Bimetallic systems. Part 21. Synthesis of vinylidene- and phenylene-bridged complexes of dinickel(II), nickel(II)–palladium(II), and nickel(II)-platinum(II) containing Ph2PCH2PPh2(dppm): crystal structures of [(SCN)Ni(µ-dppm)2(µ-CCH2)Ni(NCS)] and [ClPd(µ-dppm)2(µ-CCCl2)NiCl]

Abstract

Treatment of toluene solutions of [Ni(cod)₂](cod = cyclo-octa-1,5-diene) and Ph₂PCH₂PPh₂(dppm)(1:1.5 mol ratio) with Cl₂CCH₂ gives the vinylidene-bridged ‘A-frame’ complex [ClNi(µ-dppm)₂(µ-CCH₂)NiCl](1a). A better route to (1a) involves the combination of [Ni(cod)₂], dppm, and trans-[NiCl(CClCH₂)(PPh₃)₂](1:2:1 mol ratio) in benzene. Treatment of (1a) with LiBr, NaI, or KCNS in acetone gives the corresponding dibromide, di-iodide, or di-isothiocyanate complexes (1b), (1c), or (1d). Phenylene- and substituted phenylene-bridged A-frames of the type [XNi(µ-dppm)₂(µ-C₆H₃R)NiX][X = Cl, R = H (2a); X = Br, R = H (2b); X = Cl, R = Me (3); X = Cl, R = OH (4)] have been synthesised similarly, using trans-[NiX( C₆H₃RX)(PPh₃)₂]. By treating these substituted vinyl or aryl nickel complexes with [Pd(PPh₃)₄] and dppm, heterobimetallic A-frame complexes of the types [ClPd(µ-dppm)₂(µ-CCR₂)NiCl][R = H (5a), R = Cl (5b)] and [XPd(µ-dppm)₂(µ-C₆H₃R)NiX][X = Cl, R = H (6a); X = Br, R = H (6b)] have been obtained. By using [Pt(PPh₃)₄], dppm, and the appropriate nickel complex, [ClPt(µ-dppm)₂(µ-CCCl₂)NiCl](5c), was obtained but attempts to effect analogous reactions with other nickel complexes gave dinickel A-frames as the only bimetallic products. Hydrogen-1, ³¹P-{¹H}, and ¹H-{³¹P} n.m.r. and i.r. data are given and the crystal structures of [(SCN)Ni(µ-dppm)₂(µ-CCH₂)Ni(NCS)](1d) and [ClPd(µ-dppm)₂(µ-CCCl₂)NiCl](5b) have been determined. Crystals of (1d) are monoclinic, space group P2₁/n(P2₁/c, no. 14), a= 1 275.7(2), b= 1 508.6(3), c= 2636.6(5) pm, β= 99,75(1)°, and Z= 4; final R′= 0.0481. Crystals of (5b) are tetragonal, space group P4₁2₁2, a= 1 418.3(2), c= 2 814.5(3) pm, Z= 4; final R′= 0.0517.