Formation of a sterically crowded iridium(III)-silyl complex from the bulky terphenyl silane H3Si(C6 H3-Mes2-2,6)

Article abstract of DOI:10.1016/S0022-328X(03)00629-6

The reaction of [Ir(COE)Cl]₂ and Et₂PhP in a 1:6 ratio affords the iridium(I) complex (Et₂PhP)₃ (Cl)Ir (4) as orange crystals in good yield (80%). The ¹H- and ³¹P-NMR data are consistent with the structure of 4. The structure of 4 was determined by X-ray crystallography. The sterically hindered iridium(III)-silyl complex 5 is prepared in 63% yield by the reaction of 4 and H₃Si(C₆H₃- Mes₂-2,6) (Eq. 5). Complex 5 is isolated as colorless crystals that are thermally stable up to the temperature at which they melt (162-163 °C). The ³¹P- and ²⁹Si-NMR and IR spectroscopic data and the X-ray crystallographic analysis are consistent with the structure of 5.

Full text of DOI:10.1016/S0022-328X(03)00629-6

Journal of Organometallic Chemistry 681 (2003) 1Á4
/
www.elsevier.com/locate/jorganchem
Short Communication
Formation of a sterically crowded iridium(III)-silyl complex from the
bulky terphenyl silane H3Si(C6H3ÃMes2-2,6)
/
Richard S. Simons, Matthew J. Panzner, Claire A. Tessier, Wiley J. Youngs *
Department of Chemistry, University of Akron, Room 111 190 E, Buchtel Commons, Akron, OH 44325-3601, USA
Received 3 February 2003; received in revised form 16 June 2003; accepted 16 June 2003
Abstract
The reaction of [Ir(COE)Cl]2 and Et2PhP in a 1:6 ratio affords the iridium(I) complex (Et2PhP)3(Cl)Ir (4) as orange crystals in
1
good yield (80%). The H- and 31P-NMR data are consistent with the structure of 4. The structure of 4 was determined by X-ray
crystallography. The sterically hindered iridium(III)-silyl complex 5 is prepared in 63% yield by the reaction of 4 and H3Si(C6H3Ã
/
Mes2-2,6) (Eq. 5). Complex 5 is isolated as colorless crystals that are thermally stable up to the temperature at which they melt (162Á
/
163 8C). The 31P- and 29Si-NMR and IR spectroscopic data and the X-ray crystallographic analysis are consistent with the structure
of 5.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Silyl complexes; Iridium; Silanes; Cyclometallation
1. Introduction
and the iridium silylene complex [Cp*(PMe3)(H)IrÄ
/
SiMes2][OTf] [3]. In both cases, a H/OTf exchange
reaction is observed at the silicon atom. During the
formation of 1, we proposed that the iridium-silyl
Our group previously reported that the iridium(III)-
silyl complex (Et3P)3(H)2Ir[Si(H)Cl(C6H3Ã
/
Mes2-2,6)]
(1) forms from a H/Cl exchange reaction during the
complex (Et3P)2(H)2Ir[Si(Cl)(H)(C6H3Ã
/
Mes2-2,6)] (2a)
is generated and it affords 1 by complexation of an
reaction of (Et3P)3IrCl and H3Si(C6H3Ã
/Mes2-2,6) (Eq.
1) [1].
additional phosphine ligand (Eq. 2).
ð1Þ
In other groups, similar H/anion exchange chemistry
was observed during the formation of the iridium(III)-
ð2Þ
Increasing the steric bulk of the phosphine from Et3P
to Et2PhP was expected to prevent the complexation of
three phosphine ligands. Ideally, this would promote an
additional 1,2 hydride migration to afford the neutral
silyl complex (R3P)(TFB)(H)2Ir[Si(OTf)Ph2] (Rꢀ
/
i-Pr,
Cy; OTfꢀtriflate; TFBꢀtetrafluorobenzobarrelene) [2]
/
/
iridium
[Si(Cl)(C6H3Ã
(Eq. 3). We report herein, the complex isolated from the
reaction of H3Si(C6H3ÃMes2-2,6) with (Et2PhP)3IrCl.
silylene
complex
(Et2PhP)2(H)3IrÄ
/
/
Mes2-2,6)] (3), which has a SiÃ
/
Cl bond
* Corresponding author. Fax: ꢁ
E-mail addresses:
youngs@uakron.edu (W.J. Youngs).
/
1-330-972-7370.
tessier@chemistry.uakron.edu,
/
0022-328X/03/$ - see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/S0022-328X(03)00629-6

2
R.S. Simons et al. / Journal of Organometallic Chemistry 681 (2003) 1Á4
/
afford 5 as an off-white solid. Yield: 0.5 g, 0.5 mmol,
63%. Anal. Calc. for C54H71P3IrClSi: C, 60.68; H, 6.70.
Found: C, 61.10; H, 6.00%. 31P-NMR (C6D6): d ꢂ
/
16.7
23.2 (m, 2P). 29Si-NMR
0.8 (dt, JSiÃPtrans 168 Hz, JSiÃPcis 10
Hz). IR (Nujol, cmꢂ1): 2132(s), 2079(s), 2030(s) (IrÃ
H,
SiÃH).
(m, 1P), ꢂ
/
17.7 (m, 1P), ꢂ
/
(C6D6): d ꢂ
/
ꢀ
/
ꢀ
/
/
/
ð3Þ
2.4. X-ray crystallography
Crystals of 4 and 5 were coated in paraffin oil and
mounted on a glass fiber and placed under a stream of
nitrogen [6]. Additional experimental data are given in
2. Experimental
Table 1. All manipulations were carried out at 100 K
˚
2.1. General considerations
using MoÁKa (0.71073 A) radiation on an Bruker
/
APEX CCD diffraction system. Unit cell parameters
were obtained by indexing the peaks of the first 60
frames and refined using the entire data set. All frames
were integrated and corrected for lorentz and polariza-
tion effects using the Bruker Saint program. The
structures of 4 and 5 were solved by direct methods
[7]. For 5, the hydrogen atoms attached to the iridium
All manipulations were carried out under anaerobic
conditions in an atmosphere of nitrogen or argon. The
compounds, [Ir(COE)2Cl]2 [4] and 2,6-Mes2C6H3SiH3
[5] were prepared according to literature procedures.
Hexane and THF were freshly distilled from sodium
benzophenone ketyl. 1H-, 13C- and 29Si-NMR data were
1
recorded on a Varian 400 MHz instrument. H-NMR
(H1 and H2) were located from the difference map and
˚
data were referenced to the residual protons in C6D6 and
13C-NMR data was referenced to the deuterated solvent.
29Si-NMR data were referenced to external Me4Si. 31P-
NMR data were recorded on a Gemini 300 MHz
instrument and referenced to external H3PO4. IR data
were recorded on a Bomem FTIR instrument.
refined using the DFIX restraint (IrÃ
/
Hꢀ1.68 A).
/
Phenyl and alkyl hydrogen atoms were placed in
idealized positions and refined using a riding model.
Compounds 4 and 5 were refined to convergence using
anisotropic thermal parameters for all non-hydrogen
atoms.
2.2. Synthesis of (Et2PhP)3(Cl)Ir (4)
Table 1
Crystal data and structure refinement for 4 and 5
PEt2Ph (1.0 g, 6.0 mmol) was added by syringe to a
THF solution (50 ml) of [Ir(COE)2Cl]2 (0.89 g, 1.0
mmol) while stirring at ambient temperature. Stirring
was continued for ca. 1 h. The volume of the solution
was reduced to incipient crystallization and stored at ca.
Empirical formula
4, C30H45ClIrP3 5, C54H95ClIrP3-
Si
Formula weight
Temperature (K)
˚
Wavelength (A)
726.22
100
0.71073
1092.95
100
0.71073
¯
1; 4 Triclinic, P1; 2
¯
Crystal system, space group, Z Triclinic, P
/
/
ꢂ20 8C to afford (Et2PhP)3(Cl)Ir (4) as orange crystals.
/
Unit cell dimensions
˚
Yield: 0.6 g, 0.8 mmol, 80%. Anal. Calc. for
C30H45P3IrCl: C, 49.61; H, 6.25. Found: C, 49.99; H,
a (A)
˚
10.9277(7)
15.0014(10)
19.4813(13)
102.2170(10)
95.4280(10)
94.9610(10)
3088.6(4)
1.562
12.7418(12)
12.9520(13)
18.2470(18)
69.250(2)
71.954(2)
66.686(2)
2535.2(4)
1.432
b (A)
1
6.01%. H-NMR (C6D6): d 0.57, 2.14 (m, 12H, PCH2),
˚
c (A)
1.1 (m, 18H, PCH2CH3), 7.0, 7.6 (m, 15H, C6H5). 31P-
a (8)
b (8)
g (8)
NMR (C6D6): d ꢂ
/
1.3 (t, 1P, Jꢀ24 Hz), 10.5 (m, 2P).
/
3
˚
V (A )
Dcalc (Mg mꢂ3
)
2.3. Synthesis of 5
Absorption coefficient (mmꢂ1
)
4.582
2.840
Theta range for data collection 1.08Á
/
27.51
1.22Á27.55
/
A THF solution (50 ml) of 4 (0.6 g, 0.8 mmol) was
added to H3Si(C6H3ÃMes2-2,6) (0.8 g, 0.8 mmol) in
THF (20 ml) while stirring at dry iceÁacetone bath
temperature. The solution was warmed to ambient
temperature and stirred for an additional 16 h. The
volatile components were removed under reduced pres-
sure to yield a light yellow solid. The solid was washed
with 50 ml of hexane and collected on a glass frit to
(8)
Reflections collected/unique
/
38 531/13 842/
21 912/11 169
[Rint 0.0616)
1.138
[Rintꢀ
0.650
/0.0208)
ꢀ
/
/
Goodness-of-fit on F2
Final R indices[I ꢀ
R indices (all data)
/2s(I)]
0.0188
0.0473
0.0662
0.1426
Largest difference peak and hole 1.128 and ꢂ
/
ꢂ3
˚
(e A
)
0.371

R.S. Simons et al. / Journal of Organometallic Chemistry 681 (2003) 1Á
/
4
3
Table 2
Selected bond distances and angles for 4 and 5
4
5
˚
Bond distances (A)
Ir1Ã
Ir1Ã
Ir2Ã
Ir2Ã
/
Cl1
P1
P2
P3
2.3945(5)
2.3045(5)
2.3276(6)
2.2107(5)
Ir1Ã
Ir1Ã
Ir1Ã
/
P1
P2
P3
Si1
2.347(2)
2.336 (2)
2.363(2)
2.358(2)
2.159(3)
1.943(8)
1.910(8)
/
/
/
/
/
Ir1Ã
/
Si1Ã
/
Cl1
Si1Ã
/
C1
Si1Ã
/
C13
Bond angles (8)
P2
P1Ã
Cl1Ã
P2ÃIr1Ã
P1ÃIr1Ã
P1ÃIrÃ
P2ÃIr1Ã
/
Ir1Ã
/
171.15(2)
172.00(2)
92.66(2)
96.04(2)
85.07(2)
86.08(2)
Si1Ã
Ir1Ã
Cl1Ã
/
Ir1Ã
/
P2
143.39(7)
117.1(2)
118.15(11)
/
Ir2Ã
/
P3
/
Si1Ã
/
C1
Ir1
/
/
P3
/
Si1Ã
/
Fig. 1. Molecular structure of 4 with thermal ellipsoids drawn at 30%
probability. Hydrogen atoms have been omitted for clarity.
/
/P3
/
/Cl1
3. Results and discussion
/
/Cl1
The reaction of [Ir(COE)Cl]2 and Et2PhP in a 1:6
ratio affords the iridium(I) complex 4 as orange crystals
The iridium(III)-silyl complex 5 is prepared in 63%
Mes2-2,6)
(Eq. 5). Complex 5 is isolated as colorless crystals that
1
in good yield (80%). The H- and 31P-NMR data are
yield by the reaction of 4 and H3Si(C6H3Ã
/
consistent with the structure of 4. The structure of 4 was
determined by X-ray crystallography (Fig. 1). Selected
bond distances and angles are given in Table 2. Complex
are thermally stable up to the temperature at which they
melt (162Á
163 8C). The 31P- and 29Si-NMR and IR
/
¯
4 crystallizes in the triclinic space group P1 with two
/
spectroscopic data and the X-ray crystallographic ana-
lysis are consistent with the structure of 5. The isolation
of 5 suggests the formation of a reactive intermediate.
One possible explanation is the formation of the
anticipated iridium silylene species 3 that undergoes a
molecules in the asymmetric unit that have equivalent
structural parameters within experimental error. For
this reason, the structural parameters of only one of the
molecules will be discussed. The geometry of 4 is square
planar with P1Ã
(172.00(2)8), P3Ã
(92.66(2)8) bond angles and Ir1Ã
/
Ir1Ã
Ir1Ã
/
P2 (171.15(2)8), P3Ã
/
Ir1Ã
Ir1Ã
/
Cl1
CÃ
/
H insertion reaction with simultaneous reductive
/
/
P1 (96.04(2)8), P3Ã
/
/P2
elimination of H2 (Eq. 6). Presumably, the electron
withdrawing chloride atom further destabilizes the
electron deficient silicon atom in 3. A similar insertion
reaction was reported by West and coworkers during
defluorination of the terphenyl substituted silane
˚
/
P1 (2.305(1) A), Ir1Ã
/
˚
˚
P2 (2.328(1) A), Ir1Ã
/
P3 (2.211(1) A) and IrÃ
/
Cl1
˚
(2.395(1) A) bond distances.
F3Si(C6H3Ã
/
Mes2-2,6) [8]. In this case, a reactive fluor-
ð4Þ
Fig. 2. Molecular structure of 5 with thermal ellipsoids drawn at 30%
probability. Hydrogen atoms attached to carbon atoms have been
omitted for clarity.

4
R.S. Simons et al. / Journal of Organometallic Chemistry 681 (2003) 1Á4
/
osilylene or disilyne is proposed to undergo a CÃ
/C bond
results from the cyclometallation of an ortho-mesityl CÃ
/
H bond.
insertion reaction (Fig. 2).
The structure of 5 reveals an octahedral iridium(III)
complex that has a silyl ligand trans to one phosphine
and cis to two remaining phosphines ligands. The
hydride ligands are oriented cis to each other and cis
to the silyl ligand. The geometry at the silicon atom is
5. Supporting information available
Crystallographic data (excluding structure factors) for
4 and 5 have been deposited with the Cambridge
Crystallographic Data Center as supplemental publica-
tions numbers CCDC 202586 and 202587. Copies of the
data can be obtained, free of charge, on application to
The Director, CCDC, 12 Union Road, Cambridge CB2
distorted tetrahedral with one of the substituents being
˚
C13ꢀ1.910(8) A) to
the cyclometallated C13 atom (Si1Ã
/
/
produce a puckered six-member ring. The Si1Ã
/
Cl1
˚
˚
(2.159(3) A), Si1Ã
/
C1 (1.943(8) A) and Ir1ÃSi1
/
˚
(2.358(2) A) bond distances and are quite standard.
The bond angles at the silicon atom are normal with the
1EZ, UK (Fax: ꢁ44-1223-336033; e-mail: deposit@
/
ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk).
exception of the Ir1Ã
/
Si1Ã
/
C1 (117.1(2)8) and C13Ã
/
Si1Ã
/
Ir1 (125.1(3)8) bond angles.
Acknowledgements
We wish to thank the National Science Foundation,
the University of Akron and the Ohio Board of
Reagents for financial support.
References
[1] R.S. Simons, J.C. Gallucci, C.A. Tessier, W.J. Youngs, J.
Organomet. Chem. 654 (2002) 224.
[2] W. Chen, A.J. Edwards, M.A. Esteruelas, F.J. Lahoz, M. Oliva´n,
L.A. Oro, Organometallics 15 (1996) 2185.
[3] S.R. Klei, T.D. Tilley, R.G. Bergman, J. Am. Chem. Soc. 122
(2000) 1816.
[4] J.L. Herde, J.C. Lambert, C.V. Senoff, Inorg. Synth. 15 (1974) 18.
[5] R.S. Simons, S.T. Haubrich, B.V. Mork, M. Niemeyer, P.P. Power,
Main Group Chem. 2 (1998) 275.
(5)
[6] H. Hope, in: A.L. Wayda, A.M.Y. Darensbourg (Eds.), Experi-
mental Organometallic Chemistry ACS Symposium Series 357,
American Chemical Society, Washington, DC, 1987 (Chapter 10).
[7] SHELXTL, Version 5.11, Siemens Analytical Instruments, Madison,
WI, 1997.
4. Conclusion
In conclusion, the sterically hindered silane,
H3Si(C6H3ÃMes2-2,6) reacts with (Et2PhP)3IrCl to af-
ford a sterically hindered iridium(III)-silyl complex that
/
[8] R. Pietschnig, R. West, D.R. Powell, Organometallics 19 (2000)
2724.