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 c hlorine in toluene/CCl4 to give the novel metal-metal bonded, garnet-c olored complex 3, (NBu4)[(C6F5)2Pt(mu-C6F5Cl)(mu-C6F5)Pt(C6F5)2]. Comp ound 3 is the result of addition of one chlorine atom to a bridging C6 F5 ligand, with concomitant oxidation of the dinuclear core to a singl y bonded Pt(III)-Pt(III) unit with planar D2h geometry. Compound 1 als o reacts with an excess of Br2 or 12 in toluene to give the black, din uclear II)compound(NBu4)[(C6F5)2Pt(mu-C6F5)2Pt(C6F5)2],4, which also h as a planar core, The garnet complex 3 can also be prepared by the rea ction of the dinuclear, (C6F5)-bridged complex (NBu4)2[Pt2(mu-C6F5)2(C 6F5)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 H OMO, 15b1u, which contains an unpaired electron, takes its major contr ibution from the pi system of the bridging (C6F5) ligands, thus explai ning the vulnerability of the bridging ligand to chemical attack. Comp lex 3 has been characterized by F-19 NMR spectroscopy and by X-ray dif fraction. Complex 4 was studied by EPR spectroscopy and X-ray diffract ion. Compound 3, Pt2C52H36NF30Cl, crystallizes in the monoclinic cryst al 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, wi th a = 12.198(6) angstrom, b = 20.592(6) angstrom, c = 22.223(7) angst rom, beta = 95.23(3)degrees, V = 5559(6) angstrom3 at 21-degrees-C, an d 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 sho ws that a reversible one-electron process interconverts complexes 2 an d 4; however, oxidation of complex 4 by a process presumed to involve ligand reactivity is irreversible.