Syntheses and structures of dimethylamino-bridged bis(silylene)ruthenium and -osmium complexes

• Published in: Journal of organometallic chemistry 2002-02, Vol.645 (1), p.235-245
• Main Authors: Choo, Tong N., Kwok, Wai-Him, Rickard, Clifton E.F., Roper, Warren R., Wright, L.James
• Format: Article
• Language: English
• Subjects: Dinuclear complexes; Osmium; Ruthenium; Silylene complexes; X-ray crystal structures
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/S0022-328X(01)01331-6

Treatment of Os(SiMe 2Cl)Cl(CO)(PPh 3) 2 with an excess of the amino-substituted silane, HSiMe 2NMe 2, produces a mixture of two products, the relative proportions of which depend upon the reaction conditions. These are, Os(SiMe 2NMe 2S iMe 2)Cl(CO)(PPh 3) 2 ( 1) and Os(SiMe 2NMe 2S iMe 2)H(CO)(PPh 3) 2 ( 2). Similar treatment of Ru(SiMe 2Cl)Cl(CO)(PPh 3) 2 with HSiMe 2NMe 2 produces the ruthenium analogues of 1 and 2, Ru(SiMe 2NMe 2S iMe 2)Cl(CO)(PPh 3) 2 ( 3), and Ru(SiMe 2NMe 2S iMe 2)H(CO)(PPh 3) 2 ( 4), together with a third compound, the novel dimethylsilylene-bridged diruthenium complex, [ Ru(SiMe 2NMe 2S iMe 2)(CO)(μ-{SiMe 2}) 2(μ-Cl)RuH 2(CO)(PPh 3)] ( 5). A ligand exchange reaction occurs when 3 is treated with 1,2-bis(diphenylphosphino)ethane (dppe) yielding Ru(SiMe 2NMe 2S iMe 2)Cl(CO)(dppe) ( 6), in which the bis(silylene) ligand is retained. Crystal structures of 1, 2, 4, and 6 reveal that the RuSiNS i and OsSiNS i rings of the bis(silylene) ligand system are folded at the Si atoms and the RuSi and OsSi distances are short, while SiN distances are long. These structural data suggest some multiple bond character in the metal–silicon bonds and this is further supported by the down-field chemical shifts observed in the 29Si-NMR spectra of these compounds. A crystal structure has also been determined for the diruthenium complex 5 and this reveals a RuRu distance of 2.7557(2) Å, and two unsymmetrically bridging dimethylsilylene ligands each with a close approach to one of the ruthenium hydride ligands (SiH, 1.56(2) and 1.67(2) Å). Several complexes containing the dimethylamino-bridged bis(silylene) ligand system, including the novel diruthenium complex depicted here, have been prepared directly from the simple precursor HSiMe 2NMe 2 and have been fully characterised by spectroscopic methods and by crystal structure determinations.