The dinickel(II) compound [Ni 2 (μ-OAc) 2 (OAc) 2 (μ-H 2 O)(asy·dmen) 2 ]·2.5H 2 O, 1; undergoes facile reaction in a 1:2 molar ratio with benzohydroxamic acid (BHA) in ethanol to give the novel nickel(II) tetranuclear hydroxamate complex [Ni 4 (μ-OAc) 3 (μ-BA) 3 (asy·dmen) 3 ][OTf] 2 ·H 2 O, 2, in which the bridging acetates, bridging two nickel atoms in 1, undergo a carboxylate shift from the μ 2 -η 1 :η 1 bridging mode of binding to the μ 3 -η 1 :η 2 bridging three nickel atoms in the tetramer. The structure of complex 2 was determined by single-crystal X-ray crystallography. The two monodentate acetates, water and two bidentate bridging acetates of two moles of complex 1 are replaced by three monodentate bridging acetates and three benzohydroxamates. Three nickel atoms in the tetramer, Ni(2), Ni(3) and Ni(4) are in a N 2 O 4 octahedral environment, while the fourth nickel atom Ni(1) is in an O(6) octahedral environment. The Ni–Ni separations are Ni(1)–Ni(2)=3.108Å, Ni(1)–Ni(3)=3.104Å and Ni(1)–Ni(4)=3.110Å, which are longer than previously studied in dinuclear urease inhibited models but shorter than in the nickel(II) tetrameric glutarohydroxamate complex [Ni 4 (μ-OAc) 2 (μ-gluA 2 ) 2 (tmen) 4 ][OTf] 2 , isolated and characterized previously in this laboratory. Magnetic studies of the tetrameric complex show that the four Ni(II) ions are ferromagnetically coupled, leading to a total ground spin state S T =4. Three analogous tetranuclear nickel hydroxamates were prepared from AHA and BHA and the appropriate dinuclear complex with either sy·dmen or asy·dmen as capping ligands.