Metal Coordinated Tri- and Tetraborane Analogues

A series of triborane and tetraborane analogues have been isolated and structurally characterized utilizing chalcogenatoborate ligancis Li[BH3(EPh)] (E = S or Se). Thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] afforded bimetallic tantallaheteroborane [(Cp*Ta)(2)(mu-eta(3):eta(3)-B2H4S)(mu-eta(2):eta(2)-SBH3)] (1) and hexasulfido trimetallic complex [(Cp*Ta)(2)(mu-S)(4)(mu-SPh)(2)] (2). Compound 1 is a fused ditantallaheteroborane, in which both di- and triborane analogues are stabilized by two tantalum atoms. In an attempt to synthesize the selenium analogues of 1 and 2, room-temperature reaction of [Cp*TaCl4] with Li[BH3(SePh)] was carried out, which afforded bimetallic tantallaheteroborane [(Cp*Ta)(2){mu-eta(3):eta(3)-B3H6(SePh)}{mu-SePh}(2)] (3), monometallic tantal- laheteroboranes [Cp*Ta(SePh)(2){B4H8-n(SePh)(2)}] (4: n = 0, 5: n = 1), and trimetallic species [(Cp*Ta)(3)(mu-Se)(4){mu-Se-2(Se)}] (6). Compound 3 is the rarest example of triborane analogue {B3H6(SePh)} in the coordination sphere of two tantalum atoms. Whereas compounds 4 and 5 are examples of unsaturated metallaheteroboranes, in which the tetraborane analogues are stabilized in the coordination sphere of tantalum. One of the unique features of 3 and 5 is the presence of terminal B-SePh. Compound 6 has similar Ta3Se6 trisbutterfly core as that of 2 with additional bridging selenide unit. All the compounds have been characterized by NMR spectroscopy, mass spectrometry, IR spectroscopy and single-crystal X-ray diffraction studies.

Automated summary

A series of triborane and tetraborane analogues have been successfully synthesized and structurally characterized using chalcogenatoborate ligands with sulfur and selenium. Some of these compounds exhibit rare structural features, such as bimetallic and trimetallic tantalum heteroborane structures.