Reaction of the bis(phosphinoalkyl)silanesRSiH[(CH
2)
nPR
12]
2(R = Me or Ph,
n = 2 or 3,R
1 = Ph or Cy,
i.e., cyclohexyl; biPSiH for R= Me,
n = 2, R
1 = Ph) withPt(COD)Cl
2 (COD= cycloocta-1,5-diene), [Ir(COD)Cl]
2,
trans-M(PPh
3)
2(CO)Cl (M= Rh or Ir), or Ru
3(CO)
12affords products that are complexes of tridentate biPSi silylanalogues, in which the Si centeris anchored through attachment of
trans P atoms at thetransition-metal site. Theplatinum(II) compoundsPt[SiMe(CH
2CH
2PPh
2)
2]Cl(
1),Pt[SiMe(CH
2CH
2PCy
2)
2]Cl(
2),Pt[SiPh(CH
2CH
2PCy
2)
2]Cl(
3),Pt[SiPh(CH
2CH
2PPh
2)(CH
2CH
2PCy
2)]Cl(
4),Pt[SiMe(CH
2CH
2CH
2PPh
2)
2]Cl (
5),Pt[SiMe(CH
2CH
2CH
2PCy
2)
2]Cl(
6), andPt[SiPh(CH
2CH
2CH
2PPh
2)
2]Cl(
7),which have been characterized by
1H,
13C, and
31P NMR spectroscopy, possess distinguishablesquare faces with Me on Si projecting in one direction and the buckled(CH
2)
n backbones inthe other. Cleavage of the Pt-Si bond in Pt(biPSi)Cl(
5) by HCl affords a pair ofdiastereomersHPt[(PPh
2CH
2CH
2CH
2)
2Si(Cl)Me]Cl(
8,
8') in which the two P atoms arealso
trans. The five-coordinate, 16e, d
6Ir(III) complex IrH(biPSi)Cl (
9) is isolatedas a singlediastereomer, but octahedral IrH(biPSi)(CO)Cl is formedas a 3:1 mixture of stereoisomers(
10 and
11, CO or Cl
trans to Si,respectively,
i.e., H
trans to Cl or CO) thatreact withSnCl
2 to afford (also 3:1) the analoguesIrH(biPSi)(CO)SnCl
3 (
12 and
13). Treatment of
10and
11 (3:1) with LiAlH
4 yields a diastereomericpair of
cis-dihydrido complexesIrH
2(biPSi)(CO) (
14,
14') (1:3), accompanied by a
trans-dihydrido stereoisomer
15 and a
fac-biPSistereoisomer
16 as minor products; in
14,
14' and
15 the hydride ligands arenonequivalentand show
2JHHcis =5.1, 4.4 Hz,
2JHHtrans 0, respectively. Similar treatment withLiAl
2H
4affords monodeuterioisotopomers
14a,
14'
a, while reaction of compound
9 with LiAlH
4 underCO gas initially affords
16 as a single product thatsubsequently isomerizes to
14,
14'.Theoctahedral, 18e, d
6 Ru(II) homologuesRuH[SiMe(CH
2CH
2PPh
2)
2](CO)
2(
17) and RuH(biPSi)(CO)
2 (
18) are formed in
sealed-tube reactions atelevated temperature but in very pooryields. NMR spectroscopy suggests that in solution the biPSibackbones of
2-
7 and
9-
13are equivalent, establishing planar symmetry (point group
Cs) perpendicular to theligandtemplate, although this is not maintained in the solid state as showncrystallographicallyfor compounds
5,
9,
13, and
18. Bond distances
trans to Si are long in
5 and
13 (2.44 and2.66 Å, to Cl or SnCl
3, respectively), but in
9Ir-Cl at 2.30 Å is short, occupying the equatorialplane with Si and H in a distorted TBP structure (Si-Ir-Cl 129
).The M-Si distances are2.31 (
5), 2.29 (
9), 2.42 (
13), and2.46 Å (
18). In
9 and
13, the Hat Ir is
anti vs Me on Si (ofbiPSi), whereas in
18, the Ir-H and Si-Me bonds are
syn.