SYNTHESIS, PROPERTIES, AND STRUCTURE OF BIS(CIS-(METHYLTHIO)STILBENETHIOLATO)NICKEL(II) AND BIS(CIS-BIS(METHYLTHIO)STILBENE)NICKEL(II) IODIDE

The sulfur atoms in the bis(cis-stilbene-1,2-dithiolato)nickel(II) dianion, [Ni(S2C2Ph2)2]2− = Ni[S4C4Ph4]2−, react with alkyl halides to yield unusually stable bis(alkylthio) derivatives of composition Ni[R2S4C4Ph4], with R = alkyl. The green, diamagnetic complex with R = CH3 crystallizes in space group P21/n, with unit cell dimensions at 23 °C of a = 6.127 (3) Å, b = 8.001 (3) Å, c = 27.663 (3) Å, β = 93.81 (2)°, Z = 2, and dcald = 1.407 g cm−3, and is shown to be bis((methylthio)stilbenethiolato)nickel(II), Ni[PhC(SCH3)=C(S)Ph]2. The NiS4 moiety is essentially planar with mean Ni–S bond lengths of 2.161 (2) Å. The observed ligand C–S(CH3)- and C–S bond lengths of 1.779 (5) and 1.737 (5) Å are in the range of C–S single bonds; the C–C bond distance is 1.352 (7) Å, consistent with an essentially localized electronic structure. The Ni–S–CH3 bond angles of 105.2 (2)° are smaller than expected due to crystal packing forces. In a 1:1 inclusion compound with CH2Cl2, which crystallizes in space group P1, with unit cell dimensions a = 8.424 (3) Å, b = 13.461 (3) Å, c = 14.745 (3) Å, a = 68.93 (2)°, β = 84.08 (2)°, γ = 75.10 (2)°, Z = 2, dcald = 1.45 g cm−3, the lattice expansion causes a normalization of the Ni–S–CH3 angles to 109.2 (2)°. Variable-temperature 1H NMR measurements in solution reveal dynamic equilibria attributed to sulfur inversion and cis-trans isomerization reactions. On heating, decomposition occurs with ligand disproportionation to bis(methylthio)stilbene and nickel(II) stilbenedithiolate, [Ni(S2C2Ph2)]x. The sulfur atoms exhibit residual nucleophilic reactivity on reaction with CH3I, affording a complex of composition [(CH3)2S2C2Ph2]2NiI2, which crystallizes in space group P21/n, with a = 8.178 (3) Å, b = 11.992 (3) Å, c = 18.229 (5) Å, β = 94.28 (2)°, Z = 2, dcalod = 1.69 g cm−3. Its structure reveals a linear I–Ni–I moiety with two molecules of symmetrically S-bonded molecules of cis-bis(methylthio)stilbene as the ligands in the equatorial positions. The mean Ni–S bond and C–S(CH3) bond lengths are 2.379 (9) and 1.803 (4) Å, and the mean Ni–I bond lengths are 2.7989 (2) Å, respectively. © 1990, American Chemical Society. All rights reserved.