Intramolecular C–H Bond Activation in Bridged Dicyclopentadienyl Dimethyl Dinuclear Complexes

Abstract

Photolysis of the doubly bridged dicyclopentadienyl dimethyl dinuclear complexes [(η5-C5H2R)2(SiMe2)2]M2(CO)4Me2 (M = Ru, R = H (2a), tBu (2b); M = Fe, R = H (2c)) in benzene yields the corresponding methylene-bridged complexes [(η5-C5H2R)2(SiMe2)2]M2(CO)2(μ-CO)(μ-CH2) (3a–c) and the M–M-bonded complexes [(η5-C5H2R)2(SiMe2)2]M2(CO)4 (1a–c). Irradiation of the analogous diethyl complex [(η5-C5H2R)2(SiMe2)2]Ru2(CO)4Et2 (4) affords only 1a. Unlike the case for the doubly bridged complexes, photolysis of the singly bridged dicyclopentadienyl dimethyl diruthenium complexes [(η5-C5H4)2(EMe2)]Ru2(CO)4Me2 (E = C (5a); E = Si (5b)) in benzene yields the corresponding “twisted” ruthenium methyl complexes with a cyclopentadienyl–Ru σ bond (η5,η5:η1-C5H4(EMe2)C5H3)[Ru(CO)2][Ru(CO)2Me] (6a,b) and the similar phenyl complexes (η5,η5:η1-C5H4(EMe2)C5H3)[Ru(CO)2][Ru(CO)2Ph] (7a,b), from reaction with the benzene solvent. Plausible mechanisms for the formation of the different types of products are proposed involving intra...