Abstract
Reactions of a tungsten trisulfido complex of hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) [Et4N][Tp*WS3] (1) with 3 equiv of CuCl in CHCl3 afforded a tetranuclear anionic cluster [Et4N][Tp*W(μ3-S)3(CuCl)3] (2), while that of 1 with 3 equiv of CuNCS in MeCN produced a decanuclear neutral cluster (major product) [Tp*W(μ3-S)3Cu3(μ-NCS)3(CuMeCN)]2 (3) along with a binuclear anionic cluster (minor product) [Et4N][Tp*WO(μ-S)2(CuNCS)] (4). Solvothermal reactions of 1 with 3 equiv of CuCN in MeCN at 80 °C for 48 h followed by slowly cooling it to ambient temperature gave rise to a polymeric cluster [Tp*W(μ3-S)(μ-S)2Cu2(MeCN)(μ-CN)]n (5). Compounds 2−5 were characterized by elemental analysis, IR, UV−vis, 1H NMR, and single-crystal X-ray crystallography. The cluster anion of 2 has a [Tp*WS3Cu3] incomplete cube with one Cl atom coordinated at each Cu center. 3 is composed of an unprecedented centrosymmetric W2Cu8 cluster core in which each void of the two single incomplete cubane-like [Tp*W(μ3-S)3Cu3(μ-NCS)]+ cations is partially filled with an extra [Cu(MeCN)(μ-NCS)2]- anion via a pair of Cu−μ-NCS−Cu bridges. The cluster anion of 4 contains one WS2Cu core that is formed by an oxidized [Tp*WO(μ-S)2] species and one CuNCS fragment. 5 consists of butterfly shaped [Tp*W(μ3-S)(μ-S)2Cu2(MeCN)] fragments that are interconnected via cyanide bridges to form a 1D spiral chain extending along the c axis. The successful synthesis of 2−5 from 1 suggests that 1 may be an excellent synthon to the W/Cu/S clusters. In addition, the third-order nonlinear optical (NLO) properties of 1−3 in solution were also investigated by femtosecond degenerate four-wave mixing (DFWM) technique with a 80 fs pulse width at 800 nm. Although 2 was not detected to have NLO effects, 1 and 3 exhibited relatively good optical nonlinearities with the nonlinear refractive index n2 and the third-order nonlinear optical susceptibility χ(3) values being 0.79 × 10-13 and 0.38 × 10-14 esu (1) and 2.08 × 10-13 and 1.00 × 10-14 esu (3), respectively. The second-order hyperpolarizability γ value for 3 (5.46 × 10-32 esu) is ca. 5 times larger than that of its precursor 1.