Synthesis and reactivity of rhodium and iridium alkene, alkyl and silyl complexes supported by a phenyl-substituted PNP pincer ligand

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Dalton Trans., 2010, DOI: 10.1039/C0DT00287A

Organosilicon compounds meet subatomic physics: Muon spin resonance

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Synthesis and reactivity of rhodium and iridium alkene, alkyl and silyl

complexes supported by a phenyl-substituted PNP pincer ligand†‡

Elisa Calimano and T. Don Tilley*

Received 8th December 2009, Accepted 2nd March 2010

DOI: 10.1039/b925856f

New rhodium and iridium complexes supported by the phenyl-substituted PNP pincer ligand PNP^PhH

(HN(2-PPh₂-4-Me-C₆H₃)₂) (1) were synthesized. The reaction of 2 equiv. of 1 with [(COD)IrCl]₂

afforded the coordination complex [(PNP^PhH)Ir(COD)]Cl (2) featuring hydrogen bonding between the

N–H group and the chloride anion, as characterized by NMR spectroscopy and X-ray crystallography.

Reaction of 1 with [(COE)₂IrCl]₂or [(COE)₂RhCl]₂in benzene provided a mixture of complexes

including (PNP^PhH)MHCl₂(M = Ir (4), M = Rh (7)) and (PNP)M(COE) (M = Ir (5), M = Rh (8)).

Alkene complexes of the type (PNP^Ph)M(L) (M = Ir, L = COD (3) and COE (5); M = Rh, L = COE (8)

and L = ethylene (9)) were synthesized by reaction of (PNP^Ph)Li with the appropriate alkene chloride

complexes. Reactions of silanes with 5, 8 or 9 produced silyl hydride complexes (PNP^Ph)MH(SiR₃)

(M = Ir, R = Ph (16) and R = Et (17); M = Rh, R = Ph (18), Et (19) and Ph₂Cl (20)) via Si–H oxidative

addition. The J_SiHcoupling constants for rhodium complexes 18, 19 and 20 were determined to be ca.

35 Hz, while iridium complexes 16 and 17 exhibited coupling constants less than 10 Hz. X-Ray crystal

structures of 16 and 18 reveal isostructural complexes featuring a trigonal bipyramidal geometry about

iridium with a mer binding of the PNP^Phligand. A hydride ligand, located from the Fourier map for 18,

˚

has a short contact of 1.83(3) A with the silicon atom. Oxidative addition of iodomethane to 5 and 8

afforded (PNP^Ph)M(Me)(I)(THF) (M = Rh (14), M = Ir (12)), respectively. Arene C–H activation upon

thermolysis of 12 in benzene produced (PNP^Ph)M(Ph)(I)(THF). Iridium silyl iodide complexes

(PNP^Ph)IrI(SiR₃) (SiR₃= SiPh₃(21), SiH₂Mes (22) and SiH₂Xyl (23)) resulted from addition of

organosilanes to 12, via elimination of CH₄.

4-Me-C₆H₃)₂]).⁷The electronic properties of the silylene catalyst

appear to be crucial in this catalysis; in particular the cationic

charge on the metal complex is necessary to render the silicon

more Lewis acidic and reactive toward alkenes.⁸

Introduction

The activation of Si–H bonds by transition metal complexes

is a fundamental step in various catalytic transformations of

organosilanes.^1,2,3Within this context, research in this laboratory

has focused on the study of fundamental reaction pathways

involving Si–H bond activations via oxidative addition, s-bond

metathesis or a-hydrogen migration steps.^2a,3e,4These studies have

led to progress in the ﬁeld of organosilicon catalysis, and in

the synthesis of novel transition metal–silicon species, including

compounds that feature multiple bonds between a transition metal

and silicon.⁵

A salient feature of the synthetic route to these PNP an-

cilliary ligands is the potential to alter their steric and elec-

tronic characteristics through modiﬁcation of the substituents

on phosphorus.⁹To investigate possible effects of ligand donor

strength on the chemistry at the metal center, studies focused on

rhodium and iridium complexes of PNP^Ph(PNP^Ph= [^-N(2-PPh₂-

4-Me-C₆H₃)₂]) (1), and Si–H bond activation processes derived

therefrom. Previously, Ozerov, Kiplinger and co-workers have

reported the synthesis of PNP^PhH and have communicated its use

in development of (PNP^Ph)Lu-phosphinidene chemistry,¹⁰but the

chemistry of late transition metals with this ligand has yet to be

explored. In this contribution, the synthesis and characterization

of rhodium and iridium alkene, alkyl and hydride complexes

is described. Furthermore, Si–H activations of organosilanes

by these rhodium and iridium complexes to produce new silyl

complexes are discussed.

The development of synthetic routes to compounds possessing

a formal metal–silicon double bond (silylene complexes) has

allowed their investigation as reagents and catalysts for new

chemical transformations.^5,6Recently, efforts to develop new

alkene hydrosilation catalysts based on transition metal silylene

complexes led to discovery of a second example, with catalysts

of the type [(PNP )(H)Ir SiR₂][B(C₆F₅)₄] (PNP = [^-N(2-PⁱPr₂-

iPr

=

Department of Chemistry, University of California, Berkeley, California,

94720

† Dedicated to Uwe Rosenthal on the occasion of his 60th birthday.

Results and discussion

‡ Electronic supplementary information (ESI) available: Tables of atomic

coordinates, thermal displacement parameters, selected bond lengths and

angles, and crystallographic information ﬁles for 2, 3, 16 and 18. CCDC

reference numbers 757516–757519. For ESI and crystallographic data in

CIF or other electronic format see DOI: 10.1039/b925856f

Synthesis and characterization of (PNP^Ph)Ir alkene complexes

Addition of 2 equiv. of (PNP^Ph)H (1) to a solution of [(COD)IrCl]₂

in toluene at room temperature afforded the single product

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[(PNP^PhH)Ir(COD)][Cl] (2), which precipitated out of the reaction

mixture as a white powder in 91% yield (Scheme 1). The ¹H NMR

resonance for the NH proton at 11.65 ppm in dichloromethane-

d₂is signiﬁcantly downﬁeld-shifted with respect to that for the

free ligand (7.08 ppm in benzene-d₆),¹⁰a feature that is consistent

with the presence of a hydrogen bond between the NH and the

outersphere chloride¹¹(see structural discussion below). A broad

singlet in the ¹H NMR spectrum for the oleﬁnic protons suggests

2

that the COD ligand is symmetrically bound in an h ,h fashion

1

to the iridium center. The ¹³C{ H} NMR spectrum of 2 exhibits

a resonance at 63.8 ppm attributed to the coordinated, oleﬁnic

carbon atoms. The phosphorus nuclei in the PNP^Phligand appear

1

as a singlet at 13.7 ppm in the ³¹P{ H} NMR spectrum of 2.

As determined by VT NMR spectroscopy, a dynamic process

interconverts the vinylic COD hydrogens of 2 on the NMR time

scale. Upon cooling a solution of 2 in dichloromethane-d₂to

-80 ^◦C, the alkene resonances for the COD ligand in the ¹H

NMR spectrum resolve into two separate signals at 3.56 and

3.48 ppm, consistent with the observed geometry in the crystal

structure (see below). No N–H oxidative addition or loss of the

COD ligand was observed, even after heating complex 2 to 60 ^◦C

for 26 h in bromobenzene-d₅. In contrast, addition of 2 equiv.

of (PNP^iPr)H to [CODIrCl]₂affords (PNP^iPr)IrH(Cl) after 18 h

at ambient temperature.¹²This difference in reactivity can be

attributed to the higher tendency for more electron-rich metal

centers to undergo oxidative addition reactions and ascribed to

the differences in donor properties of PNP^iPrand PNP^Ph, as

phenyl-substituted phosphine ligands are less electron-donating

than comparable alkyl-substituted phosphines.¹³

Fig. 1 Molecular structure of 2 displaying thermal ellipsoids at the

50% probability level. H-atoms, except for those attached to N(1),

and disordered ortho-dichlorobenzene have been omitted for clarity.

˚

Selected bond lengths (A): H(1)-Cl(1) = 2.31(5), C(1)-C(2) = 1.419(7),

C(5)-C(6) = 1.404(6). Selected bond angles (^◦): P(1)-Ir(1)-P(2) = 107.68(3),

P(1)-Ir(1)-N(1) = 82.04(9), P(2)-Ir(1)-N(1) = 84.05(9), P(1)-Ir(1)-C(1) =

101.74(13),

109.91(13), P(2)-Ir(1)-C(5)

C(21)-N(1)-C(28) = 110.0(3), C(21)-N(1)-Ir(1) = 113.4(2), C(28)-N(1)-

Ir(1) = 115.5(2).

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

=

87.55(12),

83.92(11), N(1)-H(1)-Cl(1)

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

=

139(4),

state structure of 2 reveals inequivalent positions for the the two

alkene groups of the cyclooctadiene ligand.

The synthesis of (PNP^Ph)Ir(COD) (3) was achieved via de-

protonation of 2 with LiN(SiMe₃)₂in toluene to afford 3 as a

bright yellow powder in moderate yield (69%, Scheme 1). In

addition, complex 3 was synthesized by addition of 2 equiv.

of (PNP^Ph)Li (generated in situ by deprotonation of 1 with

LiN(SiMe₃)₂) to [(COD)IrCl]₂in toluene. The ¹H NMR spectrum

of 3 in dichloromethane-d₂contains two resonances for the oleﬁnic

protons on the cyclooctadiene ligand at 3.58 and 2.64 ppm. As

these resonances are shifted upﬁeld with respect to those of free

cyclooctadiene, the NMR data support a bidentate coordination

of COD to the iridum center and a 5-coordinate Ir(I) complex.

Scheme 1

1

Furthermore, the ³¹P{ H} NMR spectrum in dichloromethane-d₂

contains a singlet at 13.5 ppm, for both phosphorus nuclei of the

1

Single crystals (colorless needles) for X-ray crystallography

were obtained by vapor diffusion of heptane into a concentrated

solution of 2 in ortho-dichlorobenzene at ambient temperature.

pincer ligand. The ¹³C{ H} NMR spectrum contains two signals

for the oleﬁnic carbon nuclei at chemical shifts that are similar

to those of 2, a broad resonance at 66.1 ppm and a doublet of

doublets at 60.3 ppm from coupling to magnetically inequivalent

phosphorus nuclei.

¯

Complex 2 crystallized in the P1 space group with two molecules

of ortho-dichlorobenzene in the unit cell (Fig. 1). Structural studies

conﬁrmed the cationic nature of 2 and the presence of an outer

sphere chloride anion. Notably, the chloride anion participates

in hydrogen bonding with the hydrogen atom on the amine, as

Single crystals of 3 were obtained by vapor diffusion of pentane

into a concentrated solution of 3 in CH₂Cl₂at -35 ^◦C. The X-ray

structure of 3 reveals a distorted trigonal bipyramid coordination

geometry about the iridium atom (Fig. 2), similar to the geometry

observed for 2. The PNP ligand is bound in a facial manner

with the P–Ir–P angle at 108.50(5)^◦, instead of the more common

meridional binding usually observed with late metal complexes

supported by this monoanionic ligand framework.¹⁴The nitrogen

atom is in a trigonal planar environment with the sum of the

angles around N1 being 356.9(7)^◦. The alkene moieties of the

cyclooctadiene ligand occupy different positions of the trigonal

bipyramidal structure—one arm is in the axial position trans to

the nitrogen atom while the other is in the equatorial plane. In this

case, the unsymmetrical binding of the cyclooctadiene ligand is

˚

indicated by a Cl–H(N) distance of 2.31(5) A. The geometry about

iridium is a distorted trigonal bipyramid, with the phosphorus

atoms and one alkene moiety of the COD ligand occupying the

equatorial positions. The amido N and the second alkene arm of

the COD ligand occupy the axial positions. Thus, the PNP ligand is

bound in a facial manner to the iridium center, as further indicated

˚

by a P1-Ir1-P2 angle of 107.68(3) A. The nitrogen atom of the PNP

ligand exhibits a pyramidal bonding geometry, as illustrated by

the bond angles around this atom (C(21)-N(1)-C(28) = 110.0(3)^◦,

C(21)-N(1)-Ir(1) = 113.4(2)^◦and, C(28)-N(1)-Ir(1) = 115.5(2)^◦).

Consistent with the low temperature solution NMR data, the solid

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©

(1)

Treatment of a ﬂuorobenzene solution of [(COE)₂IrCl]₂with

2 equiv. of (PNP^Ph)Li afforded (PNP^Ph)Ir(COE) (5) after 1 h at

ambient temperature (eqn (2)). Analytically pure 5 was obtained

after removal of the LiCl salt by ﬁltration, followed by washing the

resulting bright orange powder with pentane. The oleﬁnic nuclei

1

for the cyclooctene ligand in 5 resonate at 2.98 ppm in the H

1

NMR spectrum and at 49.1 ppm in the ¹³C{ H} NMR spectrum

(benzene-d₆). Furthermore, the ³¹P{ H} NMR spectrum exhibits

1

Fig. 2 Molecular structure of 3 displaying thermal ellipsoids at the

50% probability level. H-atoms have been omitted for clarity. Selected

two overlapping broad resonances at 28.9 and 27.8 ppm. The

1

unique phosphorus resonances in the ³¹P{ H} NMR spectra are

˚

bond lengths (A): C(1)-C(2) = 1.439(6), C(5)-C(6) = 1.400(6). Se-

consistent with a square planar geometry at iridium, with the

lected bond angles (^◦): P(1)-Ir(1)-P(2) = 108.50(5), P(1)-Ir(1)-N(1) =

1

alkene bound perpendicular to the PNPIr plane. Similar ³¹P{ H}

82.25(9), P(2)-Ir(1)-N(1)

=

78.54(9), P(1)-Ir(1)-C(1)

=

109.91(12),

NMR features were observed for (PNP^iPr)Ir(COE), which was

structurally characterized by X-ray crystallography.^7b

P(1)-Ir(1)-C(6) = 86.79(11), P(2)-Ir(1)-C(2) = 98.53(11), P(2)-Ir(1)-C(5) =

90.39(11), C(29)-N(1)-C(26) = 121.4(3), C(29)-N(1)-Ir(1) = 119.9(2),

C(26)-N(1)-Ir(1) = 115.6(2).

(2)

consistent with the appearance of two distinct resonances for the

1

oleﬁnic nuclei in the ¹H and ¹³C{ H} NMR spectra.

The synthesis of PNP^Phiridium complexes from the chloride-

bridged dimer [(COE)₂IrCl]₂was also explored. Addition of

2 equiv. of 1 to [(COE)₂IrCl]₂in bromobenzene-d₅at ambient

temperature over 18 h gave a mixture of compounds as deter-

Addition of a Lewis base to alkene complexes 3 and 5 was

explored to evaluate the lability of the iridium-bound alkene lig-

ands. Thus, the phosphine adduct (PNP^Ph)Ir(PPh₃) was obtained

as a bright orange solid by addition of 1 equiv. of PPh₃to 5 in

1

mined by H and ³¹P{ H} NMR spectroscopy (eqn (1)). When

the reaction occurred in benzene, an off-white precipitate was

observed after 18 h at ambient temperature. The isolated white

precipitate was characterized by multinuclear NMR spectroscopy

and combustion analysis as (PNP^PhH)IrHCl₂(4), obtained in

33% yield. Complex 4 is insoluble in benzene, tetrahydrofuran

and ﬂuorobenzene, but exhibits high solubility in methylene

toluene in an isolated yield of 73% yield (eqn (3)). The ³¹P{ H}

1

NMR spectrum exhibits a doublet at 34.7 ppm corresponding to

the PNP ligand, and a triplet at 19.6 ppm for the coordinated

triphenylphosphine (J_PP18.2 Hz). The displacement of COD by

PPh₃in 3 is slower and requires heating to 80 ^◦C for 36 h. In

contrast, the conversion of 5 to 6 in benzene is complete after

1 h at ambient temperature. Thus, as expected, 5-coordinate 18

electron complex 3 is more substitutionally inert than 5.

1

chloride and ortho-dichlorobenzene. The H NMR spectrum of

4 in dichloromethane-d₂contains a resonance at 7.22 ppm for the

N-H proton. Another resonance at -18.43 ppm, attributed to the

Ir-H group, appears as a triplet of doublets from couplings to two

equivalent phophorus nuclei (J_PH14.2 Hz) and to the NH (J_HH

1

2.1 Hz). The ³¹P{ H} NMR spectrum contains a single resonance

(3)

at 15.4 ppm for both phosphorus nuclei of the pincer ligand. The

remaining bright red solution of the reaction mixture contains

two other complexes, as determined by NMR spectroscopy.

One of these compounds was identiﬁed as (PNP^Ph)Ir(COE)

(5) by comparison with the independently synthesized complex

(vide infra). Attempts to separate 5 from the unidentiﬁed minor

product through fractional crystallizations were not successful,

precluding the elucidation of the remaining unidentiﬁed iridium-

containing species. Recently, Schneider et al. published a detailed

analysis of a similar disproportination reaction with iridium

complexes of a different PNP ligand, HN(CH₂CH₂PⁱPr₂)₂, fea-

turing ethylene spacers. In this related system, the reaction of

HN(CH₂CH₂PⁱPr₂)₂with [(COE)₂IrCl]₂in nonprotic solvents

resulted in formation of a similar mixture of (PNP)Ir(COE) and

(PNPH)IrHCl₂.¹⁵

Synthesis and characterization of (PNP^Ph)Rh alkene complexes

The synthesis of (PNP^Ph)Rh(L) complexes was achieved through

synthetic routes that are analogous to those employed for

iridium complexes (PNP^Ph)Ir(L). Addition of 2 equiv. of 1 to

[(COE)₂RhCl]₂in bromobenzene-d₅resulted in a 1 : 1 mixture

of two products after 1.5 h at ambient temperature. As with

the analogous iridium reaction, the two products were identiﬁed

as (PNP^PhH)RhHCl₂(7) and (PNP^Ph)Rh(COE) (8) (eqn (4)).

Treatment of a benzene solution of [(COE)₂RhCl]₂with 2 equiv.

of 1 resulted in precipitation of a white powder found to contain

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7 (as a major product) and several minor species. Additionally, ¹H

NMR spectroscopy of the reaction mixture resulting from 2 equiv.

of 1 and [(COD)RhCl]₂in bromobenzene-d₅at room temperature

revealed formation of complex 7 as a minor product, along with

several unidentiﬁed rhodium-containing species.

9 contains a single resonance at 35.7 ppm appearing as a doublet

due to coupling to rhodium (J_RhP139.0 Hz).

1

The H NMR spectrum of 7 exhibits a complex multiplet at

-14.00 ppm, due to couplings to Rh and P, and to the NH proton.

(5)

31

The ¹H{ P} NMR spectrum reveals a simple doublet of doublets

for this signal, with couplings to Rh (J_RhH11 Hz) and the NH

group (J_HH3 Hz). The NH group appears as a broad singlet at

7.00 ppm in the ¹H NMR spectrum, and exhibits a correlation peak

1

with the hydride ligand in a 2D COSY experiment. The ³¹P{ H}

The lability of the alkene ligands in 8 and 9 was explored by

substitution reactions employing PPh₃. The synthesis of the PPh₃

adduct (PNP^Ph)Rh(PPh₃) (10), isolated as a bright orange powder

in 97% yield, was achieved through an analogous protocol to that

NMR spectrum contains a single resonance for phosphorus at

55.2 ppm, as a doublet with coupling to rhodium (J_RhP131.7 Hz).

Due to the minor products isolated with 7, combustion analysis

of this complex was not obtained.

of eqn (3). The ³¹P{ H} NMR spectrum of 10 contains a doublet

1

of triplets at 46.3 ppm corresponding to the triphenylphosphine

ligand (J_RhP158.1 Hz; J_PP36.1 Hz). The PNP ligand exhibits a

resonance at 40.5 ppm in the ³¹P{ H} NMR spectrum appearing

1

(4)

as a doublet of doublets. The difference in lability of the alkene in 8

and 9 was observed via small scale reactions with PPh₃in benzene-

d₆. Addition of 1 equiv. of PPh₃to ethylene complex 9 at room

temperature resulted in complete conversion to 10 within 1 h. In

contrast, displacement of the cyclooctene ligand of 8 by PPh₃in

benzene-d₆at room temperature was only 75% complete after 2 h,

as determined by NMR spectroscopy. The difference in lability

between the cyclooctene and the ethylene ligands in 8 and 9 could

be a result of the higher steric demand of the cyclooctene ligand,

which might hamper association of PPh₃in these substitution

reactions.

A higher yielding synthesis of (PNP^Ph)Rh(COE) (8) was

achieved by addition of 2 equiv. of (PNP^Ph)Li to [(COE)₂RhCl]₂,

to afford 8 as a light-orange solid in 83% yield (eqn (5)). The

¹H NMR spectrum of 8 reveals a broad doublet at 3.60 ppm,

corresponding to the alkene protons of the cyclooctene ligand. The

1

³¹P{ H} NMR spectrum contains a resonance for the PNP ligand,

as a doublet at 38.5 ppm resulting from coupling to rhodium

(J_RhP149.0 Hz). Furthermore, the ¹³C{ H} NMR spectrum reveals

1

Synthesis and characterization of (PNP^Ph)RhH(Cl)(THF)

a doublet resonance for the oleﬁnic carbons at 68.5 ppm (J_RhC

11.5 Hz), which is signiﬁcantly downﬁeld from that of the iridium

analog 5 (49.1 ppm).

Although N–H oxidative addition by group 9 complexes is facile

for (PNP^iPr)H,¹²analogous reactions for (PNP^Ph)H appear to be

more difﬁcult. The attempted synthesis of (PNP^Ph)IrH(Cl)(THF)

by reﬂuxing [(COE)₂IrCl]₂and 1 in THF resulted in an intractable

mixture of products. Yet, following a synthesis modiﬁed from that

published by Kaska et al.,¹⁶synthesis of (PNP^Ph)RhH(Cl)(THF)

(11) was achieved by reﬂuxing 1 and [(COE)₂RhCl]₂in THF for

In contrast to the iridium complex 5, which exhibits inequivalent

1

phosphorus signals, a single ³¹P{ H} NMR resonance is observed

for 8. The higher symmetry observed for 8 versus iridium alkene

complex 5 is attributed to more rapid rotation about the rhodium–

alkene bond in solution at room temperature. NMR studies at

low temperatures were undertaken to conﬁrm this. At -80 ^◦C,

◦

3 h at 75 C (eqn (6)). Complex 11 contains a coordinated THF

1

the ³¹P{ H} NMR spectrum in dichloromethane-d₂revealed

molecule, as determined by ¹H NMR spectroscopy in benzene-d₆.

The resonances associated with THF appear at 3.14 and 0.78 ppm,

shifted from 3.57 and 1.40 ppm for free THF.¹⁷Structural analysis

by a 2D NOESY NMR experiment indicates a trans arrangement

two doublets of doublets from two distinct phosphorus donors

coupling to each other and to rhodium. Hence at -80 ^◦C, the NMR

spectra exhibits unsymmetrical ligand resonances, which parallels

1

the features observed at room temperature for 5. The H NMR

1

between the THF and hydride ligands. The H NMR spectrum

spectrum of 8 at -80 ^◦C also revealed separate, broad signals for

the oleﬁnic protons at 3.47 and 2.87 ppm, further suggesting slow

rotation about the rhodium–alkene bond at this temperature. The

observed dynamic behavior at ambient temperature is attributed

to weaker backbonding from the rhodium to the alkene in 8, in

comparison to that from iridium in 5, which could result in a lower

of 11 reveals a resonance at -21.48 ppm attributed to the hydride

ligand, appearing as overlapping doublets of triplets from coupling

to phosphorus (J_PH11.9 Hz) and rhodium (J_RhH25.6 Hz). The

1

³¹P{ H} NMR spectrum of 11 contains a doublet at 34.7 ppm

with a one-bond coupling to rhodium of 110.5 Hz.

barrier for rotation about the transition metal alkene bond.

Ph

=

Similarly, addition of 2 equiv. of (PNP )Li to [(CH₂CH₂)₂-

RhCl]₂

in toluene at room temperature afforded

(PNP )Rh(CH₂CH₂) (9) in 78% isolated yield (eqn (5)).

The ethylene ligand exhibited a resonance at 3.08 ppm in the H

Ph

=

(6)

1

NMR spectrum and at 49.6 ppm (doublet with J_RhC= 12.0 Hz)

1

in the ¹³C{ H} NMR spectrum. The ³¹P{ H} NMR spectrum of

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Synthesis and characterization of (PNP^Ph)MMe(I)(THF) (M =

the reaction mixture, after removal of volatiles under vacuum,

which revealed deuteration in the aromatic region for the PNP

ligand. Previous work by Fryzuk et al. detailed C–H activation

of arene solvents from thermolysis of [(PNP)IrMe(I)] (PNP =

^-N(SiMe₂CH₂PPh₂)₂).¹⁹Similar to this system, C–H activation was

observed only for the iridium analogs with the rhodium species not

affording clean C–H activation products under these conditions

(vide infra).

Rh, Ir) and (PNP)RhMe(I)

Methyl derivatives of the (PNP^Ph)M fragment were obtained via

oxidative addition of iodomethane to the corresponding iridium

or rhodium alkene complexes. Addition of iodomethane to 5

in THF afforded (PNP^Ph)IrMe(I)(THF) (12) after 30 min at

1

room temperature (Scheme 2). The H NMR spectrum of 12 in

dichloromethane-d₂contains resonances at 3.45 and 1.54 ppm for

the THF ligand. In addition, a resonance at 0.83 ppm, appearing

as a triplet due to coupling to phosphorus (6.5 Hz), conﬁrms

the presence of a methyl ligand on iridium. Structural analysis

by 2D NOESY NMR spectroscopy indicates a trans relationship

between the methyl and THF ligands (Scheme 2). Complex 12

The synthesis of (PNP^Ph)RhMe(I)(THF) (14) followed a proce-

dure similar to that for 12. Addition of iodomethane to 8 in THF

at ambient temperature resulted in a color change to dark red.

Isolation of 14 was achieved by removal of the volatile material

under vacuum, followed by washing of the resulting red powder

with pentane to give 14 in 83% yield. Interestingly, dissolution of 14

in benzene-d₆at ambient temperature gave a color change to dark

green indicating the presence of (PNP^Ph)RhMe(I). In fact, THF-

free (PNP^Ph)RhMe(I) (15) was isolated by dissolving 14 in toluene

and removing the volatiles under vacuum to give a dark green solid.

1

also reveals an upﬁeld ¹³C{ H} resonance at -23.5 ppm, attributed

1

to the iridium methyl group, and a ³¹P{ H} NMR resonance at

9.7 ppm. No loss of THF was observed after exposure of solid 12

to vacuum for 2 h, or after removing the volatile materials under

vacuum from a solution of 12 in benzene. However, when dark

yellow 12 was dissolved in benzene, the solution acquired a faint

green color. Upon heating this solution to 85 ^◦C, the color of

the solution changed to bright green. Furthermore, monitoring a

solution of 12 in benzene-d₆from 21 to 80 ^◦C revealed a signiﬁcant

change in the ¹H chemical shift of the two THF signals from 0.87 to

1.24 ppm and from 3.12 to 3.57 ppm, respectively. The ¹H chemical

shifts observed at 80 ^◦C approximate those observed for free THF

1

The H NMR spectrum of 15 contains a resonance at 2.01 ppm

for the methyl ligand, appearing as a triplet of doublets due to

couplings to phosphorus (J_PH5.4 Hz) and rhodium (J_RhH2.4 Hz).

Notably, no loss of THF from (PNP^Ph)RhH(Cl)(THF) (11) was

observed in solution or under vacuum, despite the high trans effect

of the hydride ligand. Furthermore, thermolyses of 11, 14 or 15 in

benzene produced intractable mixtures of products rather than a

clean C–H activation product, as observed for iridium.

1

in benzene-d₆. The ³¹P{ H} NMR resonance also undergoes a

downﬁeld shift from 13.5 to 23.9 ppm upon warming to 80 ^◦C.

The color change to green and the NMR data can be attributed to

dissociation of the THF ligand to give rise to (PNP^Ph)IrMe(I) in

situ (similar PNP^iPrcomplexes with alkyl and halogen substituents

exhibit a bright green color).^12,18The dissociation of the THF is

Reactions of silanes with (PNP^Ph)IrL (L = COD and COE)

As part of an exploration of possible catalytic transformations of

organosilanes mediated by PNP^Ph-supported iridium and rhodium

complexes, stoichiometric reactions of Ir(I) complexes 3 and 5 with

silanes were investigated. Initial efforts targeted the Si–H oxidative

addition of organosilanes for the synthesis of iridium silyl hydride

complexes. Heating 3.3 equiv. of Ph₃SiH with 5 in toluene to 60 ^◦C

for 20 h gave (PNP^Ph)IrH(SiPh₃) (16) with the release of COE (eqn

(7)). Addition of excess silane is necessary for the synthesis of 16;

reaction of a stoichiometric amount of Ph₃SiH with 5 resulted in a

mixture of 5 and 16 after 20 h at 60 ^◦C in benzene. No hydrosilation

of the free alkene was observed even after heating the solution for

1

reversible; upon cooling back to room temperature, the H and

1

³¹P{ H} NMR chemical shifts revert back to the initial values.

Furthermore, the bright green color observed for the solution of

12 at higher temperatures changes to the initial yellow color.

◦

2 days at 100 C, and the excess silane was not consumed in the

reaction mixture. Multinuclear NMR spectroscopy veriﬁed the

structure of 16 as an Ir(III) silyl hydride complex. The ²⁹Si NMR

spectrum of 16 contains a resonance at -9.2 ppm, corroborating

the presence of a silyl ligand.²⁰The ¹H NMR spectrum exhibits a

resonance at -19.25 ppm appearing as a triplet from coupling to

2

phosphorus (J_PH8.8 Hz), with a J_SiHcoupling constant of 4 Hz

for the iridium hydride. The IR spectrum of a Nujol mull of 16

contains a band at 1940 cm^-1attributed to the iridium hydride

stretch.

Scheme 2

N_◦otably, thermolysis of (PNP^Ph)IrMe(I)(THF) in benzene to

120 C for 20 h resulted in the formation of (PNP^Ph)IrPh(I)(THF)

(13) via C–H activation of the solvent. Compound 13 was isolated

in 77% yield after precipitation from cold pentane (Scheme 2). A

small-scale reaction_◦in benzene-d₆carried out in a Teﬂon-sealed J.

1

Young tube at 120 C and monitored by H NMR spectroscopy

(7)

indicated the formation of both CH₄and CH₃D. The presence of

CH₄suggests that activation of the PNP ligand is also operative.

2

Ligand activation was conﬁrmed by the H NMR spectrum of

9254 | Dalton Trans., 2010, 39, 9250–9263

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Table 1 Summary of NMR and IR data for complexes 16–20

Similarly, addition of 3.5 equiv. of HSiEt₃to 5 in toluene

followed by heating in a sealed vessel for 4.5 h at 85 ^◦C produced

(PNP^Ph)IrH(SiEt₃) (17), isolated in 83% yield as a bright orange

powder (eqn (7)). No hydrosilation of cyclooctene by the excess

silane was observed after 18 h at 85 ^◦C. The ¹H NMR spectrum of

17 contains a triplet at -18.93 ppm for the iridium hydride ligand

with a ²J_SiHcoupling constant of 5.4 Hz that is similar to that of 16.

The ²⁹Si NMR resonance for the silyl ligand appears at 15.8 ppm.

A weak absorbance at 1959 cm^-1in the IR spectrum is attributed

to the Ir–H stretch.

Complex 3, (PNP^Ph)Ir(COD), also promotes the Si–H oxidative

additions of tertiary silanes Ph₃SiH and Et₃SiH. However, these

reactions to produce 16 and 17 require prolonged heating at

100 ^◦C. Even at elevated temperatures, the yield of 16 and 17

remains at ca. 50% after 3 d at 100 ^◦C. The more sluggish nature of

these reactions results from the non-labile property of the chelating

COD ligand.

¹H NMR ²⁹Si NMR

IR (n_M–H/

Compound

(d M–H) (d M–Si) ²J_SiH/Hz cm^-1)

PNP)IrH(SiPh₃) (16)

(PNP)IrH(SiEt₃) ^a(17)

(PNP)RhH(SiPh₃) (18)

(PNP)RhH(SiEt₃) (19)

-19.25

-18.93

-13.91

-14.44

-9.2

15.8

17.8

40.5

38.4

4

5.4

35.9

33.5

36.6

1940

1959

1996

2042

not

(PNP)RhH(SiPh₂Cl) (20) -14.31

observed

^aNMR acquired in CD₂Cl₂.

Reaction of 1 equiv. of Ph₂SiHCl with 8 in benzene solution,

followed by heating for 2 days at 75 ^◦C, gave complete conversion

to (PNP^Ph)RhH(SiPh₂Cl) (20) with the release of cyclooctene. The

¹H NMR spectrum of 20 contains a resonance at -14.31 ppm

appearing as an overlapping doublet of triplets, arising from

coupling to rhodium (23.9 Hz) and phosphorus (10.3 Hz). Similar

to 18 and 19, a ²J_SiHcoupling constant of 36.6 Hz was determined

Ph

=

Reactions of silanes with (PNP )RhL (L = COE and CH₂CH₂)

31

via a ²⁹Si ﬁltered ¹H{ P} NMR experiment. The ²⁹Si NMR shift

The synthesis of a rhodium silyl hydride complex was achieved

for the silyl ligand was observed at 38.4 ppm with a coupling to

rhodium of 26 Hz. Selected NMR and IR data for silyl complexes

16–20 are summarized in Table 1.

Ph

=

by heating 2 equiv. of HSiPh₃with (PNP )Rh(CH₂CH₂)

(9) at 85 ^◦C in benzene. After 18 h, complete conversion to

(PNP^Ph)RhH(SiPh₃) (18) was observed with the production of

EtSiPh₃from hydrosilation of ethylene, as conﬁrmed by NMR

spectroscopy and GC-MS (eqn (8)). Complex 18 was isolated in

72% yield after washing the resulting orange solid with pentane to

remove the silane byproduct. The ¹H NMR spectrum of 18 exhibits

a resonance for the Rh–H group at -13.91 ppm, appearing as a

doublet of triplets due to couplings to rhodium (J_RhH23.4 Hz)

and phosphorus (J_PH10.8 Hz). Compound 18 also exhibits a ²⁹Si

The differences between the spectroscopic data for iridium

vs. rhodium silyl hydride complexes warrant further discussion.

2

Of notable interest is the difference in J_SiHcoupling constants

between iridium complexes 16 and 17, and rhodium complexes 18,

19, and 20. Complexes 16 and 17 exhibit low coupling constants

below 10 Hz, indicative of complete oxidative addition of the Si–H

bond.^20,21In contrast, the larger coupling constants of ca. 35 Hz

for 18, 19 and 20, suggest a weak Si–H interaction, although

some caution should be used in interpreting observed coupling

constants as these result from the addition of one- and two-bond

couplings which are usually of opposite signs.^21b,22IR spectroscopy

for the M-H stretches do not provide further evidence for non-

classical Si–H interactions in the rhodium complexes, as u(MH)

NMR resonance at 17.8 ppm (J_SiRh22 Hz) for the silyl ligand, and

1

a

A

³¹P{ H} NMR peak as a doublet at 41.3 ppm (J_RhP133.5 Hz).

²⁹Si-ﬁltered H{ P} NMR spectrum revealed a J_SiHcoupling

1

31

2

constant of 35.9 Hz associated with the Rh–H resonance. This

²J_SiHvalue suggests the presence of a weak interaction between

the silyl and hydride ligands.^20,21The IR spectrum of 18 exhibits

a peak at 1996 cm^-1for the Rh–H stretch, which is in the region

expected for a terminal Rh–H bond.

2

stretching frequencies of h -silane late transition-metal complexes

are usually red shifted to values ca. 200–400 cm^-1lower than those

observed for 18 and 19.^20,22In fact, comparison between the IR

frequencies for the n(MH) stretches do not reveal any signiﬁcant

differences between the Ir and Rh complexes. However, a weak

interactionbetween the silylligand andthe rhodium hydride ligand

in 18, 19 and 20 is indicated by comparison of the NMR data of

18, 19 and 20 with that of the iridium analogs 16 and 17.

(8)

Non-classical Si–H interactions are sometimes described as

arrested oxidative additions, and analogous interpretations have

been used to describe dihydrogen complexes.²³In general, the

extent of oxidative addition is related to the electronic properties

of the transition metal fragment, with electron deﬁcient metal

centers being less capable of full oxidative additions.^23,24Similar

to the complexes supported by PNP^Ph, rhodium silyl hydride

Addition of 2 equiv. of Et₃SiH to 9 in benzene solution,

followed by heating at 70 ^◦C for 20 h, produced silyl complex

(PNP^Ph)RhH(SiEt₃) (19), isolated in 90% yield as a brown powder

(eqn (8)). A GC-MS of the reaction mixture conﬁrmed the

2

complexes supported by PNP^iPrexhibit J_SiHcoupling constants

1

production of Et₄Si from the hydrosilation of ethylene. The H

of ca. 30 Hz,²⁵whereas analogous (PNP^iPr)Ir complexes possess

coupling constants lower than 10 Hz.⁷Hence, in the (PNP)M (M =

Rh, Ir) systems investigated so far, the nature of the metal center

appears to be more important than that of the PNP ligand (PNP^iPr

vs. PNP^Ph). In several examples of complexes with similar ligands,

non-classical dihydrogen complexes were more commonly found

for the 2nd row transition metal analogs.²⁶Limited examples of 4d

NMR spectrum of 19 contains a resonance at -14.44 ppm for the

rhodium hydride ligand appearing as an overlapping doublet of

triplets (J_RhH24.4 Hz; J_PH11.5 Hz). Notably, the silicon satellites

31

were observed for the hydride resonance via a ²⁹Si-ﬁltered ¹H{ P}

NMR experiment (²J_SiH33.5 Hz). The IR spectrum for 19 contains

a peak at 2042 cm^-1attributed to the Rh–H stretching mode.

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and 5d complexes containing non-classical Si–H interactions and

supported by similar ancillary ligands are available for compari-

son. In one such example for group 9 metals, the orthometallated

silyl hydride [Cp*(PMe₃)Ir(H)(SiPh₂C₆H₄)][B(C₆F₅)₄]²⁷was better

described as an Ir(V) silyl hydride complex whereas the rhodium

2

analog was described as the Rh(III) species [Cp^*(PMe₃)Rh(h -

HSiPh₂C₆H₄)][B(C₆F₅)₄] (²J_SiH= 84 Hz),²⁸from the features

observed by NMR spectroscopy. Hence, the complexes presented

in this contribution present another example of 2nd and 3rd row

metals supported by the same ancillary ligand, in which only

the 2nd row transition metal complex contains a non-classical

interaction.

Structures of iridium and rhodium silyl hydride complexes

Further investigations of possible structural differences between

PNP^Phiridium and rhodium silyl hydride complexes included

X-ray diffraction experiments. Crystals suitable for X-ray diffrac-

tion were obtained by vapor diffusion of pentane into a concen-

trated solution of (PNP^Ph)IrH(SiPh₃) (16) in C₆H₅F at -30 ^◦C

(Fig. 3). The geometry about the iridium atom is a distorted

trigonal bipyramid with the phosphorus atoms occupying the

apical positions, and a meridional binding of the PNP ligand to

Fig. 4 Molecular structure of 18 displaying thermal ellipsoids at the

50% probability level. H-atoms except for H(1) have been omitted for

˚

clarity. Selected bond lengths (A): Si(1)-H(1) = 1.83(3), Rh(1)-H(1) =

1.49(3), Rh(1)-Si(1) 2.315(1). Selected bond angles (^◦): N(1)-Rh(1)-H(1) =

166.1(11), N(1)-Rh(1)-Si(1) = 141.65(7), P(1)-Rh(1)-P(2) = 159.68(3).

˚

the iridium center as indicated by a P–Ir–P angle of 159.81(4) A.

The iridium hydride was not located from the Fourier map, but

is presumed to occupy the empty site in the equatorial plane. The

˚

distance, 1.49(3) A, and the Rh–Si bond distance of 2.3148(8) A

are within normal bonding distances for rhodium hydride and

silyl ligands.³¹Interestingly, the crystal structure revealed a short

˚

Ir–Si distance at 2.322(1) A is within the normal values reported

for an iridium silyl bond.²⁹The N–Ir–Si bond angle of 140.0(1)^◦

is widened from that of the ideal trigonal bipyramid structure,

as previously documented for PNP-supported ﬁve-coordinate

complexes with a d⁶electronic conﬁguration.³⁰

˚

Si–H distance of 1.83(3) A. A Si–H bond distance below 2.0 A is

considered to be in the bonding range,^20,21aand the observed value

is consistent with the ²J_SiHcoupling constant of 35.9 Hz and with

the presence of a Si–H interaction. For comparison, transition-

2

metal h -silane complexes exhibit Si–H distances ranging between

˚

1.6 and 1.9 A, whereas free silanes exhibit Si–H bond lengths of ca.

1.5 A.³²Furthermore, the N–Rh–H and N–Rh–Si bond angles are

˚

widened to 166.1(1)^◦and 141.65(7)^◦, respectively. Comparisons

of geometrical parameters for 18 with those for the structure

of (PNP^iPr)RhH(SiMe₂Cl), reported by Ozerov et al. reveal only

small differences, since the latter complex possesses a slightly

˚

shorter Rh–Si bond length (2.26 A), a narrower N–Rh–Si bond

angle (136.83(4)^◦), and a slightly longer Si–H bond distance

25

˚

(1.93(2) A). Furthermore, only small structural differences are

observed between 16 and 18, despite the differences in observed

²J_SiHcoupling constants. However, it is difﬁcult to conclusively

address differences in Si–H distances between 16 and 18 without

determination of accurate positions for both hydrides, or full

computation analysis.

Correlations between structural parameters and ²J_SiHcoupling

constants for rhodium and iridium complexes are hampered

by the lack of availability of both Si–H distances from X-ray

structures (as hydrides are often not located from the difference

Fourier map) and ²J_SiHcoupling constants (as these are often not

reported or obtained). Isostructural complexes for rhodium and

Fig. 3 Molecular structure of 16 displaying thermal ellipsoids at the

50% probability level. H-atoms, and the ﬂuorobenzene molecule, have

˚

been omitted for clarity. Selected bond lengths (A): Ir(1)-Si(1) = 2.322(1),

Ir(1)-P(1) = 2.280(1), Ir(1)-P(2) = 2.298(1), Ir(1)-N(1) = 2.067. Selected

iridium disilyl dihydrides Cp*M(H)₂(SiEt₃)₂and (PSiP)MHCl³⁴

33

bond angles (^◦): P(1)-Ir(1)-P(2) = 159.81(4), N(1)-Ir(1)-Si(1) = 140.04(11).

(M = Rh and Ir, PSiP = [(2-Cy₂PC₆H₄)₂SiMe]^-) have been

reported. Neutron diffraction studies of both Cp*Rh(H)₂(SiEt₃)₂

and Cp*Ir(H)₂(SiEt₃)₂indicated that these are M(V) silyl dihydride

species, and this is consistent with the ²J_SiHvalue for the rhodium

analogue of 7.9 Hz. In addition, X-ray crystallography for the

isostructural complexes (PSiP)RhHCl and (PSiP)IrHCl revealed

Single crystals of (PNP^Ph)RhH(SiPh₃) (18) were obtained by

vapor diffusion of pentane into a concentrated solution of 18 in

toluene at -30 ^◦C. Crystals of 18 are isomorphous with 16 (P2₁/c

space group; similar lattice parameters, Fig. 4). The rhodium

hydride was located and reﬁned in the structure. The Rh–H bond

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˚

group and a resonance at -23.2 ppm for the silyl ligand in the ²⁹Si

NMR spectrum. Complexes 22 and 23 are thermally sensitive in

solution and decompose to a complex mixture of products after

24 h at ambient temperature, as indicated by NMR spectroscopy.

The structures of complexes 21, 22 and 23 are believed to be

square pyramidal (as depicted in eqn (9)) by analogy with other

5-coordinate complexes featuring halide and high trans-effect

ligands (such as alkyl ligands).³⁰

similar geometrical parameters with Si–H distances of 2.14(3) A

˚

and 2.24(5) A. These interatomic distances are usually assumed to

indicate the lack of a signiﬁcant non-classical interaction.³²The

²J_SiHcoupling constants for (PSiP)RhHCl and (PSiP)IrHCl are

lower than 10 Hz, and consistent with long Si–H distances. Thus,

the observed differences in coupling constants between 16 and 18,

and the short Si–H distance in the X-ray structure of 18, suggest

that the rhodium complex 18 contains a weak Si–H interaction

that is absent in the iridium analogue.

Attempted synthesis of PNP^Ph-supported rhodium and iridium

silylene complexes

Reactions of Rh(III) and Ir(III) complexes with silanes

Reactions of the Rh(III) complexes (PNP^Ph)RhH(Cl)(THF) (11),

(PNP^Ph)RhMe(I)(THF) (14) and (PNP^Ph)RhMe(I) (15) with a

variety of silanes in benzene at room temperature, or with

slight heating (to 75 ^◦C), did not afford silyl complexes of

the type (PNP^Ph)RhX(SiR₃). Organosilanes employed in these

reactions included HSiPh₃, H₂SiMes₂, H₂Si^tBu₂, H₃SiPh, H₃SiXyl

(Xyl = 3,5-dimethylphenyl), H₃SiMes and H₃SiDmp (Dmp =

2,6-dimesitylphenyl). The reaction mixtures typically included

intractable mixtures of rhodium-containing complexes or decom-

position products. Interestingly, the reaction of 1 equiv. of Ph₂SiH₂

with 11 in benzene for 24 h at ambient temperature produced

complex (PNP^Ph)RhH(SiPh₂Cl) (20) as a major product, with Si–

Several established synthetic routes to transition metal silylene

complexes involve chemical modiﬁcation of silyl ligands.⁵Two

common routes feature abstraction of an anionic substituent

(originally bound to silicon or the metal center). Abstraction

from the metal may promote a-migration from silicon to the

transition metal to produce silylene and hydride ligands. Several of

the rhodium and iridium silyl complexes described above were en-

visioned as good precursors for the synthesis of silylene complexes

analogous to those supported by PNP^iPr.⁷For example, abstraction

of a substituent on the silyl ligand of (PNP^Ph)RhH(SiPh₂Cl)

(20) appears to be a possible route to the silylene complex

Ph

+

=

[(PNP )(H)Rh SiPh₂)] . However, attempts to prepare a silylene

complex from 20 through this approach were not successful.

For example, the combination of Li(OEt₂)₃B(C₆F₅)₄and 20 in

ﬂuorobenzene at 60 ^◦C gave no reaction (after 28 h). Furthermore,

addition of [CPh₃][B(C₆F₅)₄] or AgOTf to 20 in bromobenzene-

d₅or ﬂuorobenzene gave a mixture of complexes at ambient

temperature.

1

Cl bond formation in this reaction. In addition, the H NMR

spectrum for the reaction mixture involving excess PhSiH₃with

11 in benzene-d₆revealed the formation of H₂SiPh₂, HSiPh₃, H₂,

and SiH₄, among other unidentiﬁed silane species, suggesting that

metal-catalyzed redistribution at silicon may readily complicate

reaction mixtures of this kind.

In contrast, addition of

1

equiv. of HSiPh₃to

Iridium was expected to better support a silylene ligand, due to

the inherently stronger metal–ligand bonds for this 3rd row transi-

tion metal. In fact, rhodium silylene complexes are still quite rare,

with no terminal silylene species known to date. Thus, the reac-

tions of complexes (PNP^Ph)IrI(SiPh₃) (21), (PNP^Ph)IrI(SiH₂Mes)

(22) and (PNP^Ph)IrI(SiH₂Xyl) (23) were explored to determine

whether these species could serve as precursors to iridium silylene

complexes. Reactions of interest involved abstraction or chemical

modiﬁcation of a halide ligand on the metal center. Reagents

for abstraction of anionic ligands from compounds 21, 22 and

23 included AgOTf, AgB(C₆F₅)₄, B(C₆F₅)₃, Li(OEt₂)₃B(C₆F₅)₄,

CPh₃OTf, and [CPh₃][B(C₆F₅)₄] but these attempts resulted in no

conversion or a complex mixture of products. Reagents utilized

to induce a-hydrogen eliminations³⁶from 22 and 23 included

LiN(SiMe₃)₂, LiNⁱPr₂, LiNp, LiCH₂SiMe₃, and MeLi, but these

attempts resulted in intractable mixtures of products or lack

of reaction under a variety of conditions (room temperature

to 65 ^◦C in ﬂuorobenzene or bromobenzene-d₅). As further

illustrated by difﬁculties encountered in the PNP^Phsystem, the

synthentic accessibility of transition metal silylene complexes

depends strongly on the electronic and steric properties of the

transition metal center and the silylene ligand.

(PNP^P_◦^h)IrMe(I)(THF) (12) in toluene followed by heating

at 60 C for 18 h resulted in formation of (PNP^Ph)IrI(SiPh₃) (21)

with loss of CH₄and THF (eqn (9)). Complex 21 can be isolated

as a bright green powder in 85% yield, and is analytically pure

by NMR spectroscopy and combustion analysis. Presumably, the

strong trans effect of the silyl ligand³⁵favors dissociation of THF

and stabilizes the 5-coordinate structure. The resulting green

complex is thermally stable, and does not decompose at ambient

temperature or after heating at 60 ^◦C for 18 h. Compound 21

exhibits a ²⁹Si NMR resonance at -1.5 ppm for the silyl ligand

1

and a ³¹P{ H} NMR resonance at 22.8 ppm for the PNP^Phligand.

(9)

Similarly, reactions of monosubstituted silane substrates

H₃SiMes (Mes = 2,4,6-Me₃C₆H₂) and H₃SiXyl (Xyl = 3,5-

Me₂C₆H₃) with 12 afforded (PNP^Ph)IrI(SiH₂Mes) (22) and

(PNP^Ph)IrI(SiH₂Xyl) (23), respectively. In contrast to 21, the

reactions of the primary silanes and 12 are complete within 15 min

at ambient temperature. The ¹H NMR spectrum of 22 exhibits a

Si–H resonance appearing at 3.88 ppm (¹J_SiH199.7 Hz) and the

²⁹Si NMR shift is at -34.4 ppm. Similarly, complex 23 exhibits

Concluding remarks

Initial synthetic studies of rhodium and iridium complexes

supported by the PNP^Phligand indicate that a number of clean

transformations are possible. Notably, signiﬁcant differences in

reactivity and structure were observed between the rhodium and

1

a resonance at 4.12 ppm in the H NMR spectrum for the Si–H

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©

iridium

analogs.

For

example,

thermolysis

of

were referenced relative to an 85% H₃PO₄external standard.

²⁹Si NMR spectra were referenced relative to a tetramethylsilane

standard and obtained via 2D ¹H ²⁹Si HMBC experiments unless

speciﬁed otherwise. All spectra were recorded at room temperature

unless otherwise noted. Virtual couplings are denoted by “v”,

complex multiplets by “m” and broad resonances by “br”. In

(PNP^Ph)IrMe(I)(THF) (12) in benzene resulted in the formation

of (PNP^Ph)IrPh(I)(THF) (13) via C–H activation of benzene,

whereas thermolysis of rhodium(III) analogs 11, 14 and 15

resulted in decomposition to multiple species. Further differences

between rhodium and iridium complexes supported by the PNP^Ph

ligand are observed in spectroscopic characteristics for silyl

hydride analogs. The rhodium complexes exhibit J_SiHcoupling

constants of 35 Hz, whereas the iridium silyl hydride complexes

contain small coupling constants of less than 10 Hz. X-Ray

crystallography for silyl hydride complexes revealed similar

structures for rhodium and iridium analogues, but the structure

of the rhodium silyl hydride complex 18 contains a short Si—H

distance that is consistent with a non-classical Si–H interaction.

This contribution also highlights the chemical differences that

can result from altering the electronics at the transition metal

center, by changing electron-donating phosphines containing iso-

propyl substituents by more electron-deﬁcient phosphine donors

containing phenyl substituents. Notably, attempts at the synthesis

of rhodium or iridium silylene complexes supported by PNP^Ph

ligands were unsuccesful, whereas a variety of iridium silylene

complexes supported by PNP^iPrhave been obtained.⁷Current

efforts include the exploration of other pincer systems amenable to

the study of electronic and steric factors inﬂuencing the synthesis

and reactivity of silyl and silylene species.

1

¹³C{ H} NMR spectra resonances obscured by the solvent signal

are omitted. Elemental analyses were performed by the College

of Chemistry Microanalytical Laboratory at the University of

California, Berkeley. Infrared spectra were recorded on a Nicolet

Nexus 6700 FTIR spectrometer with a liquid-nitrogen-cooled

MCT-B detector. Measurements were made at a resolution of

4.0 cm^-1.

[(PNP^PhH)Ir(COD)]Cl (2). A 50 mL Schlenk ﬂask was loaded

with 1 (0.20 g, 0.35 mmol), [(COD)IrCl]₂(0.10 g, 0.15 mmol), and

30 mL of toluene. The reaction mixture was stirred at ambient

temperature for 1 h after which a ﬁne white precipitate formed,

and then concentrated to ca. 10 mL and cooled to 0 ^◦C. The

resulting white solid was collected via ﬁltration and washed with

pentane to give 2 as a white powder. Yield: 0.27 g (91%). ¹H NMR

(CD₂Cl₂, 500 MHz): d 11.65 (1H, br s, NH), 8.01 (2H, dd, J_PH

=

8.3 Hz, J = 3.4 Hz, ArH), 7.63 (4H, m, ArH), 7.46 (6H, m, ArH),

7.31 (2H, d, J_PH= 6.1 Hz, ArH), 7.25 (2H, t, J = 7.5 Hz, ArH),

7.14 (6H, m, ArH), 7.03 (4H, t, J = 7.1 Hz, ArH), 3.78 (4H, br s,

=

HC CH), 2.28 (6H, s, ArMe), 1.41 (4H, m, CH₂), 1.34 (4H, m,

1

CH₂). ¹³C{ H} NMR (CD₂Cl₂, 125.8 MHz): d 155.4 (m), 138.7 (t,

J_CP= 2.2 Hz), 136.8 (dd, J_CP= 50.1 Hz, J_CP= 3.0 Hz), 135.4 (dd,

J_CP= 46.2 Hz, J_CP= 3.0 Hz), 134.0 (t, J_CP= 6.3 Hz), 133.3 (s),

Experimental

General considerations

132.5 (t, J_CP= 5.6 Hz), 132.0 (s), 131.6 (dd, J_CP= 39.8 Hz, J_CP

5.1 Hz), 130.5 (s), 129.8 (s), 128.7 (t, J_CP= 4.8 Hz), 128.6 (t, J_CP

=

All experiments were carried out under a nitrogen atmosphere

using standard Schlenk techniques or an inert atmosphere (N₂)

glovebox. Oleﬁn impurities were removed from pentane by

treatment with concentrated H₂SO₄, 0.5 N KMnO₄in 3 M

H₂SO₄, and NaHCO₃. Pentane was then dried over MgSO₄

4.9 Hz), 126.5 (t, J_CP= 5.0 Hz) (ArC), 63.8 (br, HC=CH), 31.7

(s, CH₂), 20.7 (s, ArMe). ³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d

1

13.7 (s). Anal. Calcd for C₅₃H₅₃NClIrP₂(includes one equivalent

of toluene): C, 64.07; H, 5.38; N, 1.41. Found: C, 64.08; H, 5.46;

N, 1.36.

˚

and stored over activated 4 A molecular sieves, and dried over

alumina. Thiophene impurities were removed from benzene and

toluene by treatment with H₂SO₄and saturated NaHCO₃. Benzene

and toluene were then dried over CaCl₂and further dried

over alumina. Tetrahydrofuran, diethyl ether, dichloromethane,

hexanes, benzene, toluene and pentane were dried using a VAC

Atmospheres solvent puriﬁcation system. Fluorobenzene was

dried over P₂O₅, degassed and distilled under N₂. Benzene-d₆

was dried by vacuum distillation from Na/K alloy. C₆D₅Br was

reﬂuxed over CaH₂for 20 h and then distilled under nitrogen.

Dichloromethane-d₂was dried by vacuum distillation from CaH₂.

(PNP^Ph)Ir(COD) (3). A 50 mL Schlenk ﬂask was loaded with

2 (0.200 g, 0.203 mmol), lithium bis(trimethylsilyl)amide (0.034 g,

0.203 mmol) and 20 mL of toluene. The reaction mixture was

stirred for 45 min, and it was then ﬁltered and dried under vacuum.

The bright yellow solid was washed with pentane, collected by ﬁl-

tration and dried under vacuum. Yield: 0.120 g (69%). Alternative

synthesis: A solution of lithium bis(trimethylsilyl)amide (0.03 g,

0.18 mmol) in toluene (2 mL) was added to a solution of 1 (0.10 g,

0.18 mmol) in toluene (7 mL) to afford a bright yellow solution.

After 45 min, [(COD)IrCl]₂(0.06 g, 0.18 mmol) was added to the

stirred reaction mixture. After 1 h, the reaction mixture was ﬁltered

through Celite to remove all insoluble material. The supernatant

was concentrated to ca. 2 mL of toluene, layered with ca. 10 mL

of pentane and placed in a -25 ^◦C freezer to afford a bright yellow

39

PNP^PhH (1),¹⁰[(COE)₂IrCl]₂,³⁷[(COD)RhCl]₂,³⁸[(COE)₂RhCl]₂

40

and [(CH₂=CH₂)₂RhCl]₂were prepared according to literature

methods. [(COD)IrCl]₂was synthesized by reﬂuxing [(COE)₂IrCl]₂

with excess COD in toluene for 18 h. All other chemicals were

purchased from commercial sources, and used without further

puriﬁcation.

1

solid. Yield: 0.11 g (72%). H NMR (CD₂Cl₂, 500 MHz): d 7.63

(4H, m, ArH), 7.42 (6H, m, ArH), 7.21–7.13 (8H, ov m, ArH),

7.10 (2H, t, J = 7.2 Hz, ArH), 6.93 (4H, t, J = 7.2 Hz, ArH), 6.81

(2H, d, J = 8.2 Hz, ArH), 3.58 (2H, m, CH=CH), 2.64 (2H, br m,

CH=CH), 2.22 (6H, s, ArMe), (2H, spt, J = 6.2 Hz, CH₂), 1.34

(2H, m, CH₂), 1.10 (2H, m, CH₂), 0.83 (2H, spt, J = 5.9 Hz, CH₂).

NMR spectra were recorded using Bruker AV-600, DRX-

1

500, AV-500, AVB-400, and AVQ-400 spectrometers. H NMR

spectra were referenced internally by the residual solvent proton

1

signal relative to tetramethylsilane. ¹³C{ H} NMR spectra were

referenced internally relative to the ¹³C signal of the NMR

¹³C{ H} NMR (CD₂Cl₂, 125.8 MHz): d 162.0 (d, J_CP= 26.9 Hz),

1

solvent relative to tetramethylsilane. ¹⁹F{ H} spectra were ref-

138.9 (d, J_CP= 44.1 Hz), 137.8 (d, J_CP= 28.8 Hz), 133.5 (m),

133.1 (s), 132.8 (m), 131. (d, J_CP= 53.3 Hz), 130.8 (s), 129.1 (d,

1

erenced relative to a C₆F₆external standard. ³¹P{ H} spectra

9258 | Dalton Trans., 2010, 39, 9250–9263

This journal is

The Royal Society of Chemistry 2010

©

J_CP= 29.2 Hz), 128.4 (m), 128.2 (m), 126.8 (m), 119.2 (m) (ArC),

66.1 (br, CH=CH), 60.3 (dd, J_CP= 27.8 Hz, J_CP= 5.4 Hz,

CH=CH), 32.3 (ov s, CH₂), 31.7 (ov s, CH₂), 20.6 (s, ArMe).

7.43 (6H, t, J = 9.1 Hz, ArH), 7.01 (2H, m, ArC), 6.94–6.87

(12H, ov m, ArH), 6.77–6.71 (5H, ov m, ArH), 6.66 (6H, td, J =

1

7.8 Hz, J = 1.5 Hz, ArH), 1.99 (6H, s, ArMe). ¹³C{ H} NMR

1

³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d 13.5 (s). Anal. Calcd for

(C₆D₆, 125.8 MHz): d 161.8 (t, J_CP= 11.7 Hz), 137.8 (dt, J_CP

48.4 Hz, J_CP= 2.31 Hz), 135.1 (t, J_CP= 24.5 Hz), 134.8 (d, J_CP

11.1 Hz), 133.9 (t, J_CP= 6.3 Hz), 133.2, 131.8, 129.0, 128.4 (d, J_CP

=

C₄₆H₄₄NIrP₂: C, 63.87; H, 5.13; N, 1.62. Found: C, 63.48; H, 5.07;

N, 1.69.

1.9 Hz), 127.0 (d, J_CP= 9.5 Hz), 125.4 (t, J_CP= 3.7 Hz), 116.1 (br

(PNP^PhH)IrHCl₂(4). A solution of 1 (0.10 g, 0.18 mmol)

in 3 mL of benzene was added to a stirred suspension of

[(COE)₂IrCl]₂(0.08 g, 0.09 mmol) in 1 mL of benzene. The reaction

mixture was stirred at ambient temperature for 18 h. Afterward,

a white precipitate was collected by ﬁltration, washed sparingly

1

m) (ArC), 20.3 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz): d

2

34.7 (d, J_PP= 18.2 Hz, PNP), 19.6 (t, J_PP= 18.2 Hz, PPh₃).

Anal. Calcd for C₆₃H₅₅NIrP₃(includes one equivalent of toluene,

as evidenced by H NMR spectroscopy): C, 68.09; H, 4.99; N,

1

1.26. Found: C, 67.86; H, 4.98; N, 1.48.

1

with benzene, and dried under vacuum. Yield: 0.05 g (33%). H

NMR (CD₂Cl₂, 500 MHz): d 7.88 (2H, dd, J = 8.2 Hz, J_PH

=

(PNP^PhH)RhHCl₂(7). A solution of 1 (0.10 g, 0.18 mmol) in

3 mL of benzene was added to a solution of [(COE)₂RhCl]₂(0.06 g,

0.09 mmol) in 1 mL of benzene. After 2 h, the white precipitate

was collected by ﬁltration, washed sparingly with benzene, and

dried under vacuum. Yield: 0.05 g. The white powder was found

to contain 7 as the major product. ¹H NMR (CD₂Cl₂, 500 MHz): d

7.86 (2H, dd, J = 8.1 Hz, J_PH= 3.6 Hz, ArH), 7.60 (4H, m, ArH),

7.46 (2H, d, J = 9.0 Hz, ArH), 7.39 (2H, d, J = 6.9 Hz, ArH),

7.32 (6H, m, ArH), 7.08 (2H, t, J = 7.1 Hz, ArH), 7.00 (1H, br s,

NH), 6.75 (8H, ov m, ArH), 2.34 (6H, s, ArMe), -14.00 (1H, m,

3.5 Hz, ArH), 7.56 (4H, vt, ArH), 7.46 (2H, d, J = 8.2 Hz, ArH),

7.37 (2H, m, ArH), 7.32 (6H, ov m, ArH), 7.22 (1H, br s, NH),

7.06 (2H, m, ArH), 6.73 (8H, m, ArH), 2.35 (6H, s, ArMe), -

1

18.43 (1H, td, ²J_PH= 14.2 Hz, J = 2.1 Hz, IrH). ¹³C{ H} NMR

(CD₂Cl₂, 150.9 MHz): d 151.3 (dd, J_CP= 8.2 Hz, J_CP= 4.1 Hz),

138.8 (t, J_CP= 3.3 Hz), 136.2 (t, J_CP= 5.1 Hz), 135.0 (dd, J_CP

=

60.2 Hz, J_CP= 4.5 Hz), 133.9 (s), 133.5 (s), 133.0 (t, J_CP= 4.8 Hz),

131.1 (br d, J_CP= 62.6 Hz), 131.1 (s), 130.6 (d, J_CP= 7.8 Hz),

130.4 (dd, J_CP= 68.3 Hz, J_CP= 3.4 Hz), 130.1 (s), 128.4 (t, J_CP

=

1

5.4 Hz), 128.0 (t, J_CP= 4.3 Hz), 127.9 (t, J_CP= 5.6 Hz), 124.6 (d,

J_CP= 3.2 Hz), 115.7 (d, J_CP= 21.0 Hz) (ArC), 21.16 (s, ArMe).

RhH, J_PH= ca. 14 Hz, J_RhH= 11 Hz, J_HH= 3 Hz). ¹³C{ H} NMR

(CD₂Cl₂, 150.9 MHz): d 149.8 (m), 138.5 (t, J_CP= 5.1 Hz), 133.7

(s), 133.6 (s), 132.9 (t, J_CP= 5.0 Hz), 131.1 (s), 130.2 (s), 128.4

(t, J_CP= 5.3 Hz), 128.3 (t, J_CP= 4.6 Hz), 128.0 (t, J_CP= 6.8 Hz)

1

³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d 15.4 (s). Anal. Calcd for

C₃₈H₃₄NCl₂IrP₂: C, 55.01; H, 4.13; N, 1.69. Found: C, 54.67; H,

4.05; N, 1.77.

1

(ArC), 21.2 (s, ArMe). ³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d

55.2 (d, J_RhP= 131.7 Hz).

(PNP^Ph)Ir(COE) (5). A 100 mL Schlenk ﬂask was loaded with

1 (1.81 g, 3.20 mmol), lithium bis(trimethylsilyl)amide (0.535 g,

3.20 mmol) and 50 mL of C₆H₅F. The reaction solution was stirred

for 1 h at ambient temperature to give a bright yellow solution.

The solution was added to a stirred suspension of [(COE)₂IrCl]₂

(1.43 g, 1.60 mmol) in 20 mL of C₆H₅F and stirring was continued

for 1 h. The reaction mixture was ﬁltered through Celite and the

remaining salts were washed with CH₂Cl₂(20 mL). The resulting

bright red solution was concentrated to a thick slurry (10 mL)

and washed with hexanes (50 mL). The resulting bright orange

powder was collected by ﬁltration and dried under vacuum to give

(PNP^Ph)Rh(COE) (8). A 100 mL Schlenk ﬂask was loaded

with 1 (1.16 g, 2.05 mmol), lithium bis(trimethylsilyl)amide

(0.343 g, 2.05 mmol) and 40 mL of toluene. The reaction solution

was stirred for 1 h at ambient temperature to produce a bright

yellow solution. This solution was added to a stirred suspension

of [(COE)₂RhCl]₂(0.736 g, 1.03 mmol) in 10 mL of toluene. After

30 min, the reaction mixture was ﬁltered to remove the LiCl

byproduct. The resulting red solution was taken to dryness under

vacuum, and the resulting solid was washed with 30 mL of hexanes

and collected by ﬁltration to afford 8 as an orange powder. Yield:

1.30 g (83%). ¹H NMR (C₆D₆, 500 MHz): d 8.03 (8H, m, ArH),

7.54 (2H, dt, J = 8.5 Hz, J = 2.3 Hz, ArH), 7.09–7.01 (14H, ov m,

ArH), 6.69 (2H, dd, J = 8.5 Hz, J = 1.6 Hz, ArH), 3.60 (2H, br d,

1

a bright orange powder. Yield: 2.33 g (84%). H NMR (C₆D₆,

300 MHz): d 8.03 (8H, br, ArH), 7.57 (2H, d, J = 8.2 Hz, ArH),

7.18 (2H, s, ArH), 7.04 (12H, m, ArH), 6.70 (2H, d, J = 8.6 Hz,

=

ArH), 2.98 (2H, br m, HC CH), 2.19 (2H, d, J = 12.9 Hz, CH₂),

J = 5.8 Hz, HC CH), 2.25 (2H, d, J = 13.0 Hz, CH₂), 2.01 (6H,

1

2.01 (6H, s, ArMe), 1.43–1.07 (10H, ov m, CH₂). ¹³C{ H} NMR

s, ArMe), 1.37-1.16 (8H, ov m, CH₂), 0.96 (2H, m, CH₂). ¹³C{ H}

(C₆D₆, 125.8 MHz): d 162.8 (br m), 134.3 (br), 132.9 (s), 132.2 (s),

130.0 (s), 128.5 (s), 126.8 (t, J_CP= 3.8 Hz), 115.5 (br) (ArC), 49.13

(s, HC=CH), 32.4 (s, CH₂), 31.9 (s, CH₂), 26.9 (s, CH₂), 20.3 (s,

NMR (C₆D₆, 125.8 MHz): d 162.0 (t, J_CP= 14.7 Hz), 135.5 (t,

J_CP= 18.4 Hz), 134.5 (t, J_CP= 6.6 Hz), 133.1 (s), 132.8 (s), 130.2

(s), 129.7 (s), 129.0 (t, J_CP= 4.5 Hz), 128.9 (s), 126.0 (t, J_CP

=

ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz): d 28.9 (br), 27.8 (br).

3.3 Hz), 116.0 (t, J_CP= 5.5 Hz) (ArC), 68.5 (d, J_RhC= 11.5 Hz,

1

Anal. Calcd for C₄₆H₄₆NIrP₂: C, 63.72; H, 5.35; N, 1.62. Found:

C, 63.33; H, 5.50; N, 2.00.

HC=CH), 32.4 (br m, CH₂), 32.3 (s, CH₂), 27.0 (s, CH₂), 20.8

1

(s, ArMe). ³¹P{ H} NMR (C₆D₆, 162.0 MHz): d 38.5 (d, J_RhP

=

149.0 Hz). Anal. Calcd for C₄₆H₄₆NP₂Rh: C, 71.04; H, 5.96; N,

1.80. Found: C, 71.02; H, 5.95; N, 1.73.

(PNP^Ph)Ir(PPh₃) (6).

A solution of triphenylphosphine

(0.018 g, 0.07 mmol) in 1 mL of toluene was added to a solution of

5 (0.060 g, 0.07 mmol) in 5 mL of toluene and the resulting solution

was stirred for 20 h. The reaction mixture was ﬁltered, and then

concentrated to ca. 1 mL under vacuum. Bright orange crystals

were obtained from a toluene (1 mL) and pentane (4 mL) mixture

at -30 C. Yield: 0.056 g (73%). H NMR (C₆D₆, 500 MHz): d

7.81 (2H, dt, J_PH= 6.2 Hz, J = 2.3 Hz, ArH), 7.65 (8H, vq, ArH),

(PNP^Ph)Rh(CH₂=CH₂) (9). A 100 mL Schlenk ﬂask was

loaded with 1 (0.41 g, 0.72 mmol), lithium bis(trimethylsilyl)amide

(0.12 g, 0.72 mmol) and 20 mL of toluene. The reaction solution

was stirred for 1 h at ambient temperature to give a bright yellow

solution. This solution was then added to a stirred suspension

of [(CH₂=CH₂)₂RhCl]₂(0.14 g, 0.36 mmol) in 10 mL of toluene.

◦

1

This journal is

The Royal Society of Chemistry 2010

Dalton Trans., 2010, 39, 9250–9263 | 9259

©

After 1.5 h, the reaction mixture was ﬁltered to remove the LiCl

byproduct. The resulting red solution was evacuated to give an

orange solid, which was washed with 30 mL of pentane and

d 34.7 (d, J_RhP= 110.5 Hz). Anal. Calcd for C₄₂H₄₁NClOP₂Rh: C,

65.00; H, 5.32; N, 1.80. Found: C, 65.14; H, 5.15; N, 1.87.

(PNP^Ph)IrMe(I)(THF) (12).

A solution of iodomethane

1

then dried under vacuum. Yield: 0.39 g (78%). H NMR (C₆D₆,

(0.12 g, 0.85 mmol) in THF (3 mL) was added to a stirred

suspension of 5 (0.51 g, 0.59 mmol) in THF (20 mL). A gradual

color change from bright orange to dark yellow was observed.

After 1 h at ambient temperature, the solution was ﬁltered and

then evaporated to dryness under vacuum. The resulting yellow-

brown solid was crystallized by diffusion of pentane (10 mL) into

a concentrated solution of 12 in CH₂Cl₂at -30 ^◦C, to afford yellow

orange crystals. Yield: 0.36 g (64%). ¹H NMR (CD₂Cl₂, 500 MHz):

d 7.84 (8H, ov m, ArH), 7.80 (2H, dt, J = 8.7 Hz, J_PH= 2.5 Hz,

ArH), 7.41–7.39 (12H, ov m, ArH), 7.18 (2H, br m, ArH), 6.96

(2H, d, J = 8.5 Hz, ArH), 3.45 (4H, br m, THF), 2.27 (6H, s,

ArMe), 1.54 (4H, ov m, THF), 0.83 (3H, t, J_PH= 6.5 Hz, IrMe).

500 MHz): d 7.84 (2H, d, J = 8.5 Hz, ArH), 7.73 (8H, br m,

ArH), 7.06 (2H, br t, ArH), 7.00 (12H, br, ArH), 6.81 (2H, d,

J = 8.4 Hz, ArH), 3.08 (4H, br, CH₂=CH₂), 1.99 (6H, s, ArMe).

1

¹³C{ H} NMR (C₆D₆, 125.8 MHz): d 162.6 (t, J_CP= 15.3 Hz),

134.4 (s), 133.9 (t, J_CP= 6.7 Hz), 133.0 (s), 130.1 (s), 129.2 (t,

J_CP= 4.6 Hz), 128.7 (s), 126.6 (t, J_CP= 3.5 Hz), 126.1 (t, J_CP

=

21.4 Hz), 116.0 (t, J_CP= 6.2 Hz) (ArC), 49.6 (d, J_RhC= 12.0 Hz,

1

CH₂=CH₂), 20.7 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 162.0 MHz): d

35.7 (d, J_RhP= 139.0 Hz). Anal. Calcd for C₄₀H₃₆NP₂Rh: C, 69.07;

H, 5.22; N, 2.01. Found: C, 68.86; H, 5.00; N, 2.19.

(PNP^Ph)Rh(PPh₃) (10). A solution of triphenylphosphine

(0.034 g, 0.130 mmol) in 1 mL of toluene was added to a suspension

of 8 (0.100 g, 0.129 mmol) in 3 mL of toluene. The resulting

reaction mixture was then transferred to a ﬂask equipped with a

Teﬂon stopcock and a magnetic stirbar, and the ﬂask was then

1

¹³C{ H} NMR (CD₂Cl₂, 125.8 MHz): d 161.2 (t, J_CP= 10.7 Hz),

136.3 (s), 134.7 (t, J_CP= 5.1 Hz), 134.2 (t, J_CP= 5.3 Hz), 133.9

(t, J_CP= 25.7 Hz), 132.7 (s), 130.6 (s), 130.5 (s), 129.0 (t, J_CP

=

27.0 Hz), 128.7 (t, J_CP= 4.8 Hz), 128.5 (t, J_CP= 5.0 Hz), 127.6

(t, J_CP= 4.3 Hz), 120.4 (t, J_CP= 26.0 Hz), 118.4 (t, J_CP= 5.8 Hz)

(ArC), 68.83 (s, THF), 25.9 (s, THF), 20.5 (s, ArMe), -23.5 (br,

◦

placed in a 70 C oil bath. After 5 h, the resulting homogenous

solution was evaporated under vacuum leaving a bright orange

powder. The powder was washed with 5 mL of pentane, collected

1

IrMe). ³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d 9.7 (s). Anal. Calcd

for C₄₃H₄₃NIIrOP₂: C, 53.20; H, 4.46; N, 1.44. Found: C, 53.32;

H, 4.39; N, 1.51.

1

by ﬁltration and dried under vacuum. Yield: 0.116 g (97%). H

NMR (C₆D₆, 500 MHz): d 7.36 (10H, ov m, ArH), 7.26 (4H, t,

J = 7.2 Hz, ArH), 7.15 (14H, ov m, ArH), 7.05 (3H, t, J = 7.2 Hz,

ArH), 6.85 (6H, t, J = 7.2 Hz, ArH), 6.76 (2H, d, J = 8.4 Hz,

(PNP^Ph)IrPh(I)(THF) (13). A 50 mL thick walled ﬂask with

a Teﬂon stopcock was loaded with a solution of 12 (0.100 g,

0.11 mmol) in 10 mL of C₆H₆. The ﬂask was placed in a 120 ^◦C

oil bath for 20 h. The resulting brown solution was evaporated

to dryness, and the resulting solid was redissolved in 2 mL of

toluene. Then, 10 mL of pentane was added to the toluene solution

and the resulting solution was placed in the -20 ^◦C freezer for

20 h. The resulting brown solid is collected by ﬁltration and dried

under vacuum to give 13. Yield: 0.089 g (77%). ¹H NMR (C₆D₆,

400 MHz): d 8.09 (6H, ov m, ArH), 7.62 (4H, m, ArH), 7.24 (2H,

br t, J_PH= 4.8 Hz, ArH), 7.08 (2H, d, J = 8.3 Hz, ArH), 7.01 (6H,

m, ArH), 6.88 (6H, m, ArH), 6.81 (d, J = 8.8 Hz), 6.40 (1H, t,

J = 7.1 Hz), 6.17 (2H, d, J = 7.4 Hz, ArH), 3.13 (4H, m, THF),

1

ArH), 6.68 (2H, br m, ArH), 2.05 (6H, s, ArMe). ¹³C{ H} NMR

(C₆D₆, 125.8 MHz): d 160.2 (t, J_CP= 15.0 Hz), 137.7 (t, J_CP

=

2.6 Hz), 137.4 (t, J_CP= 2.4 Hz), 135.2 (t, J_CP= 19.8 Hz), 135.4

(s), 134.5 (s), 134.0 (t, J_CP= 6.6 Hz), 133.2 (s), 131.6 (s), 128.9 (s),

128.9 (s), 128.3 (t, J_CP= 4.6 Hz), 127.7 (s), 127.6 (s), 124.8 (t, J_CP

=

1

3.3 Hz), 115.4 (t, J_CP= 5.9 Hz) (ArC), 20.5 (s, ArMe). ³¹P{ H}

NMR (C₆D₆, 202.5 MHz): d 46.3 (1P, dt, J_RhP= 158.1 Hz, J_PP

=

36.1 Hz), 40.5 (2P, dd, J_RhP= 118.8 Hz, J_PP= 36.4 Hz). Anal.

Calcd for C₅₆H₄₇NP₃Rh: C, 72.34; H, 5.09; N, 1.51. Found: C,

72.61; H, 5.11; N, 1.83.

(PNP^Ph)RhH(Cl)(THF) (11). A 100 mL round-bottom ﬂask

equipped with a magnetic stirbar was loaded with 1 (0.750 g,

1.33 mmol) and [(COE)₂RhCl] (0.473 g, 0.66 mmol). The solids

were dissolved in 50 mL of THF and the resulting solution was

stirred at ambient temperature. After 30 min, an insoluble brown

precipitate formed. After 2 h at ambient temperature, a reﬂux

condenser was attached to the ﬂask and the reaction mixture was

heated to 75 ^◦C for another 3 h. After cooling to room temperature,

the reaction mixture was dried under vacuum and triturated with

30 mL of hexanes to afford 11 as a bright orange powder. Yield:

1

2.03 (6H, s, ArMe), 0.59 (4H, m, THF). ¹³C{ H} NMR (C₆D₆,

125.8 MHz): d 162.2 (t, J_CP= 10.4 Hz), 142.8 (br), 137.1 (s), 134.7

(t, J_CP= 5.3 Hz), 134.6 (t, J_CP= 5.1 Hz), 134.2 (t, J_CP= 25.6 Hz),

132.9 (s), 130.3 (s), 128.9 (s), 127.7 (s), 126.0 (s), 122.4 (s), 121.7

(t, J_CP= 25.6 Hz), 119.0 (t, J_CP= 5.8 Hz) (ArC), 70.9 (s, THF),

1

25.4 (s, THF), 20.5 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 162.0 MHz):

d 12.5 (s). Anal. Calcd for C₄₈H₄₅NIIrOP₂: C, 55.81; H, 4.39; N,

1.36. Found: C, 55.63; H, 4.07; N, 1.70.

(PNP^Ph)RhMe(I)(THF)

(14). Iodomethane

(0.06

g,

1

0.860 g (84%). H NMR (C₆D₆, 500 MHz): d 8.28 (4H, q, J =

0.42 mmol) was dissolved in 2 mL of THF and the resulting

solution was added via cannula to a stirred solution of 8 (0.30 g,

0.39 mmol) in 20 mL of THF. After addition of iodomethane,

the solution turned dark red. The reaction mixture was then

evaporated to dryness under vacuum and the resulting solid was

washed with 10 mL of pentane to afford a red powder. Yield: 0.29

5.9 Hz, ArH), 7.91 (2H, dt, J = 8.7 Hz, J_PH= 2.4 Hz, ArH), 7.87

(4H, m, ArH), 7.32 (2H, t, J_PH= 4.5 Hz, ArH), 7.07–7.00 (12 H, ov

m, ArH), 6.77 (2H, dd, J = 8.7 Hz, J_PH= 1.3 Hz, ArH), 3.14 (4H,

m, THF), 2.03 (6H, s, ArMe), 0.78 (4H, m, THF), -21.48 (1H, ov

1

dt, J_RhH= 25.6 Hz, J_PH= 11.9 Hz, RhH). ¹³C{ H} NMR (C₆D₆,

1

125.8 MHz): d 162.6 (t, J_CP= 12.5 Hz), 135.4 (s), 135.3 (ov m),

135.0 (t, J_CP= 20.7 Hz), 134.5 (t, J_CP= 23.7 Hz), 132.5 (s), 130.8

(s), 129.9 (s), 129.1 (t, J_CP= 5.3 Hz), 126.5 (t, J_CP= 3.4 Hz), 122.0

(t, J_CP= 22.4 Hz), 118.0 (t, J_CP= 6.1 Hz) (ArC), 68.4 (s, THF),

g (83%). H NMR (C₆D₆, 400 MHz): d 7.96 (10H, ov m, ArH),

7.35 (2H, br m, ArH), 7.02 (6H, ov m, ArH), 6.99 (6H, br m,

ArH), 6.76 (2H, d, J = 8.6 Hz, ArH), 3.46 (4H, br m, THF), 1.97

(6H, s, ArMe), 1.87 (3H, br m, RhMe), 0.87 (4H, br m, THF).

1

25.5 (s, THF), 20.7 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz):

³¹P{ H} NMR (C₆D₆, 162 MHz): d 37.0 (d, J_RhP= 111.1 Hz).

9260 | Dalton Trans., 2010, 39, 9250–9263

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The Royal Society of Chemistry 2010

©

(PNP^Ph)RhMe(I) (15). Complex 14 (0.29 g, 0.33 mmol) was

dissolved in 5 mL of toluene, resulting in a color change from red

to green. Removal of the volatile material under vacuum afforded

the THF-free complex 15 as a dark green solid. Yield: 0.26 g

Anal. Calcd for C₄₄H₄₈NIrP₂Si: C, 60.53; H, 5.54; N, 1.60. Found:

C, 60.19; H, 5.47; N, 1.42.

(PNP^Ph)RhH(SiPh₃) (18).

A solution of triphenylsilane

(0.094 g, 0.36 mmol) in 1 mL of benzene was added to 9 (0.125 g,

0.18 mmol) in 5 mL of benzene. This solution was then transferred

to a 25 mL Teﬂon-sealed ﬂask equipped with a magnetic stirbar.

1

(quant.) H NMR (C₆D₆, 500 MHz): d 7.94 (10H, ov m, ArH),

7.03 (8H, ov m, ArH), 6.96 (6H, ov m, ArH), 6.75 (2H, d, J =

7.3 Hz, ArH), 2.01 (3H, td, J_PH= 5.4 Hz, J_RhH= 2.4 Hz, RhMe),

◦

This ﬂask was then placed in an 85 C oil bath. After 18 h, the

1

1.96 (6H, s, ArMe). ¹³C{ H} NMR (C₆D₆, 150.9 MHz): d 161.2

reaction mixture was cooled to room temperature and lyophilized

with benzene to leave a ﬁne orange powder. The powder was

washed with 5 mL of pentane, and then collected by ﬁltration.

(t, J_CP= 11.3 Hz), 135.8 (s), 135.0 (t, J_CP= 6.6 Hz), 134.8 (t, J_CP

5.6 Hz), 132.9 (s), 130.9 (s), 129.3 (t, J_CP= 5.0 Hz), 129.1 (t, J_CP

=

4.9 Hz), 122.8 (t, J_CP= 22.3 Hz), 118.8 (t, J_CP= 6.1 Hz) (ArC),

1

Yield: 0.120 g (72%). H NMR (C₆D₆, 500 MHz): d 8.1–7.6 (br,

1

20.6 (s, ArMe), 6.6 (dm, J_CRh= 26.4 Hz, RhMe). ³¹P{ H} NMR

5H, ArH), 7.79 (2H, br d, J = 7.5 Hz, ArH), 7.71 (6H, d, J =

7.0 Hz, ArH), 7.0-6.7 (7H, ov m, ArH), 6.95 (6H, ov m, ArH), 6.88

(9 H, ov m, ArH), 6.78 (6H, ov m, ArH), 1.88 (6H, s, ArMe), -13.91

(C₆D₆, 202.5 MHz): d 38.0 (d, J_RhP= 111.1 Hz). Anal. Calcd for

C₃₉H₃₅NIP₂Rh: C, 57.87; H, 4.36; N, 1.73. Found: C, 58.15; H,

4.71; N, 1.91.

2

(1H, dt, J_RhH= 23.4 Hz, J_PH= 10.8 Hz, J_SiH= 35.9 Hz, RhH).

(PNP^Ph)IrH(SiPh₃) (16).

A

solution of triphenylsilane

1

¹³C{ H} NMR (C₆D₆, 125.8 MHz): d 160.9 (t, J_CP= 13.1 Hz),

(0.078 g, 0.300 mmol) in 1 mL of toluene was added to a solution of

5 (0.075 g, 0.087 mmol) in 5 mL of toluene. The reaction solution

was transferred to a 25 mL Teﬂon–sealed reaction ﬂask equipped

with a magnetic stirbar which was then placed in a 60 ^◦C oil bath

for 20 h. After 20 h, the solution was evaporated under vacuum

to give a bright orange oily residue. Crystallization from toluene

(ca. 1.5 mL) layered with pentane (ca. 10 mL) gave pure 16 as a

142.5 (s), 137.2 (s), 136.4 (s), 134.6 (s), 134.3 (br m), 133.3 (br m),

133.0 (s), 130.1 (br m), 130.0 (s), 128.9 (s), 127.5 (s), 127.3 (s), 127.1

(s), 126.9 (t, J_CP= 3.6 Hz), 116.2 (t, J_CP= 5.2 Hz) (ArC), 20.6

1

(s, ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz): d 41.3 (d, J_RhP

=

133.5 Hz). ²⁹Si NMR (C₆D₆, 99.4 MHz): d 17.8 (J_SiRh= 22 Hz).

IR: 1996 (nRh–H). Anal. Calcd for C₅₆H₄₈NP₂RhSi: C, 72.48; H,

5.21; N, 1.51. Found: C, 72.18; H, 5.34; N, 1.43.

1

bright orange–red solid. Yield: 0.071 g (75%). H NMR (C₆D₆,

(PNP^Ph)RhH(SiEt₃) (19). A solution of Et₃SiH (0.030 g,

0.26 mmol) in 1 mL of benzene was added to 9 (0.089 g, 0.13 mmol)

in 3 mL of benzene. The solution was then transferred to a 25 mL

Teﬂon-sealed ﬂask equipped with a magnetic stirbar. This ﬂask

was then placed in a 70 ^◦C oil bath. After 20 h, the reaction mixture

was cooled to room temperature, and lyophilized with benzene to

leave a ﬁne brown powder. The powder was washed with 5 mL of

pentane, and then collected by ﬁltration. Yield: 0.090 g (90%). ¹H

NMR (C₆D₆, 500 MHz): d 7.96 (8H, br, ArH), 7.79 (2H, d, J =

8.3 Hz, ArH), 7.04 (14H, ov br, ArH), 6.78 (2H, d, J = 8.2 Hz,

ArH), 1.99 (6H, s, ArMe), 0.96 (9H, t, J = 7.7 Hz, SiCH₂CH₃),

500 MHz): d 7.86–7.80 (6H, ov m, ArH), 7.69 (6H, d, J = 7.1 Hz,

ArH), 7.01 (11H, ov m, ArH), 6.93 (2H, t, J = 7.1 Hz, ArH), 6.88

(6H, t, J = 7.2 Hz, ArH), 6.77 (6H, ov m, ArH), 6.63 (4H, t, J =

7.4 Hz, ArH), 1.86 (6H, s, ArMe), -19.25 (t, J_PH= 8.8 Hz, ²J_SiH

=

1

4 Hz, IrH). ¹³C{ H} NMR (C₆D₆, 125.8 MHz): d 161.7 (t, J_CP

11.2 Hz), 142.8 (br), 137.0 (s), 134.7 (s), 134.6 (t, J_CP= 6.5 Hz),

133.3 (t, J_CP= 6. Hz), 132.4 (s), 132.4 (t, J_CP= 26.7 Hz), 130.5

(s), 129.4 (s), 128.5 (m), 127.3 (s), 126.8 (s), 116.0 (t, J_CP= 5.5 Hz)

1

(ArC), 20.1 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz): d 32.0

(s). ²⁹Si NMR (C₆D₆, 99.4 MHz): d -9.2. IR: 1940 (nIr–H). Anal.

Calcd for C₅₆H₄₈NIrP₂Si: C, 66.12; H, 4.76; N, 1.38. Found: C,

66.00; H, 4.96; N, 1.28.

0.47 (6H, q, J = 7.7 Hz, SiCH₂CH₃), -14.44 (1H, ov dt, J_RhH

=

2

1

24.4 Hz, J_PH= 11.5 Hz, J_SiH= 33.5 Hz, RhH). ¹³C{ H} NMR

(C₆D₆, 150.9 MHz): d 160.7 (t, J_CP= 14.1 Hz), 134.1 (br), 133.6

(s), 132.3 (s), 129.8 (s), 128.2 (s), 128.1 (s), 128.1 (s), 125.8 (t,

J_CP= 21.6 Hz), 125.7 (t, J_CP= 3.6 Hz), 115.6 (t, J_CP= 6.1 Hz)

(PNP^Ph)IrH(SiEt₃) (17). A solution of triethylsilane (0.05 g,

0.40 mmol) in 1 mL of toluene was added to a solution of 5

(0.10 g, 0.12 mmol) in 5 mL of toluene. The reaction solution was

then transferred to a 25 mL Teﬂon–sealed reaction ﬂask equipped

with a magnetic stirbar, which was then placed in an 80 ^◦C oil

bath for 4.5 h. After 4.5 h, the solution was evaporated under

vacuum to give a bright orange solid. Crystallization by diffusion

of pentane into a CH₂Cl₂solution (ca. 1 mL) of 5 afforded a

bright orange–red solid. Yield (total from two crystallizations):

(ArC), 20.0 (s, ArMe), 10.8 (t, J_CP= 2.6 Hz, SiCH₂CH₃), 9.9 (s,

1

SiCH₂CH₃). ³¹P{ H} NMR (C₆D₆, 202.5 MHz): d 41.8 (d, J_RhP

=

138.7 Hz). ²⁹Si NMR (C₆D₆, 99.4 MHz): d 40.5 (J_RhSi= 20 Hz).

IR: 2042 (nRh–H). Anal. Calcd for C₄₄H₄₈NP₂RhSi: C, 67.42; H,

6.17; N, 1.79. Found: C, 67.32; H, 6.31; N, 1.85.

0.08 g (83%). ¹H NMR (CD₂Cl₂, 500 MHz): d 8.23 (4H, q, J_CP

=

(PNP^Ph)RhH(SiPh₂Cl) (20). A solution of Ph₂SiHCl (0.085 g,

0.39 mmol) in 1 mL of benzene was added to 8 (0.300 g, 0.39 mmol)

in 5 mL of benzene. This solution was then transferred to a 50 mL

Teﬂon-sealed ﬂask equipped with a magnetic stirbar. This ﬂask

was then placed in a 75 ^◦C oil bath. After 18 h, the reaction

mixture was cooled to room temperature, and lyophilized with

benzene to leave a ﬁne orange powder. The powder was washed

with 5 mL of pentane, and then collected by ﬁltration. Yield:

0.260 g (76%). The IR stretch for the Rh–H of 20 was not observed

using the standard procedure detailed previously. ¹H NMR (C₆D₆,

500 MHz): d 8.09 (4H, br, ArH), 7.78 (2H, br d, J = 8.3 Hz, ArH),

7.62 (4H, d, J = 7.1 Hz), 7.12-7.02 (10H, ov m, ArH), 6.88 (4H,

m, ArH), 6.81-6.76 (12H, ov m, ArH), 1.88 (6H, s, ArMe), -14.31

5.7 Hz, ArH), 7.53–7.47 (8H, ov m, ArH), 7.44–7.39 (6H, ov m,

ArH), 7.36–7.32 (4H, ov m, ArH), 6.93 (2H, d, J = 8.6 Hz, ArH),

6.87 (2H, t, J = 4.4 Hz, ArH), 2.14 (6H, s, ArMe), 0.50 (9H, t,

J = 7.8 Hz, CH₃), -0.07 (6H, q, J = 7.8 Hz, CH₂), -18.93 (1H,

2

1

t, J_PH= 9.4 Hz, J_SiH= 5.4 Hz, IrH). ¹³C{ H} NMR (CD₂Cl₂,

125.8 MHz): d 161.6 (t, J_CP= 11.3 Hz), 136.0 (t, J_CP= 7.1 Hz),

135.1 (t, J_CP= 25.0 Hz), 134.3 (s), 133.71 (t, J_CP= 8.8 Hz), 132.5

(t, J_CP= 26.9 Hz), 132.4 (s), 131.4 (s), 130.3 (s), 129.0 (t, J_CP

=

5.4 Hz), 128.9 (s), 128.5 (t, J_CP= 4.8 Hz), 128.3 (m), 127.6 (t,

J_CP= 3.7 Hz), 115.7 (t, J_CP= 5.4 Hz) (ArC), 20.4 (s, ArMe), 10.8

(s, CH₂), 10.4 (s, CH₃). ³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz): d

1

33.7 (s). ²⁹Si NMR (CD₂Cl₂, 99.4 MHz): d 15.8. IR: 1959 (nIr–H).

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The Royal Society of Chemistry 2010

Dalton Trans., 2010, 39, 9250–9263 | 9261

©

2

(1H, dt, J_RhH= 23.9 Hz, J_PH= 10.3 Hz, J_SiH= 36.6 Hz, RhH).

from a mixture of C₆H₅F (ca. 1 mL) and pentane (ca. 7 mL) at

-10 ^◦C to afford 23 as a bright green solid. Yield = 0.05 g (48%).

¹H NMR (C₆D₆, 400 MHz): d 7.97 (2H, dt, J = 8.6 Hz, J = 2.3 Hz,

ArH), 7.82 (4H, m, ArH), 7.75 (4H, m, ArH), 7.03 (7H, ov m,

ArH), 6.92 (7H, br m, ArH), 6.79 (2H, s, ArH), 6.75 (2H, d, J =

¹³C{ H} NMR (C₆D₆, 125.8 MHz): d 161.2 (t, J_CP= 12.1 Hz),

1

142.6 (s), 135.6 (s), 135.2 (br m), 135.0 (s), 133.8 (br m), 133.3

(s), 131.1 (br), 130.0 (br), 129.4 (br), 129.2 (s), 127.6 (s), 126.2 (t,

J_CP= 22.6 Hz), 116.2 (t, J_CP= 6.1 Hz) (ArC), 20.6 (s, ArMe).

³¹P{ H} NMR (C₆D₆, 202.5 MHz): d 42.7 (d, J_RhP= 129.3 Hz).

8.7 Hz, ArH), 6.48 (1H, s, ArH), 4.12 (2H, t, J_PH= 5.2 Hz, ¹J_SiH

=

1

²⁹Si NMR (C₆D₆, 99.4 MHz): d 38.4 (J_RhSi= 26 Hz). Anal. Calcd

for C₅₀H₄₃NClP₂RhSi: C, 67.76; H, 4.89; N, 1.58. Found: C, 67.64;

H, 4.76; N, 1.49.

202.8 Hz, SiH), 2.00 (6H, s, ArMe), 1.92 (6H, s, ArMe). ¹³C{ H}

NMR (C₆D₆, 150.9 MHz): d 161.1 (t, J_CP= 10.1 Hz), 136.8 (s),

135.6 (t, J_CP= 5.8 Hz), 134.7 (s), 134.6 (t, J_CP= 6.2 Hz), 133.8

(s), 133.5 (t, J_CP= 26.4 Hz), 132.7 (s), 131.3 (s), 131.2 (s), 130.7

1

(PNP^Ph)IrI(SiPh₃) (21).

A solution of HSiPh₃(0.05 g,

(s), 129.3 (t, J_CP= 5 Hz), 128.8 (t, J_CP= 5.3 Hz), 126.7 (t, J_CP

=

0.17 mmol) in 1 mL of toluene was added to a stirred solution of

12 (0.15 g, 0.17 mmol) in 10 mL of toluene. This reaction mixture

was transferred to a 50 mL Teﬂon-sealed ﬂask equipped with a

28.8 Hz), 124.8 (t, J_CP= 27.2 Hz), 118.4 (t, J_CP= 5.6 Hz) (ArC),

1

29.6 (s, ArMe), 21.5 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 162 MHz):

d 30.2 (br s). ²⁹Si NMR (C₆D₆, 99.4 MHz): d -23.2. Anal. Calcd

for C₄₆H₄₃NIIrP₂Si: C, 54.22; H, 4.25; N, 1.37. Found: C, 54.15;

H, 4.34; N, 1.23.

◦

magnetic stirbar. This ﬂask was then placed in a 60 C oil bath

for 18 h. The volatile materials were removed under vacuum. The

resulting green solid was washed twice with 5 mL of cold pentane

and then collected by ﬁltration. The collected solids were dried

under vacuum to give 21 as a green powder. Yield: 0.17 g (85%).

¹H NMR (C₆D₆, 500 MHz): d 7.69 (4H, q, ArH), 7.61 (6H, d,

J = 7.3 Hz, ArH), 7.41 (2H, br dt, J = 8.4 Hz, ArH), 7.37 (4H, q,

ArH), 7.23 (2H, J_PH= 4.3 Hz, ArH), 6.94 (5H, q, ArH), 6.88–6.77

(16H, ov m, ArH), 6.69 (2H, d, J = 7.7 Hz), 1.99 (6H, s, ArMe).

X-Ray crystallography. General considerations

The single-crystal X-ray analyses of compounds 2, 3, 16 and 18

were carried out at the UC Berkeley CHEXRAY crystallographic

facility. Measurements for 3 were made on a Bruker SMART 1000

area detector with graphite-monochromated Mo-Ka radiation

¹³C{ H} NMR (C₆D₆, 125.8 MHz): d 160.8 (t, J_CP= 9.6 Hz), 139.7

1

˚

(l = 0.71069 A). Measurements for 2, 16 and 18 were made

(s), 138.0 (s), 135.9 (t, J_CP= 6.0 Hz), 134.6 (t, J_CP= 26.5 Hz), 134.3

(t, J_CP= 5.7 Hz), 133.9 (s), 132.28 (s), 130.8 (s), 130.0 (s), 128.9 (s),

on an APEX-II CCD area detector with a HELIOS multilayer

mirrors monochromating device using Cu-Ka radiation (l =

˚

127.2 (s), 126.4 (dt, J_CP= 27.3 Hz, J_CP= 5.7 Hz), 118.2 (t, J_CP

=

1.54184 A). Data for 3 was integrated by the program SAINT

6.4 Hz) (ArC), 20.6 (s, ArMe). ³¹P{ H} NMR (C₆D₆, 202.5 MHz):

d 22.8 (s). ²⁹Si NMR (C₆D₆, 99.4 MHz): d -1.5. Anal. Calcd for

C₅₆H₄₇NIIrP₂Si: C, 58.84; H, 4.14; N, 1.23. Found: C, 59.14; H,

4.16; N, 1.32.

1

and analyzed for agreement using XPREP. Data for 2, 16, and

18 was integrated using the APEX2 program package. Empirical

absorption corrections for 2 and 3 were made using SADABS

or APEX2 programs. Analytical absorption corrections through

face-indexing methods for 16 and 18 were made using APEX2

software package. Structures were solved by direct methods or

Patterson methods using SHELX program package. For 18,

PLATON SQUEEZE⁴¹was used to treat disordered toluene (see

ESI). Crystallographic data are summarized in the ESI and CIF

ﬁles for all structures are also included.‡

(PNP^Ph)IrI(SiH₂Mes) (22). A solution of H₃SiMes (0.03 g,

0.17 mmol) in 1 mL of toluene was added to a stirred solution of

12 (0.15 g, 0.17 mmol) in 10 mL of toluene. The reaction mixture

turned bright green after 20 min at ambient temperature. After 1 h,

the volatile materials were removed under vacuum. The resulting

green solid was washed with 20 mL of cold pentane and dried

under vacuum to give 22 as a green powder. Yield: 0.11 g (63%).

¹H NMR (CD₂Cl₂, 500 MHz): d 7.81 (2H, dt, J = 8.7 Hz, ArH),

7.58 (4H, br q, J = 5.9 Hz, ArH), 7.49 (2H, br q, J = 6.4 Hz,

ArH), 7.44–7.37 (4H, ov m, ArH), 7.29 (4H, t, J = 7.8 Hz, ArH),

7.25 (4H, t, J = 7.6 Hz, ArH), 7.02 (2H, t, J = 5.1 Hz, ArH), 6.98

Acknowledgements

This work was supported by the National Science Foundation

under Grant No. CHE-0649583. The authors would also like

to thank Drs Fred Hollander and Antonio Di Pasquale of

the UC Berkeley CHEXRAY facility for assistance with X-

ray crystallography and Dr Chris Canlas and Rudi Nunlist for

assistance with NMR spectroscopy.

(2H, d, J = 8.7 Hz, ArH), 6.23 (2H, s, ArH), 3.88 (2H, br t, ¹J_SiH

=

199.7 Hz, SiH), 2.21 (6H, s, ArMe), 2.08 (3H, s, ArMe), 1.90 (6H,

s, ArMe). ¹³C{ H} NMR (CD₂Cl₂, 125.8 MHz): d 160.0 (t, J_CP

=

1

20.2 Hz), 144.5 (s), 139.3 (s), 134.4 (s), 133.9 (ov m), 132.1 (s),

132.0 (t, J_CP= 4.0 Hz), 130.7 (s), 130.6 (s), 129.0 (t, J_CP= 5.1 Hz),

128.3 (t, J_CP= 5.3 Hz), 128.2 (s), 126.9 (t, J_CP= 28.7 Hz), 124.0 (t,

J_CP= 26.1 Hz), 118.3 (t, J_CP= 5.6 Hz) (ArC), 23.2 (s, ArMe), 21.3

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(s, ArMe), 20.3 (s, ArMe). ³¹P{ H} NMR (CD₂Cl₂, 202.5 MHz):

1

d 25.3 (br s). ²⁹Si NMR (CD₂Cl₂, 99.4 MHz): d -34.4. Anal. Calcd

for C₄₇H₄₅NIIrP₂Si: C, 54.65; H, 4.39; N, 1.36. Found: C, 54.26;

H, 4.26; N, 1.32.

(PNP^Ph)IrI(SiH₂Xyl) (23). A solution of H₃SiXyl (0.02 g,

0.11 mmol) in toluene (3 mL) was added to a stirred solution

of 12 (0.10 g, 0.11 mmol) in toluene (7 mL). The resulting solution

was stirred for 30 min at ambient temperature and then evaporated

to dryness to give a bright green solid. The solid was recrystallized

9262 | Dalton Trans., 2010, 39, 9250–9263

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Article Doi

Synthesis and reactivity of rhodium and iridium alkene, alkyl and silyl complexes supported by a phenyl-substituted PNP pincer ligand

DOI: 10.1039/b925856f

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Full text of DOI:10.1039/b925856f

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