Heterometallic early-late π-tweezer complexes:: their synthesis, electrochemical behaviour and the solid-state structures of (η5-C5H4SiMe3)2Ti(CCPh)2 and [(η5-C5H4SiMe3)2Ti(CCPh)2]Pd(PPh3)

The reaction of [Ti](C equivalent to CPh)(2) (1) {[Ti] = (eta (5)-C5H4SiMe3)(2)Ti} with equimolar amounts of CuBr, Ni(PPh3)(3) or Pd(PPh3)(4) produces the heterobimetallic early-late transition metal complexes of general type {[Ti](C equivalent to CPh)(2)} MX [2: MX=CuBr, 3: MX = Ni(PPh3), 4: MX = Pd(PPh3) in which the respective transition metal atoms are linked by aar-bound alkynyl ligands. The solid-state structure of I and 4 is reported. In heterobimetallic 4 the Pd(0) centre possesses a trigonal-planar environment caused by the two eta (2)-coordinated Me3SiC equivalent toC ligands and the datively bonded PPh3 group. The PPh3 moiety is thereby located out of the best Ti(C equivalent to CSi)(2)Pd plane. Comparative cyclic voltammetric studies on complexes 1-4 as well as {[Ti](C equivalent to CPh)(2)}Ni(CO), for comparison, are presented. These studies reveal a strong influence of the eta (2)-coordinated low-valent transition metal complex fragments MX on the reduction behaviour of the Ti(IV) centre. (C) 2001 Elsevier Science B.V. All rights reserved.