SYNTHESIS, CRYSTAL-STRUCTURES, AND REDOX BEHAVIOR OF BIS(2-PHENYLINDENYL)NICKEL AND BIS(2-PHENYLINDENYL)ZIRCONIUM DICHLORIDE

Redox reactions of the sandwich [eta(5)-(Ph)Ind]Ni-2 complex (1) (wher e (Ph)Ind is the 2-phenylindenyl anion) in CH2Cl2 and of the bent-sand wich [eta(5)-(Ph)Ind]2ZrCl2 complex (2) in THF have been studied by lo w-temperature cyclic voltammetry. Complex 1 undergoes quasi-reversible two-step oxidation to cation 1(+) and dication 1(2+), which are stabl e at room temperature within the cyclic voltammetry time scale. Two-el ectron reduction of complex 1 is irreversible up to -50 degrees C, and this process is accompanied by destruction of the sandwich structure of the complex. Reduction of complex 2 is described by the conventiona l scheme for bent-sandwich complexes. According to this scheme, furthe r one-electron reduction of radical anion 2(.-) generates dianion 2(2- ), which eliminates two Cl- ions to afford bisindenyl sandwich complex [eta(5)-(Ph)Ind]Zr-2 (3). This complex is stable at T < -45 degrees C within the cyclic voltammetry time scale and is capable of undergoing one-electron reduction to the corresponding radical anion 3(.-). Synt hesis and crystal structures of complexes 1 and 2 are reported.