SYNTHESIS, CRYSTAL-STRUCTURE, AND REDUCTION OF BIS(2-PHENYLINDENYL)HAFNIUM DICHLORIDE

Reduction of the bent-sandwich [eta(5)-(Ph)Ind](2)HfCl2 complex (1) (w here (Ph)Ind is the 2-phenylindenyl anion) in a THF medium was studied by low-temperature cyclic voltammetry. Complex 1 is stable in THF at a temperature lower than -50 degrees C and undergoes reversible one-el ectron reduction to radical anion 1(.-). Further one-electron reductio n of 1(.-) to dianion 1(2-) is accompanied by the elimination of two C l- ions to form the bisindenyl sandwich [eta(5)-(Ph)Ind](2)Hf complex (2). This complex can undergo reversible one-electron reduction to the corresponding radical anion 2(.-), which is stable within the cyclic voltammetry time scale. At T approximate to -30 degrees C in a THF sol ution, complex 1 was reduced to a diamagnetic (apparently, binuclear) Hf-III complex, which was characterized by cyclic voltammetry. Synthes is and the crystal structure of complex 1 are reported.