Metal Coordinated Tri‐ and Tetraborane Analogues

• Published in: European journal of inorganic chemistry 2021-11, Vol.2021 (43), p.4443-4451
• Main Authors: Kar, Sourav, Bairagi, Subhash, Kar, Ketaki, Roisnel, Thierry, Dorcet, Vincent, Ghosh, Sundargopal
• Format: Article
• Language: English
• Subjects: Bimetals; Boranes; Chalcogens; Chemical Sciences; Coordination; Infrared spectroscopy; Inorganic chemistry; Mass spectrometry; Metallaheteroboranes; NMR spectroscopy; Selenium; Structure elucidation; Tantalum; Tantalum compounds
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.202100687

A series of triborane and tetraborane analogues have been isolated and structurally characterized utilizing chalcogenatoborate ligands Li[BH3(EPh)] (E=S or Se). Thermolysis of [Cp*TaCl4] in the presence of Li[BH3(SPh)] afforded bimetallic tantallaheteroborane [(Cp*Ta)2(μ‐η3:η3‐B2H4S)(μ‐η2:η2‐SBH3)] (1) and hexasulfido trimetallic complex [(Cp*Ta)3(μ‐S)4(μ‐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{μ‐η3:η3‐B3H6(SePh)}{μ‐SePh}2] (3), monometallic tantallaheteroboranes [Cp*Ta(SePh)2{B4H8‐n(SePh)n}] (4: n=0, 5: n=1), and trimetallic species [(Cp*Ta)3(μ‐Se)4{μ‐Se2(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. Diborane, triborane analogue, and tetraborane analogue stabilized in the coordination sphere of tantalum atom(s). New early transition metal coordinated triborane and tetraborane analogues have been synthesized utilizing chalcogenatoborate ligands Li[BH3(EPh)] (E=S or Se) and structurally characterized. Also, theoretical calculations have given insight into their bonding and electronic structures.