Issue 20, 2000

Preparation and reactivity of dihydrogen complexes [MX(η2-H2)P4]BF4 (M = Ru or Os; X = halogenide or SEt; P = phosphite)

Abstract

Monohydride complexes MHXP4 [M = Ru or Os; X = Cl, Br, I, SEt or N3; P = P(OEt)3, PPh(OEt)2 or PPh2OEt] were prepared by treating dihydride species MH2P4 first with CF3SO3Me and then with an excess of the anionic ligand X. In an argon atmosphere, protonation of MHXP4 with HBF4·Et2O gives dihydrogen cations [MX(η2-H2)P4]+, with X = Cl, Br, I or SEt; the classical dihydride [MH2(N3)P4]+ was obtained with the azide ligand. Instead, in a hydrogen atmosphere, protonation of MHXP4 with HBF4·Et2O gives hydride–dihydrogen [MH(η2-H2)P4]+ species, according to a proposed mechanism involving interaction of Brønsted acid with ligand X. Some [MX(η2-H2)P4]+ cations were thermally unstable and fully characterised in solution (1H and 31P NMR, variable temperature T1 measurements), whereas the [OsX(η2-H2){PPh(OEt)2}4]BF4 complexes were stable and isolated as solids. Treatment of [MX(η2-H2)P4]+ cations with alkyne PhC[triple bond, length as m-dash]CH gave evolution of H2 and formation of the vinylidene intermediate [MX{[double bond, length half m-dash]C[double bond, length half m-dash]C(H)Ph}P4]+ which, by reaction with base, afforded the final acetylide M(C[triple bond, length as m-dash]CPh)XP4 derivatives. Treatment with propargyl alcohols HC[triple bond, length as m-dash]CC(OH)RR′ of the [MX(η2-H2)P4]+ cations, instead, gave propadienylidene derivatives [MX([double bond, length half m-dash]C[double bond, length half m-dash]C[double bond, length half m-dash]CRR′)P4]BPh4 (M = Ru or Os; R = R′ = Ph or R = Ph, R′ = Me). Hydrazine complexes [MX(NH2NH2)P4]BPh4 were also prepared by substitution of the dihydrogen ligand in the new η2-H2 derivatives.

Article information

Article type
Paper
Submitted
16 Jun 2000
Accepted
23 Aug 2000
First published
26 Sep 2000

J. Chem. Soc., Dalton Trans., 2000, 3575-3584

Preparation and reactivity of dihydrogen complexes [MX(η2-H2)P4]BF4 (M = Ru or Os; X = halogenide or SEt; P = phosphite)

G. Albertin, S. Antoniutti, E. Bordignon and M. Pegoraro, J. Chem. Soc., Dalton Trans., 2000, 3575 DOI: 10.1039/B004833J

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