An easy entry to dimers [{RuX(μ-X)(CO)(P∧P}2] (X = Cl, Br;: P∧P=1,1′-bis(diphenylphosphino)ferrocene, 1,1′-bis(diisopropylphosphino)ferrocene) from η3-allylruthenium(II) derivatives [RuX(η3-2-C3H4R)(CO)(P∧P)] (R = H, Me):: Efficient catalyst precursors in transfer hydrogenation of ketones

Complexes [RuX(eta(3)-2-C3H4R)(CO)(P<^>P)] (X = Cl, Br; R = H, Me; P<^>P = dppf, dippf) (2a-d and 3a-d) have been prepared by reaction of the eta-allylruthenium(II) derivatives [RuX(eta(3)-2-C3H4R)(CO)(3)] (1a-d) with 1 equiv of the appropriate diphosphine. Treatment of 2a-d and 3a-d with HX allows the high-yield preparation of the dimeric compounds [{RUX(mu-X)(CO)(P<^>P) }(2)] (P<^>P = dppf, X = Cl (4a), Br (4b); P<^>P = dippf, X = Cl (5a), Br (5b)). Complex [{RuCl(mu-Cl)(CO)(dppf)}(2)] reacts with neutral ligands, via chloride bridge cleavage, affording the mononuclear derivatives [RuCl2(CO)(L)(dppf)] (L = CO (6a), BzNC (6b), Py (6c), PhNH2 (6d)). The structures of compounds [RUCl(eta(3)-C3H5)(CO)(dPPf)] (2a), [{RuCl(mu-Cl)(CO)(dppf)}(2)] (4a), and [RuCl2(CO)(Py)(dppf)] (6c) have been confirmed by X-ray crystallography. The catalytic activity of dimers 4a,b and 5a,b in transfer hydrogenation of ketones by propan-2-ol has also been studied.