The synthesis and characterization of carboxylate-bridged dimetallic complexes are described. By using m-terphenylderived carboxylate ligands, a series of dicobalt(II), dicobalt(III), dinickel(II), and dizinc(II) complexes were synthesized. The compounds are [CO2(mu-O2CArTol)2(O2CArTol)(2)L-2] (1), [Co-2 mu-OH2)(2)(mu-O2CArTol)(2)(O2CArTol)(2)L-2] (2a-c), [Co-2(mu-OH)(2)(mu-O2CArTol)(2)(O2CArTol)(2)L-2] (3), [Ni-2 mu-O2CArTol)(4)L-2] (4), [Ni-2(mu-(HOH)-H-...)(2) (mu-O2CArTol)(2)(O2CArTol)(2)(O2CArTol)(2)L-2 (5), and [Zn-2(mu-O2CArTol)(2)(O2CArTol)(2)L-2] (6), where (ArCO2H)-C-Tol = 2,6-di(p-tolyl)benzoic acid and L = pyridine, THF, or NNdibenzylethylenediamine. Structural analysis of these complexes revealed that additional bridging ligands can be readily accommodated within the {M-2(mu-O2CArTol)(2)}(2+) core, allowing a wide distribution of (MM)-M-... distances from 2.5745(6) to 4.0169(9) Angstrom. Unprecedented bridging units {M-2(mu-OH2)(2)(mu-O2CR)(2)}(n+) and {M-2(mu-(HOH)-H-...)(2)(mu-O2CR)(2)}(n+) were identified in 2a-c and 5, respectively, in which strong hydrogen bonding accommodates shifts of protons from bridging water molecules toward the dangling oxygen atoms of terminal monodentate carboxylate groups. Such a proton shift along the (OHO)-H-...-O-... coordinate attenuates the donor ability of the anionic carboxylate ligand, which can translate into increased Lewis acidity at the metal centers. Such double activation of bridging water molecules by a Lewis acidic metal center and a metal-bound general base may facilitate the reactivity of metallohydrolases such as methionine aminopeptidase (MAP).