Phosphinoalkylsilyl complexes. 12. Stereochemistry of the tridentate bis(diphenylphosphinopropyl)silyl (biPSi) framework: Complexation that introduces "face discrimination" at coordinatively unsaturated metal centers. X-ray crystal and molecular structures of Pt[SiMe(CH2CH2CH2PPh2) 2]Cl

Article abstract of DOI:10.1021/om970518k

Reaction of the bis(phosphinoalkyl)silanes RSiH[(CH₂)_nPR¹₂]₂ (R = Me or Ph, n = 2 or 3, R¹ = Ph or Cy, i.e., cyclohexyl; biPSiH for R = Me, n = 2, R¹ = Ph) with Pt(COD)Cl₂ (COD = cycloocta-1,5-diene), [Ir(COD)Cl]₂, trans-M(PPh₃)₂(CO)Cl (M = Rh or Ir), or Ru₃(CO)₁₂ affords products that are complexes of tridentate biPSi silyl analogues, in which the Si center is anchored through attachment of trans P atoms at the transition-metal site. The platinum(II) compounds Pt[SiMe(CH₂CH₂PPh₂)₂]Cl (1), Pt[SiMe(CH₂CH₂PCy₂)₂]Cl (2), Pt[SiPh(CH₂CH₂PCy₂)₂]Cl (3), Pt[SiPh(CH₂CH₂PPh₂)(CH₂CH ₂PCy₂)]Cl (4), Pt[SiMe(CH₂CH₂-CH₂PPh₂) ₂]Cl (5), Pt[SiMe(CH₂CH₂CH₂PCy₂) ₂]Cl (6), and Pt[SiPh(CH₂CH₂CH₂PPh₂) ₂]Cl (7), which have been characterized by ¹H, ¹³C, and ³¹P NMR spectroscopy, possess distinguishable square faces with Me on Si projecting in one direction and the buckled (CH₂)_n backbones in the other. Cleavage of the Pt-Si bond in Pt(biPSi)Cl (5) by HCl affords a pair of diastereomers HPt[(PPh₂CH₂CH₂CH₂) ₂Si(Cl)Me]Cl (8,8′) in which the two P atoms are also trans. The five-coordinate, 16e, d⁶ Ir(III) complex IrH(biPSi)Cl (9) is isolated as a single diastereomer, but octahedral IrH(biPSi)(CO)Cl is formed as a 3:1 mixture of stereoisomers (10 and 11, CO or Cl trans to Si, respectively, i.e., H trans to Cl or CO) that react with SnCl₂ to afford (also 3:1) the analogues IrH(biPSi)(CO)SnCl₃ (12 and 13). Treatment of 10 and 11 (3:1) with LiAlH₄ yields a diastereomeric pair of cis-dihydrido complexes IrH₂(biPSi)-(CO) (14,14′) (1:3), accompanied by a trans-dihydrido stereoisomer 15 and a fac-biPSi stereoisomer 16 as minor products; in 14, 14′ and 15 the hydride ligands are nonequivalent and show ²J_HHcis = 5.1, 4.4 Hz, ²J_HHtrans ≈ 0, respectively. Similar treatment with LiAl²H₄ affords monodeuterioisotopomers 14a,14′a, while reaction of compound 9 with LiAlH₄ under CO gas initially affords 16 as a single product that subsequently isomerizes to 14,14′. The octahedral, 18e, d⁶ Ru(II) homologues RuH[SiMe(CH₂CH₂PPh₂)₂](CO) ₂ (17) and RuH(biPSi)-(CO)₂ (18) are formed in sealed-tube reactions at elevated temperature but in very poor yields. NMR spectroscopy suggests that in solution the biPSi backbones of 2-7 and 9-13 are equivalent, establishing planar symmetry (point group C_s) perpendicular to the ligand template, although this is not maintained in the solid state as shown crystallographically for compounds 5, 9, 13, and 18. Bond distances trans to Si are long in 5 and 13 (2.44 and 2.66 A?, to Cl or SnCl₃, respectively), but in 9 Ir-Cl at 2.30 A? is short, occupying the equatorial plane with Si and H in a distorted TBP structure (Si-Ir-Cl 129°). The M-Si distances are 2.31 (5), 2.29 (9), 2.42 (13), and 2.46 A? (18). In 9 and 13, the H at Ir is anti vs Me on Si (of biPSi), whereas in 18, the Ir-H and Si-Me bonds are syn.

Full text of DOI:10.1021/om970518k

Organometallics 1997, 16, 5669-5680
5669
P h osp h in oa lk ylsilyl Com p lexes. 12. Ster eoch em istr y of
th e Tr id en ta te Bis(d ip h en ylp h osp h in op r op yl)silyl (biP Si)
F r a m ew or k : Com p lexa tion Th a t In tr od u ces “F a ce
Discr im in a tion ” a t Coor d in a tively Un sa tu r a ted Meta l
Cen ter s. X-r a y Cr ysta l a n d Molecu la r Str u ctu r es of
P t[SiMe(CH2CH2CH2P P h 2)2]Cl,
Ir H[SiMe(CH2CH2CH2P P h 2)2]Cl, a n d
1
Ru H[SiMe(CH2CH2CH2P P h 2)2](CO)2
Ron D. Brost, Gregg C. Bruce, Frederick L. J oslin, and Stephen R. Stobart*,†
Department of Chemistry, Auburn University, Auburn, Alabama 36849
Received J une 19, 1997X
Reaction of the bis(phosphinoalkyl)silanes RSiH[(CH2)nPR1 ]2 (R ) Me or Ph, n ) 2 or 3,
2
R1 ) Ph or Cy, i.e., cyclohexyl; biPSiH for R ) Me, n ) 2, R1 ) Ph) with Pt(COD)Cl2 (COD
) cycloocta-1,5-diene), [Ir(COD)Cl]2, trans-M(PPh3)2(CO)Cl (M ) Rh or Ir), or Ru3(CO)12
affords products that are complexes of tridentate biPSi silyl analogues, in which the Si center
is anchored through attachment of trans P atoms at the transition-metal site. The
platinum(II) compounds Pt[SiMe(CH2CH2PPh2)2]Cl (1), Pt[SiMe(CH2CH2PCy2)2]Cl (2),
Pt[SiPh(CH2CH2PCy2)2]Cl (3), Pt[SiPh(CH2CH2PPh2)(CH2CH2PCy2)]Cl (4), Pt[SiMe(CH2CH2-
CH2PPh2)2]Cl (5), Pt[SiMe(CH2CH2CH2PCy2)2]Cl (6), and Pt[SiPh(CH2CH2CH2PPh2)2]Cl (7),
which have been characterized by 1H, 13C, and 31P NMR spectroscopy, possess distinguishable
square faces with Me on Si projecting in one direction and the buckled (CH2)n backbones in
the other. Cleavage of the Pt-Si bond in Pt(biPSi)Cl (5) by HCl affords a pair of
diastereomers HPt[(PPh2CH2CH2CH2)2Si(Cl)Me]Cl (8,8′) in which the two P atoms are also
trans. The five-coordinate, 16e, d6 Ir(III) complex IrH(biPSi)Cl (9) is isolated as a single
diastereomer, but octahedral IrH(biPSi)(CO)Cl is formed as a 3:1 mixture of stereoisomers
(10 and 11, CO or Cl trans to Si, respectively, i.e., H trans to Cl or CO) that react with
SnCl2 to afford (also 3:1) the analogues IrH(biPSi)(CO)SnCl3 (12 and 13). Treatment of 10
and 11 (3:1) with LiAlH4 yields a diastereomeric pair of cis-dihydrido complexes IrH2(biPSi)-
(CO) (14,14′) (1:3), accompanied by a trans-dihydrido stereoisomer 15 and a fac-biPSi
stereoisomer 16 as minor products; in 14, 14′ and 15 the hydride ligands are nonequivalent
2
2
and show J HHcis ) 5.1, 4.4 Hz, J HHtrans ≈ 0, respectively. Similar treatment with LiAl2H4
affords monodeuterioisotopomers 14a ,14′a , while reaction of compound 9 with LiAlH4 under
CO gas initially affords 16 as a single product that subsequently isomerizes to 14,14′. The
octahedral, 18e, d6 Ru(II) homologues RuH[SiMe(CH2CH2PPh2)2](CO)2 (17) and RuH(biPSi)-
(CO)2 (18) are formed in sealed-tube reactions at elevated temperature but in very poor
yields. NMR spectroscopy suggests that in solution the biPSi backbones of 2-7 and 9-13
are equivalent, establishing planar symmetry (point group Cs) perpendicular to the ligand
template, although this is not maintained in the solid state as shown crystallographically
for compounds 5, 9, 13, and 18. Bond distances trans to Si are long in 5 and 13 (2.44 and
2.66 Å, to Cl or SnCl3, respectively), but in 9 Ir-Cl at 2.30 Å is short, occupying the equatorial
plane with Si and H in a distorted TBP structure (Si-Ir-Cl 129°). The M-Si distances are
2.31 (5), 2.29 (9), 2.42 (13), and 2.46 Å (18). In 9 and 13, the H at Ir is anti vs Me on Si (of
biPSi), whereas in 18, the Ir-H and Si-Me bonds are syn.
In tr od u ction
tion geometry3,4 but may depend also on possible
changes in electron availability at the active metal site
Selectivity in cycles that are catalyzed by soluble
transition-metal complexes is accountable for2 not only,
in terms of shape recognition of substrate by coordina-
(3) Barnhart, R. W.; Wang, X.; Noheda, P.; Bergens, S. H.; Whelan,
J .; Bosnich, B. J . Am. Chem. Soc. 1994, 116, 1721.
(4) (a) Halpern, J . In Asymmetric Synthesis; Morrison, J . D., Ed.;
Academic Press: New York, 1985; Vol. 5, pp 41-69. (b) Brown, J . M.
In Homogeneous Catalysis with Metal-Phosphine Complexes; Pignolet,
L. H., Ed.; Plenum: New York, 1983; pp 137. (c) Landis, C. R.; Halpern,
J . J . Am. Chem. Soc. 1987, 109, 1746. (d) Brown, J . M.; Evans, P. L.
Tetrahedron 1988, 44, 4905. (e) Bosnich, B. Pure Appl. Chem. 1990,
62, 1131. (f) Bogdan, P. L.; Irwin, J . J .; Bosnich, B. Organometallics
1989, 8, 1450. (g) Giovannetti, J . S.; Kelly, C. M.; Landis, C. R. J . Am.
Chem. Soc. 1993, 115, 4040.
† Current address: Department of Chemistry, University of Victoria,
British Columbia, Canada V8W 2Y2.
X Abstract published in Advance ACS Abstracts, November 15, 1997.
(1) Part 11: Auburn, M. J .; Holmes-Smith, R. D.; Stobart, S. R.;
Bakshi, P. K.; Cameron, T. S. Organometallics 1996, 15, 3032.
(2) Quan, R. W.; Li, Z.; J acobsen, E. N. J . Am. Chem. Soc. 1996,
117, 8156.
S0276-7333(97)00518-9 CCC: $14.00 © 1997 American Chemical Society

5670 Organometallics, Vol. 16, No. 26, 1997
Brost et al.
that result directly from5-7 chemical modification of the
ligand framework. Such dependence is identified ex-
plicitly in the theoretical modeling of associative dihy-
drogen approach to a coordinatively unsaturated d8
center,8 which has been shown to be controlled primarily
by electronic factors that include competing ligand trans
influences. We have been seeking to determine if the
electron-releasing properties and strong trans influence
of silyl ligands9 may alter or enhance the catalytic
performance of soluble platinum-group metal centers in
hydrogenation, hydroformylation, or hydrosilylation
reactions. Investigation of this possibility necessitates
chelate attachment as a means for suppressing silyl
elimination, which is otherwise facile, a requirement
that has been met10 by using polydentate phosphi-
noalkylsilyl (PSi) ligands for simultaneous binding
through Si and P (see A).
appears to be too restricting18 and shuts down cataly-
sis.16,19 As shown below, however, the stereochemistry
of tridentate [Ph2PCH2CH2CH2]2SiMe- (biPSi) attach-
ment (see A and B) develops distinguishable molecular
faces at an unsaturated metal center,16 a property that
is not common20 and will direct diastereoselective
substrate entry into a position trans to Si. A five-
In the hierarchy of ligand electronic effects, excep-
tionally strong σ-donor character is attributed to silyl
complexation because it has a remarkable impact11 on
the parameters that provide a measure of the relative
trans-influencing capacity. In these terms, -SiR3 ex-
ceeds both -H and -CH3 (as is shown convincingly by
crystallographic data provided below as well as data
recently12,13 reported); this empirical order is again
supported by contemporary theoretical arguments8,14,15
(based inter alia on Taft parameters) that identify
σ-donor ability as the dominant force (vs much weaker
π-donation) in trans atom or group labilization. By
directing the electronic labilizing character of silyl
complexation within the sterically controlled environ-
ment of a supporting framework, polydentate PSi ligand
attachment should be capable of exerting an unusually
powerful organizing effect over bond formation by other
atoms at the same metal center. Accordingly, complexes
so formed are strongly regioselective homogeneous
hydroformylation catalysts.16 Simple chelation, using
the analogue Ph2PCH2CH2SiMe2- (chel) of diphos (Ph2-
PCH2CH2PPh2), minimizes the steric impact of PSi
ligation;10,17 while encapsulation of the reactive site in
a tetradentate cage by [Ph2PCH2CH2CH2]3Si- (triPSi)
(5) J acobsen, E. N.; Zhang, W.; Gu¨ler, M. L. J . Am. Chem. Soc. 1991,
113, 6703.
(6) Bender, B. R.; Koller, M.; Nanz, D.; von Philipsborn, W. J . Am.
Chem. Soc. 1993, 115, 5889. See also: Tedesco, V.; von Philipsborn,
W. Organometallics 1995, 14, 3600.
(7) Schnyder, A.; Togni, A.; Wiesli, U. Organometallics 1997, 16, 255.
(8) Burk, M. J .; McGrath, M. P.; Wheeler, R.; Crabtree, R. H. J .
Am. Chem. Soc. 1988, 110, 5034. Sargent, A. L.; Hall, M. B.; Guest,
M. F. J . Am. Chem. Soc. 1992, 114, 517. Sargent, A. L.; Hall, M. B.
Inorg. Chem. 1992, 31, 317.
(9) (a) Auburn, M. J .; Stobart, S. R. Inorg. Chem. 1985, 24, 317. (b)
Auburn, M. J .; Holmes-Smith, R. D.; Stobart, S. R. J . Am. Chem. Soc.
1984, 106, 1314.
coordinate iridium(III) complex (16 electron, d6) of this
type, IrH(biPSi)Cl, is crystallographically shown to be
another example of the hitherto rare dist-TBP geometry
that was first recognized1 by us, Werner, and Fryzuk
and has subsequently been rationalized21 using molec-
ular orbital arguments by Eisenstein, Caulton et al.
In addition we have found that related “face-discrimi-
nation” in a coordinatively saturated, six-coordinate, 18-
electron dihydrido-iridium(III) analogue IrH2(biPSi)-
(CO) also leads to the existence of diastereomers in
which one H at Ir is either syn or anti vs the methyl
(10) (a) Holmes-Smith, R. D.; Stobart, S. R.; Cameron, T. S.; J ochem,
K. J . Chem. Soc., Chem. Commun. 1981, 937. (b) Grundy, S. L.;
Holmes-Smith, R. D.; Stobart, S. R.; Williams, M. A. Inorg. Chem. 1991,
30, 3333.
(11) (a) Heaton, B. T.; Pidcock, A. J . Organomet. Chem. 1968, 14,
235. (b) Appleton, T. G.; Clark, H. C.; Manzer, L. E. Coord. Chem. Rev.
1973, 10, 335.
(12) Kapoor, P.; Lo¨vqvist, K.; Oskarsson, Å. Acta Crystallogr. 1995,
C51, 611.
(18) J oslin, F. L.; Stobart, S. R. J . Chem. Soc., Chem. Commun. 1989,
504.
(19) Hendricksen, D. E.; Oswald, A. E.; Ansell, G. B.; Leta, S.;
Kastrup, R. V. Organometallics 1989, 8, 1153.
(13) Aizenberg, M; Milstein, D. J . Am. Chem. Soc. 1995, 117, 6456.
(14) Abu-Hasanayn, F.; Krogh-J espersen, K.; Goldman, A. S. Inorg.
Chem. 1993, 32, 495.
(15) Lichtenberger, D. L.; Rai-Chaudhuri, A. J . Am. Chem. Soc.
1991, 113, 2923.
(16) Stobart, S. R.; Grundy, S. L.; J oslin, F. L. U.S. Patent 4,950,-
798, 1990; Canadian Patent 1,327,365, 1994.
(17) Cameron, T. S.; Holmes-Smith, R. D.; J ochem, K.; Stobart, S.
R.; Vefghi, R.; Zaworotko, M. J . J . Chem. Soc. Dalton Trans. 1987,
969.
(20) (a) Fryzuk, M. D.; MacNeil, P. A.; Rettig, S. J . J . Am. Chem.
Soc. 1985, 107, 6708. (b) Yang, C.; Socol, S. M.; Kountz, D. J .; Meek,
D. W. Inorg. Chim. Acta 1986, 114, 119. (c) Bautista, M. T.; Earl, K.
A.; Maltby, P. A.; Morris, R. H. J . Am. Chem. Soc. 1988, 110, 4056.
(21) (a) Riehl, R.-F.; J ean, Y.; Eisenstein, O.; Pe´lissier, M. Organo-
metallics 1992, 11, 729. (b) Albinati, A.; Bakhmutov, V. I.; Caulton,
K. G.; Clot, E.; Eckert, J .; Eisenstein, O. Gusev, D. G.; Grushin, V. V.;
Hauger, B. E.; Klooster, W. T.; Koetzle, T. F.; McMullan, R. K.;
O’Loughlin, T. J .; Pelissier, M.; Ricci, R. S.; Sigalas, M. P.; Vymentis,
A. B. J . Am. Chem. Soc. 1993, 115, 7300.

Phosphinoalkylsilyl Complexes
Organometallics, Vol. 16, No. 26, 1997 5671
Anal. Calcd for C31H59ClP2PtSi: C, 49.49; H, 7.91. Found:
C, 49.07; H, 7.72.
substituent at Si (also bonded to Ir, see A). These
products are rare examples of transition-metal com-
plexes in which two hydride ligands are nonequivalent,
resulting in the resolution of 2J HH(cis) (∼5 Hz) but not of
the corresponding trans coupling (J ≈ 0) in 1H NMR
spectra at ambient temperature.
vii. P t[SiP h (CH2CH2CH2P P h 2)2]Cl (7). Similar treat-
ment of PhSiH(CH2CH2CH2PPh2)2 (0.30 g, 0.53 mmol) with
[Pt(COD)Cl2] (0.20 g, 0.53 mmol) in benzene solution with NEt3
yielded another cream-colored product (0.30 g, 72%). Anal.
Calcd for C36H37ClP2PtSi: C, 54.71; H, 4.72. Found: C, 54.72;
H, 4.95.
viii. Diaster eoisom er ic Com plexes P tH[(P P h 2CH2CH2-
CH2)2Si(Cl)Me]Cl (8,8′). Compound 5 (40 mg, 0.06 mmol)
was dissolved in a mixture of THF (5 mL) and methanol (1
mL), then acetyl chloride (5 mg, 0.06 mmol) in THF was added.
After the mixture was stirred (5 min), removal of the volatiles
left a white solid product (38 mg, 91%), shown by NMR to be
a mixture of diastereomers. Anal. Calcd for C31H36Cl2P2-
PtSi: C, 48.69; H, 4.57. Found: C, 48.21; H, 4.55.
B. Com p lexes of Ir id iu m (III). i. Ir H[SiMe(CH2CH2-
CH 2P P h 2)2]Cl (9). Solutions in benzene (10 mL) of
MeSiH(CH2CH2CH2PPh2)2 (0.12 g, 0.24 mmol) and [Ir(COD)-
Cl]2 (0.08 g, 0.12 mmol) were mixed and then stirred at
ambient temperature. After 150 min, the solvent was removed
in vacuo, leaving behind the product as a yellow powder (0.16
g, 95%). Anal. Calcd for C31H36ClIrP2Si: C, 51.26; H, 4.99.
Found: C, 51.46; H, 4.99. During refrigeration at -20 °C, a
solution of the pure complex in an ether/hexane mixture slowly
deposited shiny orange crystals that were suitable for X-ray
diffraction.
Exp er im en ta l Section
Full details of general synthetic procedures, protocol for
instrumental measurements, analytical techniques, and meth-
odology used for access to transition-metal precursors have
been given in earlier papers.9,10,17 Bis(diorganophosphino-
alkyl)organosilane (biPSiH) synthesis has also been described
elsewhere:22 these air-sensitive ligand precursors were ma-
nipulated by using syringe techniques under standard inert-
atmosphere conditions.
Syn th esis of biP Si Com p lexes. A. Of P la tin u m (II). i.
P t[SiMe(CH2CH2P P h 2)2]Cl (1). Dropwise addition of a
solution of MeSiH(CH2CH2PPh2)2 (99 mg, 0.21 mmol) in dry
THF (5 mL) to a solution of [Pt(COD)Cl2] (79 mg, 0.21 mmol)
in a mixture of THF (7 mL) and NEt3 (1 mL) resulted in rapid
formation of a white precipitate. Removal of the volatiles left
solid material, which after thorough washing left the product
(124 mg, 84%), which proved to be insoluble in benzene, CH2-
Cl2, Et2O, THF, acetone, DMF, or water. Anal. Calcd for
C
29H31ClP2PtSi: C, 49.75; H, 4.46. Found: C, 50.02; H, 4.59.
ii. Isom er ic Com p lexes Ir H[SiMe(CH2CH2CH2P P h 2)2]-
(CO)Cl (10 a n d 11). When solutions in CH2Cl2 (10 mL) of
MeSiH(CH2CH2CH2PPh2)2 (0.36 g, 0.73 mmol) and trans-[Ir-
(PPh3)2(CO)Cl] (0.57 g, 0.73 mmol) were stirred together, the
initially cloudy yellow mixture became clear and colorless.
Evaporation of the solvent left a sticky white solid that was
washed thoroughly with Et2O to afford the product as a fine
white powder (0.36 g, 66%), which was shown by NMR to be
ii. P t[SiMe(CH2CH2P Cy2)2]Cl (2). Dry benzene (10 mL)
and NEt3 (1 mL) were added to MeSiH(CH2CH2PCy2)2 (0.20
g, 0.41 mmol). Rapid addition of this mixture to a stirred
slurry of [Pt(COD)Cl2] (0.15 g, 0.41 mmol) in benzene (10 mL)
resulted in immediate dissolution of the solids to give a slightly
turbid solution. Removal of the volatiles in vacuo left a sticky
solid which was extracted with benzene (5 mL). Removal of
the latter followed by two successive similar extraction and
evaporation cycles afforded the pure product (0.25 g, 84%).
Anal. Calcd for C29H55ClP2PtSi: C, 48.09; H, 7.65. Found:
C, 48.09; H, 7.62.
a mixture of two isomers in a 3:1 ratio. Anal. Calcd for C32H36
-
ClIrOP2Si, mono-CH2Cl2 solvate: C, 47.22; H, 4.56. Found:
C, 47.18; H, 5.06.
iii. Isom er ic Com p lexes Ir H[SiMe(CH2CH2CH2P P h 2)2]-
(CO)(Sn Cl3) (12 a n d 13). The mixture of isomers 10 and 11
(80 mg, 0.11 mmol) and anhydrous SnCl2 (20 mg, 0.11 mmol)
were dissolved together in THF (10 mL) and then stirred for
60 min. Removal of the solvent left a white, powdery product
(100 mg, 100%), shown by NMR to be a mixture of isomers,
again in a 3:1 ratio. Anal. Calcd for C32H36Cl3IrOP2SiSn: C,
40.72; H, 3.84. Found: C, 40.38; H, 3.62.
iv. Isom er ic Com p lexes Ir H2[SiMe(CH2CH2CH2P P h 2)2]-
(CO)} (14, 15, a n d 16). The mixture of isomers 10 and 11
(0.11 g, 0.14 mmol) was dissolved in THF (10 mL), then excess
LiAlH4 in THF was slowly added, leading to the formation of
a yellow-grey suspension. After removal of the volatiles, the
residue was extracted with toluene (3 × 5 mL) and then the
extracts were filtered through a plug of nonabsorbent cotton.
Evaporation of the solvent yielded the off-white product (0.05
g, 52%), which was shown by NMR to consist mainly (ca. 84%)
of a mixture of a pair of diastereoisomers in a 3:1 ratio (i.e.,
14 and 14′) together with a minor proportion of two other
isomers (15 and 16). Anal. Calcd for C32H37IrOP2Si: C, 53.39;
H, 5.18. Found: C, 53.01; H, 5.03.
C. Com p lexes of R u t h en iu m (II). i. R u H [SiMe-
(CH2CH2P P h 2)2](CO)2 (17). The precursor MeSiH(CH2CH2-
PPh2)2 (0.21 g, 0.47 mmol) dissolved in a 50/50 mixture of
hexanes/THF (18 mL) was added to solid Ru3(CO)12 (0.09 g,
0.14 mmol) in a Carius tube, which was sealed then heated at
140 °C for 8 h in the dark. After this time the initially orange
solution had become bright yellow, and on cooling a yellow
solid deposited on the walls of the tube. This material was
collected (ca. 15% yield) following decantation of the super-
natent, but evaporation of the latter left a sticky residue from
which no more of the product could be isolated. Anal. Calcd
for C31H32O2P2RuSi: C, 59.31; H, 5.14. Found: C, 59.20; H,
4.97. No reaction was observed even after prolonged periods
iii. P t[SiP h (CH2CH2P Cy2)2]Cl (3). A procedure analo-
gous to that used to obtain complex 2 was followed: a solution
in benzene (10 mL) of PhSiH(CH2CH2PCy2)2 (0.15 g, 0.28
mmol) was run into a slurry of [Pt(COD)Cl2] (0.10 g, 0.28
mmol) also in benzene (10 mL), and NEt3 (1 mL) was
immediatedly added with vigorous stirring. After 10 min,
removal of the volatiles in vacuo followed by extraction of the
solid residue with benzene (2 × 10 mL) afforded the product
as an off-white solid (0.08 g, 35%). Anal. Calcd for
C
34H57ClP2PtSi: C, 51.93; H, 7.31. Found: C, 52.01; H, 6.93.
iv. P t[SiP h (CH 2CH2P P h 2)(CH2CH2P Cy2)]Cl (4). In a
similar manner to that described in A.iii, PhSiH(CH2CH2-
PCy2)(CH2CH2Ph2) (0.11 g, 0.21 mmol) and [Pt(COD)Cl2] (0.08
g, 0.21 mmol) were allowed to react in benzene (10 mL) in the
presence of NEt3 (1 mL). Recovery by extraction into benzene
afforded the product, an off-white solid (0.12 g, 75%). Anal.
Calcd for C34H45ClP2PtSi: C, 52.70; H, 5.86. Found: C, 52.18;
H, 5.62.
v. P t[SiMe(CH2CH2CH2P P h 2)2]Cl (5). After reaction of
MeSiH(CH2CH2CH2PPh2)2 (0.50 g, 1.00 mmol) with [Pt(COD)-
Cl2] (0.37 g, 1.00 mmol) also in benzene (10 mL) with NEt3 (1
mL), the cream-colored solid product was recovered as de-
scribed before (0.53 g, 73%). Anal. Calcd for C31H35ClP2PtSi:
C, 51.13; H, 4.85. Found: C, 50.99; H, 4.81. Crystals suitable
for X-ray diffraction were obtained by slow evaporation in air
of a saturated solution of the complex in diethyl ether.
vi. P t [SiMe(CH 2CH 2CH 2P Cy2)2]Cl (6). Reaction of
MeSiH(CH2CH2CH2PCy2)2 (0.18 g, 0.35 mmol) with [Pt(COD)-
Cl2] (0.13 g, 0.35 mmol) in benzene solution with NEt3 as in
A.v afforded the cream-colored solid product (0.20 g, 76%).
(22) (a) Holmes-Smith, R. D.; Osei, R. D.; Stobart, S. R. J . Chem.
Soc., Perkin Trans. 1 1983, 861. (b) J oslin, F. L.; Stobart, S. R. Inorg.
Chem. 1993, 32, 2221.

5672 Organometallics, Vol. 16, No. 26, 1997
Ta ble 1. Ca r bon -13 a n d P h osp h or u s-31 NMR Da ta a
Brost et al.
compd
δ(PR2)b
δ∆c
δ(SiR)d
δ(SiCH2)
δ(PCH2CH2)e
δ(PCH2)
2
3
4
63.3 (2981)
61.9 (2903)
44.9 (2952)
62.5 (2855)
8.6 (2825)
13.0 (2714)
8.2 (2729)
23.4 (2964)
23.0 (2959)
10.2
+61.2
+58.0
+58.6
+54.5
+25.3
+18.6
+18.2
+40.1
+39.7
+26.3
+0.6
-0.9 (66)
141 (51)
140 (49)
15.6 (118;f 17h)
3.6 (75)
5.2 (86)
143.5 (54)
-1.6
19.6 (120;f 16g)
20.3 (16g)
16.6 (9h)
8.0 (n.o.)
14.3 (102;f 18i)
19.7 (125;f 33i)
20.5 (21)
21.6 (35)
5
6
7
16.6 (35)f
16.2 (43)f
13.7 (34)f
28.8 (67f)
n.o.
26.6
18.9 (24)
8,8′
19.4
31.6
9
10
11
12
13
14
14′
3.4
4.7
6.8
5.4
5.0
8.8
7.5
19.5
14.6
17.7
14.9
18.0
19.6
20.8
21.5
20.4
19.9
20.7
20.4
21.9
22.4
32.1 (20g)
24.4 (19g)
30.6 (19g)
28.0
-16.1
-11.0
+5.7
-22.5 (126j)
-14.3 (247j)
-8.9
-5.8
+1.2
32.6
+7.8
30.5 (20g)
31.5 (20g)
-5.5
+11.2
a
b
Measured at 100.6 (13C) or 162.1 MHz (31P), Bruker WM400 spectrometer, CDCl3 solution. 1J PtP (hertz) in parentheses. c Coordination
shift: see text. R ) Me or Ph as appropriate. J PtC in parentheses. 3J PtC in parentheses. 2J PtC
.
Triplets due to virtual coupling, see
d
2
e
f
g
text. 2J PC
.
1J PC
.
2J SnP
.
h
i
j
(>72 h) when the starting materials were heated together in
refluxing THF.
ylene chains (n ) 2) terminate at nonidentical phos-
phorus donor sites (i.e., PCy2 vs PPh2); while a further
compound (5) was obtained as crystals suitable for X-ray
structure determination. Details of the latter, which
are discussed below, verify that the biPSi ligand does
indeed fit around the Pt center as a tridentate unit, with
the chloride ligand completing the coordination of d8 Pt-
(II) with the anticipated square geometry. The two
faces of the latter are nonidentical, however: the Me
group attached to Si projects in one direction, while the
buckling of the C3 methylene backbones intrudes into
the other. Such an arrangement possesses idealized Cs
symmetry, in which a single plane σ lies perpendicular
to the direction of the metal-ligand bonds (not across
the latter, like σh of regular d8 systems in the D4h point
group), relating the -PR2 groups of the biPSi skeleton.
NMR data for compounds 2-7, which are collected in
Table 1, are all in precise accord with this structural
model.
ii. Ru H[SiMe(CH2CH2CH2P P h 2)2](CO)2 (18). A sealed-
tube reaction between MeSiH(CH2CH2CH2PPh2)2 (0.24 g, 0.48
mmol) and Ru3(CO)12 (0.11 g,0.17 mmol) conducted as de-
scribed in C.i led to slow deposition, on cooling, of a small
amount of a yellow product as fine microcrystals (ca. 8% yield),
which after redissolution in a minimum of diethyl ether slowly
formed as larger crystals that were suitable for X-ray diffrac-
tion. Anal. Calcd for C33H36O2P2RuSi: C, 60.40; H, 5.53.
Found: C, 60.21; H, 5.30.
X-r a y Cr ysta l Str u ctu r e Deter m in a tion s: Com p lexes
5, 9, 13, a n d 18. The general methodology has been described
earlier,1 and similar crystallographic procedures were followed
in the present work. Unit cell parameters were obtained by
least squares on the setting angles for 25 reflections in each
case with 2θ > 300. The structures were solved by direct
methods. Refinement was by least squares. Non-hydrogen
atoms were refined anisotropically, except in the case of 18
where the phenyl carbons were refined isotropically. Full
details are provided in the Supporting Information, together
with the tables of data.
Reactions of the biPSiH ligand precursors with Pt-
(COD)Cl2, Pt(COD)Me2, or Pt(COD)(Me)Cl in the ab-
sence of NEt3 or using NaHCO3 as a base yielded
mixtures of products (31P NMR). Compounds containing
the -PCy2 group were observed to be more reactive than
Ph analogues, with NMR samples showing obvious signs
of deterioration after several hours. Mass spectra
obtained by using FAB contained prominent fragment
ions corresponding to loss of Cl from a molecular ion
corresponding to each proposed structure. Treatment
of the crystallographically characterized prototype 5
with HCl (ca. 1 mol equiv, standardized in benzene
solution) afforded a material that was shown by 31P
NMR spectroscopy to be a mixture (δ 23.4 (1J Pt,P ) 2964
Hz), 23.0 (1J Pt,P 2959 Hz)), attributable to Pt-Si bond-
cleavage centered on either of the distinguishable faces
of the molecule (see B), to yield a pair of diastereomers
8:8′ (ca. 1:4 ratio). Using acetyl chloride in methanol
as a source of HCl to try to control the stoichiometry
more accurately, a ca. 9:1 diastereoisomer distribution
was obtained, the major constituent of which was clearly
a platinum(II) trans-hydrochloride, with νPt-H (IR) at
Resu lts
A. P latin u m (II) Ch em istr y. Addition of MeSiH(CH2-
CH2PPh2)2 (biPSiH) to Pt(COD)Cl2 (COD ) cycloocta-
1,5-diene) in the presence of NEt3 led to isolation of a
white product in essentially quantitative yield that,
similar to23 platinum group metal complexes of perphen-
ylpolyphosphines including PPh2(CH2)nPPh2 (dppm, n
) 1; dppe, n ) 2) or PPh[(CH2)nPPh2]2 (tte, n ) 2; ttp,
n ) 3), was very insoluble in solvents suitable for NMR
spectroscopy. On the basis of the microanalytical data,
as well as by analogy with the way10 in which the simple
chel precursor Ph2PCH2CH2SiHMe2 attaches at Pt, this
product was formulated as a Pt(II) species Pt[(PPh2CH2-
CH2)2SiMe]Cl, 1, with a putative structure in which the
bis(phosphinoalkyl)silyl ligand occupies three sites at
the square metal center. A family of related complexes
2-7 that possessed much better solubility properties
was obtained by introduction of Cy (cyclohexyl) in place
of Ph at P or by increasing the number of backbone
methylenes from two to three; one of these (4) contains
an unsymmetrical ligand framework in which the meth-
1
2220 cm-1, J PtH ) 1263 Hz (in a triplet resonance at
2
1
-16.2 ppm, J PH ) 12.2 Hz, H NMR, see Table 1), i.e.,
wavenumber, coupling constant, and chemical shift all
typical for Pt-H trans to the weakly trans-influencing
chloride ligand.
(23) (a) Chatt, J .; Eaborn, C.; Ibekwe, S. D.; Kapoor, P. N. J . Chem.
Soc. A 1970, 1343. (b) Letts, J . B.; Mazanec, T. J .; Meek, D. W.
Organometallics 1983, 2, 696.

Phosphinoalkylsilyl Complexes
Organometallics, Vol. 16, No. 26, 1997 5673
Ta ble 2. IR a n d 1H NMR Da ta for Ir id iu m (III)
Com p lexes
compd ν(M-H)/cm-1 ν(CO)/cm-1
δ M-H/ppm (2J PH/Hz)
9
10
11
12
13
14
2200
2244
2120
n.o.
-22.38 (14.7)
2030
1979
2046
1990
1942c,d
(1942c)
n.o.
-18.16 (11.7)
-6.09 (15.7)
-11.87a (11.5)
2123
-8.43b (13.2)
2044,2022c
-8.61e (16.4), -9.98f,g (16.8)
-8.84e (16.4), -10.93f,h (19.0)
-9.51 (16.3), -9.69 (14.1)
-10.50 (15.9)i
14′ (2044,2022c)
15
16
n.o.
n.o.
n.o.
2J SnH ) 1072 Hz. 2J SnH ) 172 Hz. c IR for 14/14′ mixture.
a
b
ν(CO) at 1952 cm-1 trans to H, 2001 trans to 2H in 2H isotopomer
d
g
mixture 14a /14′a . e H trans to Si. f H trans to CO. 2J HH ) 5.1
h
i
Hz. 2J HH ) 4.4 Hz. 2J PH
) 104 Hz.
trans
midal (dist-TBP)21 chel complex1 Ir(SiMe2CH2CH2PPh2)2-
Cl, analogy with the latter suggesting1,21 an axial-
equatorial-axial relationship for the P,Si,P ligating
atoms of the biPSi framework. Thus, a single high-field
resonance at δ -22.38 in the 1H NMR is split into a
triplet by coupling to two equivalent P atoms of the
2
biPSi ligand, with J PH ) 15 Hz establishing a cis
relationship of H with P. A broad, weak absorbance in
the IR at ca. 2200 cm-1 is attributable to νIr-H. The
molecular structure of IrH(biPSi)Cl (9) has been estab-
lished definitively by X-ray structure determination (see
below), which in addition to confirming the proposed
disposition of the biPSi unit identifies an anti relation-
ship across the metal center of H (at Ir) vs Me (at Si).
F igu r e 1. The 31P NMR spectrum (101.3 MHz) of Pt[(PCy2-
CH2CH2)Si(CH2CH2PPh2)Ph]Cl, 4, showing signals due to
-PCy2 centered at δ 62.5 ppm and -PPh2 at 44.9 ppm.
The 31P resonances of the platinum complexes 2-8
were observed as ca. 1:4:1 triplet structures, through
1
coupling to 195Pt, with the magnitude of J PtP in the
range 2714-2981 Hz, indicative of a trans disposition
for the two equivalent phosphorus atoms. The chemical
shift difference ∆δ 31P between an uncomplexed phos-
phinoalkylsilane and its phosphinoalkylsilyl complex24
is also informative, being rather large (54-61 ppm
deshielded on complexation) for coordination through
formation of five-membered chelate rings but more
modest (M ) Pt) for P in six-membered cyclic framework
geometries. The 31P NMR spectrum of the single
product 4 in which the substituents on the two P atoms
are different is observed as an abx array, as depicted
in Figure 1. The latter highlights (a) the chemical shift
difference between δ -PPh2 and -PCy2 (the assignment
of which parallels that for the silane precursors, i.e., ∆δ
ca. 55 ppm in each case, Table 1), with the former more
shielded by almost 20 ppm; (b) the effect of coupling to
195Pt (i.e., x in abx); (c) most significantly, the magnitude
Reaction between trans-Ir(PPh3)2(CO)Cl (Vaska’s Com-
plex) and biPSiH afforded a product formulated on the
basis of NMR spectroscopy as a 3:1 mixture of two
octahedral stereoisomers 10 and 11 (see Scheme 1) of
the Ir(III) complex IrH(biPSi)(CO)Cl. The high-field
1
region of the H NMR spectrum contained two triplets,
with that due to the major product (10, with δ 31P -16
ppm) at δ -17.2 with 2J ) 11.7 Hz, i.e., characteris-
tic9a,10,11 of H trans to Cl; while the resonance due to
the less abundant isomer (11, δ 31P -11 ppm) is
centered at -6.09 ppm (2J cis ) 15.7 Hz), consistent with
H trans to a strongly trans-influencing ligand, i.e., CO.
Fractional crystallization afforded the major isomer (10)
as an analytically pure methylene chloride monosolvate,
the IR spectrum of which showed (in addition to bands
similar to those of the ligand precursor) a weak absorp-
tion at 2244 cm-1 assigned to νIr-H, together with a
2
of J PP which at 367 Hz is typical25 for mutually trans
much stronger peak at 2030 cm-1 attributable to νCO
.
P atoms. The 10-membered chelate arrangement as-
signed to the diastereomers 8, 8′ results in ∆δ ca. 40
ppm.
Using these assignments, it was possible to also identify
the corresponding vibrations in isomer 11 at 2120 and
1979 cm-1
.
B. Ir id iu m (III) Ch em istr y. Preliminary investiga-
tion of the corresponding iridium chemistry using the
phosphinoethylsilyl precursor again afforded products
with very limited solubility; but the bis(phosphinopro-
pyl)silane, biPSiH (i.e., C3 backbone), reacted immedi-
ately with [Ir(COD)Cl]2, with the yellow color of the
latter darkening to afford an orange reaction mixture,
from which a soluble, deep orange complex (9) was
isolated in excellent yield. This was formulated on the
basis of microanalytical data and multinuclear NMR
spectroscopy as a five-coordinate analogue IrH[SiMe-
(CH2CH2CH2PPh2)2]Cl of the distorted trigonal-bipyra-
Reaction of the 10:11 mixture with tin(II) chloride in
THF solution afforded (NMR) an iridium-tin complex
IrH(biPSi)(CO)SnCl3 as another pair of stereoisomers
(12 and 13) in the same 3:1 ratio. This time the minor
isomer (13) crystallized preferentially (CH2Cl2/Et2O),
giving material suitable for X-ray diffraction. The
molecular structure, which is discussed further below,
confirms an octahedral iridium(III) geometry in which
H and CO are trans to one another, and a distorted
trichlorostannyl ligand occupies a site trans to the Si of
the tridentate mer-biPSi framework (Scheme 1). In the
IR, compound 13 showed bands at 2123 and 1990 cm-1
(Table 2) attributed to νIr-H and νCO, respectively, with
the latter at 2046 cm-1 in 12 (trans to Si). The high-
field 1H NMR spectrum was again informative: com-
(24) Garrou, P. E. Chem. Rev. 1981, 81, 229.
(25) Al-Salem, N. A.; Empsall, H. D.; Markham, R.; Shaw, B. L.;
Weeks, B. J . Chem. Soc., Dalton Trans. 1979, 1972.

5674 Organometallics, Vol. 16, No. 26, 1997
Brost et al.
Sch em e 1a
a
Reagents: (i) SnCl2/THF; (ii) LiAlH4/THF.
pound 13 gave rise to a triplet, δ -8.43 with cis coupling
to 31P and 117,119Sn (13.2, 172 Hz, Table 2), while the
corresponding resonance for isomer 12, centered at δ
couples to two equivalent cis P atoms as well as
geminally to a single cis H. Thus, either diastereomer
shows two resonances, of which, on the basis of relative
trans influences that to lower field may tentatively be
assigned to H trans to Si with the upfield resonance due
to H trans to CO (Table 2). The spectra of two
additional minor constituents are superimposed (Figure
2). The first, which is evident as a pair of triplets near
δ -9.5 (Table 2), is assigned to the trans dihydrido
2
-11.87, showed a much bigger J Sn,H of 1072 Hz (trans)
2
with J P,H ) 11.5 Hz. Singlet SiCH3 signals (δ 0.08 and
-0.21 ppm for 12 and 13, respectively) showed coupling
to tin (4J ) 28.1 Hz) only for 13, in which Si is trans to
Sn.
Treatment of the stereoisomer mixture 10:11 with
LiAlH4 in THF afforded a product shown by NMR to be
a mixture of isomers of the dihydride IrH2(biPSi)(CO).
The high-field portion of the 1H NMR spectrum is
illustrated in Figure 2. Two pairs of signals in ca. 3:1
ratio (Table 2) appear as triplets (each J ) 16.4 Hz) of
doublets (J ) 4.4, 5.1 Hz) attributable to two mer-biPSi
diastereomers 14 and 14′, Scheme 1, in which the H
2
isomer 15 of 14,14′, with J PH ) 16.3, 14.1 Hz and no
resolvable coupling between trans H atoms. Selective
deuteriation experiments supported this interpreta-
tion: thus, in the 1H NMR, the 2H isotopomers 14a ,14′a
of 14,14′, produced by reaction of 10 and 11 with
LiAl2H4, presented triplet resonances like those of
Figure 2 in which, however, the doublet splittings

Phosphinoalkylsilyl Complexes
Organometallics, Vol. 16, No. 26, 1997 5675
H, backbone; 48 H, Cy) are compressed into an unre-
solved envelope in the δ 0.9-2.5 ppm range; while with
Ph substituents (at P or Si, i.e., in compounds 3-5 and
7), there are additional resonances to low field, as
expected. For the structurally characterized compound
5, the backbone hydrogens of the biPSi framework
appear as broad signals at δ 0.89 (4 H, on CR, adjacent
to Si) and 2.00 (4 H, on Cγ, adjacent to P) but the central
CâH2 pair are widely split at δ 1.71 (2 H) and 2.30 (2 H)
ppm. This is accompanied by a shift away from the
main Ph contour (δ 6.9-7.1, 12 H) of ortho Ph hydrogens
to δ 7.6 and 8.1 ppm (4 H each, d, 3J ) 5.5 Hz); we
attribute this substantial deshielding effect to steric
interaction with axial â-methylene hydrogens, so also
dispersing the latter. In agreement with this interpre-
tation, in the X-ray crystal structure of complex 5, the
carbons atoms that are ortho on axial Ph and â in the
backbone approach one another to within 3.35 Å.
F igu r e 2. High-field 1H NMR spectrum (250 MHz) of a
mixture of dihydrido-iridium(III) complexes IrH2(biPSi)-
(CO), mainly the diastereomers 14,14′ (1:3 ratio) together
with stereoisomers 15 and 16. Assignment of the signals
specifically to 14 vs 14′ is ambiguous and could be reversed,
and likewise distinction between Hsyn and Hanti (vs Me at
Si) of 15 is not attempted (see text and Scheme 1).
1
The H NMR spectrum of pure 10 showed SiCH3 at δ
-0.09 ppm, with a set of six methylene signals to low
field that (at 400 MHz) were unusually well-resolved
(by comparison with those for 9 or the platinum biPSi
complexes), centered at δ 0.6 (apparent dd, J ) 13.7 and
3.4 Hz) and 1.09 (apparent td, J ) 13.8 and 3.5 Hz) due
to CRH2 (i.e., R to Si), 1.65 and 2.34 (both br) due to CâH2,
and 2.50 (d, J ) 12.9 Hz) and 3.25 (apparent t, J ) 12.4
Hz), due to CγH2. Homonuclear decoupling with ir-
radiation into the resonance at δ 2.34 collapsed the
smaller coupling in both CRH2 multiplets; while irradia-
tion at the frequency corresponding to δ 1.65 collapsed
the triplet structures in δ 1.09 and 3.25 to doublets, J
) 13.0 and 13.7 Hz, respectively. Relating these
observations to the solid state structures of compounds
5 and 9, in which the biPSi framework adopts a
distorted double half-chair conformation (X-ray, see
below), a partial analysis is suggested that puts the
resonances at δ 1.09, 1.65, and 3.25 due to axial
hydrogens, i.e., with J ax-eq ) 3.5 Hz, J ax-ax ) 13 Hz,
and J gem ) ca. 12 Hz, and is in agreement with the
(2J HHcis) were absent while that of compound 15a , i.e.,
trans-IrH2H(biPSi)(CO), was unchanged from that of 15.
Finally an ab-like pattern centered at -10.5 ppm is
attributed to a fac isomer 16, with the two equivalent
H atoms coupling to trans P (2J ) 104 Hz) as well as
cis P (2J ) 15.9 Hz). This latter conclusion is supported
by the observation (1H NMR) that the same compound
(16) is formed, initially as the sole hydrido product,
when the five-coordinate complex 9 is allowed to react
with LiAlH4 under an atmosphere of CO, although
progressive isomerization to 14,14′ is detectable over 24
h (see Scheme 1).
C. Ru th en iu m (II) Ch em istr y. Simple PSi chelate
precursors including chelH react with Ru3(CO)12 at
elevated temperature under sealed-tube conditions to
afford only moderate yields (ca. 35%) of mononuclear
Ru(II) homologues Ru(chel)2(CO)2: these complexes
adopt a trans dicarbonyl geometry with chel Si atoms
cis to one another.17 We have found that although
similar reactions with the biPSi precursors MeSiH-
[(CH2)nPPh2]2 (n ) 2 or 3) yield mainly intractable
material, adventitious recovery is possible, although in
very poor yield, of yellow products that are identifiable
as hydrido(dicarbonyl)Ru(II) analogues RuH{SiMe-
[(CH2)nPPh2]2}(CO)2 (17, n ) 2; 18, n ) 3) on the basis
of microanalytical data. Each of these compounds
1
assignment for the axial CâH2 pair in 5. The H NMR
spectrum of isomer 11 was similar to that of 10,
although less well-resolved. Methylene hydrogens for
purified 13 also appeared as six envelopes (δ 0.86 (dd),
1.00 (td), 1.91 (br), 2.39 (br), 2.42 (t), 3.15 (d)), i.e., very
similar to the pattern observed for complex 10.
The appearance of the 13C NMR spectra is governed
by two important general criteria. Firstly, while the
idealized geometries for all of the complexes possess only
planar symmetry (point group Cs), the single plane does
relate backbone methylene carbon atoms that are R, â,
and γ to Si and also carbon atoms of pairs of substitu-
ents R in the phosphino fragments -PR2 (although not
pairs of atoms within each R). Secondly, the magnitude
1
showed a high-field triplet resonance in the H NMR
2
2
(17, δ -8.97, J PH ) 17 Hz; 18, δ -6.29, J PH ) 18 Hz)
due to cis coupling of a Ru-H to the two P atoms of the
tridentate PSi ligand, with a chemical shift suggesting
H trans to CO. The more soluble of the pair (18)
crystallized out of solution and was structurally char-
acterized by using X-ray diffraction (see below): the
molecule possesses octahedral geometry about Ru(II) in
which two carbonyl groups are cis and the tridentate
biPSi framework is mer; the H at Ru (not located) clearly
occupies the sixth site, that adjacent to Me (at Si), i.e.,
a syn disposition that is the opposite of the anti
configuration adopted in the hydrido-iridium complex
(9).
2
of J PP (ca. 350 Hz, q.v.) is sufficiently large compared
1
with J PC (12-17 Hz in the silane precursors, simulated
at 38 Hz for compound 5) that resonances due to carbon
atoms R to P are observed as triplets, through26 virtual
coupling (Table 1). Coupling of backbone carbons to
195Pt is also observed for compounds 2-7. The low-
(26) Becker, E. D. High Resolution NMR; Academic Press: New
York, 1969.
(27) Brinkley, C. G.; Dewan, J . C.; Wrighton, M. S. Inorg. Chim.
Acta 1986, 121, 119.
(28) Heyn, R. H.; Huffman, J . C.; Caulton, K. G. New J . Chem. 1993,
17, 797.
(29) Campion, B. K.; Heyn, R. H.; Tilley, T. D. J . Chem. Soc., Chem.
Commun. 1992, 1201.
Con for m a tion a l P r op er ties of th e Bicyclic biP Si
F r a m ew or k . In the 1H NMR spectra of complexes 2-4
and 6, in which the biPSi framework terminates in
-PCy2 groups, all methylene hydrogen signals (8 or 12

5676 Organometallics, Vol. 16, No. 26, 1997
Brost et al.
(II) (18) complexes are collected together in Table 3. The
molecular geometries are illustrated in Figures 4 -7
respectively, where important bond distances and angles
are listed in the caption in each case: the spatial
arrangement adopted by the tridentate biPSi framework
introduces a regularity amongst the four structures that
is immediately striking. Positional parameters are
included in the Supporting Information, which also
contains full tables of bond distances and angles.
Angles between the four ligating atoms at the metal
center in 5 are all very close to 90°, consistent with
square coordination as expected for d8 Pt(II). The two
faces so formed are clearly distinguished; however, the
methyl group at Si projects tetrahedrally into one, while
the other accommodates the backbones that connects
Si with P (Figure 4). The skeletal geometry of the biPSi
unit completes two six-membered ring systems that are
fused along the Pt-Si bond, with the polymethylene
bridges twisted into a double half-chair conformation
that allows the Me at Si and one Ph at each P to be
identified as axial groups. Such a stereochemistry
supports the interpretation of the NMR data, although
in the crystal the two biPSi phosphinopropyl groups are
not symmetry related, i.e., the idealized σ (Cs point
group) is not a crystallographic plane. The P-Pt-P and
Si-Pt-Cl angles are each distorted away from linearity
(176°, 173°, respectively), both in the same sense, i.e.,
toward the methyl at Si. At 2.285 (mean) and 2.307 Å,
the Pt-P and Pt-Si bond distances lie within the
narrow ranges that are typical for related structures;
the Pt-Cl bond length at 2.436(6) Å (trans to Si) is
measurably longer than corresponding distances12 trans
to either H or Me, Table 4.
F igu r e 3. The 13C NMR spectrum (62.9 MHz) of Pt(biPSi)-
Cl, 5, showing signals progressively to high frequency due
to CMe, CR, Câ, and Cγ, with the inset being a spectral
simulation of the fine structure of the Cγ resonance (see
text).
frequency (i.e., high-field) region for compound 5 il-
lustrates this effect (Figure 3). Four signals that are
progressively less shielded are assigned to CMe, CR, Câ,
and Cγ, respectively (i.e., R, â, γ to Si; Cγ adjacent to P),
exhibiting coupling to platinum of 75 (2J ), 35 (2J ), 21
(3J ), and 67 Hz, the latter confirmed by spectral simula-
tion (abmx spin system, Figure 3). Only partially
resolved triplet structure in the Me and CR resonances
3
The molecular structure of the five-coordinate com-
plex 9 closely resembles that of the platinum compound
5 in terms of the disposition of the biPSi skeleton
(Figure 5). More significantly, it bears an obvious
relationship to the geometry of its analogue1 Ir(chel)2-
Cl (chel ) -SiMe2CH2CH2PPh2), which with the P
atoms axial and the two equatorial Si centers separated
by an angle less than 90° typifies the dist-TBP config-
uration recognized recently by Eisenstein et al.21a For
Ir(chel)2Cl, this leads to wide equatorial angles of1
134.8(2)° and 138.9(2)° to the weak Cl member of the
five-coordinate ligand set. For 9, the corresponding Si-
Ir-Cl angle is less obtuse, 127.2(1)°, with the chloride
and the methyl group on Si being syn, i.e., occupying
the same molecular face (defined by the ax-eq-ax biPSi
unit). This implies that the hydride ligand is bonded
to Ir on the opposite face, i.e., it is anti vs Me at Si,
thereby resolving a structural ambiguity presented by
the spectroscopic data, which offer no distinction be-
tween the syn vs anti diastereomers of 9. It may be
inferred that if the position of the hydrogen atom
subtends a characteristically narrow angle Si-Ir-H
(possibly < 90°), i.e., with H-Ir-Cl ca. 140° like1 Si-
Ir-Cl in Ir(chel)2Cl, it will occupy a pocket generated
by the puckering of the biPSi polymethylene skeleton.
The structural relationship of 9 with Ir(chel)2Cl (which
is1 dist-TBP21) is further reinforced by Ir-P and Ir-Si
bond lengths that are almost equal (near 2.3 Å), with
the equatorial bond Ir-Cl conspicuously short1 at
2.399(2) Å, Table 4.
is attributable to very small J , to the two P atoms cis
to Si; but Cγ is split by virtual triplet structure, with
1
3
much bigger | J PP + J PC| ) 38 Hz (simulated with 1J
3
) 38 Hz, J ) 0 Hz, Figure 3). Resonances at 133.7
and 135.1 ppm, which are assigned to the inequivalent
ortho C atoms in each Ph group at P, also appeared as
2
4
triplets, J (i.e., | J + J |) ) 6 Hz; the same situation
was evident for inequivalent CR of cyclohexyl substitu-
ents at P, where these could be distinguished from other
methylene resonances (e.g., in complex 2, δ 33.4 and
35.1 are apparent triplets with J ) 14 Hz); a similar
pattern for Cγ and Cortho was repeated as a characteristic
of the family of complexes (Table 1).
Compound 7, in which Ph is attached at Si as well as
at P, gave rise to a collection of 13C signals in the 125-
135 ppm range that could be assigned similarly on the
basis of triplet splitting with ca. 1:4:1 multiplicity
(coupling to 185Pt) vs a 1:2:1 array (virtual coupling to
31P). Thus, for Ph on Si, δ C1 143.5 ppm (2J ) 54 Hz),
C2 135.3 (3J ) 27 Hz), C3, C4 (singlets, J ) 126.8, 127.5);
while for the two symmetry unrelated Ph groups on P,
δ C1 131.0, 133.2 (J ) 27, 28 Hz), C2 133.2, 135.5 (J )
5, 6 Hz), C3 127.9, 128.0 (J ) 5, 5 Hz), and C4 129.9,
130.1. Assignments for the methylene carbons in the
chemically distinct backbones of complex 4 (i.e., R or â
to Si) are ambiguous (see Table 1), and in the diaster-
eomers 8, 8′ those R and â to Si overlap with one another
around δ 18.4 ppm.
X-Ra y Cr ysta l a n d Molecu la r Str u ctu r es of Com -
p lexes 5, 9, 13, a n d 18. Crystal data for the four-
coordinate platinum(II) (5), five-coordinate iridium(III)
(9), and six-coordinate iridium(III) (13) and ruthenium-
The arrangement of the tridentate biPSi ligand
around distorted octahedral d6 Ru(II) in compound 18

Phosphinoalkylsilyl Complexes
Organometallics, Vol. 16, No. 26, 1997 5677
Ta ble 3. Cr ysta l Da ta a for Com p ou n d s 5, 9, 13, a n d 18
5
9
13
18
chem formula
fw
PtP2SiClC31H35
728.2
IrP2SiClC31H36
726.3
IrSnCl3P2SiOC32H36
944
RuP2SiO2C33H35
654.8
cryst syst
space group
Z
monoclinic
I2/a
8
monoclinic
P21/n
4
orthorhombic
Pna21 (No. 33)
4
orthorhombic
P212121
4
a, Å
b, Å
c, Å
21.581(2)
12.714(2)
22.119(2)
94.50(3)
6050(3)
2848
1.58
48.51
3421
2735
11.039(1)
24.322(1)
11.318(1)
97.79(4)
3010(2)
1440
1.6
44.91
6461
3268
26.073(3)
18.048(3)
8.761(2)
90
4122.6
1831.81
1.521
45.38
2909
2074
8.895(2)
9.858(1)
36.048(3)
90
3160.9
1349
1.38
5.85
1737
1607
B, deg
V, Å3
F(000)
Q calcd, g cm-3
µ(Mo KR), cm-1
no. of rflns colld
no. of unique rflns
no. of rflns obsd (I > 3σ(I))
no. of variables
Rb
325
0.0876
0.0841
325
0.0375
0.0449
349
0.0779
0.0762
227
0.0619
b
Rw
a
All data were collected with graphite-monochromated Mo KR radiation (λ ) 0.0709 26 Å) at 291 K using a CAD4 diffractometer. Scan
type, ω-2θ; scan range θ, (1.35 + 0.35scanθ)°; 2θmax, 46.0° throughout. R ) ∑(||Fo| - |Fc||)/∑|Fo|; Rw ) ∑w|Fo| - |Fc|)2/∑w|Fo| .
b
2
F igu r e 5. Molecular geometry of complex 9. Selected bond
F igu r e 4. Molecular geometry of complex 5. Selected bond
lengths (Å) and angles (deg): Si-Pt, 2.307(8); P(1)-Pt,
2.289(9); P(2)-Pt, 2.280; Si-Pt-Cl, 172.8(3); P(1)-Pt-Cl,
89.5(3); P(1)-Pt-Si, 89.9(3); P(2)-Pt-Cl, 90.6(3); P(2)-
Pt-Si, 89.4(3); P(2)-Pt-P(1), 175.7(3).
lengths (Å) and angles (deg): Si-Ir, 2.287(3); Cl-Ir,
2.399(2); P(l)-Ir, 2.302(2); P(2)-Ir, 2.294(2); P(l)-Ir-Cl,
93.3(1); P(2)-Ir-Cl, 91.5(1); P(2)-Ir-P(1), 167.3(1); Si-
Ir-Cl, 127.2(1); Si-Ir-P(1), 93.1(1); Si-Ir-P(2), 93.3(1).
4). It is evident that while each of the crystalline
products 9 or 18 is a pure constituent of a possible
diastereomeric pair (syn and anti), the observed stere-
ochemistry is the reverse at ruthenium (syn-18) of that
at iridium (anti-9). This is emphasized in Figure 8,
which compares the core geometries for 5, 9, and 18,
highlighting that Cl is syn vs Me in 9 but CO is anti vs
Me in 18, as well as the way in which syn vs anti
approaches (relative to Me on Si) of external substrate
to the metal center will differ (e.g., of HCl to Pt, see B).
The solid state structure of the six-coordinate iridium-
(III) trichlorostannyl complex 13 is more irregular than
those of 5, 9, and 18: the molecule appears to be
sterically crowded and the two cyclic fragments of the
biPSi framework are twisted relative to one another
along the Ir-Si direction, as shown in Figure 7 (a
projection similar to those of Figures 4-6 is included
in the Supporting Information). This reduces the
P-Si-P angle to 156.2(4)° but allows the Me at Si, the
carbonyl group on Ir, and the two chlorine atoms of the
-SnCl3 group to stagger with rather than eclipse one
is again the focus of the structure, setting up a mer
geometry (Figure 6) that mirrors the in-plane character
of PSiP ligation in 5 or 9. The hydride ligand was not
located, but its position is indicated by a vacant position
that is (unlike that in 9) adjacent to the Me group on
the Si atom. Coordination at the metal is completed
by a cis dicarbonyl unit, in which C-Ru-C is opened
up to 105.8(12)°, although the Si-Ru and Ru-C(8)
bonds are oriented almost exactly perpendicularly.
Thus, the C(7)-Ru vector points nearly 20° away from
a directly trans relationship with the Si-Ru bond, i.e.,
the carbonyl group trans to Si is displaced significantly
toward the hydride site. The resulting Si-Ru-C(7)
angle at 163.4 (10)° is, however, equal within error to
the Si-Ir-Cl angle (i.e., that also includes a M-H bond)
in1 the isoelectronic complex IrH(chel)(CO)(PPh3)Cl,
where Si is trans to Cl rather than CO. The bond
distances from Ru to C(7) (trans to Si) and C(8) (trans
to H) are not distinguishable, and Ru-Si at 2.457(7) Å
and Ru-P at 2.342 (mean) Å appear to be normal (Table

5678 Organometallics, Vol. 16, No. 26, 1997
Brost et al.
Ta ble 4. M-Liga n d Bon d Dista n ces (Å) in
Silylp la tin u m , -ir id iu m , a n d -r u th en iu m
Com p lexes
compd
M-Si
M-Pa
M-Cl ref
Pt(chel)2
Pt(biPSi)Cl (5)
2.36 2.35b
2.31 2.29
2.32 2.30
2.41 2.31
2.31 2.30
2.29 2.30
10a
c
12
1
1
2.44b
2.47b
2.51b
2.38
trans-PtCl(SiPh3)(PPh3)2
IrH(chel)(CO)(PPh3)Cl
Ir(chel)2Cld
IrH(biPSi)Cld (9)
2.40
c
c
IrH(biPSi)(CO)SnCl3 (13)
fac-IrH(PMe3)3(Me)(SiEt3)
RuH(biPSi)(CO)2 (18)
RuH(SiPh3)(PPh3)(CO)3
2.42 2.31, 2.37 (2.66)b,e
2.42 2.30-2.36f
2.46 2.34
13
c
27
28
29
2.45 2.41b
RuH(SiHPh2)(PtBu2Me)2(CO)g 2.33 2.38
RuH2(C5Me5)(SiHClmes)PiPr3
2.30 2.35
h
a
b
Mean, unless otherwise indicated. Trans to Si. c This work.
Five-coordinate cpx, dist-TBP. e Ir-Sn distance. f See text. g Five-
coordinate cpx, SQP, apical Si. Ru(IV) cpx.
d
h
F igu r e 6. Molecular geometry of complex 18. Selected
bond lengths (Å) and angles (deg): Si-Ru, 2.457(7); P(1)-
Ru, 2.348(6); P(2)-Ru, 2.335(6); C(7)-Ru, 1.96(3); C(8)-
Ru, 1.98(2); P(2)-Ru-P(1), 174.5(2); Si-Ru-P(1), 87.6(2);
Si-Ru-P(2), 88.5(2); C(7)-Ru-P(1), 90.4(7); C(7)-Ru-
P(2), 92.2(7); C(7)-Ru-Si, 163.4(10); C(8)-Ru-P(1), 93.8(7);
C(8)-Ru-P(2), 90.1(8); C(8)-Ru-Si, 90.9(7); C(8)-Ru-
C(7), 105.8(12). The phenyl rings have been simplified for
clarity.
F igu r e 8. Comparison of the core framework structures
in biPSi complexes of Pt (5), Ir (9), and Ru (18). Note the
syn arrangement of Cl at Ir and Me at Si (both up), but
CO at Ru (down) is anti vs Me at Si (up), i.e., H at Ir is
anti (9), at Ru is syn (18) vs Me (at Si).
Discu ssion
Previously, it has been shown inter alia (i) that
oxidative addition of Me2SiH(CH2)2PPh2 (chelH) at
Pt(II) or Ir(I) is chelate-assisted and is also regiospe-
cific;9,10 (ii) that HSi(CH2CH2PPh2)3 (triPSiH) will dis-
place all three molecules of coordinated triphenylphos-
phine from RhH(CO)(PPh3)3 to afford the novel anchored
rhodium(I) silyl Rh(triPSi)(CO);17 (iii) that complexation
of chelH at five-coordinate Ir(I) (which also requires
displacement of two PPh3 molecules) occurs exclusively
by coplanar entry of P, Si, and H meridionally to afford
the product IrH2(chel)(CO)(PPh3) as
a
single
stereoisomer;9a,31 (iv) that the latter undergoes slow
interchange of hydrogen atoms between the two cis
octahedral sites.31 The coordination behavior of the
biPSi framework fits logically into the context estab-
lished by these observations. Thus, attachment of a bis-
(phosphinoalkyl)silyl group (i.e., by chelate-assisted
Si-H bond addition, hydrosilylation) leads finally to a
wrap-around geometry at square Pt(II) with trans P
atoms and a Cl ligand retained trans to Si (e.g., as in
complex 5). This suggests that H enters at an axial site
in a transient, octahedral Pt(IV) configuration PtH-
(biPSi)Cl2, a relative of the complex PtH(chel)2Cl that
has been characterized directly10b by NMR, then is lost
by cis elimination of HCl to afford the observed Pt(II)
product.
F igu r e 7. Molecular geometry of complex 13. Selected
bond lengths (Å) and angles (deg): Si(1)-Ir(1), 2.42(2); Sn-
(1)-Ir(1), 2.658(3); P(1)-Ir(1), 2.37(1); P(2)-Ir(1), 2.31(1);
C(8)-Ir(1), 1.93(7); P(1)-Ir(1)-Sn(1), 93.2(3); P(2)-Ir(1)-
Sn(1), 94.8(3); P(2)-Ir(1)-P(1), 156.1(4); Si(1)-I(1)-Sn(1),
175.8(4); Si(1)-Ir(1)-P(1), 87.9(5); Si(1)-Ir(1)-P(2), 85.8(4);
C(8)-Ir(1)-Si(1), 86(2); C(8)-Ir(1)-Sn(1), 90(2); C(8)-Ir-
(1)-P(1), 102(2); C(8)-Ir(1)-P(2), 100(2).
another along the Si-Ir-Sn vector, which is nearly
linear (176°). There is a vacant site trans to CO to
account for the hydride ligand (not located), putting the
latter anti vs C(4) (i.e., the Me on Si); its position within
the biPSi pocket, especially in relation to C(5), is
unknown but could possibly explain why the bond from
Ir to P(1) is 0.06 Å longer than that to P(2). The bond
distance to Si, 2.42 (2) Å, is normal for octahedral Ir(III)
but that to Sn is very long,30 2.659 (3) Å (Table 4),
presumably as a further reflection of the high trans-
influencing character of the silyl group. The trigonal
-SnCl3 group is distorted from tetrahedral (with Cl-
Sn-Cl angles close to 90°), but a similar effect has been
observed in related structures.15
Unlike most d8 complexes (which are planar sym-
metric, D4h), in the Pt(II) compounds 1-7 reflection will
operate perpendicular to the biPSi skeleton (rather than
across it) and then only if the conformations of the two
chelate rings are identical. The juxtaposition of the
methyl group on Si and the backbone methylenes of the
biPSi skeleton imposes identical conditions on the
(30) Albinati, A.; Gunten, U.; Pregosin, P. S.; Ruegg, H. J . J .
Organomet. Chem. 1985, 295, 239.
(31) Auburn, M. J .; Stobart, S. R. J . Chem. Soc., Chem. Commun.
1984, 281.

Phosphinoalkylsilyl Complexes
Organometallics, Vol. 16, No. 26, 1997 5679
idealized symmetry properties of all the remaining
complexes (except 8,8′), with σ (Cs point group) again
perpendicular to the P-Ir-P axis (i.e., bisecting the
P-Ir-P angle). The 1H NMR data indicate that in
solution equivalence between the independent poly-
methylene chains of the bicyclic biPSi unit is established
as a result of framework nonrigidity (although in none
of the crystal structures are the two sets of nuclei
symmetry related). Thus, methylene hydrogens are
geminally differentiated, typically giving rise to six
distinguishable resonances that (unequivocally for com-
pound 10) exhibit coupling patterns that are cyclohex-
ane-like. Because the two faces at Pt are nonidentical,
detachment of Si from Pt (which takes place with
retention of the trans phosphine geometry) generates a
diastereoisomeric pair (8,8′) of hydridoplatinum(II)
products (see B), with one strongly favored over the
other, although which one is not disclosed by the
bigger for H trans vs cis to Sn (Table 2). There is also
a more surprising change in J SnP (by a factor of two,
2
Table 1), which is larger with Sn trans to Si (13) vs trans
to H (12). Treatment of the same stereoisomer distribu-
tion 10,11 with hydride (LiAlH4) directly affords a third
mixture of isomers, predominantly 14 and 14′ (1:3 ratio,
Figure 2); since each of these is a dihydrido complex
with a mer-biPSi structure and nonequivalent H atoms
(1H NMR), they are necessarily assigned as anti and
syn diastereomers (see Scheme 1), although the data do
not identify which one is the more abundant of the two.
2
Values of ca. 5 Hz for J HH(cis) (Table 2) are typi-
cal.9,20,31,33 The two other minor products of the same
reaction are tentatively identified (NMR) as the trans
dihydrido isomer 15 and the fac-biPSi isomer 16 (Scheme
1). If this is correct, complex 15 is a very rare33 example
of a trans transition-metal dihydrido complex in which
the H atoms are nonequivalent and for which the
absence of trans H,H coupling is in accord with Karplus-
type arguments; values for J HH of 5 and 17.2 Hz,
respectively,20a,c have been reported for (formally) Ir-
(III) and Fe(II) complexes, which may be the only related
systems possessing H,H trans on distinguishable octa-
hedral faces.
1
spectroscopic data. The values for J PtP in all the
platinum(II) biPSi complexes, at up to 2981 Hz (Table
1), lie at the top end of those reported for systems in
which this parameter has been linked32 to the electronic
properties of the ligand cis to P (i.e., the reverse of the
1
more familiar influence on J PtP of the ligand trans to
P, where the strongly inductive Si center leads10,11,13 to
the lowest reported values).
We have independently observed that isomer 16, the
stereochemistry of which is again assigned on the basis
of NMR, is the sole product formed initially on treat-
ment of the five-coordinate hydrochloride 9 with LiAlH4
under CO but that it subsequently undergoes slow
thermal rearrangement to yield a mixture containing
14,14′ in an identical ratio (ca. 1:3, Figure 2) to that
obtained from 10,11. Formation of a mixture of dihy-
drido complexes (14-16) from the latter, including all
three possible mer-biPSi isomers, Scheme 1, together
with the facile diastereoisomerization of 16, may be
accounted for by intramolecular H,H exchange at octa-
hedral Ir(III), as observed31 in the related cis-IrH2(chel)-
(CO)(PPh3). The existence of such nonrigidity is further
suggested by the observation that the distribution of
hydrido(deuterio) isotopomers after treatment of the
10,11 mixture with LiAl2H4 showed no evidence for any
Complex 9, which is formed by reaction of the silane
biPSiH with [Ir(COD)Cl]2, crystallizes as a single dia-
stereomer in which H is anti vs Me on Si (as shown by
X-ray diffraction) and provides another example of a
five-coordinate, 16-electron Ir(III) geometry of the type
we have structurally characterized1 previously. Addi-
tion of the silane biPSiH to trans-Ir(PPh3)2(CO)Cl,
however, is accompanied by formation of the hydridoiri-
dium(III) complex IrH(biPSi)(CO)Cl as two stereoiso-
mers, 10 and 11, that differ in the nature of the ligand
trans to Si (CO, 75%; Cl, 25%). This is consistent with
Si-H bond addition at Ir parallel8 to the CO-Ir-Cl axis
that follows initial coordination through P. Formation
of a large-ring chelate structure (resembling that of
diastereomers 8,8′, B), through substitution of PPh3 by
the more basic alkyldiphenylphosphino group of the PSi
precursor9,10,31 then displacement of the second (trans)
PPh3 ligand, will lead to diastereomeric Ir(I) intermedi-
ates that can undergo reaction to afford anti (C) or syn
(D) pairs of products. Observation of two (rather than
four) complexes implies that either 10 and 11 have
opposite stereochemistry, through stereospecific forma-
tion of one anti as in C and the other syn as in D, or
(more likely) one pair only is formed, exclusively via C
or D. Precoordination of biPSiH through a single P
atom followed by Si-H bond addition would channel the
latter through diastereomeric pathways (resulting from
chirality at Si) that would be more likely to result in
observation of all four isomers.
2
preferential site occupancy (syn vs anti) by H (i.e., in
1
the H NMR spectrum, the intensity ratio of hydrogen
signals assigned to the mono(deuterio)isotopomers 14a :
14′a :15a :16a is identical with that characteristic of the
diastereomer mixture 14-16, Figure 2).
The long Pt-Cl bond trans to Si in 5 is consistent with
Cl loss as an activating step in olefin hydroformylation
catalyzed by this and related complexes.16,34 At 2.44 Å
its length exceeds that trans to CH3 (2.41 Å) or H (2.42
Å) in the nonchelate complexes trans-Pt(PPh2R)2(Y)Cl
(Y ) R ) Me35 or36 Y ) H, R ) Et), a sequence that
follows the progression of Ir-P distances in the com-
plex13 IrH(PMe3)3(CH3)(SiEt3), i.e., 2.30, 2.34, and 2.36
Å trans to CH3, H, and SiEt3, respectively. The Ir-Si
bond in the 16-electron, five-coordinate complex 9 is, like
that1 in Ir(chel)2Cl, conspicuously shorter than those in
Recovery of an identical diastereomer distribution
after 10 and 11 are converted to 12 and 13, together
with crystallographic characterization of 13 as anti, may
suggest that all four are anti, as indicated in Scheme
1; thus, while little appears to be known about the
specifics of SnCl2 insertion, any way of forming 13 from
a syn precursor clearly requires a diastereoisomerization
step. The distinction between 12 and 13 is easily made
(33) See: Heinekey, D. M.; Hinkle, A. S.; Close, J . D. J . Am. Chem.
Soc. 1996, 117, 5353. Two-bond H-H coupling has rarely been observed
in cis dihydrido complexes because the two H atoms are most commonly
chemically equivalent (see also refs 9 and 31 for examples where this
is not so); corresponding data for related trans dihydrido complexes
remain exceedingly rare.
(34) Anderson, G. K.; Clark, H. C.; Davies, J . A. Inorg. Chem. 1983,
22, 427, 434.
(35) Bennett, M. A.; Clark, P. W.; Robertson, G. B.; Whimp, P. O.
J . Organomet. Chem. 1973, 63, C15.
1
2
in the H NMR, where J SnH is an order of magnitude
(32) Meek, D. W.; Tau, K. D. Inorg. Chem. 1979, 17, 3574.
(36) Eisenberg, R.; Ibers, J . A. Inorg. Chem. 1965, 4, 773.

5680 Organometallics, Vol. 16, No. 26, 1997
Brost et al.
octahedral 18-electron analogues (Table 4). The short
Ir-Cl bond in the same compound is characteristic1 of
a dist-TBP structure21 in which the Cl ligand is not
brought into a directly trans relationship with either H
or Si. The Si-Ir-Cl angle is, at 127°, close to the
smaller of the two angles H-Ir-Cl (131° and 156°) in
the solid state structure21b (neutron diffraction) of
IrH2(PPhtBu2)2Cl. In this latter complex, the hydride
configuration28 (isoelectronic with the iridium complex
9). In particular, unsaturation at such a center coupled
with the cis disposition of H and CO in 18 suggests that
this system will be active as a catalyst for hydroform-
ylation, but before this possibility can be investigated
further an efficient route to compounds like 17 or 18
will be required.
Ack n ow led gm en t. We thank Auburn University,
Imperial Oil Ltd., and the NSERC, Canada, for financial
support, Dr. G. W. Bushnell for assistance with the
X-ray crystallography, and Drs. R. A. Gossage and A.
McAuley for useful discussions.
1
distinguished in the slow-limit H NMR spectrum (-100
°C) as pseudo-trans37 to Cl is assigned at δ -20.1,
suggesting that with a shift of -22.4 the H position in
9 may be the result of an angle at Ir of only a little less
than 156°, i.e., putting Si-Ir-H similar to Si-Ir-Si
(86°) in Ir(chel)2Cl. If the CO group is labilized trans
to Si in the octahedral compound 18, its ejection may
provide access to a five-coordinate ruthenium(II) mono-
carbonyl, i.e., another example of a 16-electron, d6
Su p p or tin g In for m a tion Ava ila ble: Text giving ad-
ditional details of the X-ray study, figures giving additional
ORTEP views, and tables giving crystal data, positional and
thermal parameters, and bond distances and angles for 5, 9,
13, and 19 (33 pages). Ordering information is given on any
current masthead page.
(37) Hauger, B. E.; Gusev, D.; Caulton, K. G. J . Am. Chem. Soc.
1994, 116, 208.
OM970518K