Synthesis of multiply-bonded dichromium complexes with a variety of formamidinate ligands

A series of dichromium tetraformamidinate complexes with (ArNCHNAr)(-) wher e Ar is X2C6H3 or XC6H4 and X is the remote substituent 3,5-Cl-2, 3,4-Cl-2, p-Cl, p-CF3, m-CF3, p-OCH3 or m-OCH3 has been synthesized, and the structu res of four of the compounds determined by X-ray crystallography. The Cr-Cr bond distances of the complexes structurally characterized are 1.9072(10) Angstrom [Cr-2((p-ClC6H4N)(2)CH)(4)], 1.9162(10) Angstrom [Cr-2((3,5-Cl2C6H 3N)(2)CH)(4)], 1.9018((8) Angstrom [Cr-2((m-CF3C6H4N)(2)CH)(4) ], and 1.917 8(11) Angstrom [Cr-2((m-OCH3C6H4N)(2)CH)(4)]. H-1 NMR spectroscopy and elec trochemistry were performed on the series. The diamagnetic anisotropy of th e Cr-Cr bond was calculated from X-ray crystallographic and H-1 NMR data an d correlates with the Hammett constant of the formamidine ligands. (C) 1999 Elsevier Science Ltd. All rights reserved.