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Organometallics 1990, 9, 816-825
Preparation, Structure, and Divergent Fluxional Behavior of Cationic Dinuclear Iron Acetylides [Fp"P(CrC-R)]BF, (R = H, Ph) Munetaka Akita, Masako Terada, Shuji Oyama, and Yoshihiko Moro-oka" Research Laboratory of Resources Utilization, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 227, Japan Received August 14, 1989
Cationic diiron p-acetylide complexes [ F P 2 ( C ~ C - R ) ] B F 4[2a, FP2 = F P * ~R, = H; 2b, FP2 = Fp*,, R = Ph; 2c, FP2 = Fp*Fp, R = Ph; 2d, Fp,, R = Ph; F P = (05-C5Me5)Fe(CO)2 (Fp*), (T~-C,H,)F~(CO), (Fp)] are prepared by the ligand-exchange reaction of [FP+(THF)]BF,with FP-C=C-R ( l a , FP = Fp*, R = H; lb, FP = Fp*, R = Ph; IC, F P = Fp, R = Ph). Molecular structures of la, l b , 2a, and 2b were determined by single-crystal X-ray diffraction studies. Spectroscopic analyses of 2 reveal the dominant contribution of a a-complex resonance form, ($-M-C=C--R)M+ (A), as well as fluxional behavior. For [Fp*2(C=t-H)]BF4 (2a)the I3C NMR absorptions of the two ethynyl carbon atoms, distinctively observed at lower temperature (
