Asymmetrical A-Frame Triplatinum Clusters Bridged by Small Organic Molecules and Bis((diphenylphosphino)methyl)phenylphosphine

Reactions of the linear triplatinum complex Pt(3)(&mgr;-dpmp)(2)(XylNC)(2)](2+) (3) with small organic molecules led to formation of asymmetrical A-frame triplatinum complexes with an additional bridge across one of the metal-metal bonds, where dpmp is bis((diphenylphosphino)methyl)phenylphosphine. Reaction of complex 3 with electron deficient alkynes (R(1)C&tbd1;CR(2): R(1) = R(2) = CO(2)Me; R(1) = H, R(2) = CO(2)Me; R(1) = R(2) = CO(2)Et) afforded a new series of triplatinum clusters formulated as Pt(3)(&mgr;-dpmp)(2)(&mgr;-R(1)CCR(2))(XylNC)(2)](PF(6))(2) (5a, R(1) = R(2) = CO(2)Me; 5b, R(1) = H, R(2) = CO(2)Me; 5c, R(1) = R(2) = CO(2)Et) in good yields. The complex cation of 5b was characterized by X-ray crystallography to have an asymmetrical A-frame structure comprising three Pt atoms bridged by two dpmp ligands, in which an acetylene molecule was inserted into one of the Pt-Pt bonds (triclinic, P&onemacr;, a = 19.507(3) ?, b = 20.327(4) ?, c = 14.499(4) ?, alpha = 107.69(2) degrees, beta = 102.08(2) degrees, gamma = 71.30(1) degrees, V = 5148 ?(3), Z = 2, R = 0.070, and R(w) = 0.084). The Pt-Pt bond length is 2.718(1) ? and the Pt.Pt nonbonded distance is 3.582(1) ?. Treatment of 3 with an excess of HBF(4).Et(2)O gave the asymmetrical cluster Pt(3)(&mgr;-dpmp)(2)(&mgr;-H)(XylNC)(2)](BF(4))(3).CH(2)Cl(2) (6.CH(2)Cl(2)), in 61% yield, and a similar reaction with p-NO(2)C(6)H(4)NC led to the formation of Pt(3)(&mgr;-dpmp)(2)(&mgr;-R(3)NC)(XylNC)(2)](PF(6))(2).CH(2)Cl(2) (7.CH(2)Cl(2)) in 94% yield (R(3) = p-NO(2)C(6)H(4)). Complexes 6 and 7 are assumed to have a single atom-bridged, asymmetrical A-frame structures. Reaction of the complex syn-Pt(2)(&mgr;-dpmp)(2)(XylNC)(2)](2+) (1) with MCl(2)(cod)] (M = Pt, Pd) gave the dimer-monomer combined trinuclear cluster Pt(2)MCl(2)(&mgr;-dpmp)(2)(XylNC)(2)](PF(6))(2) (8a, M = Pt, 89%; 8b, M = Pd, 55%). The structure of 8a was determined by X-ray crystallography to be comprised of a metal-metal-bonded diplatinum core and a monomeric platinum center bridged by two dpmp ligands with a face-to-face arrangement (triclinic, P&onemacr;, a = 18.082(7) ?, b = 19.765(6) ?, c = 15.662(4) ?, alpha = 98.51(2) degrees, beta = 94.24(3) degrees, gamma = 109.82(2) degrees, V = 5161 ?(3), Z = 2, R = 0.069, and R(w) = 0.080). The Pt-Pt bond length is 2.681(2) ? and the Pt.Pt nonbonded distance is 3.219(2) ?. The heteronuclear complex 8b was transformed to an A-frame trinuclear cluster, Pt(2)PdCl(&mgr;-Cl)(&mgr;-dpmp)(2)(XylNC)](PF(6))(2) (9), which was characterized by X-ray crystallography (monoclinic, C2/c, a = 33.750(9) ?, b = 28.289(9) ?, c = 23.845(8) ?, beta = 118.19(4) degrees, V = 20066 ?(3), Z = 8, R = 0.082, and R(w) = 0.077). The diplatinum unit (Pt-Pt = 2.606(2) ?) is connected to the mononuclear Pd center by a chloride bridge (Pt.Pd = 3.103(3) ?, Pt-Cl-Pd = 79.6(3) degrees ).