Trimetallic Chalcogenide Species: Synthesis, Structures, and Bonding

In an attempt to isolate boron-containing tri-niobium polychalcogenide species, we have carried out prolonged thermolysis reactions of [Cp*NbCl4] (Cp* = eta(5)-C5Me5) with four equivalents of Li[BH2E3] (E = Se or S). In the case of the heavier chalcogen (Se), the reaction led to the isolation of the tri-niobium cubane-like cluster [(NbCp*)(3)(mu(3)-Se)(3)(BH)(mu-Se)(3)] (1) and the homocubane-like cluster [(NbCp*)(3)(mu(3)-Se)(3)(mu-Se)(3)(BH)(mu-Se)] (2). Interestingly, the tri-niobium framework of 1 stabilizes a selenaborate {Se3BH}(-) ligand. A selenium atom is further introduced between boron and one of the selenium atoms of 1 to yield cluster 2. On the other hand, the reaction with the sulfur-containing borate adduct [LiBH2S3] afforded the trimetallic clusters [(NbCp*)(3)(mu-S)(4){mu-S-2(BH)}] (3) and [(NbCp*)(3)(mu-S)(4){mu-S-2(S)}] (4). Both clusters 3 and 4 have an Nb3S6 core, which further stabilizes {BH} and mono-sulfur units, respectively, through bi-chalcogen coordination. All of these species were characterized by B-11{H-1}, H-1, and C-13{H-1} NMR spectroscopy, mass spectrometry, infrared (IR) spectroscopy, and single-crystal X-ray crystallography. Moreover, theoretical investigations revealed that the triangular Nb-3 framework is aromatic in nature and plays a vital role in the stabilization of the borate, borane, and chalcogen units.

Automated summary

Through thermolysis reactions, boron-containing tri-niobium polychalcogenide species were successfully isolated and characterized using various methods. The study revealed the significant role of the tri-niobium framework in stabilizing borate, borane, and chalcogen units.