Synthesis of the sterically crowded cycloheptatrienyl complexes [M(CO)(PPh3)2(η-C7H7)]+ (M = Mo or W): X-ray crystal structures of [W(CO)(PPh3)2(η-C7H7)][BF4] and [W(CO)2(PPh3)(η-C7H7)][BF4] · CH2Cl2

Syntheses of the first examples of bis(triphenylphosphine)cycloheptatrienyl complexes [M(CO)(PPh3)2(η-C7H7)]+ (M = Mo or W) are described. The X-ray structure of the W complex reveals structural modifications consistent with a sterically crowded system.