THE CHEMISTRY OF CYCLOHEPTATRIENYL COMPLEXES OF MOLYBDENUM AND TUNGSTEN - LIGAND SUBSTITUTION VIA A RING SLIPPED INTERMEDIATE IN CATIONIC CARBONYLISONITRILE DERIVATIVES

Reaction of [M(CO)2(NCMe)(eta-7-C7H7)]+ (M = Mo or W) with one equivalent of CNBu(t)) affords [M(CO)2(CNBu(t))(eta-7-C7H7)]+ (1, M = Mo; 2, M = W), which react with further CNBu(t)) to give the ring slipped products [M(CO)2(CNBu(t))3(eta-3-C7H7)]+ (3, M = Mo; 4, M = W). At 20-degrees-C, 3 slowly converts to a mixture of [Mo(CO)(CNBu(t))2(eta-7-C7H7)]+ (5) (the formal substitution product of 1 with CNBu(t)) and [Mo(CO)(CNBu(t))4(eta-3-C7H7)]+ (7). On heating to 50-degrees-C, 7 yields 5 and [Mo(CNBu(t))3(eta-7-C7H7)]+ (8). Reflux of [W(CO)2(CNBu(t))3(eta-3-C7H7)]+ (4) in 2-butanone affords [W(CO)(CNBu(t)2(eta-7-C7H7)]+ (6) as the major reaction product.