Three new types of platinum(II) oxo complexes-[(1,5-COD)Pt(mu(3)-O)(AuL)](2)(BF4)(2) [1, L = PPh3, PPh2Et, PPh2-i-Pr, P(o-tol)(3), P(p-tol)(3), P(p-MeOC6H4)(3), P(p-CF3C6H4)(3)], [(1,5-COD)Pt{mu(3)-O(AuL)(2)}(2)](BF4)(2) (2), and [(1,5-COD)Pt-4(mu(3)-O)(2)Cl-2]X-2 (3, X = BF4; 3a, X = CF(3)SO3)-are obtained from oxo/chloro exchange reactions between (1,5-COD)PtCl2 and [(LAu)(3)(mu(3)-O)]BF4. Crystals of 1 (L = PPh3) from CDCl3 are triclinic, , with (-100 degrees C) a = 9.187(4) Angstrom., b = 12.149(3) Angstrom, c 17.680(6) Angstrom, alpha = 99.58(2)degrees, beta = 102.86(2)degrees, gamma = 111.63(2)degrees, V = 1720(1) Angstrom(3), and Z = 1. Crystals of 3a from CH2Cl2/toluene are trigonal, P3(1)21, with a = 11.8878(4) Angstrom, c = 29.3193(15) Angstrom, V = 3588.3(3) Angstrom(3), and Z = 3. The structure of the cationic portion of 1 shows a planar (COD)Pt(mu-O)(2)Pt(COD) unit with slightly out-of-plane LAu+ groups linearly coordinated to the oxo Ligands. The structure of the cationic portion of 3a is similar and shows a slightly folded (COD)Pt(mu-O)(2)Pt(COD) unit with out-of-plane [(COD)PtCl](+) groups coordinated to the ore ligands. Solutions of 3 in untreated CH2Cl2 or CD2Cl2 deposit crystals of [(1,5-COD)(4)Pt-4(mu(3)-O)(2)(mu(2)-OH)](BF4)(3) (4) which are monoclinic, P2(1)/n, with a = 18.624(4) Angstrom, b = 14.760(2) Angstrom, c = 15.584(5) Angstrom, beta = 95.538(12)degrees, V = 4264(2) Angstrom(3), and Z = 4. The core structure of the cationic portion of 4 shows a tetranuclear platinum cation in which the metal atoms occupy the corners of a distorted tetrahedron and two mu(3)-oxo ligands and one mu(2)-hydroxo ligand bridge the four platinum atoms. Reaction of 1 (L = PPh3) with PPh3 gives OPPh3 and [(Ph3P)(3)PtAuPPh3]BF4 (5) which is also obtained from (Ph3P)(4)Pt and Ph3PAuBF4. Crystals of 5 from THF are monoclinic, P2(1)/c, with a = 20.426(6) Angstrom, b = 13.4980(11) Angstrom, 24.703(9) Angstrom, beta = 97.166(15)degrees, V = 6758(3) Angstrom(3), and Z = 4. The structure of 5 consists of an L3Pt-AuL cation where the Au atom is linear 2-coordinate and the Pt atom is distorted square-planar 4-coordinate.