SYNTHESIS AND ELECTRONIC AND MOLECULAR-STRUCTURES OF ETA-CYCLOHEPTATRIENYL ETA-CYCLOPENTADIENYL DERIVATIVES OF VANADIUM, NIOBIUM, AND TANTALUM - PHOTOELECTRON SPECTROSCOPIC, ELECTROCHEMICAL, AND X-RAY CRYSTALLOGRAPHIC STUDY - Green, J; Green, M; Kaltsoyannis, N; Mountford, P; Scott, P; Simpson, S (1992)