SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF THE PT2(II,III) COMPLEX (NBU4)[(C6F5)2PT(MU-C6F5)2PT(C6F5)2] AND THE PT2(III,III) COMPLEX (NBU4)[(C6F5)2PT(MU-C6F5CL)(MU-C6F5)PT(C6F5)2] - NOVEL LIGAND REACTIVITY OF A BRIDGING C6F5 GROUP

The previously reported trinuclear, (C6F5)-bridged compound (NBu4)[Pt2(mu-C6F5)2(mu-AgOEt2)(C6F5)4], 1, reacts with an excess of molecular chlorine in toluene/CCl4 to give the novel metal-metal bonded, garnet-colored complex 3, (NBu4)[(C6F5)2Pt(mu-C6F5Cl)(mu-C6F5)Pt(C6F5)2]. Compound 3 is the result of addition of one chlorine atom to a bridging C6F5 ligand, with concomitant oxidation of the dinuclear core to a singly bonded Pt(III)-Pt(III) unit with planar D2h geometry. Compound 1 also reacts with an excess of Br2 or 12 in toluene to give the black, dinuclear Pt(II)-Pt(III)compound(NBu4)[(C6F5)2Pt(mu-C6F5)2Pt(C6F5)2],4, which also has a planar core, The garnet complex 3 can also be prepared by the reaction of the dinuclear, (C6F5)-bridged complex (NBu4)2[Pt2(mu-C6F5)2(C6F5)4],2, with Cl2 in CCl4, and by the reaction of compound 4 with Cl2 in CH2Cl2/CCl4. An SCF-Xalpha-SW study of compound 4 shows that the HOMO, 15b1u, which contains an unpaired electron, takes its major contribution from the pi system of the bridging (C6F5) ligands, thus explaining the vulnerability of the bridging ligand to chemical attack. Complex 3 has been characterized by F-19 NMR spectroscopy and by X-ray diffraction. Complex 4 was studied by EPR spectroscopy and X-ray diffraction. Compound 3, Pt2C52H36NF30Cl, crystallizes in the monoclinic crystal system, space group C2/c, with a = 12.101(3) angstrom, b = 21.047(6) angstrom, c = 21.977(8) angstrom, beta = 95.57(3)degrees, V = 5571(3) angstrom3 at -83-degrees-C, and Z = 4. A model of 353 parameters was refined to residuals of R = 0.0629, R, = 0.0909, and quality of fit = 1.708. Compound 4, Pt2C52H36NF30, is monoclinic, space group C2/c, with a = 12.198(6) angstrom, b = 20.592(6) angstrom, c = 22.223(7) angstrom, beta = 95.23(3)degrees, V = 5559(6) angstrom3 at 21-degrees-C, and Z = 4. The structure was refined to residuals of R = 0.043 1, R(w) = 0.0498, and quality of fit = 0.998. The Pt-Pt distances are 2.573(2) and 2.611(2) angstrom in 3 and 4, respectively. Cyclic voltammetry shows that a reversible one-electron process interconverts complexes 2 and 4; however, oxidation of complex 4 by a process presumed to involve ligand reactivity is irreversible.