Role of Metals and Thiolate Ligands in the Structures and Electronic Properties of Group 5 Bimetallic–Thiolate Complexes

• Published in: Inorganic chemistry Vol. 59; no. 17; pp. 12494 - 12503
• Main Authors: Saha, Koushik, Kaur, Urminder, Raghavendra, Beesam, Ghosh, Sundargopal
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08.09.2020
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.0c01588

Syntheses, structures, and electronic properties of group 5 metal–thiolate complexes that exhibit unusual coordination modes of thiolate ligands have been established. Room-temperature reaction of [Cp*VCl2]3 (Cp* = η5-C5Me5) with Na5[B­(SCH2S)4] led to the formation of [Cp*VO­{(SCH2)2S}] (1). The solid-state X-ray structure of 1 shows the formation of six-membered l,3,5-trithia-2-vanada­cyclo­hexane that adopted a chair conformation. In a similar fashion, reactions of heavier group 5 precursors [Cp*MCl4] (M = Nb or Ta) with Na5[B­(SCH2S)4] yielded bimetallic thiolate complexes [(Cp*M)2(μ-S)­{μ-C­(H)­S3-κ2 S:κ2 S′,S″}­{μ-SC­(H)­S-κ2 C:κ2 S‴,S′′′′}] (3a: M = Nb and 3b: M = Ta). One of the key features of molecules 3a and 3b is the presence of square-pyramidal carbon, which is quite unusual. The reactions also yielded bimetallic methanedithiolate complexes [(Cp*Nb)2(μ-S)­(μ-SCH2S-κ2 S,S′)­(μ,η2:η2-BH3S)] (2) and [(Cp*Ta)2(μ-O)­(μ-SCH2S-κ2 S,S′)­(μ-H)­{μ-S2C­(H)­SCH2S-κ2 S″:κ2 S‴,S′′′′}] (4). Complex 2 contains a methanedithiolate ligand that stabilizes the unsaturated niobaborane species. On the other hand, one ((mercapto­methyl)­thio)­methane­di­thiolate ligand {C2H4S3} is present in 4, which is coordinated to metal centers and exhibits the {μ-κ2 S″:κ2 S‴,S′′′′} bonding mode. Along with the formation of 3b and 4, the reaction of [Cp*TaCl4] with Na5[B­(SCH2S)4] yielded [(Cp*Ta)2(μ-S)­{μ-(SBS)­S­(CH2S)2(BH2S)-κ2 B:κ2 S:κ4 S′,S″,S‴,S′′′′}] (5) containing a trithiaborate unit (BS3). Complex 5 consists of pentacoordinate boron that resides in a square-pyramidal environment. All the complexes have been characterized by multinuclear NMR, UV–vis spectroscopy, mass spectrometry, and single-crystal X-ray diffraction studies.