms have been omitted for clarity.

Ta ble 1. Selected Bon d Dista n ces (Å) a n d An gles

trile complexes and their reactions with terminal alkynes,

(d eg) for (η⁶-C₆Me₆)Cl₂Ru (P R₃) (1b,c)

(2) structural characterization of a series of η⁶-C₆Me₆-

(η⁶-C₆Me₆)Cl₂Ru-

(PMe₃) (1b)

(η⁶-C₆Me₆)Cl₂Ru-

(PPh₃) (1c)

phosphine-ruthenium-carbene complexes, (3) complete

analysis of the dynamic behavior of these carbene

Ru-P

2.343(3)

2.422(3)

2.424(3)

2.215(11)

82.4(11)

84.96(11)

90.31(10)

257.31

2.3607(10)

2.4117(10)

2.4118(10)

2.249(4)

84.99(3)

88.22(4)

1

complexes by H, ¹³C{¹H}, and ³¹P{¹H} variable-tem-

Ru-Cl(1)

perature NMR spectroscopy and NOE experiments, (4)

four new complexes (including two new complex types)

containing the [(η⁶-C₆Me₆)ClRu(DPVP)] moiety, and (5)

the use of (η⁶-C₆Me₆)Cl₂Ru(DPVP) to catalyze the

hydration of phenylacetylene.

Ru-Cl(2)

Ru-C(avg.)

P-Ru-Cl(1)

P-Ru-Cl(2)

Cl(1)-Ru-Cl(2)

88.16(4)

261.37

a

∑

a

∑

) the sum of the P-Ru-Cl(1), P-Ru-Cl(2), and Cl(1)-

Resu lts a n d Discu ssion

Ru-Cl(2) angles.

Str u ctu r a l Ch a r a cter iza tion of (η⁶-C₆Me₆)Cl₂Ru -

(P R₃) (1). Bridge cleavage of the dimeric [(η⁶-C₆Me₆)-

RuCl₂]₂complex with 2 equiv of a phosphine gives the

yield of 2b and a 28% yield of 2c as orange-yellow

powders. Complex 2c was contaminated with the triply

chloride bridged dimer [(η⁶-C₆Me₆)Ru(µ-Cl)₃Ru(η⁶-C₆-

Me₆)]PF₆,⁴which was removed by repeated recrystalli-

zations from CH₂Cl₂/Et₂O.

reported complexes (η⁶-C₆Me₆)Cl₂Ru(PR₃) (1; PR₃

)

diphenylvinylphosphine (DPVP) (a ),⁴PMe₃(b),⁵PPh₃

(c)⁶). The physical properties and NMR and IR spectral

data for 1a -c have been reported.^4-6The molecular

structures of 1b,c were determined, and views of their

crystal structures are given in Figure 1. Selected bond

distances and angles are given in Table 1. The struc-

tures of 1b,c consist of isolated molecules with no

unusual intermolecular contacts, and their metrical

parameters compare favorably with those of similar

three-legged piano-stool (η⁶-arene)Cl₂Ru(PR₃) complexes

in which the Ru(II) atoms possess a pseudo-octahedral

geometry.^4,7

Complex 2b is quite soluble in acetone, CH₃OH, and

CH₃NO₂, less soluble in CH₂Cl₂and CHCl₃, and not

soluble in ether and hydrocarbons. Complex 2c follows

the same trend, but it is less soluble than 2b in all

solvents. Complexes 2b,c are not stable for extended

periods in any solvent. Complexes 2b,c were identified

by the appearance of ν(CtN) stretching vibrations (at

2322 and 2328 cm^-1, respectively) in their infrared

spectra and the resonances for coordinated CH₃CN in

their ¹H and ¹³C{¹H} NMR spectra (see Experimental

Section). Also characteristic of the formation of cationic

species, their ³¹P{¹H} NMR resonances are shifted

downfield relative to those of 1b,c. Similar observations

have been made for the transformation of (η⁶-arene)-

Syn th esis a n d Ch a r a cter iza tion of [(η⁶-C₆Me₆)-

Cl(P R₃)Ru (NCCH₃)]P F ₆(2). Reaction of 1a -c with 1

equiv of NaPF₆in acetonitrile/CH₂Cl₂solutions readily

gave the cationic complexes [(η⁶-C₆Me₆)Cl(PR₃)Ru-

(NCCH₃)]PF₆(2a -c) and NaCl, as was reported for 2a .³

Removal of NaCl followed by crystallization gave an 87%

RuCl₂(PR₃)⁴to [(η⁶-arene)RuCl(PR₃)(NCCH₃)]PF₆for

3

several arene and PR₃combinations.

The Ru(II)/Ru(III) redox potentials of complexes 1a -c

have been reported to be 0.47,⁴0.32,⁸and 0.47 V,⁸

respectively. This shows the PMe₃complex to be more

easily oxidized because of the greater σ-donor ability of

(4) Redwine, K. D.; Hansen, H. D.; Bowley, S.; Isbell, J .; Sanchez,

M.; Vodak, D.; Nelson, J . H. Synth. React. Inorg. Met.-Org. Chem. 2000,

30, 379.

(5) Werner, H.; Werner, R. Chem. Ber. 1982, 115, 3766.

(6) Bennett, M. A.; Huang, T.-N.; Latten, J . L. J . Organomet. Chem.

1984, 272, 189.

(7) Bennett, M. A.; Robertson, G. B.; Smith, A. K. J . Organomet.

Chem. 1972, 43, C41.

(8) Sˇteˇpnicˇka, P.; Gyepes, R.; Lavastre, O.; Dixneuf, P. H. Organo-

metallics 1997, 16, 5089.

4742 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

Sch em e 2. Syn th esis of Meth oxya lk ylca r ben e

Com p lexes 3 a n d 4

PMe₃, and it indicates very similar σ-donor abilities of

PPh₃and DPVP. For complexes 2a -c, the redox couples

are more positive, as expected for cationic species. The

redox couple for 2a was reported to be 0.96 V,³and the

redox couple of 2b was found to be 1.03 V, an unex-

pected trend. Complex 2c shows only an oxidation wave

(1.21 V) and several electrochemical events at negative

potentials, indicating redox instability of this complex.

As will be shown later, reactions with 2c result in large

amounts of decomposition in all solvents and under all

conditions utilized; therefore, its decomposition under

electrochemical stress is not unexpected.

We initially prepared 2a because of our desire to

prepare [(η⁶-C₆Me₆)ClRu(η³-DPVP)]PF₆(C), which con-

tains the hybrid hemilabile phosphaallyl ligand η³-

DPVP.

1

Ta ble 2. Selected ¹³C{¹H}, H, a n d ³¹P {¹H} NMR

Sp ectr a l Da ta for th e Meth oxya lk ylca r ben e

Com p lexes [(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₃]⁺

(3) a n d [(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₂P h ]⁺(4),

in p p m (J in Hz)

Complex C would be the arene analogue of the novel

Cp and Cp* complexes A and B, prepared previously in

our laboratories,^1,2from the corresponding [(Cp/Cp*)-

Ru(η¹-DPVP)₂(NCCH₃)]PF₆complexes by removal of

CH₃CN in vacuo. Both in solution and in the solid state

A and B contain the η³-phosphaallyl ligand, which is

stabilized by π-electron donation from Ru to the CHd

CH₂group. The vinyl moiety in A and B is easily

displaced by a variety of two-electron-donor ligands

(Scheme 1). As would be expected on the basis of the

greater electron-donating ability of C₅Me₅vs C₅H₅, B

is more easily formed than A from the corresponding

[(Cp/Cp*)Ru(η¹-DPVP)₂(NCCH₃)]PF₆species.²Since both

Cp* and Cp are better electron-donating ligands than

η⁶-C₆Me₆, we expected that C might be difficult to obtain

from its corresponding acetonitrile complex 2a . Heating

2a at 112 °C for 2 weeks under reduced pressure gave

a complex mixture, as seen by ¹H and ³¹P{¹H} NMR

spectroscopy, from which we have been able to isolate

neither C nor 2a . Nonetheless, 2a is a cationic species

with a very labile CH₃CN ligand that is readily replaced

by alkynes. Use of 2a eliminates the need for reaction

with NaPF₆and subsequent removal of NaCl, since this

step has already been accomplished in the preparation

of 2a from 1a . Reaction of 2a with alkynes proceeded

cleanly and with high yields (78-90%); therefore, we

have employed it and complexes 2b,c in our studies.

δ(¹H)

δ(³¹P)

PR₃

δ(¹³C) RudC OCH₃CH₃

CH₂

DPVP (3a ) 327.99 (19.9)

PMe₃(3b) 330.86 (21.2)

PPh₃(3c) 331.00 (19.6)

4.38 2.87

4.48 2.98

4.18 2.91

4.50

31.31

10.50

38.14

a

DPVP (4a ) 314.54 (14.5)

5.07, 3.23 (12.5) 27.95

5.04, 4.50 (13.0) 8.12

a

PMe₃(4b) 323.10 (20.64) 4.59

a

PPh₃(4c) 316.60 (18.65) 4.50

4.76, 2.65

(13.03)

36.06

a

Reference 9a.

NMR spectroscopy. Diagnostic ¹³C{¹H}, ¹H, and ³¹P{¹H}

NMR data for the six carbene complexes are compared

in Table 2. The carbene carbon chemical shifts all occur

between 310 and 335 ppm with two-bond P-C coupling

constants on the order of 18-20 Hz. The ¹H NMR

spectral data of the carbene ligands vary only slightly.

The vinyl protons of the DPVP group in 3a and 4a show

the characteristic^1-4set of multiplets between 6.9 and

5.3 ppm (see Experimental Section).

Complexes 3a -c and 4a -c were characterized by

X-ray crystallography. Views of the structures of the

cations are shown in Figure 2; selected bond distances

are given in Table 3, and selected bond angles are given

in Table 4. The bond lengths and angles are similar

among the cations of each molecule. Analysis of all six

structures shows a distorted-octahedral geometry about

Ru with the η⁶-C₆Me₆ligand occupying three facial

coordination sites and the three remaining ligands (Cl,

PR₃, and carbene) completing the coordination sphere.

The RudC(carbene) bond lengths of 1.94-2.02 Å are

similar to those reported for other structurally charac-

terized Ru carbene complexes.^8,9d,10The dihedral angles

vary considerably among the complexes (37.9-59.6°),

Syn th esis, Ch a r a cter iza tion , a n d X-r a y Cr ysta l

Str u ctu r es of Meth oxya lk ylca r ben es [(η⁶-C₆Me₆)-

Cl(P R₃)Ru dC(OCH₃)CH₂R′]P F ₆(R′ ) H (3), P h (4)).

Reaction of 2a -c with HCtCSiMe₃and HCtCPh gave

the methoxymethylcarbene complexes [(η⁶-C₆Me₆)Cl-

(PR₃)RudC(OCH₃)CH₃]PF₆(3a -c) and the methoxy-

benzylcarbene complexes [(η⁶-C₆Me₆)Cl(PR₃)RudC-

(OCH₃)CH₂Ph]PF₆(4a -c), respectively, as shown in

Scheme 2. The formation of complexes 3b and 4b,c was

confirmed by comparison of their NMR spectral data

with those reported by Dixneuf and co-workers.⁹The

new complexes 3a ,c and 4a were also characterized by

(9) (a) Le Bozec, H.; Ouzzine, K.; Dixneuf, P. H. Organometallics

1991, 10, 2768. (b) Ouzzine, K.; Le Bozec, H.; Dixneuf, P. H. J .

Organomet. Chem. 1986, 317, C25. (c) Dixneuf, P. H. Pure Appl. Chem.

1989, 61, 1763. (d) Pilette, D.; Ouzzine, K.; Le Bozec, H.; Dixneuf, P.

H.; Rickard, C. E. F.; Roper, W. R. Organometallics 1992, 11, 809.

F igu r e 2. Structural drawings of the cations of [(η⁶-C₆Me₆)Cl(PR₃)RudC(OCH₃)CH₃]PF₆(PR₃) DPVP (3a ), PMe₃(3b), PPh₃(3c)) and [(η⁶-C₆Me₆)Cl(PR₃)RudC(OCH₃)-

CH₂Ph]PF₆(PR₃) DPVP (4a ), PMe₃(4b), PPh₃(4c)) showing the atom-numbering schemes (30% probability ellipsoids). Hydrogen atoms have been omitted for clarity.

4744 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

Ta ble 3. Selected Bon d Dista n ces (Å) for Meth oxya lk ylca r ben e Com p ou n d s

[(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₂R′]P F ₆(3a -c a n d 4a -c)

Ru-C(14)

Ru-P

Ru-Cl

Ru-C (av)

C(14)-C(15)

C(14)-O

3a

3b

3c

4a

4b

4c

1.964(10)

2.015(8)

1.962(10)

1.956(7)

1.955(13)

1.939(10)

2.342(3)

2.311(3)

2.351(3)

2.3364(18)

2.327(4)

2.354(2)

2.400(3)

2.403(3)

2.400(3)

2.3993(18)

2.407(3)

2.404(3)

2.295(13)

2.278(11)

2.320(11)

2.334(7)

2.303(14)

2.322(10)

1.497(16)

1.523(14)

1.490(14)

1.515(9)

1.508(17)

1.529(13)

1.309(12)

1.256(11)

1.300(12)

1.328(8)

1.306(14)

1.288(10)

Ta ble 4. Selected Bon d An gles (d eg) for Meth oxya lk ylca r ben e Com p ou n d s

[(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₂R′]P F ₆(3a -c a n d 4a -c)

P-Ru-C(14)

Cl-Ru-C(14)

P-Ru-Cl

Ru-C(14)-C(15)

Ru-C(14)-O

O-C(14)-C(15)

dihedral angle^a

3a

3b

3c

4a

4b

4c

86.6(3)

81.9(3)

86.2(3)

86.09(19)

82.5(4)

88.8(3)

89.1(3)

89.8(3)

90.8(3)

91.7(2)

93.0(4)

91.7(3)

85.19(11)

85.55(12)

88.75(10)

87.06(7)

84.44(14)

84.32(9)

124.5(8)

121.6(8)

124.3(8)

127.6(5)

126.8(10)

127.3(8)

118.5(8)

116.7(6)

118.3(8)

115.7(5)

115.5(9)

115.8(7)

117.0(9)

118.5(9)

117.2(10)

116.7(6)

117.6(12)

116.8(9)

79.9

78.1

92.3

37.9

59.6

57.7

a

Defined as the angle between the C(arene centroid)-Ru-C(carbene) and CH₂R-C(carbene)-OCH₃planes.

where the dihedral angle is defined as the angle

between the C(arene centroid)-Ru-C(carbene) and

CH₂R-C(carbene)-OCH₃planes. This difference in

observed dihedral angles led us to study the dynamic

behavior of these complexes by variable-temperature

NMR spectroscopy.

Dyn a m ic Beh a vior of th e Meth oxya lk ylca r ben e

Com p lexes [(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₂R′]-

P F ₆(3a -c, 4a -c). Three canonical representations can

be drawn for these Fisher-type carbene complexes (I-

III).^10a,11These representations differ in the localization

mol.¹²VT NMR spectroscopic studies agree with the

theoretical predictions.¹³Theoretical and variable-tem-

perature NMR spectroscopic studies of ruthenium-

vinylidene complexes show the barrier to rotation about

the Ru-C bond to be 9-10 kcal/mol.¹⁴Theoretical

studies predict the lower energy conformations to be

that with a “vertical” carbene for cyclopentadienyl

(CpML₂) complexes and that with a “horizontal” carbene

for (arene)ML₂complexes. For most of the reported

structurally characterized CpMLL′ carbenes, the verti-

cal orientation is found. For the three reported structur-

ally characterized (arene)MLL′ carbenes ([(η⁶-C₆Me₆)-

Ru(dC(OCH₃)CH₂Fc){((η⁵-C₅H₄PPh₂)Fe(η⁵-C₅H₄COOH))-

P}(Cl)]PF₆(Fc ) ferrocenyl),⁸[(η⁶-C₆Me₆)(PMe₃)ClRud

C(OCH₃)CHdCPh₂]PF₆,^9dand (η⁶-C₆H₆)(CO)₂CrdC(OEt)-

Ph¹⁵) a horizontal orientation was found. These differ-

ences have been interpreted on the basis of both

electronic (maximum attractive π overlap and minimiz-

ing orbital energies) and steric influences.

For the methoxyalkylcarbenes described here, the

dihedral angles vary from 37.9 to 59.6°, indicating

interplay of electronic and steric influences in the solid

state. We have attempted no molecular orbital calcula-

tions to discern the complete nature of the electronic

influences on the solid-state structures. We have deter-

mined the rotational barriers for this series of complexes

to gain knowledge of the degree of Ru-C double vs

single bond character, i.e. canonical form I vs forms II

and III. ¹H NOE experiments showed all six complexes

to be dynamic at room temperature. Variable-temper-

ature ¹H, ³¹P{¹H}, and ¹³C{¹H} NMR spectra were

recorded for acetone-d₆solutions of each of the com-

plexes (3a -c and 4a -c) between +50 and -90 °C. The

of electron density in the three-atom π system (Ru-C-

O). If we consider a carbene to be a neutral two-electron-

donor ligand, the other two electrons in the RudC

double bond must come from the metal. Hence, greater

electron density on the metal (low oxidation state and/

or electron-donating substituents) favors form I and a

rigid metal-carbon bond about which little to no rota-

tion is anticipated. As the electron-donating ability of

the metal decreases, forms II and III become more

important. In the limit of no contribution from I, forms

II and III suggest free rotation about a Ru-C single

bond. Complexes with contributions from all three forms

are then expected to show hindered rotation about the

ruthenium-carbon bond, the magnitude of the barrier

being dependent upon the amount of Ru_dπfC_pπback-

donation.

Theoretical studies of the bonding in late-transition-

metal carbene complexes predict barriers to rotation

about the MdC double bond on the order of 6-12 kcal/

(12) (a) Schilling, B. E. R.; Hoffmann, R.; Lichtenberger, D. L. J .

Am. Chem. Soc. 1979, 101, 585. (b) Kostic´, N. M.; Fenske, R. F.

Organometallics 1982, 1, 974. (c) Kostic´, N. M.; Fenske, R. F. J . Am.

Chem. Soc. 1982, 104, 3879. (d) Hofmann, P. In Transition Metal

Carbene Complexes; Verlag Chemie: Weinheim, Germany, 1983; p 73.

(13) (a) Brookhart, M.; Tucker, J . R.; Flood, T. C.; J ensen, J . J . Am.

Chem. Soc. 1980, 102, 1203. (b) Studabaker, W. B.; Brookhart, M. J .

Organomet. Chem. 1986, 310, C39. (c) Kegley, S. E.; Brookhart, M.;

Husk, G. R. Organometallics 1982, 1, 760. (d) Brumaghim, J . L.;

Girolami, G. S. Chem. Commun. 1999, 953. (e) Guerchais, V.; Lapinte,

C.; The´pot, J .-Y.; Toupet, L. Organometallics 1988, 7, 604.

(10) (a) Schubert, U. In Transition Metal Carbene Complexes; Verlag

Chemie: Weinheim, Germany, 1983; p 113. (b) Bianchini, C.; Masi,

D.; Romerosa, A.; Zanobini, F.; Peruzzini, M. Organometallics 1999,

18, 2376. (c) Stockman, K. E.; Sabat, M.; Finn, M. G.; Grimes, R. N. J .

Am. Chem. Soc. 1992, 114, 8733. (d) Consiglio, G.; Morandini, F.; Ciani,

G. F.; Sironi, A. Organometallics 1986, 5, 1976.

(11) (a) Collman, J . P.; Hegedus, L. S.; Norton, J . R.; Finke, R. G.

Principles and Applications of Organotransition Metal Chemistry;

University Science Books: Mill Valley, CA, 1987; pp 119-136. (b)

Schubert, U. Coord. Chem. Rev. 1984, 55, 261.

(14) (a) Consiglio, G.; Morandini, F. Inorg. Chim. Acta 1987, 127,

79. (b) Urtel, K.; Frick, A.; Huttner, G.; Zsolnai, L.; Kircher, P.; Rutsch,

P.; Kaifer, E.; J acobi, A. Eur. J . Inorg. Chem. 2000, 33.

(15) Schubert, U. J . Organomet. Chem. 1980, 185, 373.

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4745

F igu r e 4. Eyring plot of the temperature dependence of

the two-site exchange processes seen to occur in the OCH₃

resonance of [(η⁶-C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₃]PF₆

(3a ). Temperatures -30 °C and above were treated by

analysis of line widths; temperatures -40 °C and below

were treated by analysis of the chemical shift differences.

1

F igu r e 3. Variable-temperature H NMR spectra of [(η⁶-

C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₃]PF₆(3a ) from +30 °C to

-80 °C in acetone-d₆, clearly showing splitting of the CH₃,

OCH₃, and η⁶-C₆Me₆resonances with decreasing temper-

ature. The resonances marked with an asterisk (*) are due

to solvents.

PMe₃complexes 3b and 4b showed very little change

(and no splitting of resonances) upon lowering the

1

temperature in their H and ³¹P{¹H} NMR spectra; we

conclude that the carbene ligand is freely rotating about

the Ru-C bond at all temperatures above -90 °C.

Electronically, this indicates a very low or negligible

barrier to rotation and a large contribution from canoni-

cal form II and/or III. Sterically, this result could be

anticipated because of the relatively small size of the

PMe₃ligand.

Complexes 3a ,c and 4a ,c show a very interesting

phenomenon. The ¹H VT NMR spectral data for complex

3a are shown in Figure 3; the corresponding Eyring plot

is given in Figure 4. The Eyring plot clearly shows the

presence of two separate, though probably interrelated,

dynamic processes. The activation enthalpy and entropy

for the dominant process at lower temperature are 2.3

kcal/mol and -35.4 cal/(mol K), respectively, which gives

F igu r e 5. Low-temperature (-80 °C) ¹H NOE experiments

on [(η⁶-C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₃]PF₆(3a ). Irra-

diation of one of the OCH₃resonances shows complete spin-

saturation transfer to the other OCH₃resonance (top).

Irradiation of one of the CH₃resonances shows complete

spin-saturation transfer to the other CH₃resonance (bot-

tom).

∆G^q

) 12.8 kcal/mol. The corresponding values for

this small, and in any case proton-proton NOE’s cannot

exceed 50%. Thus, Figure 5 clearly demonstrates spin

saturation transfer due to chemical exchange rather

than NOE effects. We have (somewhat arbitrarily)

assigned the higher energy process to hindered rotation

about the Ru-P bond. Similarly, we have assigned the

lower energy process to hindered rotation about the

Ru-C bond. This is suggestive of a fair contribution

from canonical forms II and/or III and a steric contribu-

tion from the bulk of the DPVP ligand.

298

the process dominant at higher temperature are ∆H^q)

9.4 kcal/mol, ∆S^q) -4.9 cal/(mol K), and ∆G^q₂₉₈) 10.8

kcal/mol. The coalescence temperatures observed for

these processes are -30 °C (seen in the OCH₃, CH₃, and

η⁶-C₆Me₆resonances) and -35 °C (seen in the vinyl

proton resonances of DPVP), which give ∆G^q_Cvalues of

approximately 11.0 and 10.8 kcal/mol, respectively.

Proton NOE experiments at -80 °C show spin-satura-

tion transfer rather than NOE enhancements upon

irradiation of any resonance in the spectrum (see Figure

5), indicating that the molecule continues to be dynamic

even at low temperatures. One would not expect to see

large-magnitude negative NOE values for compounds

The ³¹P{¹H} VT NMR spectral data for 4a have been

analyzed by an Eyring plot and show only one dynamic

process with activation parameters of ∆H^q) 5.5 kcal/

mol, ∆S^q) -20.0 cal/(mol K), and ∆G^q) 11.5 kcal/

298

4746 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

Ta ble 5. Rota tion a l Ba r r ier s (k ca l/m ol) a n d

Dih ed r a l An gles (d eg) for

[(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)R′]P F ₆

PR₃

3a DPVP CH₃

4a DPVP CH₂Ph free rotation ∆G^q) 11.5

R′

RudC (∆G^q) Ru-P (∆G^q) dihedral angle

∆G^‡) 10.8 ∆G^q₂₉₈) 12.8

79.9

37.9

78.1

59.6

92.3

57.7

298

3b PMe₃CH₃

free rotation free rotation

4b PMe₃CH₂Ph free rotation free rotation

3c PPh₃CH₃

free rotation ∆G^q≈ 12.5

273

4c PPh₃CH₂Ph free rotation ∆G^q≈ 11

248

mol. We attribute this dynamic behavior to hindered

rotation about the Ru-P bond.

The PPh₃complexes 3c and 4c also show only one

dynamic process between +25 and -90 °C, and the ¹³C-

{¹H} VT NMR very clearly demonstrates that process

to be hindered rotation about the Ru-P bond. Low-

temperature ¹³C{¹H} NMR spectra of both compounds

show three sets of resonances each for the ipso, ortho,

meta, and para carbons of the phenyl rings. In the

spectra of complex 3c at -60 °C, the P-C coupling

constants are resolved (see the Experimental Section).

formation of 4a from 1a is nearly complete in ∼1.5 h

but takes 24 h from 2a (see Experimental Section), and

4b,c are reportedly formed in 10-30 min from 1b,c^9a

but take more than 1 day from 2b,c. As mentioned

earlier, the acetonitrile complexes are not indefinitely

stable in solution, and we have found that impure

solutions of all of the carbene complexes slowly decom-

pose in solution (i.e., upon crystallization attempts),¹⁶

the PPh₃complexes being especially unstable. From the

reactions with 2a -c we saw evidence (¹H and ¹³C{¹H}

NMR and IR) for the formation of Ru-carbonyl species.

(We also isolated a small amount of [(η⁶-C₆Me₆)Cl(PPh₃)-

Ru(CO)]PF₆as red crystals from a prolonged reaction

of 1c with HCtCPh and NaPF₆.) These observations

indicate that beginning with complexes 2a -c is not the

most favorable route to choose.

The carbonyl species observed most probably resulted

from attack on an intermediate vinylidene species by

adventitious water in the reaction solvents (MeOH and

CH₂Cl₂) by a previously described mechanism. The first

step is coordination of the alkyne to the site on the metal

vacated by CH₃CN. This probably occurs initially in an

η²-alkyne fashion with facile conversion to the η¹-

vinylidene species, as postulated¹⁷for several metal

complexes. The R-carbon of late-transition-metal vi-

nylidenes is readily attacked by nucleophiles,^9,11ain-

cluding water,¹⁸to give disubstituted carbenes. Hydroxy-

carbenes can undergo â-hydride elimination followed by

reductive elimination of an organic molecule to give the

carbonyl species. Each of these types of species have

been isolated from similar reactions by many

groups.^9,11a,17-19

1

The H variable-temperature NMR spectra also show

this phenomenon in the 7-8 ppm region for the PPh₃

1

protons of both 3c and 4c. From the H NMR spectra,

the coalescence temperatures are estimated to be 0 °C

for 3c and -25 °C for 4c, giving ∆G^q= 12.5 kcal/mol

273

for 3c and ∆G^q= 11 kcal/mol for 4c. No splitting of

248

the η⁶-C₆Me₆, OCH₃, CH₃, or CH₂resonances was seen

above -90 °C. This observation can be explained by

taking into account steric contributions (PPh₃was the

largest phosphine studied) and electronic contributions

(forms II and/or III). Data for the six carbene complexes

are collected in Table 5.

Both reviewers have suggested that the dynamic

behavior of 3a could be a result of hindered rotation

about the C-O bond due to the dominance of form III,

as previously reported for [(η⁵-C₅Me₅)Ru(CO)₂(CHOCH₃)]-

PF₆.^13eWe believe that this is not the case for the

following reasons. For 3a the dynamic behavior is

clearly a reversible process, whereas that for [(η⁵-C₅-

Me₅)Ru(CO)₂(CHOCH₃)]PF₆is irreversible. No NOE is

observed at -80 °C between the CH₃and OCH₃reso-

nances. Such NOE would be expected for hindered CO

rotation. Further, the η⁶-C₆Me₆CH₃resonance splits

into two resonances at low temperature. For a freely

rotating η⁶-C₆Me₆moiety parallel to the plane of the two

isomers of a methoxymethylcarbene group (which should

be the more stable geometry), only one η⁶-C₆Me₆CH₃

resonance should be observed.

Com p a r ison of Rea ction Rou tes: 1a -c + Na P F ₆

f Meth oxya lk ylca r ben es (Eq 1) or 2a -c f Meth -

oxya lk ylca r ben es (Eq 2). Complex 4a was prepared

in 51% yield directly from 1a with NaPF₆and HCtCPh

in a MeOH/CH₂Cl₂mixture. As we predicted (vide

supra), complexes 4a and 3b were formed in higher

yields by starting with the cationic complexes 2a ,b than

by starting with the neutral complexes 1a ,b and

NaPF₆: 2a f 4a (78%) vs 1a f 4a (51%) and 2b f 3b

(100%) vs 1b f 3b (61%).^9aHowever, this was not the

case for the preparations of 3c and 4b,c. (The prepara-

tion of 3a was not attempted from 1a after it was

produced in 90% yield starting with 2a .) The reactions

of 2a -c appear to be slower than those of 1a -c and

NaPF₆, as determined by ³¹P{¹H} NMR spectroscopic

monitoring of reaction progress. For example, the

The ¹³C{¹H} NMR spectra for [(η⁶-C₆Me₆)ClRu(PR₃)-

(CO)]PF₆show the carbonyl carbon resonances as

doublets at ∼195 ppm with two-bond P-C coupling

constants of ∼25 Hz. Infrared spectroscopy shows ν(CO)

stretching vibrations at ∼2013 cm^-1. All other spectral

data are as expected (see Experimental Section).

Syn th esis a n d Ch a r a cter iza tion of th e Oxa cyclic

Car ben e [(η⁶-C₆Me₆)Cl(DP VP )Ru dC(CH₂CH₂CH₂)O]-

(16) Dixneuf and co-workers have stated that complexes 4b,c are

“stable methoxybenzylcarbene-ruthenium complexes”, but they do not

specify whether as solids or in solution (see ref 9a, p 2769).

(17) Bruce, M. I. Chem. Rev. 1991, 91, 197.

(18) (a) Davies, S. G.; McNally, J . P.; Smallridge, A. J . Adv.

Organomet. Chem. 1990, 30, 1. (b) Gamasa, M. P.; Gimeno, J .; Lastra,

E.; Lanfranchi, M.; Tiripicchio, A. J . Organomet. Chem. 1992, 430, C39.

(c) Bruce, M. I.; Swincer, A. G. Aust. J . Chem. 1980, 33, 1471.

(19) Bianchini, C.; Casares, J . A.; Peruzzini, M.; Romerosa, A.;

Zanobini, F. J . Am. Chem. Soc. 1996, 118, 4585.

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4747

Sch em e 3. Novel Rea ction s of 1a a n d 2a w ith

Ter m in a l Alk yn es

F igu r e 6. Structural drawing of the cation of [(η⁶-C₆Me₆)-

Cl(DPVP)RudC(CH₂)₃O]PF₆(5) showing the atom-num-

bering scheme (30% probability ellipsoids). Hydrogen atoms

have been omitted for clarity.

Ta ble 6. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for [(η⁶-C₆Me₆)Cl(DP VP )Ru dC(CH₂)₃O]P F ₆(5)

Distances

Ru(1)-C(27)

Ru(1)-P(1)

1.958(7)

2.339(2)

2.396(2)

2.297(8)

1.258(10)

C(27)-C(28)

C(27)-O(1)

C(28)-C(29)

C(29)-C(30)

C(30)-O(1)

1.495(9)

1.308(8)

1.512(9)

1.486(11)

1.466(8)

P F ₆(5). A CH₂Cl₂solution of 1a was treated with 1

equiv of NaPF₆and 5 equiv of 3-butyn-1-ol and stirred

overnight. The solution was filtered to remove NaCl, and

the volume of the filtrate was reduced in vacuo. Addition

Ru(1)-Cl(1)

Ru(1)-C(arene) (av)

C(13)-C(14)

Angles

of Et₂O produced [(η⁶-C₆Me₆)Cl(DPVP)RudC(CH₂)₃O]-

PF₆(5) as an air-stable yellow powder in 71% yield after

recrystallization (see Scheme 3).

C(27)-Ru(1)-Cl(1) 88.1(2)

Ru(1)-C(27)-O(1)

Ru(1)-C(27)-C(28) 129.8(5)

122.3(5)

C(27)-Ru(1)-P(1)

Cl(1)-Ru(1)-P(1)

87.1(2)

85.63(7) C(28)-C(27)-O(1)

107.9(6)

The cyclic oxycarbene is evidenced by the resonances

at 313.25 (²J (PC) ) 14.0 Hz), 88.58, 21.13, and 55.78

ppm for the carbene and CH₂carbons, respectively, in

the ¹³C{¹H} NMR spectrum. Similar cyclic oxycarbenes

show these resonances at 317.38 (²J (PC) ) 22.0 Hz),

87.98, 21.54, and 55.96 ppm for [(η⁶-C₆Me₆)Cl(PMe₃)-

five-membered ring showed the typical puckered-

envelope conformation with deviations from planarity

of +0.0609 (C(27)), -0.1445 (C(28)), +0.1731 (C(29)),

-0.1400 (C(30)), and +0.0505° (O(1)).

Un exp ected Syn th esis of a Novel P h osp h or u s

Ylid e. In an attempt to prepare a vinylcarbene complex

similar to [(η⁶-C₆Me₆)RuCl(PMe₃)dC(OCH₃)CHdCRR′]-

PF₆,^9dcomplex 1a was reacted with 1 equiv of NaPF₆

and 5 equiv of 1,1-diphenylprop-3-yn-1-ol, HCtCC(OH)-

Ph₂, in 1:1 MeOH/CH₂Cl₂. The solution quickly turned

from red-orange to dark red to nearly black. After 24 h

of stirring at room temperature, the solvent volume of

the dark red solution was reduced in vacuo. Addition of

Et₂O caused the precipitation of an orange powder that

was identified by ¹H and ³¹P{¹H} NMR spectroscopy as

the starting material (1a ). After several such precipita-

tions of starting material, the novel ylide complex [(η⁶-

RudC(CH₂)₃O]PF₆and 299.50 (²J (PC) not resolved),

4a

80.86, 23.41, and 55.81 ppm for [(η⁵-C₅Me₅)(DPVP)₂Rud

C(CH₂)₃O]PF₆.²The -(CH₂)₃- protons resonate as

multiplets between 5.2 and 1.5 ppm, similar to what is

reported for other cyclic oxycarbenes.^2,9a,20The charac-

teristic multiplets for the vinyl protons in 5 are seen at

6.63, 6.11, and 5.41 ppm.

Complex 5 was characterized by X-ray crystallogra-

phy, and a view of the cation is shown in Figure 6.

Selected bond distances and angles are listed in Table

6. Analysis shows a distorted-octahedral structure about

Ru with the η⁶-C₆Me₆ligand occupying three facial

coordination sites. The three remaining ligands (Cl,

DPVP, and carbene) complete the coordination sphere.

The RudC(carbene) bond length of 1.958(7) Å is similar

to the RudC bond length found for the RudC(carbene)

C₆Me₆)ClRuC(dCdCPh₂)PPh₂CHdCH₂]PF₆(6) was ob-

tained as impure oily red crystals in 16% yield.

Alternatively, the reaction of complex 2a and HCtCC-

(OH)Ph₂in MeOH/CH₂Cl₂produced complex 6 in 24%

yield, also as impure oily red crystals. The structure of

6 was established by X-ray crystallography.

Two views of the cation of 6 are shown in Figure 7:

the first is of the entire cation; the phenyl groups, except

for the ipso carbons, have been removed for clarity in

the second view. Table 7 lists selected bond distances

of [(η⁵-C₅Me₅)(DPVP)₂RudC(CH₂)₃O]⁺(1.942 Å).²The

(20) (a) Bruce, M. I.; Swincer, A. G.; Thomson, B. J .; Wallis, R. C.

Aust. J . Chem. 1980, 33, 2605. (b) Gamasa, M. P.; Gimeno, J .; Gonzalez-

Cueva, M.; Lastra, E. J . Chem. Soc., Dalton Trans. 1996, 2547.

4748 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

Ta ble 7. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for

[(η⁶-C₆Me₆)ClRu C(dCdCP h ₂)P P h ₂CHdCH₂]P F ₆(6)

Distances

Ru(1)-C(27)

Ru(1)-P(1)

2.122(7)

2.902(2)

2.396(2)

2.270(9)

2.193(7)

2.185(7)

C(13)-C(14)

C(27)-C(28)

C(28)-C(29)

C(27)-P(1)

P(1)-C(13)

1.395(11)

1.289(9)

1.319(9)

1.758(7)

1.782(7)

Ru(1)-Cl(1)

Ru(1)-C(arene) (av)

Ru(1)-C(13)

Ru(1)-C(14)

Angles

83.9(2) Ru(1)-C(27)-P(1)

C(27)-Ru(1)-Cl(1)

C(27)-Ru(1)-C(13)

C(27)-Ru(1)-C(14)

C(13)-Ru(1)-C(14)

Cl(1)-Ru(1)-C(13)

Cl(1)-Ru(1)-C(14)

C(27)-P(1)-C(13)

C(27)-P(1)-C(15)

C(27)-P(1)-C(21)

C(15)-P(1)-C(21)

C(13)-P(1)-C(21)

96.4(3)

74.6(3) Ru(1)-C(27)-C(28) 134.1(6)

97.2(3) C(28)-C(27)-P(1) 129.5(6)

37.2(3) C(27)-C(28)-C(29) 178.5(7)

108.1(2) C(28)-C(29)-C(30) 119.2(7)

81.8(2) C(28)-C(29)-C(36) 119.3(7)

95.3(3) C(30)-C(29)-C(36) 121.4(6)

115.1(3) P(1)-C(13)-C(14)

113.1(3) P(1)-C(13)-Ru(1)

108.1(3) C(14)-C(13)-Ru(1)

113.6(3)

119.7(6)

93.2(3)

71.1(4)

antibonding molecular orbital. Similar CdC bond elon-

gation upon metal coordination is seen for the Cp and

1

Cp* complexes [(η⁵-C₅H₅)Ru(η¹-DPVP)(η³-DPVP)]PF₆

and [(η⁵-C₅Me₅)Ru(η¹-DPVP)(η³-DPVP)]PF₆,²in which

one of the vinyl groups is coordinated to ruthenium. The

CdC bond distances are 1.399(5)¹and 1.51(3) Å²for the

η³-DPVP ligands and 1.306(5)¹and 1.24(2) Å²for the

η¹-DPVP ligands. The Ru-C(27) bond distance of 2.122(7)

Å is indicative of a Ru-C(sp²) single bond, rather than

a RudC(sp²) double bond, and is similar to the Ru-

C(sp²) distance reported for (η⁵-C₅H₅)(CO)(PPrⁱ)RuC-

3

(PPh₂)dCdCPh₂(2.139(5) Å).^21aThe C(27)-C(28) and

C(28)-C(29) bond distances (1.289(9) and 1.319(9) Å,

respectively) and the C(27)-C(28)-C(29) angle (178.5(7)°)

support an allenyl formulation. They are similar to the

metrical parameters reported by Esteruelas and co-

workers^21afor (η⁵-C₅H₅)(CO)(PPrⁱ₃)RuC(PPh₂)dCdCPh₂.

Finally, as can be seen from Figure 7, the phosphorus

atom has tetrahedral geometry, with the average angle

about P being 109°. The unusual phosphorus ylide in

this complex is stabilized in its dipolar form by coordi-

nation to ruthenium.

In the ¹H NMR spectrum, the resonances for the

protons of the vinyl group have been shifted significantly

upfield (4.06 to 3.69 ppm) from those of uncoordinated

vinyl protons (typically 7.0 to 5.3 ppm for cationic

arene-Ru complexes³). This confirms the decreases in

CdC bond order and in deshielding upon η²-coordination

to ruthenium. Similarly, the vinyl carbon resonances are

seen at 28.35 ppm (¹J (PC) ) 88.1 Hz) and 66.5 ppm vs

the normal 130-135 ppm range. The carbons of the

allenyl chain resonate at 89.92, 204.94, and 111.70 ppm

(C(27), C(28), and C(29) in Figure 7). For similar ylide

(or allenyl-phosphonio) complexes,²¹the same carbon

resonances are found at 71-84, 210-217, and 101-104

ppm, respectively. The IR spectrum contains the char-

acteristic CdCdC stretch at 1976 cm^-1and CHdCH₂

F igu r e 7. Structural drawings of the cation of [(η⁶-C₆Me₆)-

ClRuC(dCdCPh₂)PPh₂CHdCH₂]PF₆(6) showing the full

atom-numbering scheme (top, 30% probability ellipsoids)

and the unique central geometry of the ylide (bottom;

phenyl ring carbons, except C_i, have been omitted for

clarity; 40% probability ellipsoids). Hydrogen atoms have

been omitted for clarity in both views.

and angles. The Ru atom is in a distorted-octahedral

geometry, with the η⁶-C₆Me₆ligand occupying one face

and the Cl, allenyl, and vinyl ligands occupying the

three sites of the opposite face. Of particular significance

are the Ru-P separation, the vinyl CdC bond length,

the Ru-C(27) bond length, and the allenyl geometry.

The Ru-P separation of 2.902(2) Å is quite a bit longer

than the sum of the atomic radii of Ru and P (1.32 and

1.10 Å, respectively), indicating the absence of a bonding

interaction between Ru and P. The C(13)-C(14) bond

is slightly elongated (1.395(11) vs 1.258-1.289 Å for the

uncoordinated vinyl of DPVP) due to σ-donation to Ru

from the CdC π molecular orbital and π-back-donation

of electron density from ruthenium into the CdC π*-

stretch at 1448 cm^-1

.

Complex 6 most probably resulted from intramolecu-

lar attack of the coordinated DPVP phosphorus on C_R

(21) (a) Esteruelas, M. A.; Go´mez, A. V.; Lo´pez, A. M.; Modrego, J .;

On˜ate, E. Organometallics 1998, 17, 5434. (b) Cadierno, V.; Gamasa,

M. P.; Gimeno, J .; Lo´pez-Gonza´lez, M. C.; Borge, J .; Garc´ıa-Granda,

S. Organometallics 1997, 16, 4453.

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4749

Sch em e 4. P r op osed Mech a n ism for F or m a tion of

th e Novel Ylid e Com p lex 6

F igu r e 8. Structural drawing of the cation of [(η⁶-C₆Me₆)-

ClRuCHdC(DPVP)CMe₂NH₂]PF₆(8) showing the atom-

numbering scheme (30% probability ellipsoids). Hydrogen

atoms on C(27) and N(1) are in calculated positions and

have an arbitrary radius of 1 Å. All other hydrogen atoms

have been omitted for clarity.

equiv of aminoalkyne in refluxing CH₂Cl₂or with 4

equiv of aminoalkyne in refluxing dichloroethane gave

starting material, complex 7 (<10% yield), and the

a

Reference 9a.

ruthenacycle [(η⁶-C₆Me₆)ClRuCHdC(DPVP)CMe₂NH₂]-

PF₆(8; <10% yield), also characterized initially by an

X-ray structural determination (Figure 8). Complexes

7 and 8 have not-too-different structures (e.g., both are

cyclic complexes and both have a dangling rather than

a chelating vinylphosphine). For complex 7, the geminal

CH₂protons next to the carbene carbon are found as a

singlet at 1.25 ppm, and the gem-dimethyl protons are

found as a singlet at 1.76 ppm in the ¹H NMR spectrum.

The observance of singlets rather than separate, coupled

resonances is indicative of nitrogen inversion within the

ring that causes the diastereotopic protons to be chemi-

cal shift equivalent. Also, there is only one resonance

in the ¹³C{¹H} NMR spectrum for the gem-dimethyl

carbon atoms (15.11 ppm). The singlet resonance at 1.42

of the allenylidene intermediate postulated in reactions

of (η⁶-C₆Me₆)RuCl₂(PR₃) complexes with HCtCC(OH)-

Ph₂,^9drather than the expected intermolecular attack

by MeOH (Scheme 4). This attack is facilitated by the

ability of the vinyl group to coordinate to Ru in an η²

fashion. This coordination behavior of the vinyl group

in DPVP was previously demonstrated by Nelson and

co-workers in the bisphosphine complexes [(η⁵-C₅H₅)-

Ru(η¹-DPVP)(η³-DPVP)]PF₆and [(η⁵-C₅Me₅)-Ru(η¹-

1

2

DPVP)(η³-DPVP)]PF₆already discussed.

Rea ction w ith a n Am in oa lk yn e, 1,1-Dim eth yl-2-

p r op a r gyla m in e. We next attempted a reaction for

which we have seen no direct precedentsthat of 1a or

2a with an aminoalkyne (rather than an hydroxy-

alkyne). We anticipated the formation of a methoxy-

(aminoethyl)carbene ({Ru}dC(OCH₃)CH₂CMe₂NH₂) or,

with excess aminoalkyne behaving as a base, deproto-

nation^10b,22of a vinylidene to form an (aminoalkynyl)-

ruthenium complex ({Ru}sCtCCMe₂NH₂). Instead, we

have isolated two other complexes. Reaction of 2a with

excess dimethylpropargylamine in MeOH/CH₂Cl₂at

room temperature for 30.5 h gave less than 10% isolated

yield of the cyclic aminocarbene [(η⁶-C₆Me₆)Cl(DPVP)-

1

ppm in the H NMR spectrum was assigned to the NH

proton on the basis of integration and the fact that it is

not present in the HETCOR spectrum.

For complex 8, the CH proton attached to Ru (Ru-

CHdC) gives rise to a downfield chemical shift (9.73

ppm) that was assigned by its integration and P-H

coupling constant (24.0 Hz). Similar to complex 7, the

gem-dimethyl protons are chemical shift equivalent, and

they give rise to a singlet at 1.33 ppm. Their attached

carbon atoms are also chemical shift equivalent (30.95

ppm). The diastereotopic NH₂protons are found at 4.84

and 4.19 ppm with an H-H coupling constant of 10.5

Hz, indicating a strong Ru-N bond in solution as well

as in the solid state. One of these protons is also long-

range-coupled to phosphorus (⁴J (PH) ) 4.5 Hz). The

vinyl protons for both complexes resonate in the ex-

pected downfield region (7.3-6.2 ppm). There is a

RudCCH₂CMe₂NH)]PF₆(7), whose identity was con-

firmed by an X-ray crystal structure determination that

gave a poor data set but sufficient information to

establish bond connectivities (refer to Scheme 3 for a

structural drawing). Reaction of 1a and NaPF₆with 1

(22) Antonova, A. B.; Ioganson, A. A. Russ. Chem. Rev. (Engl.

Transl.) 1989, 58, 693 and references therein.

4750 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

Ta ble 8. Selected Bon d Dista n ces (Å) a n d An gles

(d eg) for

[(η⁶-C₆Me₆)ClRu CHdC(DP VP )CMe₂NH₂]P F ₆(8)

Distances

Ru(1)-C(27)

2.020(7)

2.402(2)

2.220(8)

1.337(10)

C(28)-C(29)

C(29)-N(1)

N(1)-Ru(1)

C(28)-P(1)

1.521(10)

1.515(9)

2.133(6)

1.789(7)

Ru(1)-Cl(1)

Ru(1)-C(arene) (av)

C(27)-C(28)

Angles

C(27)-Ru(1)-Cl(1)

C(27)-Ru(1)-N(1)

N(1)-Ru(1)-Cl(1)

84.9(2)

76.5(3)

C(27)-C(28)-C(29) 119.2(6)

P(1)-C(28)-C(29) 120.8(5)

82.59(19) C(28)-C(29)-N(1) 103.3(6)

C(29)-N(1)-Ru(1) 116.3(4)

Ru(1)-C(27)-C(28) 119.9(5)

C(27)-C(28)-P(1)

120.0(6)

Sch em e 5. P r op osed Mech a n ism for F or m a tion of

th e Ru th en a cycle 8

F igu r e 9. Structural drawing of the cation of [(η⁶-C₆Me₆)-

Cl(DPVP)Ru(CO)]PF₆(9) showing the atom-numbering

scheme (30% probability ellipsoids). Hydrogen atoms have

been omitted for clarity. Selected bond distances (Å) and

angles (deg): Ru(1)-C(27), 1.933(10); Ru(1)-P(1), 2.330(2);

Ru(1)-Cl(1), 2.382(2); Ru(1)-C(arene, average), 2.291(11);

C(27)-O(1), 1.005(10); C(27)-Ru(1)-P(1), 86.9(3); C(27)-

Ru(1)-Cl(1), 90.4(3); Cl(1)-Ru(1)-P(1), 85.45(9); Ru(1)-

C(27)-O(1), 174.2(9).

difference in the ³¹P{¹H} chemical shifts of 7 and 8 that

initially helped us determine that we indeed had

produced two different complexes, a fact that was

confirmed by the X-ray crystallographic determinations.

A view of the structure of the cation of complex 8 is

shown in Figure 8, with selected bond lengths and

angles collected in Table 8. Of note is the Ru-C(27)

bond distance (2.02(7) Å), which is on the high end of

RudC(sp²) bond lengths and on the low end of Ru-

C(sp²) bond lengths. There is a double bond between

C(27) and C(28), as evidenced by the bond distance of

1.337(10) Å and the 360° sum of angles about C(28)

(119.2(6)° + 120.8(5)° + 120.0(6)°). The rest of the

metallacyclic ring is comprised of single bonds, i.e.,

C(28)-C(29) (1.521(10) Å), C(29)-N (1.515(9) Å), and

N-Ru (2.133(6) Å). The five-membered ring shows the

typical puckered-envelope conformation with deviations

from planarity of -0.0915 (Ru), +0.1513 (N), +0.0418

(C(27)), +0.0483 (C(28)), and -0.1498° (C(29)). The

DPVP phosphorus is in a tetrahedral environment, with

the average bond angle about phosphorus being 109.5°,

and all P-C bonds show no PdC double-bond character,

making this a tetravalent phosphonium center. The

charges are balanced with Ru(II), neutral η⁶-C₆Me₆,

anionic Cl^-, anionic alkyl (C^-), neutral :N, cationic P⁺,

1.5 equiv of HCtCC(OH)Ph₂in CH₂Cl₂quickly pro-

duced a purple solution, characteristic of allenylidene

species,⁹which was stirred for 4.5 h. After this time,

the solvents were removed in vacuo, and crystallization

of the red-purple oil was attempted from CH₂Cl₂/Et₂O.

The mixture decomposed upon recrystallization at-

tempts, yielding only a very small amount (<10% yield

based upon Ru) of the triply bridged dimer [(η⁶-C₆-

4

Me₆)Ru(µ-Cl)₃Ru(η⁶-C₆Me₆)]PF₆as fine red crystals.

Apparently CH₃OH stabilizes the ylide complex 6.

Attem p t To Syn th esize a Vin ylid en e. As in the

previous synthesis, our attempt to prepare a vinylidene

from 2a and phenylacetylene in the absence of MeOH

gave an unexpected product. A solution of 2a in CH₂-

Cl₂was stirred with 1 equiv of HCtCPh for 21 days

under nitrogen and gave an orange oil, crystallization

of which gave the carbonyl complex [(η⁶-C₆Me₆)Cl-

(DPVP)Ru(CO)]PF₆(9) in 11% yield. Complex 9 showed

a ν(CtO) vibration at 2014 cm^-1in its infrared spec-

trum and a doublet at 196.49 ppm (²J (PC) ) 24.9 Hz)

in its ¹³C{¹H} NMR spectrum. All aspects of the ¹H, ¹³C-

{¹H}, and ³¹P{¹H} NMR spectra are as expected. An

X-ray structural determination showed the familiar

distorted-octahedral coordination of Ru with no unusual

interionic contacts. A view of the cation is shown in

Figure 9.

Electr och em istr y. Complexes 3-6 and 8 were also

characterized by cyclic voltammetry, and their observed

Ru(II)/Ru(III) redox couples are summarized in Table

9. In both series of methoxycarbene complexes (3a -c

and 4a -c) the PMe₃complexes are the easiest to

oxidize, as is expected, because PMe₃is a better σ-donor

than either PPh₃or DPVP. Dixneuf and co-workers

report the Ru(II)/Ru(III) couple for 4b at 1.15 V vs

SCE,^9awhich translates to 0.70 V vs Ag/AgCl and

corrected for Fc/Fc⁺(Fc ) ferrocene) at 0.49 V. Ad-

-

and anionic PF₆as counterion.

A possible mechanism for the formation of 8 is shown

in Scheme 5. η²-Alkyne coordination is followed by a

shift in electron density on the way to an η¹-vinylidene

complex. However, vinylidene formation is intercepted

by P attack on the (probably transient) carbocation,

followed by N coordination to the vacant coordination

site on Ru.

Attem p t To Syn th esize a n Allen ylid en e. An at-

tempt to prepare either an allenylidene or the ylide 6

from the reaction of 2a and HCtCC(OH)Ph₂in the

absence of MeOH gave neither. The reaction of 2a with

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4751

Ta ble 9. Electr och em ica l Da ta for Com p lexes 3-6 a n d 8^a

E_1/2(Ru(II)/Ru(III)), V

E_p,a- E_p,c, mV

[(η⁶-C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₃]PF₆(3a )

[(η⁶-C₆Me₆)Cl(PMe₃)RudC(OCH₃)CH₃]PF₆(3b)

[(η⁶-C₆Me₆)Cl(PPh₃)RudC(OCH₃)CH₃]PF₆(3c)

[(η⁶-C₆Me₆)Cl(DPVP)RudC(OCH₃)CH₂Ph]PF₆(4a )

[(η⁶-C₆Me₆)Cl(PPh₃)RudC(OCH₃)CH₂Ph]PF₆(4c)

[(η⁶-C₆Me₆)Cl(DPVP)RudC(CH₂)₃O]PF₆(5)

[(η⁶-C₆Me₆)ClRuC(dCdCPh₂)PPh₂CHdCH₂]PF₆(6)

0.91

0.83

0.96

0.93

0.98

0.96

183

141

232

189

170

134

0.98^b

0.43

92

[(η⁶-C₆Me₆)ClRuCHdC(DPVP)CMe₂NH₂]PF₆(8)

[(η⁶-C₆Me₆)Cl(PPh₃)Ru(CO)]PF₆

0.63^b

a

Conditions: measured in CH₂Cl₂solution with 0.1 M tetrabutylammonium hexafluorophosphate as supporting electrolyte; glassy

carbon working electrode; platinum-wire auxiliary electrode; Ag/AgCl reference electrode; scan rate 250 mV/s; all potentials vs Fc/Fc⁺.

b

E_p,aonly; irreversible.

ditionally, each of these cationic carbene complexes

reflects the expected decreased electron density at Ru

compared to the neutral complexes 1a -c (0.47,⁴0.32,⁸

and 0.47 V,⁸respectively; vide ante). Complex 5 shows

a redox couple very near the potentials of the methoxy-

carbene complexes and is, to the best of our knowledge,

the only five-membered oxacyclic carbene complex to be

electrochemically characterized. Also without reported

values with which to compare are complexes 6 and 8

(irreversible oxidation at 0.98 V and E_1/2) 0.43 V,

respectively). Complex 7 could not be purified enough

for electrochemical measurements, and complex 9 showed

no electrochemical events above the solvent current. The

PPh₃analogue of 9 showed only an oxidation wave (at

0.63 V) with no return reduction wave, again pointing

to the instability of PPh₃complexes seen throughout

this research (vide ante the irreversible oxidation of 2c

and the decomposition of PPh₃complexes reported

throughout this paper).⁸

Ca ta lysis. Tokunaga and Wakatsuki reported the

successful use of (η⁶-C₆H₆)RuCl₂(PR₃) (PR₃) PPh₂(C₆F₅)

and P(3-C₆H₄SO₃Na)₃) for the anti-Markovnikov hydra-

tion of terminal alkynes.²³By varying the PR₃group

and the amount of excess PR₃in the reaction mixture,

they selectively produced the desired aldehydes in fair

yields. A preliminary experiment with complex 1a ,

based upon their methods, has proven fruitful (eq 3).

Tokunaga and Wakatsuki to explain the formation of

both aldehydes and ketones.²³The presence of hexa-

methylbenzene in the organic product has two probable

origins: loss from 1a to form the catalytically active

species or loss from 1a during workup and vacuum

distillation. Tokunaga and Wakatsuki monitored the

1

loss of C₆H₆from one of their Ru species (by H NMR

spectroscopy) and postulate that the active catalytic

species in their experiments is of the type [RuCl₂{PPh₂-

(C₆F₅)}_x], for which they have independent data.²³If our

catalytically active species is similar, i.e. of the type

[RuCl₂(DPVP)_x], the presence of free η⁶-C₆Me₆in the

product would be explained. Or, independent of the

nature of the active catalytic species, if hexane washing

and chromatography during workup did not fully re-

move all the Ru-containing material, η⁶-C₆Me₆could

have been liberated from this material along with (or

after) acetophenone as a product of the heat-induced

decomposition of complex 1a . Either route could also

have led to the unidentified compound seen in the GC/

MS spectrum at m/z 194.

Characterization of the inorganic species produced,

optimization of reaction conditions, and reactions with

other alkynes are in progress.

Su m m a r y

Two new η⁶-C₆Me₆-phosphine-Ru-CH₃CN com-

plexes (2b,c) were synthesized and characterized, and

their reactions with terminal alkynes were investigated.

It was found that reactions of the neutral complexes (η⁶-

C₆Me₆)RuCl₂(PR₃) (1) with terminal alkynes in the

presence of NaPF₆and MeOH to form methoxycarbene

complexes generally proceed more rapidly, with fewer

side products, than do reactions of the cationic com-

plexes [(η⁶-C₆Me₆)Cl(PR₃)Ru(NCCH₃)]PF₆(2) with ter-

minal alkynes in MeOH. The dynamic behavior of two

series of methoxyalkylcarbene complexes (3 and 4) was

investigated by NOE and VT NMR experiments, and

the data are explained by invoking both steric and

electronic arguments.

Phenylacetylene was heated at reflux in 95% EtOH in

the presence of 2.5 mol % of 1a for 17 h. GC/MS and H

1

NMR spectroscopy of the extracted organic product

showed the presence of acetophenone (81.4%), hexa-

methylbenzene (15.7%), and an as yet unidentified

substance (2.9%), but no phenylacetaldehyde. Acetophe-

none was isolated in 70% yield based upon phenylacety-

lene. The inorganic fraction has yet to be fully charac-

terized, but it does show several infrared absorption

bands in the M-CO region (1967-2073 cm^-1). This

could indicate a mechanism similar to that proposed by

In all, 12 previously unreported complexes of ruthe-

nium have been synthesized and characterized, includ-

ing the novel complexes of a phosphorus ylide (6), a

cyclic aminocarbene (7), and a nitrogen-containing ru-

thenacycle (8). (η⁶-C₆Me₆)RuCl₂(DPVP) was shown to

catalytically hydrate phenylacetylene to give acetophe-

none with no evidence for phenylacetaldehyde produc-

tion.

(23) Tokunaga, M.; Wakatsuki, Y. Angew. Chem., Int. Ed. Engl.

1998, 37, 2867.

4752 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

orange solution of the appropriate acetonitrile complex (2a -

c; 0.25 g, ∼0.45 mmol) in 1:1 MeOH/CH₂Cl₂(10 mL) was added

a 2-fold excess of (trimethylsilyl)acetylene (HCtCSiMe₃) and

the mixture was stirred for 43-49 h. The solvents were

removed in vacuo, and the resulting yellow to orange powders

were crystallized from CH₂Cl₂/Et₂O.

P R₃) DP VP (3a ). Reaction time: 49 h. Yield: 0.23 g (90%).

Mp: 188-191 °C. Anal. Calcd for C₂₉H₃₇ClF₆OP₂Ru: C, 48.78;

H, 5.22; Cl, 4.96. Found: C, 48.60; H, 5.17; Cl, 4.81.

Exp er im en ta l Section

Gen er a l Com m en ts. All reactions were carried out under

a nitrogen atmosphere, and workups were performed without

precaution to exclude air. The complexes (η⁶-C₆Me₆)Cl₂Ru(PR₃)

(PR₃) diphenylvinylphosphine (DPVP) (1a ),⁴PMe₃(1b),⁵PPh₃

(1c)⁶) and [(η⁶-C₆Me₆)Cl(DPVP)Ru(NCCH₃)]PF₆(2a )³were

prepared by literature methods. (Trimethylsilyl)acetylene was

purchased from Lancaster, phenylacetylene, 3-butyn-1-ol, and

1,1-dimethylpropargylamine were purchased from Aldrich, and

1,1-diphenyl-3-propyn-1-ol was purchased from GFS Chemi-

cals. Acetonitrile was distilled from CaH₂prior to use. NMR

spectra were recorded on a Varian Unity Plus-500 FT NMR

spectrometer operating at 500 MHz for ¹H, 125 MHz for ¹³C,

and 202 MHz for ³¹P. Proton and carbon chemical shifts were

referenced to residual solvent resonances; phosphorus chemical

shifts were referenced to an external 85% aqueous solution of

H₃PO₄. All shifts to low field, high frequency are positive. NOE

experiments were performed with the pulse sequence reported

by Shaka and co-workers.²⁴FT-IR spectra were recorded on a

Perkin-Elmer Spectrum BX spectrometer in CH₂Cl₂solution

on NaCl windows or as Nujol mulls on CsI windows (abbrevia-

tions: shp ) sharp, st ) strong, m ) medium, w ) weak, br

) broad). Cyclic voltammograms were recorded at 25 °C in

freshly distilled CH₂Cl₂containing 0.1 M tetrabutylammonium

hexafluorophosphate using a BAS CV50-W voltammetric

analyzer. A three-electrode system was used. The working

electrode was glassy carbon, the auxiliary electrode was a

platinum wire, and the reference electrode was Ag/AgCl

(aqueous) separated from the cell by a Luggin capillary. The

Fc/Fc⁺couple occurred at 490 mV²⁵under the same conditions.

Melting points were determined on a Mel-Temp apparatus and

are uncorrected. Elemental analyses were performed by Gal-

braith Laboratories, Knoxville, TN.

¹H NMR (499.84 MHz, CD₃NO₂): δ 7.58-7.47 (m, 10H, Ph),

2

3

6.63 (ddd, J (PH) ) 24.4 Hz, J (H_aH_b) ) 18.3 Hz, J (H_aH_c) )

3

12.4 Hz, 1H, H_a), 6.22 (dd, J (PH) ) 38.5 Hz, J (H_aH_c) ) 12.4

Hz, 1H, H_c), 5.48 (ddd, ³J (PH) ) 19.2 Hz, ³J (H_aH_b) ) 18.3 Hz,

²J (H_bH_c) ) 0.8 Hz, 1H, H_b), 4.38 (s, 3H, OCH₃), 2.87 (s, 3H,

CH₃), 1.99 (s, 18H, η⁶-C₆Me₆). ¹³C{¹H} NMR (125.71 MHz, CD₃-

NO₂): δ 327.99 (d, ²J (PC) ) 19.9 Hz, RudC), 134.22 (d, ²J (PC)

2

) 10.1 Hz, C_o), 133.40 (d, J (PC) ) 9.2 Hz, C_o), 131.25 (s, C_p),

1

130.98 (br s, C_â), 130.83 (s, C_p), 130.77 (d, J (PC) ) 51.8 Hz,

1

C_R), 130.77 (d, J (PC) ) 51.8 Hz, C_i), 129.04 (d, J (PC) ) 48.8

3

Hz, C_i), 128.49 (d, J (PC) ) 10.4 Hz, C_m), 128.28 (d, J (PC) )

10.2 Hz, C_m), 107.38 (d, J (PC) ) 2.4 Hz, η⁶-C₆Me₆), 66.38

(s, OCH₃), 39.05 (s, CH₃), 14.91 (s, η⁶-C₆Me₆). ³¹P{¹H} NMR

(202.35 MHz, CD₃NO₂): δ 31.31 (s, DPVP), -145.00 (sept,

¹J (PF) ) 707.8 Hz, PF₆).

P R₃) P Me₃(3b). Reaction time: 43 h. Yield: 0.39 g

(100%). Characterization data have been reported.^9a

P R₃) P P h ₃(3c). Reaction time: 4.5 days. Yield: e10%

after recrystallization. (There was enough formed to confirm

formation of 3c by NMR spectroscopy, but it was always

contaminated with [(η⁶-C₆Me₆)₂Ru₂Cl₃]PF₆,⁴and impure solu-

tions slowly decomposed in all solvents.) Complex 3c was also

formed by reaction of 1c (0.464 g, 0.778 mmol) and NaPF₆

(0.134 g, 0.800 mmol) with HCtCSiMe₃(0.58 mL, 4.1 mmol)

in MeOH/CH₂Cl₂(1:1, 40 mL) for 24 h. Complex 3c was

isolated as yellow crystals after filtration (to remove NaCl) and

crystallization from acetone/Et₂O in 35.9% yield (0.213 g).

(There was no evidence for formation of the triply chloride

bridged dimer in this preparation.) Anal. Calcd for C₃₃H₃₉ClF₆-

OP₂Ru: C, 51.87; H, 5.14; Cl, 4.64. Found: C, 51.69; H, 5.03;

Syn th esis of th e Aceton itr ile Com p lexes [(η⁶-C₆Me₆)-

Cl(P R₃)Ru (NCCH₃)]P F ₆(2b,c). P R₃) P Me₃(2b). To a red

solution of (η⁶-C₆Me₆)Cl₂Ru(PMe₃) (1b; 0.407 g, 0.991 mmol)

in 10 mL of CH₂Cl₂was added 50 mL of CH₃CN and a solution

of NaPF₆(0.168 g, 0.997 mmol) in 10 mL of CH₃CN. The

reaction mixture became cloudy within a few minutes. The

mixture was stirred for 12 h and then gravity-filtered to

remove NaCl. The solvents were removed in vacuo to give 2b

as a yellow powder in 86.5% yield (0.481 g); mp 195 °C. Anal.

Calcd for C₁₇H₃₀ClF₆NP₂Ru: C, 36.39; H, 5.39; Cl, 6.32.

Found: C, 36.20; H, 5.17; Cl, 6.38. IR (cm^-1; Nujol): 2293 w

ν(CtN), 843, 559 st ν(PF). ¹H NMR (499.84 MHz, acetone-

d₆): δ 2.68 (d, ⁵J (PH) ) 1.5 Hz, 3H, CH₃CN), 2.18 (d, J (PH) )

1.0 Hz, 18H, η⁶-C₆Me₆), 1.57 (d, ²J (PH) ) 11.0 Hz, 9H, PMe₃).

¹³C{¹H} NMR (125.70 MHz, acetone-d₆): δ 126.99 (s, CH₃CN),

100.17 (d, J (PC) ) 2.6 Hz, η⁶-C₆Me₆), 16.21 (s, η⁶-C₆Me₆), 14.98

1

Cl, 4.52. H NMR (499.84 MHz, acetone-d₆): δ 7.6-7.4 (br m,

15H, Ph), 4.18 (s, 3H, OCH₃), 2.91 (d, ⁴J (PH) ) 1.0 Hz, 3H,

CH₃), 1.93 (d, J (PH) ) 1.0 Hz, 18H, η⁶-C₆Me₆). ¹³C{¹H} NMR

(125.71 MHz, acetone-d₆): δ 331.00 (d, ²J (PC) ) 19.6 Hz, Rud

3

C), 134.86 (br s, C_o), 131.92 (br s, C_p), 129.51 (d, J (PC) ) 9.2

Hz, C_m), 108.60 (d, J (PC) ) 2.4 Hz, η⁶-C₆Me₆), 67.19 (s, OCH₃),

(d, J (PC) ) 33.6 Hz, PMe₃), 3.83 (s, CH₃CN). ³¹P{¹H} NMR

1

3

40.87 (d, J (PC) ) 1.3 Hz, CH₃), 15.89 (s, η⁶-C₆Me₆). ³¹P{¹H}

(202.34 MHz, acetone-d₆): δ 4.84 (s, PMe₃), -145.00 (sept,

NMR (202.33 MHz, acetone-d₆): δ 38.14 (s, PPh₃), -145.00

¹J (PF) ) 707.8 Hz, PF₆).

1

(sept, J (PF) ) 708.0 Hz, PF₆).

P R₃) P P h ₃(2c). Similarly, 2c was prepared from 1c in

27.6% yield (0.185 g), mp 180 °C dec. Anal. Calcd for C₃₂H₃₆

Syn th esis of th e Meth oxyben zylca r ben e Com p lexes

[(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₂P h ]P F ₆(4a -c). These

complexes were prepared in the same manner as complexes

3a -c using phenylacetylene, HCtCPh, in place of (trimeth-

ylsilyl)acetylene.

-

ClF₆NP₂Ru: C, 51.43; H, 4.86; Cl, 4.74. Found: C, 51.19; H,

5.01; Cl, 4.63. IR (cm^-1; Nujol): 2297 w ν(CtN), 841 st ν(PF).

¹H NMR (499.84 MHz, acetone-d₆): δ 7.68-7.64 (m, 6H, Ph

5

H_o), 7.59-7.51 (m, 9H, Ph H_m, Ph H_p), 2.22 (d, J (PH) ) 1.5

P R₃) DP VP (4a ). Reaction time: 24 h. Yield: 0.18 g (78%).

Complex 4a was also prepared from 1a , NaPF₆, and HCtCPh

in 51% yield as described above for 3c. Mp: 130 °C dec. Anal.

Calcd for C₃₅H₄₁ClF₆OP₂Ru: C, 53.20; H, 5.23; Cl, 4.49.

Found: C, 53.04; H, 5.31; Cl, 4.57.

Hz, 3H, CH₃CN), 1.91 (d, J (PH) ) 1.0 Hz, 18H, η⁶-C₆Me₆). ¹³C-

{¹H} NMR (125.70 MHz, acetone-d₆): δ 135.54 (d, ²J (PC) )

4

3

9.7 Hz, C_o), 132.01 (d, J (PC) ) 2.3 Hz, C_p), 129.48 (d, J (PC)

) 10.2 Hz, C_m), 128.70 (s, CH₃CN), 101.64 (d, J (PC) ) 2.6 Hz,

η⁶-C₆Me₆), 15.65 (s, η⁶-C₆Me₆), 3.67 (s, CH₃CN). ³¹P{¹H} NMR

(202.33 MHz, acetone-d₆): δ 33.84 (s, PPh₃), -145.00 (sept,

¹J (PF) ) 707.8 Hz, PF₆).

Syn th esis of th e Meth oxym eth ylca r ben e Com p lexes

[(η⁶-C₆Me₆)Cl(P R₃)Ru dC(OCH₃)CH₃]P F ₆(3a -c). To a red-

(24) Stott, K.; Stonehouse, J .; Keeler, J .; Hwang, T.-L.; Shaka, A.

J . J . J . Am. Chem. Soc. 1995, 117, 4199.

(25) Gagne´, R. R.; Koval, C. A.; Lisensky, G. C. Inorg. Chem. 1980,

19, 2854.

¹H NMR (499.84 MHz, CDCl₃): δ 7.15-7.63 (m, 15H, Ph), 6.87

2

3

(ddd, J (PH) ) 23.0 Hz, J (H_aH_b) ) 18.0 Hz, J (H_aH_c) ) 12.3

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4753

3

Hz, 1H, H_a), 6.19 (dd, J (PH) ) 40.0 Hz, J (H_aH_c) ) 12.3 Hz,

Hz, 1H, H_R), 4.90 (apparent q, ²J (H_RH_R′) ) ³J (H_R′H_â) )

3

2

1H, H_c), 5.39 (dd, J (PH) ) 19.5 Hz, J (H_aH_b) ) 18.0 Hz, 1H,

H_b), 5.07 (d, ²J (H_a′H_b′) ) 12.5 Hz, 1H, H_a′), 4.50 (s, 3H, OCH₃),

3.23 (d, ²J (H_a′H_b′) ) 12.5 Hz, 1H, H_b′), 1.80 (s, 18H, η⁶-C₆Me₆).

¹³C{¹H} NMR (125.71 MHz, CDCl₃): δ 314.54 (²J (PC) ) 14.5

Hz, RudC), 134.97 (d, ²J (PC) ) 10.3 Hz, C_oDPVP), 132.61 (d,

²J (PC) ) 8.8 Hz, C_oDPVP), 132.14 (d, ⁴J (PC) ) 2.3 Hz, C_p

³J (H_R′H_â′) ) 8.0 Hz, 1H, H_R′), 3.17 (ABXYZ, J (H_γH_γ′) ) 21.5

3

4

3

Hz, J (H_γH_â′) ) 9.0 Hz, J (PH) ) 9.0 Hz, J (H_γH_â) ) 5.5 Hz,

2

4

1H, H_γ), 3.07 (ABXYZ, J (H_γH_γ′) ) 21.5 Hz, J (PH) ) 9.0 Hz,

³J (H_γ′H_â) ) 8.5 Hz, J (H_γ′H_â′) ) 7.0 Hz, 1H, H_γ′), 2.01 (m, 1H,

3

H_â), 1.90 (s, 18H, η⁶-C₆Me₆), 1.53 (m, 1H, H_â′). ¹³C{¹H} NMR

2

(125.71 MHz, CDCl₃): δ 313.28 (d, J (PC) ) 19.6 Hz, RudC),

4

2

DPVP), 131.56 (C_iPh), 131.34 (s, C_â), 131.09 (d, J (PC) ) 2.1

134.15 (d, J (PC) ) 10.2 Hz, C_o), 132.97 (d, J (PC) ) 9.4 Hz,

1

4

Hz, C_pDPVP), 131.27 (d, J (PC) ) 72.9 Hz, C_R), 130.13 (s, C_o

C_o), 131.59 (d, J (PC) ) 2.5 Hz, C_p), 131.22 (br s, C_â), 131.07

Ph), 128.90 (s, C_mPh), 128.86 (d, ³J (PC) ) 10.6 Hz, C_mDPVP),

128.63 (d, ³J (PC) ) 10.3 Hz, C_mDPVP), 127.55 (s, C_pPh),

(d, ⁴J (PC) ) 2.3 Hz, C_p), 130.51 (d, ¹J (PC) ) 47.9 Hz, C_R),

1

3

130.23 (d, J (PC) ) 45.6 Hz, C_i), 128.62 (d, J (PC) ) 10.4 Hz,

C_m), 128.47 (d, ³J (PC) ) 10.3 Hz, C_m), 128.00 (d, ¹J (PC) ) 49.8

Hz, C_i), 107.36 (d, J (PC) ) 2.1 Hz, η⁶-C₆Me₆), 88.46 (s, C_R′),

55.75 (s, C_γ′), 22.02 (s, C_â′), 15.72 (s, η⁶-C₆Me₆). ³¹P{¹H} NMR

(202.33 MHz, CDCl₃): δ 34.32 (s, DPVP), -145.01 (sept, ¹J (PF)

) 712.2 Hz, PF₆).

127.00 (d, J (PC) ) 51.3 Hz, C_iDPVP), 109.64 (s, η⁶-C₆Me₆),

1

67.91 (s, OCH₃), 54.43 (s, CH₂), 15.91 (s, η⁶-C₆Me₆). ³¹P{¹H}

NMR (202.33 MHz, CDCl₃): δ 27.95 (s, DPVP), -144.96 (sept,

¹J (PF) ) 712.6 Hz, PF₆).

P R₃) P Me₃(4b). Reaction time: 93 h. Yield: e10%.

Formation was confirmed by comparison with reported^9aNMR

spectral data. The crude mixture decomposed to give green

solutions of [(η⁶-C₆Me₆)Cl(PMe₃)Ru(CO)]PF₆(vide infra) and

free η⁶-C₆Me₆upon crystallization attempts. Full characteriza-

tion data have been reported.^9a

Syn th esis of th e Novel Ylid e [(η⁶-C₆Me₆)ClRu C(dCd

CP h ₂)P P h ₂CHdCH₂]P F ₆(6). Meth od A. Complex 6 was

prepared from 0.201 g (0.368 mmol) of 1a , 0.061 g (0.366 mmol)

of NaPF₆, and 0.381 g (1.83 mmol) of 1,1-diphenylprop-3-yn-

1-ol, HCtCC(OH)Ph₂, in 40 mL of MeOH/CH₂Cl₂(1:1, v/v).

The red-orange solution quickly became dark red, nearly black.

The reaction mixture was stirred for 24 h. Reduction of the

solvent volume on a rotary evaporator and addition of Et₂O

precipitated starting material 1a as an orange powder, which

was collected by gravity filtration. Solvent removal from the

filtrate gave a purple oil that afforded more 1a upon repeated

crystallizations from CH₂Cl₂/Et₂O. Finally, red crystals (0.048

g, 16%) of 6 were obtained from CH₂Cl₂/Et₂O.

Meth od B. To a solution of 0.200 g (0.288 mmol) of 2a in

10 mL of MeOH/CH₂Cl₂(1:1, v/v) was added 0.067 g (0.322

mmol) of HCtCC(OH)Ph₂. The mixture was stirred for 25.5

h, after which time the solvents were removed in vacuo. The

residue was washed with Et₂O and crystallized from CH₂Cl₂/

Et₂O with recovery of starting material (2a ) and decomposition

predominant. Final yield: 0.028 g (24.3%). Mp: 202 °C dec.

Anal. Calcd for C₄₁H₄₁ClF₆P₂Ru: C, 58.19; H, 4.88; Cl, 4.19.

Found: C, 58.27; H, 4.69; Cl, 4.03. IR (cm^-1; CDCl₃): 1976 br,

w ν(CdCdC), 1448 m ν(CHdCH₂), 846, 548 st ν(PF).

P R₃) P P h ₃(4c). Reaction time: 11 days. Yield: e10%.

Formation was confirmed by comparison with reported^9aNMR

spectral data. The crude mixture decomposed to give green

solutions of [(η⁶-C₆Me₆)Cl(PPh₃)Ru(CO)]PF₆(vide infra) upon

crystallization attempts. Full characterization data have been

reported.^9a

Ch ar acter ization Data for [(η⁶-C₆Me₆)Cl(P Me₃)Ru (CO)]-

P F ₆. ¹H NMR (499.84 MHz, acetone-d₆): δ 2.61 (s, 18H, η⁶-

C₆Me₆), 2.21 (d, J (PH) ) 12.0 Hz, 9H, PMe₃). ¹³C{¹H} NMR

2

(125.71 MHz, acetone-d₆): δ 196.64 (d, ²J (PC) ) 24.6 Hz, Ru-

CO), 113.38 (d, J (PC) ) 2.4 Hz, η⁶-C₆Me₆), 16.92 (s, η⁶-C₆Me₆),

16.23 (d, ¹J (PC) ) 38.1 Hz, PMe₃). ³¹P{¹H} NMR (202.33 MHz,

1

acetone-d₆): δ 18.68 (s, PMe₃), -139.38 (sept, J (PF) ) 708.8

Hz, PF₆).

Ch a r a cter iza tion Da ta for [(η⁶-C₆Me₆)Cl(P P h ₃)Ru (CO)]-

P F ₆. Mp: 188 °C dec. IR (cm^-1; CH₂Cl₂): 2012 st, sh ν(CO).

¹H NMR (499.84 MHz, acetone-d₆): δ 7.66-7.55 (m, 15H, Ph),

2.12 (d, J (PH) ) 1.0 Hz, 18H, η⁶-C₆Me₆). ¹³C{¹H} NMR (125.71

MHz, acetone-d₆): δ 198.30 (d, ²J (PC) ) 25.5 Hz, Ru-CO),

2

4

134.92 (d, J (PC) ) 10.1 Hz, C_o), 133.06 (d, J (PC) ) 2.0 Hz,

3

C_p), 130.10 (d, J (PC) ) 10.8 Hz, C_m), 115.33 (d, J (PC) ) 2.1

Hz, η⁶-C₆Me₆), 16.58 (s, η⁶-C₆Me₆). ³¹P{¹H} NMR (202.33 MHz,

1

acetone-d₆): δ 40.47 (s, PPh₃), -145.00 (sept, J (PF) ) 707.6

Hz, PF₆).

Syn th esis of [(η⁶-C₆Me₆)Cl(DP VP )Ru dC(CH₂)₃O]P F ₆

(5). To a solution of 0.200 g (0.366 mmol) of 1a and 0.069 g

(0.369 mmol) of NaPF₆in 40 mL of MeOH/CH₂Cl₂(1:1, v/v)

was added 0.14 mL (1.9 mmol) of 3-butyn-1-ol, HCtCCH₂CH₂-

OH. After 24 h, the solvents were removed in vacuo. Filtration

of a CH₂Cl₂solution of the product removed NaCl, and

crystallization from CH₂Cl₂/Et₂O gave 0.189 g (71%) of 5 as a

yellow powder. Mp: 161-179 °C. Anal. Calcd for C₃₀H₃₇ClF₆-

OP₂Ru: C, 49.63; H, 5.14; Cl, 4.88. Found: C, 49.50; H, 4.89;

Cl, 4.63.

¹H NMR (499.84 MHz, CDCl₃): δ 7.89-7.05 (m, 20H, Ph), 4.06

(ddd, ³J (PH) ) 19.7 Hz, ³J (H_aH_b) ) 12.2 Hz, ²J (H_bH_c) ) 1.6

3

Hz, 1H, H_b), 3.81 (ddd, J (PH) ) 29.4 Hz, J (H_aH_c) ) 9.6 Hz,

²J (H_bH_c) ) 1.6 Hz, 1H, H_c), 3.69 (ddd, ²J (PH) ) 19.6 Hz,

3

³J (H_aH_b) ) 12.2 Hz, J (H_aH_c) ) 9.6 Hz, 1H, H_a), 1.95 (s, 18H,

η⁶-C₆Me₆). ¹³C{¹H} NMR (125.71 MHz, CDCl₃): δ 204.94 (d,

4

²J (PC) ) 1.8 Hz, C₂), 134.72 (d, J (PC) ) 2.6 Hz, C_pDPVP),

134.13 (d, ⁴J (PC) ) 2.8 Hz, C_pDPVP), 132.66 (d, ²J (PC) ) 11.8

Hz, C_oDPVP), 130.86 (d, ³J (PC) ) 10.2 Hz, C_mDPVP), 130.56

3

2

(d, J (PC) ) 11.7 Hz, C_mDPVP), 129.15 (d, J (PC) ) 12.6 Hz,

C_oDPVP), 128.96 (s, C_oPh), 128.71 (s, C_oPh), 128.71 (s, C_m

Ph), 128.64 (s, C_pPh), 128.45 (s, C_mPh), 128.42 (s, C_pPh),

128.32 (s, C_iPh), 127.78 (s, C_iPh), 125.57 (d, ¹J (PC) ) 64.1

1

Hz, C_iDPVP), 121.43 (d, J (PC) ) 68.5 Hz, C_iDPVP), 111.70

3

(d, J (PC) ) 20.4 Hz, C₃), 108.92 (s, η⁶-C₆Me₆), 89.92 (s, C₁),

66.58 (s, C_â), 28.35 (d, ¹J (PC) ) 88.1 Hz, C_R), 15.46 (s,

η⁶-C₆Me₆). ³¹P{¹H} NMR (202.33 MHz, CDCl₃): δ 36.58 (s,

1

DPVP), -145.01 (sept, J (PF) ) 712.7 Hz, PF₆).

¹H NMR (499.84 MHz, CDCl₃): δ 7.42-7.54 (m, 10H, Ph), 6.63

Rea ction s w ith 1,1-Dim eth ylp r op a r gyla m in e, HCtCC-

(CH₃)₂NH₂. Meth od A. To a solution of 0.380 g (0.544 mmol)

of 2a in 18 mL (1:1, v/v) of MeOH/CH₂Cl₂was added 0.4 mL

(3.8 mmol) of HCtCC(CH₃)₂NH₂. The solution gradually

changed color from orange to a deep red-black over the 30.5 h

2

3

(ddd, J (PH) ) 22.0 Hz, J (H_aH_b) ) 18.2 Hz, J (H_aH_c) ) 12.2

3

Hz, 1H, H_a), 6.11 (dd, J (PH) ) 39.7 Hz, J (H_aH_c) ) 12.2 Hz,

3

1H, H_c), 5.41 (dd, J (PH) ) 19.5 Hz, J (H_aH_b) ) 18.2 Hz, 1H,

H_b), 5.20 (apparent q, J (H_RH_R′) ) ³J (H_RH_â) ) ³J (H_RH_â′) ) 8.0

2

4754 Organometallics, Vol. 19, No. 23, 2000

Hansen and Nelson

reaction time. The solvents were removed in vacuo, giving an

oily red material and a white solid. The red material was

dissolved in MeOH/CH₂Cl₂, and this solution was filtered to

remove the white solid; Et₂O was added to the filtrate to

crystallize the product(s). (The white solid was not character-

ized.) Repeated crystallizations gave brown to black oils from

which a small amount of the cyclic carbene complex 7 was

isolated. The ¹H NMR spectra consistently evidenced the

presence of starting material (2a ) in varying amounts. This

prompted us to try the next two methods to increase the

amount of 2a that reacted.

24.0 Hz, ³J (H_aH_b) ) 18.0 Hz, ³J (H_aH_c) ) 12.5 Hz, 1H, H_a), 6.90

3

(dd, J (PH) ) 46.5 Hz, J (H_aH_c) ) 12.5 Hz, 1H, H_c), 6.29 (dd,

³J (PH) ) 23.0 Hz, ³J (H_aH_b) ) 18.0 Hz, 1H, H_b), 4.84 (dd,

⁴J (PH) ) 4.5 Hz, ²J (HH) ) 10.5 Hz, 1H, NH₂), 4.19 (d, ²J (HH)

) 10.5 Hz, 1H, NH₂), 2.06 (s, 18H, η⁶-C₆Me₆), 1.33 (s, 6H,

CMe₂). ¹³C{¹H} NMR (125.71 MHz, acetone-d₆): δ 217.74 (d,

²J (PC) ) 7.0 Hz, Ru-C), 143.34 (s, C_â), 135.59 (d, ⁴J (PC) )

4

2

2.9 Hz, C_p), 135.48 (d, J (PC) ) 2.9 Hz, C_p), 135.27 (d, J (PC)

) 9.7 Hz, C_o), 135.12 (d, ²J (PC) ) 10.4 Hz, C_o), 130.94 (d,

³J (PC) ) 12.7 Hz, C_m), 130.84 (d, ³J (PC) ) 12.8 Hz, C_m), 121.77

(d, ¹J (PC) ) 77.1 Hz, C_R), 121.76 (d, ¹J (PC) ) 111.0 Hz, C_i),

1

121.12 (d, J (PC) ) 86.4 Hz, C_i), 95.43 (s, η⁶-C₆Me₆), 68.68 (d,

Meth od B. Dimethylpropargylamine (0.06 mL, 0.51 mmol)

was passed through a filter pipet containing Na₂CO₃(to

remove H₂O) directly into a solution of 0.251 g (0.460 mmol)

of 1a in 15 mL of CH₂Cl₂. To this solution was added 0.076 g

(0.453 mmol) of NaPF₆and 5 mL of CH₂Cl₂. When they were

heated to reflux, all components were taken into solution, and

the red color darkened. The mixture was refluxed for 42.5 h,

and then the solvents were removed in vacuo to give a brown

oil that was dissolved in CH₂Cl₂and filtered (nothing was

visually removed). The solvent volume was reduced to 2 mL

in vacuo, and Et₂O was added to precipitate an orange powder

(identified by ¹H NMR spectroscopy to be 1a ) and a brown oil.

Repeated precipitations gave 0.047 g of recovered 1a (18.7%).

Continued crystallizations gave a small amount of yellow

crystalline 7 and a small amount of red-brown crystalline 8,

²J (PC) ) 30.2 Hz, CMe₂), 30.95 (s, CMe₂), 16.06 (s, η⁶-C₆Me₆).

³¹P{¹H} NMR (202.33 MHz, acetone-d₆): δ 7.10 (s, DPVP),

1

-145.00 (sept, J (PF) ) 706.6 Hz, PF₆).

Rea ction of 2a a n d HCtCC(OH)P h ₂in th e Absen ce of

MeOH. To an orange solution of 2a (0.319 g, 0.457 mmol) in

10 mL of CH₂Cl₂was added 0.1 g (0.480 mmol) of HCtCC-

(OH)Ph₂. The color changed from orange to purple within

minutes. After 4.5 h the solvents were removed in vacuo to

yield a purple-red oil. Attempted crystallizations from CH₂-

Cl₂and Et₂O gave a small amount of crystalline [(η⁶-C₆Me₆)₂-

Ru₂Cl₃]PF₆(which was identified by an X-ray crystallographic

unit cell determination and ¹H NMR spectroscopy⁴) and

decomposition of the remainder of the material present.

Rea ction of 2a a n d HCtCP h in th e Absen ce of MeOH.

A solution of 0.307 g (0.440 mmol) of 2a in 10 mL of CH₂Cl₂

was stirred with 0.05 mL (0.455 mmol) of HCtCPh for 21 days,

by which time the CH₂Cl₂had evaporated. The orange oil was

dissolved in a minimum volume of CH₂Cl₂, washed with

hexane, and crystallized from CH₂Cl₂/Et₂O. The carbonyl

complex [(η⁶-C₆Me₆)Cl(DPVP)Ru(CO)]PF₆(9) was thus ob-

tained in 11.4% yield (0.034 g) as yellow crystals from an

otherwise decomposition-laden mixture.

1

as evidenced by H NMR spectroscopy.

Meth od C. To an orange suspension of 0.296 g (0.541 mmol)

of 1a in 40 mL of 1,2-dichloroethane was added 0.24 mL (2.3

mmol) of HCtCC(CH₃)₂NH₂and 0.100 g (0.595 mmol) of

NaPF₆. Again, all components were taken into solution upon

heating to reflux, and the color of the mixture changed from

orange to red to brown. The reaction was monitored by ¹H

NMR spectroscopy, which showed the continued presence of

1a , 7, and 8 after 56 h of reflux. At this time, 15 mL of absolute

EtOH was added in an attempt to make the reaction medium

more polar. The mixture was refluxed for another 14 h, at

which time the ¹H NMR spectrum of an aliquot showed the

same ratios of 1a , 7, and 8 as before. The reaction mixture

was cooled to room temperature and subjected to column

chromatography (2 × 5 cm²) on silica (200-400 mesh, Natland

Int. Corp.) with eluting solvents CH₂Cl₂, acetone, and MeOH,

sequentially. ¹H NMR spectroscopy showed that the eluted

products contained 1a (CH₂Cl₂), 1a and 7 (CH₂Cl₂and 1:1 CH₂-

Cl₂/acetone), and 1a and 8 (acetone). Crystallizations of these

fractions from CH₂Cl₂/hexane and acetone/Et₂O gave 1a , 7,

and 0.02 g (0.03 mmol) of mostly pure 8 as yellow-orange

crystals from which NMR spectral data were obtained.

Neither 7 nor 8 were obtained pure enough, in large enough

quantities, to allow for elemental analyses. All NMR spectro-

scopic data showed traces to large amounts of starting materi-

als and generally mixtures of 7 and 8.

Complex 9 was also obtained by bubbling CO(g) through

an acetone solution (20 mL) of 2a (0.222 g, 0.319 mmol) for 4

h, followed by removal of solvents in vacuo. Yield: 0.190 g

(86.9%). Mp: 192-201 °C. Anal. Calcd for C₂₇H₃₁ClF₆OP₂Ru:

C, 47.41; H, 4.57; Cl, 5.19. Found: C, 47.29; H, 4.36; Cl, 5.02.

IR (cm^-1; CH₂Cl₂): 2014 sh, st ν(CO). IR (cm^-1; Nujol): 814,

1

557 st ν(PF). H NMR (499.84 MHz, CDCl₃): δ 7.47-7.63 (m,

10H, Ph), 6.71 (ddd, ²J (PH) ) 25.2 Hz, ³J (H_aH_b) ) 17.9 Hz,

³J (H_aH_c) ) 12.0 Hz, 1H, H_a), 6.14 (dd, ³J (PH) ) 42.5 Hz,

³J (H_aH_c) ) 12.0 Hz, 1H, H_c), 5.41 (dd, ³J (PH) ) 21.5 Hz,

³J (H_aH_b) ) 17.9 Hz, 1H, H_b), 2.00 (s, 18H, η⁶-C₆Me₆). ¹³C{¹H}

NMR (125.70 MHz, CDCl₃): δ 196.49 (d, ²J (PC) ) 24.9 Hz,

2

Ru-CO), 133.72 (d, J (PC) ) 9.9 Hz, C_o), 133.34 (d, J (PC) )

9.9 Hz, C_o), 132.65 (d, ⁴J (PC) ) 2.4 Hz, C_p), 132.56 (s, C_â),

132.23 (d, J (PC) ) 2.8 Hz, C_p), 130.16 (d, J (PC) ) 53.0 Hz,

C_R), 129.38 (d, ³J (PC) ) 10.8 Hz, C_m), 129.07 (d, ³J (PC) ) 10.8

Hz, C_m), 126.18 (d, J (PC) ) 55.6 Hz, C_i), 126.77 (d, J (PC) )

54.9 Hz, C_i), 113.57 (d, J (PC) ) 1.9 Hz, η⁶-C₆Me₆), 16.20 (s,

η⁶-C₆Me₆). ³¹P{¹H} NMR (202.33 MHz, CDCl₃): δ 34.41 (s,

4

1

[(η⁶-C₆Me₆)Cl(DP VP )R u dCCH ₂CMe₂NH )]P F ₆(7). ¹H

NMR (499.84 MHz, CDCl₃): δ 7.71-7.67 (m, 4H, H_oPh), 7.54-

1

DPVP), -145.00 (sept, J (PF) ) 712.4 Hz, PF₆).

Ca ta lysis. Phenylacetylene (2 mL, 18 mmol) was added to

a suspension of 1a (0.250 g, 0.457 mmol) in 10 mL of 95%

EtOH. Upon heating, all components were taken into solution,

and the color darkened. After a 17 h reflux, the solution was

cooled to room temperature and the solvents were removed in

vacuo to give a red oil. The oil was washed several times with

hexane, and the yellow washings were passed through a flash

column packed with Celite and silica, with most of the red

inorganic material being left on the Celite. The inorganic

fraction was then washed from the column with CH₂Cl₂and

MeOH. Solvent removal and vacuum distillation (0.27 mmHg,

78 °C) of the organic fraction yielded 1.534 g of a pale yellow

2

3

7.44 (m, 6H, H_m,pPh), 6.66 (ddd, J (PH) ) 24.5 Hz, J (H_aH_b)

3

) 18.5 Hz, J (H_aH_c) ) 12.7 Hz, 1H, H_a), 6.30 (ddd, J (PH) )

3

2

41.5 Hz, J (H_aH_c) ) 12.7 Hz, J (H_bH_c) ) 1.5 Hz, 1H, H_c), 6.24

(ddd, ³J (PH) ) 22.0 Hz, ³J (H_aH_b) ) 18.5 Hz, ³J (H_bH_c) ) 1.5

Hz, 1H, H_b), 2.22 (s, 18H, η⁶-C₆Me₆), 1.76 (s, 6H, CMe₂), 1.25

(s, 2H, CH₂), 1.42 (s, 1H, NH). ¹³C{¹H} NMR (125.71 MHz,

CDCl₃): δ 134.77 (s, C_â), 132.15 (d, ¹J (PC) ) 105.1 Hz, C_i),

131.89 (d, ⁴J (PC) ) 2.4 Hz, C_p), 131.31 (d, ²J (PC) ) 9.9 Hz,

C_o), 131.03 (d, ¹J (PC) ) 98.2 Hz, C_R), 128.55 (d, ³J (PC) ) 11.9

Hz, C_m), 96.11 (d, J (PC) ) 3.3 Hz, η⁶-C₆Me₆), 31.51 (s, CMe₂),

29.62 (s, CH₂), 16.75 (s, η⁶-C₆Me₆), 15.11 (s, CMe₂). ³¹P{¹H}

NMR (202.33 MHz, CDCl₃): δ 23.68 (s, DPVP), -144.72 (sept,

¹J (PF) ) 712.6 Hz, PF₆).

1

viscous liquid. H NMR and FT-IR spectroscopy and GC/MS

have identified the products as acetophenone, hexamethyl-

benzene, and an unknown compound in a ratio of 81.4:15.7:

2.9. The red inorganic fraction has not been fully characterized

as yet.

[(η⁶-C₆Me₆)ClRu CHdC(DP VP )CMe₂NH₂]P F₆(8). Mp: 198

1

3

°C dec. H NMR (499.84 MHz, acetone-d₆): δ 9.73 (d, J (PH)

2

) 24.0 Hz, CH), 8.08-7.67 (m, 10H, Ph), 7.31 (ddd, J (PH) )

Novel Ruthenium(II) Carbene Complexes

Organometallics, Vol. 19, No. 23, 2000 4755

Ta ble 10. Cr ysta llogr a p h ic Da ta

1b

1c

3a

3b

3c

4a

empirical formula

C

₁₅H₂₇Cl₂PRu

C₃₀H₃₃Cl₂PRu

C₂₉H₃₇ClF₆-

OP₂Ru

714.05

C₁₈H₃₃ClF₆-

OP₂Ru‚C₃H₆O

635.98

C₃₃H₃₉ClF₆-

OP₂Ru‚C₄O

828.14

C₃₅H₄₁ClF₆-

OP₂Ru‚C_1.50H₃O_0.50

819.18

fw

410.31

596.50

cryst syst

space group

a (Å)

b (Å)

c (Å)

orthorhombic

Pbca

15.2968(14)

17.8266(10)

26.3270(17)

90

triclinic

P1h

orthorhombic

P2₁2₁2₁

8.3402(8)

13.7264(12)

27.022(3)

90

monoclinic

P2₁/n

17.385(6)

8.9043(15)

18.548(3)

90

91.92(2)

90

2869.6(13)

4

monoclinic

P2₁/c

14.840(2)

8.616(3)

29.172(4)

90

94.846(5)

90

3716.7(14)

4

monoclinic

C2/c

24.2254(13)

10.6895(14)

29.163(2)

90

104.479(6)

90

7312.0(12)

8

8.9314(11)

9.0629(9)

17.8273(17)

89.243(8)

89.432(11)

65.522(8)

1313.2(2)

2

R (deg)

â (deg)

γ (deg)

V (Å³)

Z

90

7179.1(9)

16

1.518

1.247

0.0772/0.0734

3093.5(5)

4

1.533

0.755

0.0819/0.1391

d_calcd(g/cm³)

1.509

0.879

0.0521/0.1051

1.472

0.805

0.0808/0.1977

1.480

0.642

0.0748/0.1797

1.488

0.650

0.0636/0.1734

µ (mm^-1

)

R1(F)/wR2(F²)^a

4b

4c

5

6

8

9

empirical formula

C

₂₄H₃₇ClF₆-

OP₂Ru

C₃₉H₄₃ClF₆-

OP₂Ru‚CH₂Cl₂

925.12

triclinic

P1h

9.243(3)

10.934(4)

20.766(5)

78.132(18)

83.389(18)

89.359(19)

2039.9(10)

2

C₃₀H₃₇ClF₆-

OP₂Ru

726.06

monoclinic

P2₁/c

13.8695(7)

8.3371(6)

26.956(2)

90

96.906(6)

90

3094.4(4)

4

1.559

0.756

0.0628/0.1083

C₄₁H₄₁ClF₆P₂Ru

C₃₁H₄₁ClF₆-

NP₂Ru

740.11

triclinic

P1h

9.8514(17)

11.0147(13)

16.392(2)

77.717(8)

76.579(11)

87.082(11)

1690.6(4)

2

C₂₇H₃₁ClF₆-

OP₂Ru

683.98

monoclinic

P2₁/c

10.7954(9)

15.450(2)

17.280(2)

90

91.623(7)

90

2881.0(6)

4

1.577

0.807

fw

654.00

orthorhombic

Pbca

13.3348(17)

15.537(4)

27.037(3)

90

846.20

monoclinic

P2₁/n

10.3675(8)

23.5252(12)

16.4003(15)

90

101.269(7)

90

3922.9(5)

4

1.433

0.606

0.0678/0.1580

cryst syst

space group

a (Å)

b (Å)

c (Å)

R (deg)

â (deg)

γ (deg)

V (Å³)

Z

90

5601.6(17)

8

1.551

0.825

0.0910/0.1519

d_calcd(g/cm³)

1.506

0.718

0.0830/0.1393

1.454

0.692

0.0883/0.2225

µ (mm^-1

)

R1(F)/wR2(F²)^a

0.0692/0.1449

a

2

Final R indices have I > 2σ(I). R1(F) ) ∑(|F_o| - |F_c|)/∑(|F_o|); wR2(F²) ) [∑w(|F_o| - |F_c|)²/∑w(|F_o|)²]^1/2

.

X-r a y Cr ysta llogr a p h ic Stu d ies. Single crystals of 1b,c,

3a -c, 4a -c, 5, 6, 8, and 9 suitable for X-ray diffraction were

obtained as follows: slow diffusion of Et₂O into a CHCl₃

solution of complex 1c, slow diffusion of hexane into a benzene

solution of complex 1b, slow diffusion of Et₂O into CH₂Cl₂

solutions of complexes 3a ,c, 4a ,b, and 9, slow diffusion of Et₂O

into a CHCl₃/acetone solution of complex 3b, and slow diffusion

of Et₂O into acetone solutions of complexes 4c, 5, 6, and 8.

The crystals were mounted on glass fibers, coated with epoxy,

and placed on a Siemens P4 diffractometer. Intensity data

were collected in the ω mode with graphite monochromated

Mo KR radiation (λ ) 0.710 73 Å). Three check reflections,

monitored every 100 reflections, showed random (<2%) varia-

tion during the data collections. The data were corrected for

Lorentz, polarization effects, and absorption (using an empiri-

cal model derived from azimuthal data collections). Scattering

factors and corrections for anomalous dispersion were taken

from a standard source.²⁶Calculations were performed within

the Siemens SHELXTL Plus (version 5.10) software package

on a PC. The structures were solved by direct methods (1b,

3a , and 9) or by Patterson methods (1c, 3b,c, 4a -c, 6, and 8).

Anisotropic thermal parameters were assigned to all non-

hydrogen atoms. Hydrogen atoms were refined at calculated

positions with a riding model in which the C-H vector was

fixed at 0.96 Å. Hydrogen atoms were not added to the solvent

Et₂O molecule in the structure solution of 3c. There is half of

an acetone molecule in the unit cell of 4a . The data were

refined by the method of full-matrix least squares on F². Final

cycles of refinement converged to the R1(F) and wR2(F²) values

given in Table 10, where w^-1) σ²(F) + 0.001F².

Ack n ow led gm en t. An award from the Research

Corp., for which we are grateful, supported this re-

search. We thank J ohnson Matthey Aesar/Alfa for a

generous loan of RuCl₃‚H₂O and the National Science

Foundation (Grant No. CHE-9214294) for funds to

purchase the 500 MHz NMR spectrometer.

Su p p or tin g In for m a tion Ava ila ble: Listings of atom

coordinates, bond distances and angles, thermal parameters,

anisotropic refinements, and hydrogen atom coordinates for

1b,c, 3a -c, 4a -c, 5, 6, 8, and 9. This material is available

free of charge via the Internet at http://pubs.acs.org.

(26) International Tables for X-Ray Crystallography; D. Reidel:

Boston, MA, 1992; Vol. C.

OM0004949

Article Doi

Novel ruthenium(II) carbene complexes: Products of the reactions of 1-alkynes with (η6-C6Me6)Cl2Ru(PR3)

DOI: 10.1021/om0004949

Source and publish data:

Authors:

Article abstract of DOI:10.1021/om0004949

Full text of DOI:10.1021/om0004949

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