Controlled acidolysis of hexacarbonyltris(μ-alkoxo)dirhenium(I) anions: Facile synthesis of hexacarbonylbis(μ-alkoxo)-[μ-1,1′-bis(diphenylphosphino)ferrocene] dirhenium(I) complexes and nonacarbonyltris(μ-methoxo)(μ3-methoxo)trirhenium(I)

Abstract

The complexes [Re2(μ-OR)2(μ-dppf)(CO)6] (R = H, 1; Me, 2; Et, 3; Ph, 4) were synthesized by the controlled acidolysis of the anions [Re2(μ-OR)3(CO)6]- (R = H, Me, Et) and [Re2(μ-OH)(μ-OPh)2(CO)6]- (5), respectively, in the presence of dppf (1,1′-bis(diphenylphosphino)-ferrocene). The dppf ligands in complexes 1-4 undergo a twisting motion in solution at room temperature, which, in the case of 3, is correlated with the restricted rotation of the ethyl groups about the O-CH2 bonds. Complex 3 is an interesting example of an organometallic complex in which the two exchanging positions of the methylen protons of an ethyl group are nonequivalent, while the exchanging positions of the methyl group are equivalent. Controlled acidolysis of [Re2(μ-OMe)3(CO)6]- under 1 atm of CO pressure affords the complex [Re3(μ-OMe)3(μ3-OMe)(CO) 9]- (6), which consists of Re3 triangle held together by one face-capping and three bridging methoxo groups, with no Re-Re bonds. The crystal structures of 1, 3, 5, and 6, were determined by single-crystal X-ray diffraction analysis. The synthetic relationship of dirhenium-dialkoxo, dirhenium-trialkoxo, and trirhenium-tetraalkoxo entities is established.