Nucleophilic substitution reactions at the Si–Cl bonds of the dichloro(methyl)silyl ligand in five- and six-coordinate complexes of ruthenium(II) and osmium(II)

Abstract

Treatment of either RuHCl(CO)(PPh 3) 3 or MPhCl(CO)(PPh 3) 2 with HSiMeCl 2 produces the five-coordinate dichloro(methyl)silyl complexes, M(SiMeCl 2)Cl(CO)(PPh 3) 2 ( 1a, M = Ru; 1b, M = Os). 1a and 1b react readily with hydroxide ions and with ethanol to give M(SiMe[OH] 2)Cl(CO)(PPh 3) 2 ( 2a, M = Ru; 2b, M = Os) and M(SiMe[OEt] 2)Cl(CO)(PPh 3) 2 ( 3a, M = Ru; 3b, M = Os), respectively. 3b adds CO to form the six-coordinate complex, Os(SiMe[OEt] 2)Cl(CO) 2(PPh 3) 2 ( 4b) and crystal structure determinations of 3b and 4b reveal very different Os–Si distances in the five-coordinate complex (2.3196(11) Å) and in the six-coordinate complex (2.4901(8) Å). Reaction between 1a and 1b and 8-aminoquinoline results in displacement of a triphenylphosphine ligand and formation of the six-coordinate chelate complexes M(SiMeCl 2)Cl(CO)(PPh 3)(κ 2( N, N)-NC 9H 6NH 2-8) ( 5a, M = Ru; 5b, M = Os), respectively. Crystal structure determination of 5a reveals that the amino function of the chelating 8-aminoquinoline ligand is located adjacent to the reactive Si–Cl bonds of the dichloro(methyl)silyl ligand but no reaction between these functions is observed. However, 5a and 5b react readily with ethanol to give ultimately M(SiMe[OEt] 2)Cl(CO)(PPh 3)(κ 2( N, N-NC 9H 6NH 2-8) ( 6a, M = Ru; 6b, M = Os). In the case of ruthenium only, the intermediate ethanolysis product Ru(SiMeCl[OEt])Cl(CO)(PPh 3)(κ 2( N, N-NC 9H 6NH 2-8) ( 6c) was also isolated. The crystal structure of 6c was determined. Reaction between 1b and excess 2-aminopyridine results in condensation between the Si–Cl bonds and the N–H bonds with formation of a novel tridentate “NSiN” ligand in the complex Os(κ 3( Si, N, N)-SiMe[NH(2-C 5H 4N)] 2)Cl(CO)(PPh 3) ( 7b). Crystal structure determination of 7b shows that the “NSiN” ligand coordinates to osmium with a “facial” arrangement and with chloride trans to the silyl ligand.