An example of a direct axial interaction of a platinum(II) atom with a Mo-2 core through a uniquely designed tridentate ligand 6-(diphenylphosphino)-2-pyridonate (abbreviated as pyphos) is described. Treatment of PtX(2)-(pyphosH)(2) (2a, X = Cl; 2b, X = Br; 2c, X = I) with a 1:1; mixture of Mo-2(O2CCH3)(4) and [Mo-2(O2CCH3)(2)(NCCH3)(6)](2+) (3a) in dichloromethane afforded the linear trinuclear complexes [Mo(2)PtX(2)(pyphos)(2)(O2CCH3)(2)](2) (4a, X = Cl; 4b, X = Br; 4c, X = I). The reaction of [Mo-2(O(2)CCMe(3))(2)(NCCH3)(4)](2+) (3b) with 2a-c in dichloromethane afforded the corresponding pivalato complexes [Mo(2)PtX(2)(pyphos)(2)(O(2)CCM(3))(2)](2) (5a, X = Cl; 5b, X = Br; 5c, X = I), whose bonding nature is discussed on the basis of the data from Raman and electronic spectra as well as cyclic voltammograms. The linear trinuclear structures in 4b and 5a-c were confirmed by NMR studies and X-ray analyses : 4b, monoclinic, space group C2/c, a = 34.733(4) Angstrom, b = 17.81(1) Angstrom, c = 22.530(5) Angstrom, beta = 124.444(8)degrees, V = 11498(5) Angstrom(3), Z = 8, R = 0.060 for 8659 reflections with I > 3 sigma(I) and 588 parameters; 5a, triclinic, space group , a = 13.541(3) Angstrom, b = 17.029(3) Angstrom, c = 12.896(3) Angstrom, alpha = 101.20(2)degrees, beta = 117.00(1)degrees, gamma = 85.47(2)degrees, V = 2599(1) Angstrom(3), Z = 2, R = 0.050 for 8148 reflections with I > 3 sigma(I) and 604 parameters; 5b, triclinic, space group , a = 12.211(2) Angstrom, b = 20.859(3) Angstrom, c = 10.478(2) Angstrom, alpha = 98.88(1)degrees, beta = 112.55(2)degrees, gamma = 84.56(1)degrees, V = 2433.3(8) Angstrom(3), Z = 2, R = 0.042 for 8935 reflections with I > 3 sigma(I) and 560 parameters; 5c, monoclinic, space group P2(1)/n, a = 13.359(4) Angstrom, b = 19.686(3) Angstrom, c = 20.392(4) Angstrom, beta = 107.92(2)degrees, V = 5101(2) Angstrom(3), Z = 4, R = 0.039 for 8432 reflections with I > 3 sigma(I) and 560 parameters.