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Issue 22, 1997
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Ruthenium(II) tris(pyrazolyl)borate complexes.† Reversible vinylidene complex formation

Abstract

A convenient high-yield route to [Ru{HB(pz)3}Cl(PPh3)([double bond, length half m-dash]C[double bond, length half m-dash]CHR)] (pz = pyrazolyl; R = Ph, SiMe3, Bun, But, CO2Et or C6H9) has been found through the intermediary [Ru{HB(pz)3}Cl(PPh3)(dmf )] (dmf = dimethylformamide) which has been crystallographically characterized. This complex is readily obtained on treatment of [Ru{HB(pz)3}Cl(cod)] (cod = cycloocta-1,5-diene) with 1 equivalent of PPh3 in boiling dmf. The vinylidene moiety in complexes of the type [Ru{HB(pz)3}Cl(PPh3)([double bond, length half m-dash]C[double bond, length half m-dash]CHR)] is remarkably labile being easily replaced by nucleophiles L = PMe3, PPh3, MeCN, pyridine or CO to give [Ru{HB(pz)3}Cl(PPh3)L]. With the exceptions of L = PMe3 or CO, these reactions are reversible. The complex [Ru{HB(pz)3}Cl(PPh3)(CO)] has been characterized by X-ray crystallography. On treatment of [Ru{HB(pz)3}Cl(PPh3)([double bond, length half m-dash]C[double bond, length half m-dash]CHPh)] with an excess of HC[triple bond, length half m-dash]CR′ (R′ = SiMe3, Bun, But, CO2Et or C6H9) the neutral vinylidene complex [Ru{HB(pz)3}Cl(PPh3)([double bond, length half m-dash]C[double bond, length half m-dash]CHR′)] was reversibly formed. Comparative studies and extended-Hückel molecular orbital calculations have been performed to elucidate the nature of the bonding in the various vinylidene complexes. The bonding between the metal center and the vinylidene ligand is dominated by the dyz (metal)–p (vinylidene) interaction. If this contribution is small, reconversion of the vinylidene complex into an η2-alkyne complex can be accomplished.

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Article information


J. Chem. Soc., Dalton Trans., 1997, 4209-4216
Article type
Paper

Ruthenium(II) tris(pyrazolyl)borate complexes.† Reversible vinylidene complex formation

C. Slugovc, V. N. Sapunov, P. Wiede, K. Mereiter, R. Schmid and K. Kirchner, J. Chem. Soc., Dalton Trans., 1997, 4209
DOI: 10.1039/A702194A

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