Synthesis of η2-cyclooctene iridium and rhodium complexes supported by a novel P,N-chelate ligand and their reactivity toward hydrosilanes: Facile Cl migration from metal to silicon via silylene complex intermediates and formation of a base-stabilised silylene complex

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Silylium ions in catalysis

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Kinetic studies of reactions of organosilylenes: what have they taught us?

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www.rsc.org/dalton | Dalton Transactions

Synthesis of g²-cyclooctene iridium and rhodium complexes supported by a

novel P,N-chelate ligand and their reactivity toward hydrosilanes: facile Cl

migration from metal to silicon via silylene complex intermediates and

formation of a base-stabilised silylene complex†

Hisako Hashimoto,* Toshinori Suzuki and Hiromi Tobita*

Received 6th April 2010, Accepted 10th June 2010

DOI: 10.1039/c0dt00264j

2

h -Cyclooctene iridium and rhodium complexes bearing a P,N-chelate ligand C₆H₃Me-3-PCy₂-4-NMe₂

2

(abbreviated as P^cyN), (P^cyN-P,N)MCl(h -coe) (1: M = Ir, 2: M = Rh), were synthesised and reactions

toward several sterically hindered hydrosilanes were investigated to clarify their reactivity. The reaction

of 1 with H₂SiMes₂(Mes = mesityl = 2,4,6-trimethylphenyl) proceeded at 40 ^◦C to give a di-iridium

complex bridged by a chlorosilylene ligand (P^cyN-P,N)₂Ir₂H₂(m-Cl)(m-H)(m-SiClMes) (5). The reaction

of 1 with HSiMe₂SiMes₂Me occurred at room temperature to afford HSiMesMe₂and a silyl complex 6

formed by metallation of an ortho-methyl group of Mes, which slowly dimerised to give a dinuclear

complex containing a chlorosilyl ligand (P^cyN-P,N)₂Ir₂H(m-Cl)(m-H)[m-SiMeCl(C₆H₃-2,4-Me₂-6-CH)-

Si,C,C] (7). The formation of complexes 5, 6 and 7 suggests that facile migration of Cl from Ir to Si

occurs probably via silylene iridium intermediates. Treatment of 1 with HSiMe₂SiMe₂OMe at room

temperature yielded a methoxy-bridged bis(silylene) complex (P^cyN-P,N)IrHCl[SiMe₂··O(Me)··SiMe₂-

Si,Si] (8) quantitatively, whose X-ray crystal structure was determined as the ﬁrst iridium complex of

this type. The reactions of 1 and 2 with a bulky trihydrosilane H₃SiC(SiMe₃)₃underwent an

intramolecular g-Si–Me activation to afford (P^cyN-P,N)MH_n[SiMe₂C(SiMe₃)₂SiClMe-Si,Si] (9: M = Ir,

n = 3; 10: M = Rh, n = 1). Complex 1 even reacted with an extremely sterically hindered

terphenylhydrosilane H₃SiDmp (Dmp = 2,6-dimesitylphenyl) in the presence of PMe₃to give a

chlorosilyl complex (P^cyN-P,N)IrH₂(PMe₃)(SiHClDmp) (11) without intramolecular bond activation.

Complex 1 also reacted with H₃SiTrip (Trip = 2,4,6-triisopropylphenyl) in the presence of excess

4-(dimethylamino)pyridine (DMAP) at room temperature to give a chlorido(dihydrosilyl) complex

(P^cyN-P,N)IrHCl(DMAP)(SiH₂Trip) (12) instantaneously. Treatment of complex 12 with

LiB(C₆F₅)₄·2.5Et₂O provided a cationic DMAP-stabilised silylene complex

[(P^cyN-P,N))IrH₂(DMAP)(SiHTrip ← DMAP)][B(C₆F₅)₄] (13).

complexes are closely related to each other in a sense that these

Introduction

are interconvertible via 1,2-group migration for which the reaction

Oxidative addition of Si–H bonds of hydrosilanes to transition

condition and direction largely depend on the properties of

metal complexes and subsequent formation of silyl complexes

the metal fragments. Considerable attention have been devoted

and/or silylene complexes are key steps involved in many im-

to the chemistry of silyl and silylene complexes during the

portant reactions such as hydrosilylation of unsaturated organic

last two decades. Understanding the fundamental properties

substrates and redistribution of substituents on hydrosilanes.¹

of a variety of silyl and silylene complexes is important and

In particular, the redistribution reaction involves the cleavage

can contribute to the development of new methodologies of

and formation of generally robust Si–C bonds or other s-Si–E

activation and transformation of organic substrates and silicon

compounds.

In the course of our recent studies to develop isolable and reac-

tive terminal silylene complexes, we have succeeded in synthesis-

=

(E

O, N, etc.) bonds of hydrosilanes.²This type of s-bond

activation frequently occurs as a result of group migration on

silylene and silyl(silylene) complexes: we have demonstrated it

by a mechanistic research using an isolated silyl(silylene) iron

complex in our previous work.³Thus, silyl complexes and silylene

=

ing neutral silyl(silylene) complexes Cp*(OC)(Me₃Si)M SiMes₂

(M = Fe,³Ru;⁴Mes = mesityl = 2,4,6-trimethylphenyl) and hy-

=

drosilylene complexes Cp*(CO)_n(H)M SiH{C(SiMe₃)₃} (M = W,

n = 2;⁵M = Ru, n = 1⁶) by the reactions of carbonyl(methyl) com-

plexes with sterically hindered hydrosilanes HSiMe₂SiMes₂Me and

H₃SiC(SiMe₃)₃, respectively, through the initial formation of silyl

complexes followed by 1,2-group migration as the key steps. The

latter type of silylene complexes were found to react cleanly with

a variety of unsaturated organic compounds such as ketones,^5,7

nitriles,^6,8oxiranes⁹and a,b-unsaturated carbonyl compounds.¹⁰

Department of Chemistry, Graduate School of Science, Tohoku Univer-

sity, Aoba-ku, Sendai 980-8578, Japan. E-mail: hhashimoto@m.tains.

tohoku.ac.jp, tobita@m.tains.tohoku.ac.jp; Fax: (+81) 22-795-6543;

Tel: (+81) 22-795-6541

† Electronic supplementary information (ESI) available: X-Ray analysis

of P^cyN, 2 and 4·C₇H₈. CCDC reference numbers 772158–772169. For

ESI and crystallographic data in CIF or other electronic format see DOI:

10.1039/c0dt00264j

9386 | Dalton Trans., 2010, 39, 9386–9400

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The Royal Society of Chemistry 2010

©

However, these complexes have not yet been applied to catalysts,

at present.

analysis as well as by X-ray diffraction study (see, Fig. S1 and

Table S1 in ESI).†

Recently, the metal complexes bearing P,N-chelate ligands

are attracting considerable attention in the ﬁeld of coordination

chemistry and organometallic chemistry.¹¹The P,N-ligand having

two electronically fairly different coordination sites often makes

its metal complex hemilabile, and also strongly inﬂuences the

geometries of its metal complexes. By these unique properties,

the P,N-ligand is believed to facilitate fundamental steps involved

in catalytic reactions and would also control their selectivity. For

these reasons, a number of transition metal complexes supported

by P,N-ligands have recently been synthesised^12–14and some of

them have been applied to catalysts for hydrogenation of oleﬁns,¹²

ketones¹³and imines.¹⁴

In order to introduce the P^cyN ligand onto iridium and rhodium

centres, the reactions of P^cyN with [Ir(m-Cl)(coe)₂]₂and [Rh(m-

Cl)(coe)₂]₂in toluene at room temperature were performed by

applying the general synthetic method of diphosphine dinuclear

complexes [M(m-Cl)(diphosphine)₂]₂.¹⁸As a result, mononuclear

2

h -cyclooctene complexes (P^cyN-P,N)MCl(h -coe) (1: M = Ir,

2: M = Rh) were obtained even if the 1 : 1 reaction between

P^cyN and [M(m-Cl)(coe)₂]₂was done. Complexes 1 and 2 were

ﬁnally prepared in 75% and 94% yields, respectively, from the 2 : 1

reaction of P^cyN and [M(m-Cl)(coe)₂]₂(Scheme 2). The formation

2

of mononuclear h -cyclooctene complexes in the case of the P,N-

ligand could be explained by different donating ability of the two

coordinating sites: The electron donation of the amine site to the

metal atom is stronger than that of the phosphine site because

the amine ligand lacks p-accepter ability. As a result, the p-back

donation from the metal to the oleﬁn at the trans position to the

amine site becomes strong and prevents the dissociation of the

oleﬁn from the metal centre. Both 1 and 2 were characterised by

multinuclear NMR, elemental analysis and X-ray crystallography.

Inspired by these examples of the P,N-chelate complexes,

we started to develop a novel P,N-chelate ligand in order to

synthesise silylene complexes bearing it. So far, there is an

example of silylene complex having a rigid tridentate P,N,P-

+

=

chelate ligand [(PNP)IrH SiRR¢] , which operates as a catalyst

for hydrosilylation of oleﬁns,¹⁵but the ones bearing a bidentate

P,N-ligand have not been reported yet.

We synthesised a new P,N-chelate ligand C₆H₃Me-3-PCy₂-

4-NMe₂(abbreviated hereafter as P^cyN) that has two bulky

cyclohexyl groups on the phosphorus atom, and then derived

2

it to some iridium and rhodium complexes bearing a h -

2

cyclooctene ligand. We then examined the reactions of the h -

cyclooctene complexes with several bulky or functionalized hy-

drosilanes, i.e. H₂SiMes₂, HSiMe₂SiMes₂Me, HSiMe₂SiMe₂OMe,

H₃SiC(SiMe₃)₃, H₃SiDmp (Dmp = 2,6-dimesitylphenyl) and

H₃SiTrip (Trip = triisopropylphenyl). These reactions resulted in

formation of several silyl complexes, silylene-bridged complexes

and base-stabilised bis(silylene) complexes bearing the P,N-

chelate ligand. Some reactions apparently involved Cl migration

from the metal centre to the silicon atom with formation of silylene

complex intermediates. We also performed chlorido abstraction

from a chlorido(silyl) complex with LiB(C₆F₅)₄·2.5Et₂O, which

produced a cationic base-stabilised silylene complex. We report

here the details of these reactions and product characterisation,

and discuss the reaction mechanisms.

Scheme 2 Synthesis of P,N-chelate complexes 1–4.

For example, the ³¹P NMR signal of 1 appears at 20.7 ppm,

which is low-ﬁeld shifted from that of the free P^cyN ligand

1

(-12.1 ppm) upon coordination to the metal. Similarly, the H

NMR signal of the NMe₂group of 1 (3.18 ppm) is also low-ﬁeld

shifted from that of the free P^cyN ligand (2.72 ppm). The NMR

data of 2 resembles those of 1.

The X-ray crystal structure analysis of 1 and 2 revealed that

their overall structures were essentially the same. Therefore, the

structure of 1 will only be discussed here (The structure of 2

is depicted in ESI, Fig. S2).† The ORTEP drawing illustrated

in Fig. 1 reveals that complex 1 takes a square-planar geometry

typical of d⁸16-_◦electron metal complexes. Selected bond lengths

Results and discussion

Syntheses of a new P^cyN ligand and its iridium and rhodium

complexes

A new P,N-ligand C₆H₃Me-3-PCy₂-4-NMe₂(P^cyN), which has

a phenylene unit¹⁶and two bulky cyclohexyl groups on the

phosphorus atom, was synthesised in Et₂O at room temperature

by the reaction of ClPCy₂with ortho-lithiated N,N-dimethyl-p-

toluidine prepared according to Hauser’s method¹⁷(Scheme 1).

Pure P^cyN was isolated as colourless crystals in 50% yield after

recrystallisation from pentane and was characterised by ¹H,

˚

(A) and angles ( ) are given in Table 1. The Cl and oleﬁn ligands

are at the trans positions to P and N atoms, respectively. The Ir1–

˚

N1 bond length (2.186(7) A) is in a normal range of N–Ir(I) dative

◦

˚

Table 1 Selected bond lengths (A) and angles ( ) for 1

Ir1–P1

Ir1–Cl1

Ir1–C23

C1–P1

2.190(2)

2.428(2)

2.114(9)

1.830(8)

Ir1–N1

Ir1–C22

C22–C23

C2–N1

2.186(7)

2.136(9)

1.410(14)

1.473(10)

1

¹³C{ H} and ³¹P{ H} NMR and mass spectra, and elemental

P1–Ir1–N1

85.0(2)

93.6(2)

94.6(3)

38.8(4)

N1–Ir1–Cl1

C22–Ir1–P1

C23–Ir1–P1

87.8(2)

91.7(2)

95.9(3)

Cl1–Ir1–C22

Cl1–Ir1–C23

C22–Ir1–C23

Scheme 1 Synthesis of the P^cyN ligand.

The Royal Society of Chemistry 2010

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Dalton Trans., 2010, 39, 9386–9400 | 9387

©

Fig. 1 ORTEP view of 1 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

Fig. 2 ORTEP view of 3 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

˚

bond lengths. On the other hand, the Ir1–P1 bond (2.190(2) A)

and, therefore, most of the following reactions were performed

using 1. Since there are some previous successful examples¹⁹to

obtain terminal silylene complexes by introducing a bulky mesityl

substituent onto the silicon atom, we ﬁrst examined the reaction

of complex 1 with H₂SiMes₂. Thus, 1 was treated with 1 equiv.

of H₂SiMes₂in C₆D₆at 40 ^◦C. The reaction was completed

after 3h to give a chlorosilylene-bridged di-iridium complex

(P^cyN-P,N)₂Ir₂H₂(m-Cl)(m-H)(m-SiClMes) (5) in 60% NMR yield

together with mesitylene (MesH) and some minor unidentiﬁed

products (eqn (1)). The yield of mesitylene was not able to be

determined correctly because its ¹H NMR signals were overlapped

with those of cyclohexyl and aryl groups of 5. Complex 5 was

isolated in 36% yield by a preparative-scale experiment in toluene

and recrystallisation from THF–pentane at room temperature.

is fairly shorter than usual P–Ir(I) bonds, probably because of the

trans inﬂuence of the electron-withdrawing Cl ligand. As a result,

the Ir–N1 and Ir1–P1 bonds happen to be almost the same in

˚

spite of the large difference of the atomic radii of nitrogen (0.75 A)

˚

and phosphorus (1.06 A). Another notable feature of the structure

of 1 is that, in the coordinated oleﬁn C–C double bond, the C22

atom takes a corner of the square composed of P1, N1, Cl1 and

C22 atoms, while the C23 atom is located out of the plane of the

square. At present, the reason is not clear because there are no

close contacts between the ligands. A packing effect of the crystal

or some electronic factors might cause this distortion.

2

The h -coordinated cyclooctene ligand in 1 was found to be

replaced by phosphines at room temperature. Thus, treatment

of 1 with PMe₃in toluene at room temperature gave (P^cyN-

P,N)IrCl(PMe₃) (3) in 87% yield (Scheme 2). Similarly, (P^cyN-

P,N)IrCl(PPh₃) (4) was obtained in 94% yield by treatment with

PPh₃. These complexes 3 and 4 were characterised by NMR,

elemental analysis and X-ray diffraction study.

(1)

1

In the H NMR spectrum of 3, the signal of PMe₃appears

at 1.67 ppm as a doublet (²J_HP= 7.3 Hz) and that of NMe₂at

3.31 ppm as a doublet (⁴J_HP= 1.8 Hz) coupled with PMe₃trans to

the NMe₂moiety. A mutual cis conﬁguration between PCy₂and

The structure of 5 was conﬁrmed by X-ray diffraction study.

The ORTEP drawing of 5 is shown in Fig. 3 and selected bond

◦

˚

lengths (A) and angles ( ) are given in Table 3. Although the

quality of the crystal of 5 was rather low and carbon and nitrogen

atoms had to be reﬁned with isotropic thermal parameters, the

overall structure was unambiguously determined to be a di-iridium

complex bridged by a chlorosilylene and a chlorido ligand. The

positions of three hydrogen atoms of IrH₃were not determined

by X-ray crystallography. But, as the dihedral angle between

the Ir1–Si1–Ir2 plane and the Ir1–Cl1–Ir2 plane is 114.1(3)^◦,

1

PMe₃is indicated by a small value of ²J_pp(19 Hz) in the ³¹P{ H}

NMR spectrum. The molecular structure of 3·C₇H₈is depicted in

Fig. 2 and that of 4 in ESI, Fig. S2 (the overall structure of 4 closely

resembles that of 3 and will not be discussed here).† Selected bond

◦

˚

lengths (A) and angles ( ) for 3·C₇H₈are listed in Table 2. Fig. 2

shows that 3 also adopts a square-planar structure and PMe₃is

located at a position trans to the NMe₂.

Reactions of iridium complex 1 with dihydrosilane and

hydrodisilanes

2

Among the above-mentioned complexes, h -cyclooctene iridium

complex 1 was found to be the most convenient precursor

◦

˚

Table 2 Selected bond lengths (A) and angles ( ) for 3·C₇H₈

Ir1–P1

Ir1–N1

C1–P1

2.173(3)

2.209(8)

1.830(9)

Ir1–P2

Ir1–Cl1

C2–N1

2.209(3)

2.406(3)

1.476(13)

P1–Ir1–N1

Cl1–Ir1–P2

84.9(2)

85.76(11)

N1–Ir1–Cl1

P2–Ir1–P1

88.7(2)

100.92(10)

Fig. 3 ORTEP view of 5 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

9388 | Dalton Trans., 2010, 39, 9386–9400

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©

◦

˚

complex intermediate B. To the vacant p orbital of the silylene

ligand of B, the chlorido ligand coordinates intramolecularly with

a lone pair and then undergoes 1,2-migration from Ir to Si to

give a chlorosilyl complex C. Similar 1,2-group migrations on

silylene complexes have been well documented.^1,2Coordinatively

unsaturated C further reacts with another molecule of 1 to give E

through oxidative addition of the Si–C bond of the Si–Mes moiety.

Although the source is not clear, E abstracts two hydrogen atoms

from somewhere (probably from the solvent) and, ﬁnally, MesH

is liberated together with cyclooctene to afford 5. In this case, the

produced terminal silylene complex B is not stable enough and

dimerises to give 5.

Table 3 Selected bond lengths (A) and angles ( ) for 5

Ir1–Ir2

Ir1–P1

Ir2–Si1

Ir2–Cl1

Ir1–N1

2.8547(9)

2.198(6)

2.294(5)

2.481(6)

2.345(19)

Ir1–Si1

Ir1–Cl1

Ir2–P2

Si1–Cl2

Ir2–N2

2.306(5)

2.539(6)

2.170(6)

2.409(11)

2.44(2)

P1–Ir1–Si1

P1–Ir1–Ir2

Si1–Ir1–Ir2

Si1–Ir2–P2

P2–Ir2–N2

Ir1–Si1–Ir2

Cl1–Ir1–Ir2–Si1

106.0(2)

148.9(2)

51.44(12)

106.5(2)

83.7(5)

P1–Ir1–N1

N1–Ir1–Ir2

P2–Ir2–Ir1

Si1–Ir2–Ir1

N2–Ir2–Ir1

Ir1–Cl1–Ir2

82.7(5)

121.8(4)

152.22(14)

51.84(12)

120.9(5)

69.3(2)

76.7(2)

114.1(3)

Therefore, we next tried to prevent dimerisation of the silylene

complex by introducing a bulky trimethylsilyl group instead of a

hydrogen. By this change, we have previously succeeded in isolating

silyl(silylene) complexes as mentioned in Introduction.^3,4

The reaction of 1 with HSiMe₂SiMes₂Me in C₆D₆was mon-

the supplementary angle is widely open. Therefore, a bridging

hydrogen atom must be positioned in its open space. The Ir1–N1

˚

and Ir2–N2 bond lengths are 2.345(19) and 2.44(2) A, respectively,

which are much longer than those of general Ir(I)–N bonds and

even longer than the Ir1–P1 and Ir2–P2 bond lengths. This is

attributable to the strong trans inﬂuence of the bridging silylene

ligand.

1

itored by ¹H, ²⁹Si{ H} and ³¹P{ H} NMR spectroscopy at

room temperature (Scheme 4). After 18 h, 1 was consumed

completely and monomesitylsilane HSiMesMe₂was formed in

69% NMR yield. During the reaction, several iridium complexes

1

The H NMR spectrum of 5 also provides information on the

1

were formed and disappeared according to the ³¹P{ H} NMR

positions of three hydrido ligands of IrH₃. Thus, two kinds of

hydrido signals appear at -6.12 ppm with 1 H intensity and at

-26.02 ppm with 2 H intensity. The former is assigned to the

bridging hydrido ligand because it clearly shows a triplet pattern

due to the coupling with two equivalent phosphorus atoms. The

relatively large coupling constant (²J_HP= 64.6 Hz) suggests that

the bridging hydrido ligand is almost trans to each PCy₂moiety.

The latter signal shows a higher-order coupling pattern due to

two phosphorus and one hydrogen atoms and is assigned to two

equivalent terminal hydrido ligands.

The formation of the chlorosilylene-bridged complex 5 implies

the generation of a silylene complex intermediate and subsequent

Cl migration from Ir to the silylene silicon atom. A possible

mechanism that can explain the formation of 5 is shown in

Scheme 3. Initially, oxidative addition of the hydrosilane and

elimination of the cyclooctene ligand produces 16e silyl complex

A. Then, 1,2-H migration from Si to Ir occurs to give silylene

spectra. In order to isolate a mainly produced iridium com-

plex, a preparative-scale experiment in toluene was carried out.

After 3 h at room temperature, the reaction was stopped and

1

the NMR spectra were measured. The H and ³¹P{ H} NMR

spectra showed the formation of a silyl complex tentatively for-

mulated as (P^cyN-P,N)IrH[SiMeCl(C₆H₃-2,4-Me₂-6-CH₂-Si,C)]

(6) in approximately 60% yield. However, recrystallisation of

crude 6 from toluene–pentane resulted in isolation of a dinu-

clear complex (P^cyN-P,N)₂Ir₂H(m-Cl)(m-H)[m-SiMeCl(C₆H₃-2,4-

Me₂-6-CH)-Si,C,C] (7) instead of 6 in 47% yield. Based on the

¹H NMR spectrum, 7 was almost quantitatively produced on the

assumption that two molecules of 6 reacted to give one molecule

of 7 with releasing a “SiMeMes” unit. The structure of 7 was

conﬁrmed by X-ray diffraction study and NMR spectroscopy.

Scheme 4 Reactions of 1 with HSiMe₂SiMes₂Me.

We suggested the tentative structure of 6 based on the following

data. In the ¹H NMR spectrum of 6, a doublet signal with ²J_HP

=

9.3 Hz appears at -24.04 ppm that is assigned to IrH. The small

²J_HPvalue is consistent with the mutual cis geometry of the hydrido

and the PCy₂ligands. There are also three singlets for aryl-methyl

groups, a singlet for SiMe and two singlets for inequivalent two

NMe groups in addition to multiplet signals for cyclohexyl groups

Scheme 3 A possible mechanism for the reaction of 1 with H₂SiMes₂.

This journal is

The Royal Society of Chemistry 2010

Dalton Trans., 2010, 39, 9386–9400 | 9389

©

based on a single doublet pattern (²J_HP= 23.4 Hz). Moreover,

the two large ²J_HPvalues of the former suggests that the bridging

hydrogen atom is positioned at trans to both two PCy₂ligands,

◦

˚

Table 4 Selected bond lengths (A) and angles ( ) for 7

Ir1–Ir2

Ir1–Cl1

Ir1–N1

Si1–Cl2

Ir2–P2

2.7155(5)

2.668(2)

2.297(8)

2.150(4)

2.207(2)

2.075(9)

Ir1–Si1

Ir1–P1

Ir1–C55

Ir2–Cl1

Ir2–N2

2.281(3)

2.257(2)

2.073(9)

2.581(3)

2.294(8)

2

while the small J_HPsuggests that the terminal hydrido ligand is

positioned at cis to the PCy₂. The methyne proton of the bridging

carbene ligand is also observed as a doublet of doublet (²J_HP= 5.2

and 3.3 Hz) at 5.91 ppm. Accordingly, the carbene carbon signal

Ir2–C55

1

is observed at 120.6 ppm as a doublet of doublet in the ¹³C{ H}

P1–Ir1–N1

Ir2–Ir1–C55

P1–Ir1–Ir2

Si1–Ir1–Ir2

P2–Ir2–N2

Ir1–Ir2–C55

P2–Ir2–Ir1

Cl1–Ir2–N2

Ir1–C55–Ir2

83.7(2)

49.1(2)

146.24(6)

91.81(2)

84.2(2)

49.1(2)

151.65(7)

99.7(2)

81.8(3)

N1–Ir1–Ir2

C55–Ir1–P1

P1–Ir1–Si1

Ir2–Ir1–Cl1

N2–Ir2–Ir1

C55–Ir2–P2

Ir1–Ir2–Cl1

Ir1–Cl1–Ir2

126.2(2)

99.9(3)

NMR spectrum.

97.75(9)

57.28(5)

122.2(2)

105.1(2)

60.44(5)

62.28(5)

The generation of HSiMesMe₂from this reaction suggests that

redistribution of substituents on silicon atoms occurred probably

via a silyl(silylene) complex intermediate. To trap the silyl(silylene)

intermediate by intramolecular coordination of the methoxy

group, HSiMe₂SiMe₂OMe was employed as a substrate.^1e,1f,21

Complex 1 reacted instantaneously with HSiMe₂SiMe₂OMe

at room temperature to give the expected methoxy-bridged

bis(silylene) complex (P^cyN-P,N)IrHCl[SiMe₂··O(Me)··SiMe₂-

Si,Si] (8), which was isolated in 99% yield as yellow crystals

(eqn (2)).

and aryl-protons. The signals for the Ir–CH₂seem to be overlapped

with those of the cyclohexyl groups. The ³¹P{ H} NMR spectrum

1

exhibits a singlet at 57.0 ppm in a normal region for a phosphine

ligand.

The X-ray crystal structure _◦of 7 is depicted in Fig. 4 and selected

˚

bond lengths (A) and angles ( ) are listed in Table 4. Fig. 4 clearly

(2)

reveals that 7 is a chlorido-bridged diiridium complex having an

unsymmetrical structure due to the attachment of a silyl group to

the Ir1 atom. The silyl group bears a chloro group, a methyl group

and an aryl group that has originally been a mesityl group, of which

one of ortho-substituents was changed to a carbene bridging ligand

caused by double C–H activation that bridges two iridium atoms.

Both terminal and bridging hydrogen atoms, which are observed

by ¹H NMR (vide infra), could not be located. The positions of P1,

N1, Ir1, C55, Ir2, P2 and N2 atoms are almost co-planar: The sum

of the angles around Ir1 made by P1, N1, C55 and Ir2, and the

corresponding value around Ir2 are both close to 360^◦. The Ir1–

Complex 8 was characterised based on NMR spectroscopy,

elemental analysis and X-ray crystallography. The hydrido signal

of IrH is observed at -20.87 ppm as a doublet (²J_HP= 11.5 Hz)

1

in the H NMR spectrum (C₆D₆). The relatively small coupling

constant indicates the cis geometry of the hydrido ligand to the

PCy₂moiety. The signal of OMe appears at 2.92 ppm that is

signiﬁcantly upﬁeld-shifted compared with that (3.27 ppm) of free

HSiMe₂SiMe₂OMe. This upﬁeld shift in an aromatic solvent is

characteristic of the methoxy proton signal of methoxy-bridged

bis(silylene) complexes.^1e,1f,21The ²⁹Si signals of two SiMe₂are

˚

N1 (2.297(8) A) and Ir2–N2 (2.294(8) A) bond lengths are fairly

longer than usual Ir(I)–N bond lengths because of the relatively

strong trans inﬂuence of the bridging carbene ligand. The Ir1–Ir2

2

observed at 42.4 and 69.7 ppm as doublets with J_SiP= 1.8 and

˚

bond length (2.7155(5) A) is within a range of normal Ir–Ir single

1

177 Hz, respectively, in the ²⁹Si{ H} NMR spectrum. The signal

20

˚

bond length (2.51–3.09 A).

2

at 42.4 ppm having a small J_SiPvalue is assigned to the SiMe₂

at a cis position to PCy₂, while the one having a large ²J_SiPvalue

is assigned to the other SiMe₂. These chemical shifts are close to

those of known methoxy-bridged bis(silylene) complexes (56.3–

128.6 ppm).^1e,1f

The X-ray diffraction study conﬁrmed the structure of 8 as

shown in Fig. 5. This is the ﬁrst iridium example of structurally

Fig. 4 ORTEP view of 7 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

The existence of a terminal and a bridging hydrido ligand is

1

demonstrated by the H NMR spectrum of 7, which shows two

sets of signals for IrH at -5.27 and -28.77 ppm. The former is

assigned to the bridging hydrido ligand based on the pattern of a

doublet of doublet (²J_HP= 72.0 and 59.8 Hz) coupled with two

phosphorus atoms, while the latter to the terminal hydrido ligand

Fig. 5 ORTEP view of 8 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms except H1 are omitted for clarity.

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◦

˚

Table 5 Selected bond lengths (A) and angles ( ) for 8·C₇H₈

Ir1–Si1

Ir1–P1

Ir1–Cl1

Si1–O1

Si1–Si2

P11–C1

Si1–Ir1–Si2

P1–Ir1–N1

P1–Ir1–Cl1

Si1–Ir1–H1

N1–Ir1–Cl1

Si2–Ir1–H1

Ir1–Si1–O1

Ir1–Si2–O1

Si1–Si2–O1–C26

Ir1–Si1–O1–C26

2.336(2)

2.308(2)

2.497(2)

1.804(7)

2.694(3)

1.816(9)

71.63(9)

81.7(2)

97.16(7)

71(6)

91.9(2)

83(6)

92.9(2)

95.1(2)

153.1(9)

-170.0(7)

Ir1–Si2

Ir1–N1

Ir1–H1

Si2–O1

O1–C26

N1–C2

Si2–Ir1–P1

N1–Ir1–Si1

Cl1–Ir1–Si1

H1–Ir1–P1

Cl1–Ir1–Si2

H1–Ir1–N1

Si1–O1–Si2

2.267(2)

2.319(7)

1.44(15)

1.810(6)

1.437(10)

1.476(11)

101.96(8)

103.2(2)

94.53(8)

98(6)

95.44(8)

89(6)

96.4(3)

Ir1–Si1–Si2–O1

Ir1–Si2–O1–C26

159.4(3)

169.9(7)

characterised alkoxy-bridged bis(silylene) complex. Selected bond

◦

˚

lengths (A) and angles ( ) are given in Table 5. The H1 atom

attached to Ir was found and reﬁned isotropically. The Ir centre

takes a distorted-octahedral geometry with a P,N-chelate ligand,

a methoxy-bridged bis(silylene) ligand, a hydrido and a chlorido

ligand. The Ir1–Si1 and Ir1–Si2 bond lengths are 2.336(2) and

˚

2.267(2) A, respectively, and the latter is comparable with the

15b,19b

˚

=

reported Ir Si double bond lengths (2.21–2.26 A)

both are close to the shorter end of the reported Ir–Si single

bond lengths (2.23–2.45 A) of Ir(III) complexes. The small but

and

20

˚

signiﬁcant difference between Ir1–Si1 and Ir1–Si2 bond lengths

is attributable to the different donor ability of P- and N-donor

ligands. As mentioned above, the N-donor ligand is a simple s-

donor but the P-donor ligand can also act as a p-acceptor by its

P–R s*-orbital besides as a s-donor. Therefore, p-back donation

from the metal to the silylene SiMe₂unit trans to the P-donor

ligand is competitive with that to the P-donor ligand, while there

is no such competition for the SiMe₂unit trans to the N-donor

ligand. As a result, p-back donation to the SiMe₂unit trans to the

N-donor ligand becomes stronger and the Ir1–Si2 bond shortens

in comparison with the Ir1–Si1 bond. This means that in the two

canonical forms I and II illustrated in Chart 1, form I is dominant

in this complex 8 by the inﬂuence of the asymmetric P,N-chelate

ligand.

Scheme 5 Possible mechanisms for the formation of 6, 7 and 8.

hydrodisilanes, after formation of disilanyl complex A¢ in a manner

similar to the formation of A in Scheme 3, 1,2-silyl migration

occurs to give silyl(silylene) complex B¢. The next step depends

on the substituents. When two Mes groups are on silicon, from

silyl(silylene) complex B¢, 1,3-Mes migration proceeds to give F,

from which HSiMesMe₂is reductively eliminated. Subsequent 1,2-

Cl migration on G and C–H activation on an o-Me group of

the mesityl group produce complex 6. Then, 6 reacts with G to

give dinuclear complex I bridged by hydrido and chlorido ligands.

Finally, oxidative addition of a C–H bond of the methylene bound

to an Ir centre to the other Ir centre yields a carbene-bridged di-

iridium complex 7 with releasing a “SiMesMe” unit. When a OMe

group is involved in the substituents, the silyl(silylene) complex

B¢ is trapped by intramolecular coordination of the methoxy

group to the silylene ligand to give a methoxy-bridged bis(silylene)

complex 8.

Chart 1 Two possible canonical forms for 8.

Reactions of complex 1 or 2 with several sterically hindered

trihydrosilanes

In addition, the dihedral angle between the Ir1–Si1–Si2 plane

and the Si1–Si2–O1 plane is 159.4(3)^◦and, therefore, the Ir1–

Si1–Si2–O1 four-membered ring takes a butterﬂy geometry. The

deviation of the O1 atom from the Ir1–Si1–Si2 plane is attributable

to the steric repulsion between the chlorido ligand and methyl

groups of SiMe₂in the same side as that of the chlorido ligand in

All the above-mentioned reactions demonstrate that silylene

complexes and/or silyl(silylene) complexes can be generated on

this P,N-chelate complex system, but mesityl groups are not

bulky enough to stabilise the mononuclear terminal silylene

complexes. Therefore, we next investigated the reactions of the

P,N-complexes with some more sterically hindered hydrosilanes.

As we have previously obtained terminal silylene complexes having

a C(SiMe₃)₃group from H₃SiC(SiMe₃)₃,^5–6we attempted the

reaction of 1 with H₃SiC(SiMe₃)₃. The reaction proceeded at

room temperature to generate a single product, which was ﬁnally

˚

8: The Cl1---C23 (3.68 A) and Cl1---C25 (3.61 A) distances are

shorter than the sum of van der Waals radii (3.75 A) of Cl and Me

groups.

Possible mechanisms for the formation of 6, 7 and 8 are

summarised in Scheme 5. In the case of the reactions of 1 with

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©

determined to be (P^cyN-P,N)IrH₃[SiMe₂C(SiMe₃)₂SiClMe-Si,Si]

(9) (Scheme 6) by X-ray crystallography. Complex 9 was formed

in 82% NMR yield but was isolated as light yellow crystals in low

yield (17%) because of decomposition during recrystallisation.

˚

bond length (2.440(2) A) is comparable with those of reported silyl

15b,19b

˚

Ir(V) complexes (2.33–2.48 A),

but the Ir1–Si1 bond length

˚

(2.307(3) A) is rather shorter than them. This is attributable to the

existence of the Si1–Cl1 bond with a low-lying Si–Cl s* orbital

that can accept p-back donation from Ir and causes the Ir1–Si1

bond to shorten. Similar examples of M–Si bond shortening have

been reported previously.²³

All NMR data of 9 are consistent with the structure. Especially,

in the ¹H NMR spectrum, ﬁve inequivalent SiMe signals are

observed. A hydrido signal appears at -8.81 ppm as a single

doublet (²J_PH= 9.5 Hz) with 3 H intensity at room temperature.

This signal became very broad at lower temperatures but did not

decoalesce even at -90^◦C. This indicates that the three hydrido

ligands exchange rapidly in solution. Moreover, the T₁value of

the IrH signal was determined to be 0.65 s (at room temperature),

2

which suggests that 9 is not a Ir(h -H₂)H complex but a classical

IrH₃complex.²⁴

An analogous reaction was carried out using rhodium complex

2, with an expectation that Rh is a second-raw metal that is

less electron-rich than Ir and, therefore, might not undergo

a similar intramolecular activation. The reaction between 2

and H₃SiC(SiMe₃)₃was not observed at room temperature but

Scheme 6 Reactions of 1 and 2 with H₃SiC(SiMe₃)₃.

The crystal structure of 9 is il_◦lustrated in Fig. 6 and selected

˚

bond lengths (A) and angles ( ) are listed in Table 6. It is

◦

proceeded upon heating to 60 C. Yellow crystals of (P^cyN-

clear that a newly formed ligand SiMe₂C(SiMe₃)₂SiClMe makes

a chelate ring with Ir through coordination of its two silicon

atoms. This ligand is apparently generated from a C(SiMe₃)₃

group via intramolecular activation of a g-Si–Me bond and 1,2-Cl

migration. The mechanism will be discussed later in detail. The

P,N-chelate ligand and the new bis(silyl) chelate ligand are not

co-planar but twisted to each other. Although the three hydrogen

atoms of IrH₃were not found, they could be positioned in the

open spaces in the N1–Ir1–Si1 angle (163.0(2)^◦), the N1–Ir1–

Si2 angle (119.8(2)^◦) and the P1–Ir1–Si2 angle (125.64(9)^◦). With

these postulated three hydrido positions, 9 is suggested to take

a seven-coordinated structure having a Ir(V) centre. The Ir1–Si2

P,N)RhH[SiMe₂C(SiMe₃)₂SiClMe-Si,Si] (10), which has a struc-

ture similar to 9 except having only one hydrido ligand on Rh

(Scheme 6), was isolated in 65% yield and also characterised by

X-ray diffraction, spectroscopic data and elemental analysis.

There is a disorder of the positions of Cl and Me groups at

the SiMeCl moiety of 10 in the crystal. The molecular structure

with 59% occupancy factor is illustrated in Fig. 7. In contrast

to 9, 10 is a ﬁve-coordinate complex with a Rh(III) centre and

almost takes a square-pyramid geometry with the Si1 atom at the

apical position, according to the sum of the bond angles (359(3)^◦)

around Rh1 except Si1 (Table 7). The Rh1–Si1 and Rh1–Si2 bond

˚

lengths are 2.2624(13) and 2.3230(12) A, respectively, and both

are within the range of the reported silyl Rh(III) complexes (2.20–

20

˚

2.44 A). The reason for the shortening of the Rh1–Si1 bond

could be understood similarly to the case of 9.

Fig. 6 ORTEP view of 9 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

◦

˚

Table 6 Selected bond lengths (A) and angles ( ) for 9

Ir1–Si1

Ir1–P1

Si1–Cl1

Si1–C25

2.307(3)

2.314(2)

2.113(4)

1.923(10)

1.835(9)

105.54(9)

119.8(2)

125.64(9)

103.3(3)

98.2(3)

Ir1–Si2

Ir1–N1

Si1–C22

Si2–C25

2.440(3)

2.325(8)

1.918(2)

1.935(9)

1.469(13)

82.1(2)

163.0(2)

68.37(9)

87.6(4)

Fig. 7 ORTEP view of 10 with a 59% occupancy factor. The thermal

ellipsoids are drawn at the 50% probability level. The hydrogen atoms

except H1 are omitted for clarity.

P1–C1

N1–C2

1

The ¹H, ²⁹Si{ H} and ³¹P{ H} NMR data of 10 essentially

P1–Ir1–Si1

N1–Ir1–Si2

Si2–Ir1–P1

Ir1–Si1–C25

C25–Si2–Ir1

P1–Ir1–N1

N1–Ir1–Si1

Si1–Ir1–Si2

Si1–C25–Si2

1

resemble those of 9 except the following observations in the H

NMR spectrum: A signal for RhH appears at -8.91 ppm with 1

H intensity as a doublet (27.9 Hz) of doublet (83.9 Hz) due to the

couplings with rhodium and phosphorous atoms.

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˚

2,6-Mes₂(Dmp)] that are resistant to intramolecular activation,

and demonstrated their usefulness to stabilise kinetically otherwise

unstable species such as metallostannylenes Cp(CO)₃M-Sn-Ar

(M = Cr, W; Ar = Dmp).^25cBy employing the Dmp ligand, Youngs

et al. have reported the synthesis of a cationic silylene complex

Table 7 Selected bond lengths (A) and angles ( ) for 10·C₇H₈

Rh1–Si1

Rh1–P1

Rh1–H1

Si1–C22

Si2–C26

N1–C2

2.2624(13)

2.3196(11)

1.65(8)

2.104(10)

1.959(4)

1.456(6)

Rh1–Si2

RhI–N1

Si1–Cl1

Si1–C26

P1–C1

2.3230(12)

2.299(3)

2.111(6)

1.891(4)

1.839(4)

+

26

=

[(Et₃P)₃(H)₂Ir SiHDmp] . Tilley also prepared neutral silylene

27

=

complexes Cp*(OC)(H)Os SiHAr (Ar = Dmp, Trip). Our ﬁrst

attempt of the reaction between 1 and H₃SiDmp was unsuccessful

that led to a complex mixture, but the initial treatment of 1 with

PMe₃, which generates 3 in solution, and subsequent reaction with

H₃SiDmp at room temperature for 15 h gave a chlorosilyl complex

(P^cyN-P,N)IrH₂(PMe₃)(SiHClDmp) (11) (Scheme 8). Complex

11 was isolated in 65% yield (from 1) by recrystallisation from

THF–hexane at room temperature as colourless crystals and fully

characterised. The direct reaction of isolated 3 with H₃SiDmp

also gave 11 but in lower yield. No geometrical isomers for 11

were observed or isolated.

P1–Rh1–Si1

Si1–Rh1–Si2

Si2–Rh1–P1

Si1–Rh1–H1

Rh1–Si1–C26

C26–Si2–Rh1

126.88(4)

68.60(4)

103.17(4)

59(3)

104.99(14)

100.60(13)

P1–Rh1–N1

N1–Rh1–Si1

N1–Rh1–H1

Si2–Rh1–H1

Si1–C26–Si2

82.29(10)

121.94(10)

89(3)

85(3)

84.3(2)

Possible mechanisms for the formation of 9 and 10 are illustrated

in Scheme 7. The initial steps resemble those in the reactions

of 1 with H₂SiMes₂(Scheme 3) until C¢¢. On the coordinatively

unsaturated silyl complex C¢¢ one of g-Si–Me bonds is activated by

the metal centre to give four-membered bis(silyl) chelate complex

J and subsequent 1,2-H migration and 1,2-Me migration produce

trihydrido complex 9 in the Ir system. In the Rh system, reductive

elimination of H₂occurs to afford monohydrido complex 10

probably because rhodium prefers a lower oxidation state than

iridium. The ﬁnal 1,2-H and 1,2-Me migration steps may be

induced by the unsaturated metal centre generated by the N

donor’s hemilabile behaviour, but the details are not clear at

present. In the case of the Rh system, such migrations could

also proceed after elimination of H₂. In any case, extensive

intramolecular activation was observed in these reactions. This

means that the metal centres with a P^cyN-chelate ligand are very

active and the distal parts of the trisyl group that can approach to

it are attacked by it.

Scheme 8 The synthesis of chlorosilyl complex 11.

The X-ray crystal structure of 11 (Fig. 8) clearly shows the

coordination of PMe₃and a new chlorosilyl ligand besides the

P^cyN ligand, although the hydrogen atoms on Ir and Si were not

found. Apparently, the two spaces trans to the N donor ligand

and to PMe₃are open and, therefore, would be occupied by

hydrogen atoms so that 11 takes an octahedral geometry. The

silyl ligand is located trans to the PCy₂ligand probably to avoid

a steric congestion anticipated for the cis conﬁguration. The

˚

Ir1–Si1 bond length (2.331(2) A) is comparable with the Ir–Si

+15b

˚

bond length (2.323(2) A) in [(PNP)Ir(H)SiH₂Dmp]

(Table 8).

˚

The Ir1–P1and Ir1–P2 bond lengths (2.3023(18) and 2.332(2) A,

respectively) are normal values for the Ir(I)–P bonds. On the other

˚

hand, the Ir1–N1 bond length (2.306(6) A) is much longer than

those of usual Ir(I)–N bonds, because of the trans inﬂuence of a

hydrido ligand.

Scheme 7 Possible mechanisms for the formation of 9 and 10.

Finally, the well-deﬁned, hindered aryl groups were used to

prevent the intramolecular activation of the ligand. Power have

previously developed some bulky terphenyl groups²⁵[e.g. C₆H₃-

Fig. 8 ORTEP view of 11 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms are omitted for clarity.

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◦

˚

Table 8 Selected bond lengths (A) and angles ( ) for 11·0.5·C₄H₈O

Table 9 Selected bond lengths (A) and angles ( ) for 12 CH₂Cl₂·C₅H₁

Ir1–Si1

Ir1–P2

Si1–Cl1

N1–C2

P1–Ir1–N1

P1–Ir1–P2

P2–Ir1–N1

Cl1–Si1–C25

Cl1–Si1–Ir1–N1

2.331(2)

2.332(2)

2.155(3)

1.474(10)

82.2(2)

104.25(7)

98.8(2)

Ir1–P1

Ir1–N1

P1–C1

2.3023(18)

2.306(6)

1.838(7)

Ir1–Si1

Ir1–N1

Ir1–Cl1

P1–C1

P1–Ir1–N1

N2–Ir1–Si1

P1–Ir1–Cl1

N2–Ir1–H1

N1–Ir1–Cl1

Si1–Ir1–H1

2.321(2)

2.353(5)

2.4846(13)

1.834(5)

83.39(11)

90.39(12)

99.11(5)

89(2)

Ir1–P1

Ir1–N2

Ir1–H1

N1–C2

N1–Ir1–N2

Si1–Ir1–P1

Cl1–Ir1–N2

H1–Ir1–P1

Cl1–Ir1–Si1

H1–Ir1–N1

2.2199(13)

2.150(4)

1.55(6)

1.476(7)

88.7(2)

96.85(5)

89.45(12)

84(2)

90.58(5)

93(2)

Si1–Ir1–N1

P2–Ir1–Si1

Ir–Si1–Cl1

C25–Si1–Ir1

105.1(2)

88.92(7)

116.68(10)

125.3(2)

102.9(2)

12.8(2)

93.97(12)

82(2)

In the ¹H NMR spectrum of 11, two hydrido signals of IrH₂are

observed at -26.47 and -10.82 ppm. The coupling patterns and the

coupling constants agree with the structure illustrated in Scheme 8.

For example, the latter signal appears as a doublet (120.6 Hz) of

doublet (21.9 Hz) of doublet (5.3 Hz) due to the couplings with two

inequivalent phosphorus atoms and a hydrogen atom, respectively,

and, therefore, is assigned to the hydrido ligand in a position trans

and cis to two phosphorus ligands. The SiH proton signal appears

at 5.67 ppm as a doublet of doublet due to the couplings with the

bent away from two Cy groups on the phosphorus to avoid steric

˚

congestion. The Ir1–Si1 bond length (2.321(2) A) is anormal single

bond length for silyl Ir(III) complexes (Table 9). The Ir1–P1 bond

˚

length (2.2199(13) A) is shorter than the corresponding length

˚

(2.302(2) A) in 11, while the Ir1–N1 bond length (2.353(5) A) is

˚

much longer than the Ir1–N2 (DMAP) bond (2.150(4) A) and

˚

even longer than that (2.306(6) A) in 11. This is obviously because

a silyl ligand with very strong trans inﬂuence is positioned trans to

the N1 atom.

1

two phosphorus atoms. In the ²⁹Si{ H} NMR spectrum, a signal

appears at 1.2 ppm that is a reasonable chemical shift for the

1

silyl group bearing H and Cl atoms. The ³¹P{ H} NMR spectrum

shows two signals at -51.9 ppm for PMe₃and at 40.3 ppm for

PCy₂. This assignment was based on the fact that only the latter

signal has a coupling with the silicon atom trans to the PCy₂.

Interestingly, the reaction between 1 and H₃SiTrip successfully

proceeded only in the presence of excess DMAP, which is a strong

Lewis base, to produce (P^cyN-P,N)IrHCl(DMAP)(SiH₂Trip) (12)

that is not a chlorosilyl complex but a chlorido(dihydrosilyl) com-

plex, in contrast to 11. Complex 12 was formed in 91% NMR yield

and isolated in 66% yield as colourless crystals by recrystallisation

from a CH₂Cl₂–pentane mixture (eqn (3)). No other geometrical

isomers were observed in this system. The structure of 12 was

conﬁrmed by X-ray crystallography and NMR spectroscopy.

The molecular structure of 12 is depicted in Fig. 9, which shows

that 12 takes a typical octahedral geometry by the coordination

of DMAP, Cl, H, a P,N-ligand and a dihydrosilyl ligand. The

H1 atom on Ir was found and reﬁned but two hydrogen atoms

on Si were not found. In this case, the silyl ligand is coordinated

to Ir at the trans position to the N-donor ligand and DMAP

at the trans position to the P-donor ligand. The Trip group is

(3)

The ¹H NMR spectrum of 12 shows a doublet assigned to IrH

2

at -22.51 ppm with J_HP= 20.1 Hz that supports the mutual cis

geometry of the hydrido and phosphine ligands. Two sets of signals

for diastereotopic hydrogen atoms of the SiH₂appears at 3.99 (d,

²J_HH= 5.6 Hz) and 4.20 ppm (t, ²J_HH= J_HP= 5.6 Hz) due to the

3

chiral Ir centre. The former is only coupled with the geminal proton

atom, while the latter is additionally coupled with the phosphorus

atom. The ²⁹Si{ H} NMR spectrum exhibits a signal at -74.5 ppm

1

2

as a doublet with J_SiP= 15 Hz. This chemical shift is largely

upﬁeld-shifted compared to those of usual silyl complexes, but is

comparable with those of the dihydrosilyl iridium complexes such

as [(PNP)Ir(H)SiH₂Ar]⁺(d_Si= -50.9 ppm for Ar = Dmp, d_Si

=

-74.1 ppm for Ar = Trip).^15b

From the observed difference between 11 and 12 in structure,

i.e. 11 has a chlorosilyl ligand but 12 has a dihydrosilyl ligand, it is

conceivable that at least a chlorido(silylene) intermediate such as

B¢¢ in Scheme 7 is formed and is followed by 1,2-Cl migration in the

case of 11, whereas a similar chlorido(silylene) intermediate is not

formed in the case of 12. Under the condition for the formation

of 12, excess DMAP effectively coordinates to the metal centre

to saturate it and prevents 1,2-H migration such as the step A¢¢

→ B¢¢ in Scheme 7. We also added DMAP in the reaction of

1 with H₃SiDmp, and PMe₃in the reaction of 1 with H₃SiTrip,

but none of them gave good results. This implies the difﬁculty of

controlling the 1,2-H and 1,2-Cl migrations on this P,N-chelate

complex system by the combination of the ligands on the metal

and the substituents on the silicon atom.

At any rate, both complexes 11 and 12 have a chloro group

on Si or Ir, which could be abstracted by an appropriate

reagent to produce a cationic silylene complex. Thus, we next

Fig. 9 ORTEP view of 12 with ellipsoids drawn at the 50% probability

level. The hydrogen atoms except H1 are omitted for clarity.

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attempted the reactions of 11 and 12 with several Li salts as

Cl-abstraction reagents. We could not get good results by the

reactions of 11 with the Li salt, but in the case of complex

12, treatment with LiB(C₆F₅)₄·2.5Et₂O in the presence of ex-

cess (10 equiv.) DMAP in CD₂Cl₂at room temperature for

4 h provided a DMAP-coordinated cationic silylene complex

[(P^cyN-P,N)IrH₂(DMAP)(SiHTrip ← DMAP)][B(C₆F₅)₄] (13) in

91% NMR yield (eqn (4)). Complex 13 was characterised by

possible geometrical isomers for the products. This is attributable

to the electronic effect of the P,N-chelate ligand mentioned in

Introduction. Reactivity study of the obtained silyl and silylene

complexes 11, 12 and 13 are under investigation.

Experimental

General procedures and materials

1

¹H, ²⁹Si{ H} and ³¹P{ H} NMR spectroscopy as well as high-

All manipulations were performed using either standard Schlenk

techniques under nitrogen or argon atmosphere, or vacuum

line techniques, or in a glovebox under nitrogen atmosphere.

Hexane, pentane and toluene were distilled from sodium ben-

zophenone ketyl. Et₂O, THF, THF-d₈, C₆D₆, and CD₂Cl₂

were dried over calcium hydride and stored in a glovebox

prior to use. N,N-dimethyl-p-toluidine and tetramethylethylene-

diamine (TMEDA) were distilled under a reduced pressure

and under a nitrogen atmosphere, respectively. Alkyl lithium

reagents (n-BuLi/hexane and Me₃SiCH₂Li/pentane) were pur-

chased and titrated with s-BuOH before use. [Ir(m-Cl)(coe)₂]₂

(coe = cyclooctaene),²⁸[Rh(m-Cl)(coe)₂]₂,²⁹H₂SiMes₂(Mes =

C₆H₂-2,4,6-Me₃),³⁰HSiMe₂SiMes₂Me,³¹HSiMe₂SiMe₂OMe,³²

resolution mass spectroscopy.

(4)

1

In the H NMR spectrum of 13, two sets of hydrido signals

of IrH₂are observed at -6.17 and -4.98 ppm non-equivalently

because they are diastereotopic due to the chiral Si centre that is

coordinated by DMAP. These signals are coupled with each other

and with the PCy₂at a cis position to the IrH₂, in which the former

H₃SiC(SiMe₃)₃,³³H₃SiDmp (Dmp

=

C₆H₂-2,6-Mes₂)³⁴and

H₃SiTrip (Trip = C₆H₂-2,4,6-ⁱPr₃)³⁵were prepared by the literature

procedures. Other reagents were purchased and used as they were

received. NMR spectra were recorded on a Bruker AVANCE-

300 Fourier transform spectrometer at 25 ^◦C. ¹H NMR chemical

shifts were referenced to the residual proton of deuterated solvents

2

signal exhibits a triplet pattern (²J_HH= J_HP= 11.7 Hz) by accident,

while the latter signal appears as a doublet of doublet (²J_HH= 11.7,

²J_HP= 15.9 Hz). The SiH signal appears at 6.12 ppm as a doublet

(C₆D₅H:d 7.15; OC₄D₇H:d 3.15; CDHCl₂: d 5.32). ¹³C{ H} NMR

1

3

1

due to the coupling with PCy₂with J = 8.5 Hz. The ²⁹Si{ H}

NMR spectrum shows a signal at 4.1 ppm as a doublet due to the

coupling with PCy₂with ²J = 19 Hz. The small coupling constant

clearly indicates a mutual cis geometry of the silyl and phosphine

ligands. The chemical shift is downﬁeld-shifted by about 80 ppm

compared to that (-74.5 ppm) of the precursor, i.e. silyl complex

12, and the downﬁeld shift is attributable to the existence of some

double bond character on the Ir–Si bond in 13. Moreover, the

high-resolution mass spectrum of 13 clearly shows the molecular

ion peak for the cationic part at m/z = 1002.5544 that agrees

well with the calculated value (m/z = 1002.5557) and its isotopic

pattern is well reproduced by the calculated one.

chemical shifts were referenced to the solvent carbon (C₆D₆: d

1

128.0, THF-d₈: d 67.4 (a-carbon)). ²⁹Si{ H} and ³¹P{ H} NMR

chemical shifts were referenced to an external standard, TMS (d

0) and 85% H₃PO₄(d 0), respectively. IR spectra were obtained on

a HORIBA FT-730 spectrometer. Mass spectra were recorded on

a Shimadzu GCMS-QP5050A mass spectrometer (70 eV). High-

resolution mass spectra (HR-MS) were measured on a Bruker-

Daltonics APEX III mass spectrometer (70 eV) and elemental

analysis were performed on a Yanako JM-10 CHN analyzer at

Research and Analytical Centre for Giant Molecules, Tohoku

University.

Synthesis of C₆H₃Me-3-PCy₂-4-NMe₂(P^cyN). To a solution of

N,N-dimethyl-p-toluidine (0.656 g, 5.00 mmol) in hexane (18 mL)

was added dropwise (7 min) a solution containing TMEDA

(0.884 g, 7.60 mmol), hexane (4 mL) and 1.51 M of n-BuLi in

hexan_◦e (5.01 mL, 7.57 mmol). The resulting mixture was stirred

at 25 C for 4 h and then added ClPCy₂(1.76 g, 7.56 mmol) in

Et₂O (4 mL). The reaction mixture was stirred over night and the

volatiles were removed under reduced pressure to give a mixture

of a yellow oil and precipitate of LiCl. The mixture was ﬁltered

to remove LiCl and the LiCl was washed with hexane (7 ¥ 5 mL).

The washings were collected and the solvent was removed to give

an orange oil, which was then puriﬁed by distillation (90 ^◦C,

0.1 mmHg) to afford a white solid. Recrystallisation of the white

solid from pentane at -30 ^◦C yielded C₆H₃Me-3-PCy₂-4-NMe₂as

colourless crystals in 50% yield (0.822 g, 2.48 mmol). (Found: C

75.81, H 10.35, N 4.29. Calcd for C₂₁H₃₄NP: C 76.09, H 10.34, N

4.23%); d_H(300 MHz, C₆D₆) 1.0–2.2 (m, 22 H, Cy), 2.19 (s, 3 H,

C₆H₃Me), 2.72 (s, 6 H, NMe₂), 6.95 (dd, ³J 8.1, ⁴J_HP3.9, 1 H, 5-H

of C₆H₃), 6.99 (d, ³J 8.1, 1 H, 6-H of C₆H₃), 7.31 (s, 1 H, 2-H of

Conclusions

In conclusion, iridium and rhodium complexes bearing a new

P,N-chelate ligand (P^cyN) were synthesised and their reactivity

toward hydrosilanes was investigated. Iridium complex 1 reacted

smoothly with several bulky hydrosilanes at room temperature

to produce (i) dinuclear complexes, (ii) bis(silyl) complexes and

(iii) silyl complexes depending on the substituents of hydrosilanes:

Complexes of the types (i), (ii) and (iii) were obtained by the

reactions of 1 with hydrosilanes containing moderately bulky aryl

groups (Mes), a very bulky alkyl group [C(SiMe₃)₃] and highly

sterically hindered aryl groups (Dmp, Trip), respectively. Some

reactions apparently involved Cl migration from M to Si with

formation of silylene complex intermediates. One of the products

of type (iii), a chlorido(silyl) complex 12, was further converted

to a cationic base-stabilised silylene iridium complex 13 via Cl

abstraction with a Li salt. It would also be noted that only a single

isomer was formed even in the cases where there were several

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©

C₆H₃); d_C(75.5 MHz, C₆D₆) 21.1 (s, C₆H₃Me), 26.9 (s), 27.6 (d,

J_CP8), 27.7 (d, J_CP12), 29.7 (d, J_CP10), 30.9 (d, J_CP17), 34.2 (d,

J_CP17) (Cy), 46.0 (d, J_CP6, NMe₂), 119.9 (d, J_CP3), 130.3, 131.9,

132.2, 133.8 (d, J_CP2), 158.1 (d, J_CP18) (C₆H₃); d_P(121.5 MHz,

C₆D₆) -12.1; m/z (EI) 332 (M⁺+1, 7), 331 (M⁺, 33), 316 (M⁺-

Me, 12), 248 (M⁺- Cy, 100), 166 (M⁺+ 1 - 2Cy, 44), 150 (M⁺-

Me - 2Cy, 16), 134 (M⁺+ 1 - 2Me - 2Cy, 15).

(300 MHz, C₆D₆) 0.8–1.8 (m, 22 H, Cy), 2.06 (s, 3 H, C₆H₃Me),

3.44 (d, ⁴J_HP1.5, 6 H, NMe₂), 6.7–7.5 (m, 12 H) and 8.2–8.3 (m,

6 H), (C₆H₃and Ph); d_C(75.5 MHz, THF-d₈) 20.6 (s, C₆H₃Me),

27.1, 27.3, 28.0 (d, J_CP11), 30.2 (d, J_CP4), 30.6 (d, J_CP4), 35.5 (d,

J_CP33) (Cy), 52.7 (d, J_CP2, NMe₂), 122.0 (d, J_CP9), 127.4 (d, J_CP

10), 129.2, 129.6, 132.0, 132.3, 136.5, (d, J_CP11), 137.4 (d, J_CP5),

138.3, 138.9, 162.3 (dd, J_CP15, J_CP2) (C₆H₃or Ph); d_P(121.5 MHz,

C₆D₆): 14.7 (d, ²J_PP19, PPh₃), 38.1 (d, ²J_PP19, PCy₂).

Synthesis of (P^cyN-P,N)IrCl(g²-coe) (1). A solution of [Ir(m-

Cl)(coe)₂]₂(1.20 g, 1.34 mmol) and P^cyN (0.888 g, 2.68 mmol)

in toluene (43 mL) was stirred at 25 ^◦C for 1.5 h. The volatiles

were removed under reduced pressure and the resulting solid was

dissolved in a minimum amount of THF and layered by pentane to

yield a yellow solid of 1 in 75% yield (1.34 g, 2.00 mmol). (Found:

C 52.00, H 7.33, N 1.92. Calcd for C₂₉H₄₈ClIrNP: C 52.04, H 7.23,

N 2.09%); d_H(300 MHz, C₆D₆) 1.0–2.4 (m, 28 H, Cy and coe),

2.01 (s, 3 H, C₆H₃Me), 2.5–2.7 (m, 4 H, Cy and coe), 3.2–3.5 (m,

2 H, coe), 3.6–3.8 (m, 2 H, coe), 3.18 (s, 6 H, NMe₂), 6.7–6.9 (m,

2 H, C₆H₃), 7.13 (s, 1 H, C₆H₃); d_C(75.5 MHz, THF-d₈) 20.7 (s,

C₆H₃Me), 26.0–33.3 (m, Cy and coe), 49.0 (s, coe), 52.5 (s, NMe₂),

122.4 (d, J_CP9), 131.3, 133.7 (d, J_CP40), 133.5, 138.1 (d, J_CP5),

163.4 (d, J_CP14) (C₆H₃); d_P(121.5 MHz, C₆D₆) 20.7.

Reaction of 2 with H₂SiMes₂: synthesis of

(P^cyN-P,N)₂Ir₂H₂(l-Cl)(l-H)(l-SiClMes) (5)

NMR-scale experiment (method A). In an NMR tube

equipped with a Teﬂon needle valve on the top, a solution of 1

(10 mg, 0.015 mmol) in C₆D₆(ca. 0.5 mL) containing Si(SiMe₃)₄

(ca. 1 mg) as an internal standard was prepared and the valve

1

was closed under N₂atmosphere. After measuring a H NMR

spectrum of the solution, H₂SiMes₂(4 mg, 0.02 mmol) was added

to it. The NMR sample was then heated at 40 ^◦C for 3 h. The ¹H

NMR spectrum of the reaction mixture showed the formation of

5 in 60% NMR yield.

Synthetic-scale experiment (method B). In a Schlenk ﬂask

(30 mL), a solution of 1 (10 mg, 0.015 mmol) and H₂SiMes₂

(0.080 g, 0.020 mmol) in toluene (10 mL) was heated at 40 ^◦C

for 3 h. After removal of volatiles, the residue was dissolved in

a minimum amount of THF and layered by fourfold amount of

pentane. The layered solution was kept at room temperature to give

yellow crystals of 6 in 36% yield (0.068 g, 0.054 mmol). (Found:

C 48.16, H 6.44, N 2.24. Calcd for C₅₁H₈₂Cl₂Ir₂N₂P₂Si: C 48.29,

H 6.52, N 2.21%); d_H(300 MHz, C₆D₆) -26.02 (m, 2 H, terminal

Synthesis of (P^cyN-P,N)RhCl(g²-coe) (2). In a procedure sim-

ilar to the synthesis of 1, a solution of [Rh(m-Cl)(coe)₂]₂(0.800 g,

1.12 mmol) and 1 (0.740 g, 2.23 mmol) in toluene (30 mL) was

stirred at 25 ^◦C for 1.5 h to afford a yellow solid of 3 in 94% yield

(1.25 g, 2.10 mmol). (Found: C 59.97, H 8.09, N 2.40. Calcd for

C₂₉H₄₈ClNPRh: C 60.05, H 8.34, N 2.41%); d_H(300 MHz, C₆D₆)

1.0–2.1 (m, 28 H, Cy and coe), 2.00 (s, 3 H, C₆H₃Me), 2.5–2.8 (m,

4 H, Cy and coe), 3.4–3.6 (m, 2 H, coe), 3.9–4.0 (m, 2 H, coe), 3.21

(s, 6 H, NMe₂), 6.7–6.9 (m, 2 H, C₆H₃), 7.0–7.1 (m, 1 H, C₆H₃);

d_C(75.5 MHz, THF-d₈) 20.7 (s, C₆H₃Me), 27.3–35.1 (m, Cy and

coe), 52.2 (s, NMe₂), 66.2 (d, J_CRh14, coe), 122.8 (d, J_CP11), 131.3,

131.3 (d, J_CP32), 133.7, 137.8 (d, J_CP5), 162.0 (d, J_CP17) (C₆H₃);

d_P(121.5 MHz, C₆D₆) 56.9.

2

IrH), -6.12 (t, J_HP64.6, 1 H, m-H), 0.5–2.5 (m, 40 H, Cy), 2.10

(s, 6 H, C₆H₃Me), 2.16 (s, 3 H, p-Me of Mes), 2.8–3.1 (m, 4 H,

Cy), 3.38 (br, 6 H, o-Me of Mes), 3.44 (s, 6 H, NMe), 3.69 (s, 6 H,

NMe), 6.7–7.0 (m, 4 H, C₆H₃or m-H of Mes), 7.1–7.2 (m, 2 H,

C₆H₃or m-H of Mes), 7.3–7.4 (m, 2 H, C₆H₃or m-H of Mes). d_P

(121.5 MHz, C₆D₆) 42.7.

Synthesis of (P^cyN-P,N)IrCl(PMe₃) (3). A solution of [Ir(m-

Cl)(coe)₂]₂(0.150 g, 0.167 mmol) and P^cyN (0.111 g, 0.336 mmol)

in toluene (9 mL) was stirred at 25 ^◦C for 1.5 h. After removal

of volatiles, toluene (8 mL) and then PMe₃(0.026 g, 0.34 mmol)

were added slowly. The resulting solution was stirred for another

1.5 h and the solvent was removed under reduced pressure. The

residue was washed with pentane and dried to give a yellow solid

of 3 in 87% yield (0.185 g, 0.292 mmol). (Found: C 45.13, H 6.65,

N 2.04. Calcd for C₂₄H₄₃ClIrNP₂: C 45.38, H 6.82, N 2.21%);

Reaction of 1 with HSiMe₂SiMes₂Me.

NMR-scale experiment. In a procedure similar to Method A

for 5, a solution of 1 (10 mg, 0.015 mmol) in C₆D₆(ca. 0.5 mL)

containing Si(SiMe₃)₄was treated with HSiMe₂SiMes₂Me (5 mg,

1

0.02 mmol) at room temperature for 18 h. ¹H and ²⁹Si{ H} NMR

spectra showed the formation of HSiMesMe₂in 69% NMR yield

together with some iridium complexes.

2

d_H(300 MHz, C₆D₆) 1.0–2.1 (m, 20 H, Cy), 1.67 (d, J_HP7.3, 9

Synthetic-scale experiment. In a procedure similar to method

B for 5, a solution of 1 (0.200 mg, 0.299 mmol) and

HSiMe₂SiMes₂Me (0.108 g, 0.317 mmol) in toluene (10 mL)

was stirred at room temperature for 3 h. After removal of

volatiles, the residue was washed with pentane and dried under

reduced pressure to give a yellow solid containing chlorosilyl

iridium complex (P^cyN-P,N)IrH[SiMeCl(C₆H₃-2,4,-Me₂-6-CH₂)-

Si,C] (6) in approximately 60% yield (0.130 g, 0.180 mmol).

The solid was recrystallised from toluene–pentane at room

temperature for 3 h to afford yellow crystals of chlorido-bridged

diiridium complex (P^cyN-P,N)₂Ir₂H(m-Cl)(m-H)[m-SiMeCl(C₆H₃-

2,4,-Me₂-6-CH)-Si,C,C] (7) in 43% yield (0.049 g, 0.038 mmol)

(when 7 is assumed to be formed from two molecules of 6 with

releasing “SiMeMes”). 6: d_H(300 MHz, C₆D₆) -24.04 (d, ²J_HP9.3,

H, PMe₃), 2.08 (s, 3 H, C₆H₃Me), 2.5–2.6 (m, 2 H, Cy), 3.31 (d,

⁴J_HP1.8, 6 H, NMe₂), 6.7–6.9 (m, 2 H, C₆H₃), 7.3–7.4 (m, 1 H,

C₆H₃); d_C(75.5 MHz, THF-d₈) 20.5 (d, J_CP38, PMe₃), 20.6 (s,

C₆H₃Me), 26.9–36.7 (m, Cy), 52.8 (d, J_CP2, NMe₂), 121.5 (d, J_CP

8), 130.5, 131.6, 136.0, 136.4 (d, J_CP5), 162.0 (d, J_CP12) (C₆H₃).

2

d_P(121.5 MHz, C₆D₆) -40.8 (d, J_PP19, PMe₃), 40.8 (d, J_PP19,

PCy₂).

Synthesis of (P^cyN-P,N)IrCl(PPh₃) (4). In a procedure similar

to the synthesis of 3, complex 4 was prepared in 94% yield

(1.55 g, 1.90 mmol) as a yellow solid by using PPh₃(0.528 g,

2.01 mmol), [Ir(m-Cl)(coe)₂]₂(0.901 g, 1.01 mmol) and P^cyN

(0.666 g, 2.01 mmol) in toluene (40 mL). (Found: C 56.69, H 5.67,

N 1.52. Calcd for C₃₉H₄₉ClIrNP₂: C 57.02, H 6.01, N 1.71%); d_H

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1 H, IrH), 1.38 (s, 3 H, SiMeCl), 0.8–2.5 (m, 22 H, Cy), 2.04 (s,

3 H, C₆H₃Me or C₆H₂Me₂), 2.37 (s, 3 H, C₆H₃Me or C₆H₂Me₂),

2.42 (s, 3 H, C₆H₃Me or C₆H₂Me₂), 2.78 (s, 3 H, NMe), 2.88 (s,

3 H, NMe), 6.7–7.5 (m, 5 H, C₆H₃and C₆H₂); d_P(121.5 MHz,

C₆D₆) 57.0. 7: d_H(300 MHz, C₆D₆) -28.77 (d, ²J_HP23.4, 1 H, IrH),

-5.27 (dd, ²J_HP72.0, 59.8, 1 H, m-H), 1.50 (s, 3 H, SiMeCl), 2.07 (s,

3 H, C₆H₃Me or C₆H₂Me₂), 2.08 (s, 3 H, C₆H₃Me or C₆H₂Me₂),

0.5–2.6 (m, 44 H, Cy), 2.43 (s, 3 H, C₆H₃Me or C₆H₂Me₂), 2.77

(s, 3 H, C₆H₃Me or C₆H₂Me₂), 3.49 (s, 3 H, NMe), 3.50 (s, 3 H,

NMe), 3.69 (s, 3 H, NMe), 4.16 (s, 3 H, NMe), 5.91 (dd, ²J_HP5.2,

3.3, 1 H, m-CH), 6.70 (s, 1 H, C₆H₃or C₆H₂), 6.8–7.2 (m, 5 H,

C₆H₃or C₆H₂), 7.3–7.5 (m, 2 H, C₆H₃or C₆H₂); d_H(75.5 MHz,

C₆D₆) 13.8 (SiMe), 20.6–22.3 (m, C₆H₃Me or C₆H₂Me₂), 26.7–

40.5 (m, Cy), 58.4, 60.6, 62.3, 62.6 (NMe), 120.6 (dd, J_CP10,

8, m-CH), 122.6–138.6 (m), 142.7, 160.0 (d, J_CP14), 160.5 (d,

J_CP13), 176.8 (C₆H₃or C₆H₂); d_Si(59.6 MHz, C₆D₆) 15.5 (d,

²J_SiP10); d_P(121.5 MHz, C₆D₆) 30.5 (d, ³J 36, PCy₂), 36.1 (d, ³J

36, PCy₂); m/z (ESI) 1280.4356 (M⁺, C₅₂H₈₂Cl₂Ir₂N₂P₂Si requires

1280.4334).

6.6–6.8 (m, 2 H, C₆H₃). A signal of another aryl proton seems to

be overlapped with that of C₆D₅H; d_Si(59.6 MHz, C₆D₆) -43.0 (d,

²J_SiP16, SiMe₂), -14.8 (d, ²J_SiP32, SiMeCl), -5.9 (s, SiMe₃), -1.3

(d, ⁴J_SiP2, SiMe₃); d_P(121.5 MHz, C₆D₆) 42.1.

Reaction of

2

with H₃SiC(SiMe₃)₃: synthesis of (P^cyN-

P,N)RhH[SiMe₂C(SiMe₃)₂SiClMe-Si,Si] (10). A solution of 2

(0.200 g, 0.336 mmol) and H₃SiC(SiMe₃)₃(0.088 g, 0.34 mmol) in

toluene (15 mL) was heated at 60 ^◦C for 5 h and the volatiles were

◦

removed. The residue was recrystallised from toluene at -30 C

to give yellow crystals of 10 in 65% yield (0.165 g, 0.219 mmol).

(Found: C 55.24, H 8.57, N 1.80; Calcd for C₃₁H₆₂NPRhSi₄·C₇H₈

(including one molecule of toluene as a crystal solvent): C 55.48,

H 8.58, N 1.70%); d_H(300 MHz, C₆D₆) -8.91 (dd, ¹J_HRh27.9, ²J_HP

83.6, 1 H, RhH), 0.57 (s, 9 H, SiMe₃), 0.71 (s, 9 H, SiMe₃), 0.87 (s, 3

H, SiMe₂), 1.02 (s, 3 H, SiMe₂), 1.0–1.9 (m, 18 H, Cy), 2.1–2.6 (m,

4 H, Cy), 1.41 (s, 3 H, SiMeCl), 2.02 (s, 3 H, C₆H₃Me), 2.847 (s, 3

H, NMe), 2.852 (s, 3 H, NMe), 6.84 (m, 2 H, C₆H₃); d_C(75.5 MHz,

C₆D₆) 7.0 (s, SiMe), 7.4 (s, SiMe), 11.3 (d, J_CP3 Hz, SiMe), 12.0

(d, J_CP4, SiMe), 16.0 (s, C(SiMe₃)₂), 21.4 (s, C₆H₃Me), 22.7 (d, J_CP

8, SiMe), 26.3–30.9 (m, Cy), 54.1 (d, J_CP10, NMe₂), 121.4 (d, J_CP

8), 132.0, 132.3, 132.6 (d, J_CP15), 136.5 (d, J_CP3), 158.4 (d, J_CP17)

C₆H₃); d_Si(59.6 MHz, C₆D₆) -7.1 (d, ¹J_SiRh27, SiMe₂), -6.4 (s, Si

Me₃), -4.1 (d, ⁴J_SiP1, SiMe₃), 24.3 (dd, ¹J_SiRh42, ²J_SiP5, SiMeCl);

d_P(121.5 MHz, C₆D₆) 36.0 (d, ¹J_PRh= 131 Hz).

Reaction of 1 with HSiMe₂SiMe₂OMe: synthesis of (P^cyN-

P,N)IrHCl[SiMe₂··O(Me)··SiMe₂-Si,Si] (8). To a solution of

1 (0.100 g, 0.150 mmol) in toluene (6 mL) was added

HSiMe₂SiMe₂OMe (0.023 g, 0.15 mmol) with stirring. Soon after

the addition, the volatiles were removed under reduced pressure

and the residue was washed with pentane to give a yellow solid of

8 in 99% yield (0.105 g, 0.149 mmol). (Found: C 49.78, H 7.20, N

1.81; Calcd for C₂₆H₅₀ClIrNOPSi₂·C₇H₈(including one molecule

of toluene as a crystal solvent) C 49.57, H 7.31, N 1.75%); d_H

Reaction of

P,N)IrH₂(PMe₃)(SiHClDmp) (11). To

3

with H₃SiDmp: synthesis of (P^cyN-

toluene solution

a

2

(300 MHz, C₆D₆) -20.87 (d, J_HP11.5, 1 H, IrH), 0.62 (s, 3 H,

of 3, which was freshly prepared from 2 (0.101 g, 0.150 mmol) and

PMe₃(0.012 g, 0.15 mmol) in toluene (5 mL) with stirring at room

temperature for 1.5 h, was added H₃SiDmp (0.050 g, 0.15 mmol)

in toluene (1.5 mL). The mixture was stirred at room temperature

for 16 h. After removal of volatiles, the residue wad recrystallised

from a THF solution layered by hexane at room temperature to

give colourless crystals of 11 in 65% yield (0.095 g, 0.097 mmol).

(Found: C 58.87, H 7.58, N 1.56; Calcd for C₄₈H₇₁ClIrNP₂Si C

58.84, H 7.30, N 1.43%); d_H(300 MHz, CD₂Cl₂) -26.47 (dt, ²J_HP

12.6, ²J 6.4, 1 H, IrH), -10.82 (ddd, ²J_HP120.6, 21.9, ²J 5.3, 1 H,

SiMe), 0.66 (d, ⁴J_HP1.8, 3 H, SiMe), 0.85 (s, 3 H, SiMe), 0.86 (d,

⁴J_HP1.8, 3 H, SiMe), 1.0–2.7 (m, 22 H, Cy), 2.08 (s, 3 H, C₆H₃Me),

2.92 (s, 3 H, OMe), 3.24 (s, 3 H, NMe), 3.45 (s, 3 H, NMe), 7.0–7.1

(m, 2 H, C₆H₃), 7.2–7.3 (m, 1 H, C₆H₃); d_C(75.5 MHz, C₆D₆)

0.4 (d, J_CP10, SiMe), 3.2 (s, SiMe), 8.0 (d, J_CP11, SiMe), 10.3 (s,

SiMe), 20.5 (s, C₆H₃Me), 25.8–31.0 (m, Cy), 38.7 (d, J_CP17, Cy),

40.0 (d, J_CP24, Cy), 50.7 (d, J_CP5, OMe), 57.2 (s, NMe), 64.8 (s,

NMe), 120.9 (d, J_CP9), 131.9, 132.4, 136.1 (d, J_CP3), 136.6 (d, J_CP

24), 160.8 (d, J_CP17) (C₆H₃); d_Si(59.6 MHz, C₆D₆) 42.2 (d, ²J_SiP2,

2

3

SiMe₂), 69.7 (d, J_SiP177, SiMe₂); d_P(121.5 MHz, C₆D₆) 40.1 (s,

IrH), 0.98 (d, J_HP6.9, 9 H, PMe₃), 1.0–2.6 (m, 22 H, Cy), 2.06

²J_Psi177).

(br, 6 H, p-Me of Dmp), 2.20 (br, 12 H, o-Me of Dmp), 2.36 (s, 3

H, C₆H₃Me), 2.75 (s, 3 H, NMe), 3.26 (s, 3 H, NMe), 5.67 (dd,

³J_HP18.7, 11.0 Hz, 1 H, SiH), 6.6–6.9 (m, 4 H, ArH), 7.1–7.5 (m,

6 H, C₆H₃or C₆H₂); d_C(75.5 MHz, CD₂Cl₂) 20.0 (dd, J_CP26, 2,

PMe₃), 20.8, 21.0, 22.4 (br), 22.8 (Me), 26.0–39.7 (m, Cy), 59.0 (d,

J_CP5, NMe), 65.6 (d, J_CP4, NMe), 120.2 (d, J_CP10), 127.4–128.6

(m), 131.5, 131.7, 135.6, 136.8–137.8 (m), 141.8, 147.9, 162.3 (d,

Reaction of 1 with H₃SiC(SiMe₃)₃: synthesis of

(P^cyN-P,N)IrH₃[SiMe₂C(SiMe₃)₂SiClMe-Si,Si] (9)

NMR-scale experiment. In a procedure similar to method A

for 5, a solution of 1 (8 mg, 0.01 mmol), H₃SiC(SiMe₃)₃(3 mg,

0.01 mmol), and Si(SiMe₃)₄(ca. 1 mg) in C₆D₆(0.5 mL) was stirred

J

_CP20) (ArC); d_Si(59.6 MHz, CD₂Cl₂) 1.2 (dd, ²J_SiP191, ²J_SiP18);

2 2

1

at room temperature for 4.5 h. H, ²⁹Si{ H} and ³¹P{ H}NMR

d_P(121.5 MHz, C₆D₆) -51.9 (d, J_PP20, PMe₃), 40.3 (d, J_PP20,

²J_Psi191, PCy₂).

spectra showed the formation of 9 in 82% NMR yield.

Synthetic-scale experiment. In a procedure similar to method

B for 5, a solution of 1 (0.200 g, 0.229 mmol) and H₃SiC(SiMe₃)₃

(0.079 g, 0.30 mmol) in toluene (15 mL) was stirred at room

temperature for 5 h. Recrystallisation of the reaction mixture

from toluene at -30 ^◦C afforded 9 as yellow crystals in 17% yield

(0.041 g, 0.052 mmol). d_H(300 MHz, C₆D₆) -8.81 (d, ²J_HP9.5, 3 H,

IrH₃), 0.63 (s, 9 H, SiMe₃), 0.68 (s, 9 H, SiMe₃), 1.0–2.5 (m, 22 H,

Cy), 1.11 (s, 3 H, SiMe₂), 1.19 (s, 3 H, SiMe₂), 1.51 (s, 3 H, SiMeCl),

2.00 (s, 3 H, C₆H₃Me), 3.13 (s, 3 H, NMe), 3.23 (s, 3 H, NMe),

Reaction of 11 with LiB(C₆F₅)₄·2.5Et₂O. In a procedure

similar to method A for 5, an NMR sample containing 11

(10 mg, 0.010 mmol), LiB(C₆F₅)₄·2.5Et₂O (9 mg, 0.01 mmol), and

Si(SiMe₄)₄(ca. 1 mg) in CD₂Cl₂was prepared and the reaction

1

was monitored by H NMR spectroscopy, which only showed

instantaneous formation of a complex mixture. A similar reaction

was also performed in the presence of DMAP, but it also gave a

complex mixture.

This journal is

The Royal Society of Chemistry 2010

Dalton Trans., 2010, 39, 9386–9400 | 9397

©

Reaction of 2 with H₃SiTrip in the presence of excess DMAP:

Reaction of 12 with LiB(C₆F₅)₄·2.5Et₂O in the presence of DMAP:

synthesis of [(P^cyN-P,N)IrH₂(DMAP)(SiHTrip ←

DMAP)][B(C₆F₅)₄] (13).

synthesis of (P^cyN-P,N)IrHCl(DMAP)(SiH₂Trip) (12).

NMR-scale experiment. In a procedure similar to method A

for 5, a solution of 2 (10 mg, 0.015 mmol), H₃SiTrip (4 mg,

0.02 mmol), DMAP (9 mg, 0.08 mmol), and Si(SiMe₄)₄(ca. 1 mg)

NMR-scale experiment. In a procedure similar to method A

for 5, an NMR sample containing 12 (15 mg, 0.017 mmol),

LiB(C₆F₅)₄·2.5Et₂O (14 mg, 0.017 mmol), DMAP (20 mg,

0.17 mmol) and Si(SiMe₄)₄(ca. 1 mg) in CD₂Cl₂was prepared and

1

in C₆D₆was prepared. The reaction was monitored by H and

1

³¹P{ H} NMR spectroscopy, which showed the instantaneous

1

formation of 12 in 91% NMR yield.

the reaction was monitored by H, ²⁹Si{ H} and ³¹P{ H} NMR

spectroscopy. After 4 h at room temperature, 13 was formed in 91%

NMR yield. d_H(300 MHz, CD₂Cl₂) -6.17 (t, ²J_HP= J_HH11.7, 1

2

H, IrH), -4.98 (dd, ²J_HP15.9, ²J 11.7, 1 H, IrH), 1.0–3.0 (m, 22 H,

Cy), 1.18 (d, ³J 6.9, 6 H, CHMe₂), 1.33 (d, ³J 6.6, 6 H, CHMe₂),

1.41 (d, ³J 5.4, 6 H, CHMe₂), 2.40 (s, 3 H, C₆H₃Me), 5.95 (dd, ³J

Synthetic-scale experiment. In a procedure similar to method

B for 5, to a solution of 1 (0.100 g, 0.150 mmol) and DMAP

(0.091 g, 0.75 mmol) in toluene (5 mL) was added H₃SiTrip

(0.035 g, 0.15 mmol) at room temperature. Soon after the

addition, the volatiles were removed and the resulting residue was

recrystallised from a CH₂Cl₂solution layered by pentane to give

colourless crystals of 12 in 66% yield (0.091 g, 0.099 mmol). d_H

(300 MHz, CD₂Cl₂) -22.51 (d, ²J_HP20.1, 1 H, IrH), 0.7–3.5 (m, 22

H, Cy), 1.00 (d, ³J 5.7, 6 H, CHMe₂), 1.16 (d, ³J 6.9, 6 H, CHMe₂),

3

6.8, 2.9, 1 H, ArH of DMAP), 6.12 (d, J_HP8.5, 1 H, SiH), 6.35

(dd, ³J 6.8, 2.9, 1 H, ArH of DMAP), 6.56 (s, 2 H, m-H of Trip),

7.3–7.5 (m, 3 H, ArH of P,N-chelate ligand), 8.30 (dd, ³J 6.8, 2.9,

1 H, ArH of DMAP), 9.15 (dd, ³J 6.8, 2.9, 1 H, ArH of DMAP).

The signal of CHMe₂is overlapped with those of Cy. The signals

of NMe₂of the P,N-ligand and DMAP are overlapped with those

3

2

1.20 (d, J 6.6, 6 H, CHMe₂), 2.40 (s, 3 H, ArMe), 2.53 (s, 3 H,

of free DMAP. d_Si(59.6 MHz, CD₂Cl₂) 4.1 (d, J_SiP19, SiHTrip

NMe of P,N-chelate ligand), 2.77 (s, 3 H, NMe of P,N-chelate

← DMAP); d_P(121.5 MHz, CD₂Cl₂) 31.9; m/z (ESI) 1002.5544

ligand), 2.86 (s, 6 H, NMe of DMAP), 3.99 (d, ²J 5.6, 1 H, SiH),

(M⁺- B(C₆F₅)₄, C₅₀H₈₀IrN₅PSi requires 1002.5557).

3

4.20 (t, ²J_HH= J_HP5.6, 1 H, SiH), 5.53 (dd, ³J 6.9, 3.3, 1 H, ArH

3

of DMAP), 6.41 (dd, J 6.9, 3.3, 1 H, ArH of DMAP), 6.65 (s,

X-Ray crystallography

2 H, m-H of Trip), 7.2–7.5 (m, 3 H, ArH of P,N-chelate ligand),

3

7.64 (dd, J 6.9, 2.4, 1 H, ArH of DMAP), 9.41 (dd, J 6.9, 2.4,

1 H, ArH of DMAP); d_C(75.5 MHz, CD₂Cl₂) 20.9 (C₆H₃Me),

24.1–24.4 (m, CHMe₂), 26.5–39.7 (m, Cy), 32.6 (CHMe₂), 34.7

(CHMe₂), 39.1 (CHMe₂), 51.5 (NMe), 56.6 (NMe), 107.1 (d, J_CP

9), 119.3, 122.1 (d, J_CP8), 131.5–137.1 (m), 147.9, 149.0, 153.6,

154.7, 159.3 (d, J_CP20), 159.8 (ArC); d_Si(59.6 MHz, CD₂Cl₂)

-74.5 (d, ²J_SiP15); d_P(121.5 MHz, C₆D₆) 17.8; m/z (ESI) 914.4310

(M⁺- H, C₄₃H₆₉ClIrN₃PSi requires 914.4311).

Diffraction measurements were made on a RIGAKU RAXIS-

RAPID Imaging Plate diffractometer with graphite monochro-

mated Mo-Ka radiation. Crystals of 1, 3, 5 and 7–12 were

coated with liquid parafﬁn, mounted on a nylon loop, and held

in a place under a cold stream of N₂on the diffractometer. A

total of 44 images, corresponding to 220.0^◦oscillation angles,

were collected with 2 different goniometer settings. Empirical

absorption collections were made using the program NUMABS.³⁶

Table 10 Crystallographic data for complexes 1, 3·C₇H₈, 5, 7·C₇H₈and 8·C₇H₈

1

3·C₇H₈

5

7·C₇H₈

8·C₇H₈

Formula

FW

T/K

C₂₉H₄₈ClIrNP

669.30

150(2)

Triclinic

¯

P1

9.6406(7)

12.0199

13.9025(7)

105.000(2)

108.743(4)

98.988(2)

2

1422.23(17)

1.563

4.862

C₂₄H₄₃ClIrNP₂·C₇H₈C₅₁H₈₂Cl₂Ir₂N₂P₂Si

C₅₂H₈₁Cl₂Ir₂N₂P₂Si·C₇H₈

C₂₆H₅₀ClIrNOPSi₂·C₇H₈

727.32

1272.55

150(2)

1371.65

799.60

150(2)

Monoclinic

150(2)

Triclinic

¯

P1

12.1763(8)

15.2748(8)

17.6511(12)

150(2)

Monoclinic

P2₁/c

12.0805(5)

16.3211(8)

18.1653(8)

Crystal system

Space group

Monoclinic

P2₁/c

P2₁

˚

a/A

9.2063(5)

18.9042(12)

18.4783(12)

14.6736(9)

10.0455(7)

19.8282(14)

71.710(2)

108.567(3)

69.440(2)

2

˚

b/A

˚

c/A

a/^◦

b/^◦

g /^◦

Z

93.2856(9)

80.573(2)

92.365(2)

4

2

4

3

˚

V/A

3210.6(3)

1.505

4.361

2770.6(3)

1.525

5.007

0.13 ¥ 0.12 ¥ 0.11

1.08–27.48

1276

2913.2(3)

1.564

4.769

0.17 ¥ 0.15 ¥ 0.11

1.22–27.42

1378

3578.5(3)

1.484

3.943

0.13 ¥ 0.12 ¥ 0.07

1.68–27.48

1632

r/Mg m^-3

m/mm^-1

Crystal size/mm³

2q range/^◦

F(000)

0.12 ¥ 0.12 ¥ 0.08 0.17 ¥ 0.15 ¥ 0.14

1.64–27.44

676

1.54–27.48

1472

No. of unique data

6450

7012

12 190

12 585

8173

No. of data with I > 2s(I) 5572

5499

332

1.133

9069

234

1.102

9998

614

1.255

6128

374

1.227

No. of parameters

300

GOF on F²

1.234

R₁, wR₂[I > 2s(I)]

R₁, wR₂(all data)

0.0588, 0.1271

0.0766, 0.1416

0.0733, 0.1355

0.1018, 0.1512

0.0896, 0.2060

0.1278, 0.2353

0.0601, 0.1426

0.0854, 0.1565

0.0833, 0.1335

0.1221, 0.1488

9398 | Dalton Trans., 2010, 39, 9386–9400

This journal is

The Royal Society of Chemistry 2010

©

Table 11 Crystallographic data for complexes 9, 10·C₇H₈, 11·C₄H₈O and 12·CH₂Cl₂·C₅H₁₂

9

10·C₇H₈

11·0.5C₄H₈O

12·CH₂Cl₂·C₅H₁₂

Formula

FW

T/K

C₃₁H₆₄ClIrNPSi₄

821.81

150(2)

Monoclinic

P2₁/c

11.5618(3)

18.3157(4)

17.9750(3)

C₃₁H₆₂ClNPRhSi₄· C₇H₈

C₄₈H₇₁ClIrNP₂Si·0.5C₄H₈O

C₄₃H₇₀ClIrN₃PSi·CH₂Cl₂·C₅H₁₂

822.64

150(2)

1015.79

150(2)

1072.80

150(2)

Crystal system

Space group

Triclinic

¯

P1

Triclinic

¯

P1

Triclinic

¯

P1

˚

a/A

9.53940(10)

13.1147(2)

19.6455(5)

70.960(4)

77.3979(19)

71.675(3)

2

2187.11(7)

1.249

0.623

0.20 ¥ 0.19 ¥ 0.17

1.11–27.48

876

9660

7779

11.9670(4)

12.5030(3)

18.2016(5)

80.8548(13)

77.1201(17)

68.214(2)^◦

2

2456.49(12)

1.373

2.896

0.14 ¥ 0.12 ¥ 0.12

1.15–27.48

1048

11 141

9520

11.7958(7)

12.2790(7)

18.9266(8)

104.795(3)

99.527(4)

92.1081(15)

2

2604.9(2)

1.368

2.805

0.22 ¥ 0.22 ¥ 0.19

1.13–27.43

1112

11 632

10 517

˚

b/A

˚

c/A

a/^◦

b/^◦

g /^◦

Z

96.0413(11)

4

3

˚

V/A

3785.29(17)

1.442

3.788

0.12 ¥ 0.12 ¥ 0.09

1.59–27.48

1688

8508

6769

359

1.298

r/Mg m^-3

m/mm^-1

Crystal size/mm³

2q range/^◦

F(000)

No. of unique data

No. of data with I > 2s(I)

No. of parameters

GOF on F²

R₁, wR₂[I > 2s(I)]

R₁, wR₂(all data)

404

1.167

0.0635, 0.1351

0.0869, 0.1448

519

1.215

0.0604, 0.1397

0.0788, 0.1517

513

1.218

0.0438, 0.1113

0.0530, 0.1200

0.0800, 0.1634

0.1082, 0.1751

The structures were solved by Patterson and Fourier transform

methods and reﬁned by full-matrix least-squares method on F²

using SHELXS-97.³⁷

Hashimoto, A. Matsuda and H. Tobita, Organometallics, 2006, 25,

472–476.

4 H. Hashimoto, J. Sato and H. Tobita, Organometallics, 2009, 28, 3963–

3965.

The details of the analysis of these complexes are described in

supporting information. Crystallographic data of 1, 3·C₇H₈, 5,

7·C₇H₈and 8·C₇H₈are summarised in Table 10 and those of 9,

10·C₇H₈, 11·0.5C₄H₈O and 12·CH₂Cl₂·C₅H₁₂are summarised in

Table 11.

5 T. Watanabe, H. Hashimoto and H. Tobita, Angew. Chem., Int. Ed.,

2004, 43, 218–221.

6 M. Ochiai, H. Hashimoto and H. Tobita, Angew. Chem., Int. Ed., 2007,

46, 8192–8194.

7 M. Ochiai, H. Hashimoto and H. Tobita, Dalton Trans., 2009, 1812–

1814.

8 T. Watanabe, H. Hashimoto and H. Tobita, J. Am. Chem. Soc., 2006,

128, 2176–2177.

9 H. Hashimoto, M. Ochiai and H. Tobita, J. Organomet. Chem., 2007,

692, 36–43.

10 T. Watanabe, H. Hashimoto and H. Tobita, J. Am. Chem. Soc., 2007,

129, 11338–11339.

11 (a) F. Speiser, P. Braunstein and L. Saussine, Acc. Chem. Res., 2005, 38,

784–793; (b) A. Kermagoret and P. Braunstein, Organometallics, 2008,

27, 88–99.

Acknowledgements

This work was supported by the Ministry of Education, Culture,

Sports, Science and Technology of Japan (Grants-in-Aid for

Scientiﬁc Research no. 18064003, 19550056 and 21550054).

12 J. Cipot, R. McDonald, M. J. Ferguson, G. Schatte and M. Stradiotto,

Organometallics, 2007, 26, 594–608.

13 K. Abdur-Rashid, R. Guo, A. J. Lough, R. H. Morris and D. Song,

Adv. Synth. Catal., 2005, 347, 571–579.

14 M. Ito, A. Sakaguchi, C. Kobayashi and T. Ikariya, J. Am. Chem. Soc.,

2007, 129, 290–291.

15 (a) E. Calimano and T. D. Tilley, J. Am. Chem. Soc., 2008, 130, 9226–

9227; (b) E. Calimano and T. D. Tilley, J. Am. Chem. Soc., 2009, 131,

11161–11173.

16 (a) H. P. Fritz, I. R. Gordon, K. E. Schwarzhans and L. M. Venanzi,

J. Chem. Soc., 1965, 5210–5216; (b) W. Levason, K. G. Smith, C. A.

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Synthesis of η2-cyclooctene iridium and rhodium complexes supported by a novel P,N-chelate ligand and their reactivity toward hydrosilanes: Facile Cl migration from metal to silicon via silylene complex intermediates and formation of a base-stabilised silylene complex

DOI: 10.1039/c0dt00264j

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