TRANSITION-METAL (PHOSPHINOALKYL)SILANOLS - LIGAND FUNCTIONALITY DESIGNED FOR SURFACE ATTACHMENT - CHEMISTRY OF P-COORDINATED ((DIPHENYLPHOSPHINO)ALKYL)DIMETHYLSILANOL COMPLEXES OF RUTHENIUM, RHODIUM, AND IRIDIUM

The Si-C bond in the phosphinomethysilane Ph2PCH2SiMe2H (1) is very sensitive to cleavage by H2O, MeOH, or HCl, affording (Me2SiO)2O, SiHMe2(OMe), or SiHMe2Cl respectively, together with PPh2Me. By contrast, the ethyl congener Ph2PCH2CH2SiMe2H (2) of 1, which is unaffected by H2O Or MeOH, gives Ph2PCH2CH2-SiMe2Cl on treatment with HCl. The phosphonium salts [Ph2P(Me)(CH2)(n)SiMe2H][I] (3, n = 1; 4, n = 2) are formed quantitatively on treatment of 1 or 2 with Mel. A number of transition metal complexes react with silanes 1 and 2 to yield products in which the Si-H bond remains intact: thus [Ru(eta6-arene)(mu-Cl)Cl]2 With 1 or 2 gives [Ru(eta6-arene)Cl2(L)] (arene = p-cym [cym = cymene, i.e. isopropyltoluene], 5, L = 1; arene = p-cym, 6, L = 2; arene = C6Me6, 7, L = 2; arene = C6H6, 8, L = 2), [RuCpCl(PPh3)2](Cp = eta5-C5H5) gives [RuCpCl(PPh3)(L)] (9, L = 1; 10, L = 2), [Ru2Cp2(C2Ph2)(CO)3] With 2 gives [Ru2Cp2(CO)3(PPh2CH2CH2SiMe2H)] (11), and [M(eta5-C5Me5)(mu-Cl)Cl]2 with 2 gives [M(eta5-C5Me5)Cl2(PPh2CH2CH2SiMe2H)] (12, M = Rh; 13, M = Ir). The Si-H bonds in complexes 6 and 12 are sensitive to hydrolysis that effects transformation of the monodentate phosphinoalkylsilane into a ''dangling'' silanol, i.e. [Rh(eta5-C5Me5)Cl2(PPh2CH2CH2SiMe2OH)] (14) (from 12), for which the X-ray crystal structure is described, and [Ru(eta6-cym)Cl2(PPh2CH2CH2SiMe2OH)] (15) (from 6). Nucleophilic displacement at Si in compounds 5 and 6 is general so that treatment of 5 with HX gives [Ru(eta6-cym)Cl2(PPh2CH2SiMe2X)] (16, X = Cl; 18, X = OMe; 21, X = O(CH2)13CH3) while the products [Ru(eta6-cym)Cl2(PPh2CH2CH2SiMe2X)] (17, X = Cl; 19, X = OMe; 20, X = OEt; 22, X = OCH2CH2C(Me) = CH2; 23, X = OC11H17) are formed from 6. The unusual reactivity of the Si-H bond in this family of complexes is further illustrated by the isolation of [Ru(eta6-cym)Cl(PPh2CH2CH2SiMe2F)2] [PF6] (24) from a reaction in which the only source of F is the classically unreactive PF6- ion.