Synthesis and X-ray crystal structure of an oxorhenium(V) complex with a double Schiff base

The reaction of the double Schiff bases, RL, formed from 2,6-diformyl-4-methyl-phenol and p-RC6H4NH2 (R=H, Me, OMe, Cl) with ReOCl3(PPh3)(2) afforded red coloured complexes of the type (ReOCl3)-O-V(RL). The X-ray structure of the R=Me complex (crystal data: ReOCl3(MeL). CH2Cl2, triclinic, space group <P(1)over bar>, a=8.736(2), b=10.632(3), c=16.575(5) Angstrom, alpha=104.64(2)degrees, beta=93.22(2)degrees, gamma=110.57(2)degrees, V= 1376.6(7) Angstrom(3), Z=2, R=3.06%, R-w,=3.51%) revealed meridional chloro coordination in an ReOCl3(ON) coordination sphere. The RL ligand binds in the bidentate ON mode, the second imine function occurring in the protonated form (N-H...O hydrogen bonding). IR and H-1 NMR data indicate that the solid-state structure is substantially retained in solution. The complexes display a quasireversible (ReO)-O-VI/(ReO)-O-V couple whose potential depends on the R substituent. (C) 1998 Elsevier Science S.A. All rights reserved.