Abstract
Two isostructural crown-like heteroselenometallic cluster compounds, [Et4N](4)[(mu(5)-WSe4)(CuX)(5)(mu-X)(2)] (X = Cl 1, Br 2), were prepared from the reactions of [Et4N](2)[WSe4] with CuX and [Et4N]X center dot xH(2)O in the presence of 2-picoline and characterized by single-crystal diffraction analysis. The [(mu(5)-WSe4)(Cu-X)(5)(mu-X)(2)](4-)p anions in the cluster compounds consists of five CuX fragments coordinated to the five edges of the tetrahedral [WSe4](2-) moiety along with two bridging halides connected to each of the two pairs of the symmetric copper atoms, exhibiting a novel crown-like core structure. The nonlinear optical absorption and refraction of cluster compound 2 were determined to be alpha(2) = 6.15 x 10(-10) m/W and n (2) = 4.18 x 10(-11) esu, respectively.