Structural and electronic analysis of bimetallic thiolate complexes of group-5 transition metal ions

The chemistry of group-5 transition metals, namely vanadium, niobium, and tantalum supported by thiolate ligand framework, has been described. Special emphasis has been given to the electronic and structural properties of binuclear thiolate complexes of group-5 metals exhibiting interesting coordination modes of the chelating thiolate ligands. The mild thermolysis of [(CH2S2)(4)B]Na-5 with [Cp*VCl2](3) afforded the divanadium trithiocarbonate complex, [(Cp*V)(2)(mu-CS3-kappa S-2,S')(mu-H2CS2-kappa S-2 '',S ''')] (1) along with [{S(CH2S)(2)}VOCp*] (2). The single crystal X-ray structure of 1 illustrates that the trithiocarbonate and methanedithiolate ligands are symmetrically coordinated to two {Cp*V} units. However, reaction of the heavier group-5 metal precursor, [Cp*NbCl4] with [(CH2S2)(4)B]Na-5 at 60 degrees C in toluene produced a bimetallic trithiolate complex [(Cp*Nb)(2)(mu-SCS2-kappa S-1:kappa C-3,S',S '')(mu-S)(2)] (3) along with [(Cp*Nb)(2)(mu,eta(2):eta(2)-SH3B)(mu-S)(mu-H2CS2-kappa S-2,S')]. In a similar manner, [Cp*TaCl4] led to the formation of ditantalum thiolate complexes [(Cp*Ta)(2)(mu-S)(mu-S2CH2CHS2- kappa S-2: kappa S-2',S '')(mu-H)(mu-S2CH2- kappa S-2 ''',S '''')] (4) and [Cl(Cp*Ta)(2)(mu-H)(mu-S2CH2-kappa S-2,S')(mu-S)(mu-S2CH2-kappa S-2 '':kappa S-1 ''')] (5) along with [(Cp*Ta)(2)(mu-S){mu- (BH2S)(CH2S)(2)(BS3)-kappa B-2:kappa S-2:kappa S-4',S '',S ''',S ''''}]. However, the reaction of LiBH(4)middotTHF with [Cp*TaCl4] followed by the thermolysis in the presence of S(2)CmiddotPPh(3) led to the formation of [(Cp*Ta)(2)(mu-S)(mu-S2CH2- kappa S-2,S')(mu-H)(mu-CHS3-kappa S-2 '':kappa S-2 ''',S '''')] (6) along with [(Cp*Ta)(2)(mu-S2CH2-kappa S-2,S')(2)(mu-H)(mu,eta(2):eta(2)-B2H5 )] (I) and [(Cp*Ta)(2)(mu,eta(2):eta(2)-B2H6)(2)] (II). Complex 3 is an example of trithiolate {CS3} stabilized bimetallic niobium complex. The (dimercaptomethyl)-methanedithiolate ligand (C2H3S4) in 4 is coordinated to both the tantalum centres via three sulfur donors and displayed exclusive bonding mode (mu,kappa S-2:kappa S-2',S ''). Complex 5 consists of two methanedithiolate ligands (S2CH2) with different coordination towards the metal centres, whereas methanetrithiolate (HCS3) and methanedithiolate (S2CH2) units are symmetrically coordinated to both the tantalum centres in complex 6 . This study demonstrates that the electronic properties of these complexes vary depending on the metal centres and thiolate ligands. This is reflected in the paramagnetic behaviour of the vanadium complex 1 . In contrast, the niobium and tantalum thiolate complexes 3, 4 , 5 and 6 are diamagnetic. Further, theoretical investigations provided the insights into the electronic structures and bonding of these group-5 metal thiolate complexes. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

This study focuses on the chemistry of group-5 transition metals vanadium, niobium, and tantalum supported by thiolate ligand framework, emphasizing the electronic and structural properties of binuclear thiolate complexes. Different coordination modes of the chelating thiolate ligands were observed in the complexes of each metal, indicating variations in electronic properties. The paramagnetic behavior of the vanadium complex contrasted with the diamagnetic properties of the niobium and tantalum thiolate complexes.