FE-57 MOSSBAUER SPECTROSCOPIC STUDIES ON M(CO)(5)(AZAFERROCENE) COMPLEXES (M=CR, MO, W) - THE CRYSTAL-STRUCTURES OF W(CO)(5)(AZAFERROCENE) AND W(CO)(5)(2,5-DIMETHYLAZAFERROCENE)

Fe-57 Mossbauer spectroscopic studies on M(CO)(5)(azaferrocene) comple xes (M = Cr, Mo, W) as well as the crystal structures of W(CO)(5)(azaf errocene) and W(CO)(5)(2,5-dimethylazaferrocene) are reported. The com plexation of azaferrocene to the M(CO)(5) moiety brings about only a s mall change in the quadrupole splitting. The structures of both tungst en complexes reveal a significant shortening of the W-C bonds trans to the nitrogen. These data indicate that azaferrocene behaves as a rela tively strong sigma-donor and there is no evidence for any pi-acceptor properties. (C) 1997 Published by Elsevier Science S.A.