Synthesis of mono- and bi-metallic dithiocarboxylate-alkyne complexes from sunlight driven insertion reaction and their antibacterial activity

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

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-κ²S:κ²S',S″}{μ-SC(H)S-κ²C:κ²S‴,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-κ²S,S')(μ,η²:η²-BH₃S)] (2) and [(Cp*Ta)₂(μ-O)(μ-SCH₂S-κ²S,S')(μ-H){μ-S₂C(H)SCH₂S-κ²S″:κ²S‴,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-κ²S″:κ²S‴,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)-κ²B:κ²S:κ⁴S',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.