Discrete mononuclear and dinuclear nickel(II) complexes of alkane- and areneselenolates: Syntheses, structures, and properties of (Et(4)N)(2)[Ni-2(Se(CH2)(3)Se)(3)], (Ph(4)P)(2)[Ni(SePh)(4)], and (Ph(4)P)(2)[Ni-2(mu-2,4,6-(Me)(3)C6H2Se)(2)(2,4,6-(Me)(3)C6H2Se)(4)]center dot 8CH(3)CN

Reaction of the alkanediselenolate (Et4N)2(Se(CH2)3Se) with NiCl2·6H2O in ethanol/acetonitrile mixture affords the dimeric complex (Et4N)2[Ni2(Se(CH2) 3Se)3] (1), in which the coordination geometry around each Ni(II) center is square planar. In contrast, reaction of the areneselenolate PhSe- with NiCl2·6H2O in acetonitrile gives rise to (Ph4P)2[Ni(SePh)4] (2), which comprises a distorted tetrahedral NiSe4 chromophore. When the bulky areneselenolate 2,4,6-(Me)3C6H2Se- is used, the same reaction affords the dimeric complex (Ph4P)2[Ni2(μ-2,4,6-(Me)3C 6H2Se)2(2,4,6-(Me)3C 6H2Se)4]·8CH3CN (3), which contains square planar NiSe4 chromophores. Unfavorable steric interactions among o-methyl groups, nickel, and the Se atoms do not allow a tetrahedral coordination sphere around nickel in 3. Complex 1 crystallizes in the orthorhombic space group Pna21 with a = 16.645(3) Å, b = 20.214(6) Å, c = 11.428(3) Å, V = 3846(3) Å3, and Z = 4. The structure of 1 was refined to R = 7.34% on the basis of 1694 (I > 4σ(I)) data. Complex 2 crystallizes in the orthorhombic space group Pca21 with a = 17.617(7) Å, b = 13.758(5) Å, c = 24.776(11) Å, V = 6005(4) Å3, and Z = 4. The structure of 2 was refined to R = 6.45% on the basis of 4034 (I > 4σ(I)) data. Complex 3 crystallizes in the triclinic space group P1 with a = 14.443(3) Å, b = 14.751(3) Å, c = 15.351(3) Å, α = 75.66(3)°, β= 71.09(3)°, γ = 65.18(3)°, V = 2784.4(10) Å3, and Z = 1. The structure of 3 was refined to R = 7.34% on the basis of 7236 (I > 4σ(I)) data. These Ni(II) selenolate complexes are sensitive to oxygen, and their formation is hindered by the presence of water in the reaction mixture. The average Ni-Se bond lengths in all the homoleptic square planar selenolates are shorter than the average Ni-Se bond length in the tetrahedral complex [Ni(SePh)4]2-.