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

Reaction between the dimeric metal complexes, [M2(μ-OAcF)2(OAcF)2(μ-H2O)(tmen)2], M=Co(II), Ni(II), and aceto- and benzohydroxamic acids (AHA, BHA) gives the novel trimeric complexes, [M3(μ-OAcF)4(μ-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 · 4H2O, tmen and RHA gives the dibridged hydroxamate dimers [M2(μ-OAcF)(μ-RA)2(tmen)2] [OAcF].