| Abstract
| - Tridentate attachment of the biPSifragment{−SiR[(CH2)nPR12]2,R = Me; n = 3; R1 = Ph} atPtII, IrIII, or RuII affordscomplexes in which syn vs anti molecular faces aredistinguished by the disposition of the ligand assembly. Thediastereomeric octahedral Ir complex IrH(biPSi)(CO)Clreacts with LiAlH4 to yield a total of four dihydridodiastereomersIrH2(biPSi)(CO).
- Reaction of the bis(phosphinoalkyl)silanesRSiH[(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) withPt(COD)Cl2 (COD= cycloocta-1,5-diene), [Ir(COD)Cl]2,trans-M(PPh3)2(CO)Cl (M= Rh or Ir), or Ru3(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(CH2CH2PPh2)2]Cl(1),Pt[SiMe(CH2CH2PCy2)2]Cl(2),Pt[SiPh(CH2CH2PCy2)2]Cl(3),Pt[SiPh(CH2CH2PPh2)(CH2CH2PCy2)]Cl(4),Pt[SiMe(CH2CH2CH2PPh2)2]Cl (5),Pt[SiMe(CH2CH2CH2PCy2)2]Cl(6), andPt[SiPh(CH2CH2CH2PPh2)2]Cl(7),which have been characterized by 1H, 13C, and31P NMR spectroscopy, possess distinguishablesquare faces with Me on Si projecting in one direction and the buckled(CH2)n backbones inthe other. Cleavage of the Pt−Si bond in Pt(biPSi)Cl(5) by HCl affords a pair ofdiastereomersHPt[(PPh2CH2CH2CH2)2Si(Cl)Me]Cl(8,8‘) in which the two P atoms arealsotrans. The five-coordinate, 16e, d6Ir(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 withSnCl2 to afford (also 3:1) the analoguesIrH(biPSi)(CO)SnCl3 (12 and13). Treatment of 10and 11 (3:1) with LiAlH4 yields a diastereomericpair of cis-dihydrido complexesIrH2(biPSi)(CO) (14,14‘) (1:3), accompanied by atrans-dihydrido stereoisomer 15 and afac-biPSistereoisomer 16 as minor products; in 14,14‘ and 15 the hydride ligands arenonequivalentand show2JHHcis =5.1, 4.4 Hz,2JHHtrans ≈0, respectively. Similar treatment withLiAl2H4affords monodeuterioisotopomers14a,14‘a, while reaction of compound9 with LiAlH4 underCO gas initially affords 16 as a single product thatsubsequently isomerizes to 14,14‘.Theoctahedral, 18e, d6 Ru(II) homologuesRuH[SiMe(CH2CH2PPh2)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 and9−13are equivalent, establishing planar symmetry (point groupCs) perpendicular to theligandtemplate, although this is not maintained in the solid state as showncrystallographicallyfor compounds 5, 9, 13, and18. Bond distances trans to Si are long in5 and 13 (2.44 and2.66 Å, to Cl or SnCl3, 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 antivs Me on Si (ofbiPSi), whereas in 18, the Ir−H and Si−Me bonds aresyn.
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