Dihydrogen complexes of electrophilic metal centers: Observation of Cr(CO)5(H2), W(CO)5(H2) and [Re(CO)5(H2)]+

Article abstract of DOI:10.1021/ja0433370

Photolysis of dichloromethane solutions of M(CO)₆ (M = Cr, W) at low temperature in the presence of hydrogen gas affords W(CO)₅(H₂) (1) and Cr(CO)₅(H₂) (2). Complexes 1 and 2 are characterized as dihydrogen complexes based on short T₁ values for the hydride resonances and a large HD coupling of 35.3 Hz (W) and 35.8 Hz (Cr) in the HD derivatives. A cationic analogue, [Re(CO)₅(H₂)]⁺ (3), was prepared by reaction of Re(CO)₅Cl with [Et₃Si][B(C₆F₅)₄] in fluorobenzene under hydrogen. Complex 3-d₁ exhibits J_HD = 33.9 Hz. Complex 3 is strongly acidic, with complete deprotonation by diethyl ether; complexes 1 and 2 are moderately acidic. Deprotonation of 1 is complete in the presence of one equivalent of triethylamine. Copyright