Reaction of CuBr2 or Cu(ClO4)(2).6H(2)O and sodium benzoate with the tridentate ligand 2,6-bis(morpholinomethyl)-4-methylphenol (Hbmmk) in methanol yields two copper complexes [Cu4OBr4(bmmk)(2)].2MeOH (1) and [Cu4O(OBz)4(bmmk)2] H2O (2). The compounds were characterized by single-crystal X-ray diffraction studies and are shown to contain W-oxo-bridged cluster compounds of the new type [Cu(4)OX(4)L(6)] 1 crystallizes in the monoclinic space group P2(1)/c with a = 12.693(2) Angstrom, b = 12.378(2) Angstrom, c = 29.293(6) Angstrom, S = 96.32(3)degrees, V = 4574.4 Angstrom(3), and Z = 4. Discrepancy values of R = 0.0324 and R(w) = 0.0309 were obtained for 5544 independent reflections and 517 adjustable parameters. The complex has a central mu(4)-bridging oxygen surrounded tetrahedrally by four copper atoms (average Cu-O distance 1.917 Angstrom). By copper pairing two of the Cu...Cu distances (average 3.000 Angstrom) are significantly shorter than the other four (average 3.193 Angstrom). The four bromine ligands and the two phenoxo groups of the deprotonated bmmk ligand are in a mu(2)-bridging mode and bridge each of the Cu...Cu vectors. The structure is completed by four terminal, N-bonded morpholine groups, one of them attached to each of the copper atoms. All copper centers are in trigonal bipyramidal coordination. Crystals of 2 are also monoclinic, space group P2(1), with a = 11.889(2) Angstrom, b = 20.250(4) Angstrom, c = 12.481(3) Angstrom, beta = 95.12(2)degrees, V = 2992.8 Angstrom(3), and Z = 2. R = 0.0874 and R(w) = 0.0879 for 4792 independent reflections and 776 adjustable parameters. The complex consists of a central Cu4O tetrahedron (average Cu-O = 1.925 Angstrom). As in 1, copper pairing leads in 2 to two short (average 2.992 Angstrom) and four long Cu Cu distances (average 3.216 Angstrom), The bromine ligands of 1 are replaced in 2 by mu(1,3)-bridging benzoate groups. The more rigid benzoate framework leads to three different coordination polyhedra around the copper atoms : octahedral for Cu(1), square planar for Cu(2), and square pyramidal for Cu(3) and Cu(4). Magnetic susceptibility measurements in the temperature range 4.2-475.4 K indicate significant antiferromagnetic coupling between the copper(II) centers of both complexes. The experimental data were fitted to a modified Heisenberg model with two coupling constants J(12) and J(13) The best least-squares fit parameters were g = 2.19, J(12) = -296 cm(-1), J(13) = -36 cm(-1), and x(p) = 2.4% for 1 and g = 2.01, J(12) = -175 cm(-1), J(13) = -18 cm(-1), and x(p) = 0.8% for 2. The susceptibilities calculated with this model were found to be highly insensitive to J(13) but very sensitive to J(12).