Discrete Mononuclear and Dinuclear Nickel(II) Complexes of Alkane- and Areneselenolates: Syntheses, Structures, and Properties of (Et4N)2[Ni2(Se(CH2)3Se)3], (Ph4P)2[Ni(SePh)4], and (Ph4P)2[Ni2(μ-2,4,6-(Me)3C6H2Se)2(2,4,6-(Me)3C6H2Se)4]·8CH3CN

Reaction of the alkanediselenolate (Et 4 N) 2 (Se(CH 2 ) 3 Se) with NiCl 2 ·6H 2 O in ethanol/acetonitrile mixture affords the dimeric complex (Et 4 N) 2 [Ni 2 (Se(CH 2 ) 3 Se) 3 ] ( 1 ), in which the coordination geometry around each Ni(II) center is square planar. In contrast, reaction of the areneselenolate PhSe - with NiCl 2 ·6H 2 O in acetonitrile gives rise to (Ph 4 P) 2 [Ni(SePh) 4 ] ( 2 ), which comprises a distorted tetrahedral NiSe 4 chromophore. When the bulky areneselenolate 2,4,6-(Me) 3 C 6 H 2 Se - is used, the same reaction affords the dimeric complex (Ph 4 P) 2 [Ni 2 (μ-2,4,6-(Me) 3 C 6 H 2 Se) 2 (2,4,6-(Me) 3 C 6 H 2 Se) 4 ]·8CH 3 CN ( 3 ), which contains square planar NiSe 4 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 Pna 2 1 with a = 16.645(3) Å, b = 20.214(6) Å, c = 11.428(3) Å, V = 3846(3) Å 3, 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 Pca 2 1 with a = 17.617(7) Å, b = 13.758(5) Å, c = 24.776(11) Å, V = 6005(4) Å 3, 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 P 1̄ 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) Å 3, 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 - .