Fine tuning of reactivity and structure of bis(σ)borate and borate complexes of manganese by systematic ligand variation

C. Nandi (1) , K. Saha (1) , S. Gomosta (1) , V. Dorcet (2) , S. Ghosh (1)

1 IIT Madras - Indian Institute of Technology Madras
2 ISCR - Institut des Sciences Chimiques de Rennes

The complexes with fac-[M(CO)3]+ units of group-7 metals are interesting synthons for the development of target-specific drugs. Therefore, thermolysis reaction of Re2(CO)10 with various borate ligands have been investigated as a possible route to isolate bis(σ)borate complexes of rhenium. The reaction of trihydrobis(benzothiazol-2-yl)amideborate, Na[(H3B)bbza](bbza = bis(benzothiazol-2-yl)amine)with Re2(CO)10 led to the formation of distorted octahedral rhenium complexes [(CO)2Re{N(C7H4NS)2}2], 1 and [(CO)2Re{N(C7H4NS)2}{C6H4N(Me)O}], 2. In order to increase the library of complexes containing fac-{M(CO)3}+ moieties as well as to check the lability of the metal–carbonyl bond, reactivity of manganese borate complexes [Mn(CO)3(μ-H)2BHNCSC6H4(NR)], 3 (R = NCSC6H4)and [Mn(CO)3{κ3-S,S′,H-H2B(mbz)2}], 6 (mbz = 2-mercapto-benzothiazolyl)with different ligands were carried out. Photolysis of 3 with excess phosphine ligands (PPh2Me or PMe2Ph)yielded manganese phosphine complexes [Mn(CO)2(PL2L′)2{N(C7H4NS)2}], (4a L = Ph, L′ = Me; 4b L = Me, L′ = Ph). Interestingly, the reaction of 3 with tBuNC yielded mono/bis(tBuNC)-substituted manganese borate complexes [Mn(μ-H)2(BHNCSC6H4)(NR)(CO)xLy], 5a–b (5a x = 2, y = 1; 5b x = 1; y = 2; L = tBuNC; R = NCSC6H4)and [Mn(μ-H)2BH{N(NCSC6H4)2}(CO)(tBuNC)2], 5c. Compounds 5b and 5c are structural isomers with a different coordination mode of the bbza ligand. Under similar reaction conditions, photolysis of 6 with PPh3 in toluene generated borate complex of manganese [Mn(CO2){κ3-S,S′,H-H2B(mbz)2}(PPh3)], 7. All the compounds were characterised by multi-nuclear NMR, IR spectroscopy and mass spectrometry. Density functional theory (DFT)calculations were carried out to investigate the bonding and electronic structures of these compounds.

Keywords: Phosphine; Manganese; Rhenium; tBuNC; Bis(σ)borate

Domains: Chemical Sciences; Coordination chemistry

C. Nandi, K. Saha, S. Gomosta, V. Dorcet, S. Ghosh. Fine tuning of reactivity and structure of bis(σ)borate and borate complexes of manganese by systematic ligand variation. Polyhedron, 2019, 172, pp.191-197. ⟨10.1016/j.poly.2019.04.041⟩. ⟨hal-02161850⟩