Complexation and proton transfer by hydroxamic acids in model inhibited metallohydrolases:: formation of metal hydroxamate trimers

Reaction between the dimeric metal complexes, [M-2(mu-OAcF)(2) (OAcF)(2) (mu-H2O)(tmen)(2)], M = Co(II), Ni(II), and aceto- and benzohydroxamic acids (AHA, BHA) gives the novel trimeric complexes, [M-3(mu-OAcF)(4)(mu-RA)(2)(tmen)(2)], M=Co(II), Ni(II); RA = AA, BA, in which each hydroxamate bridges two metal centres via its deprotonated hydroxyl and the carbonyl oxygen bonds one metal centre only together with the doubly protonated salt [(tmen).2H][OAcF](2). In contrast, self-assembly from M(OAcF)(2).4H(2)O, tmen and RHA gives the dibridged hydroxamate dimers [M-2(mu-OAcF)(mu-RA)(2)(tmen)(2)] [OAcF]. (C) 2004 Elsevier B.V. All rights reserved.