Synthesis and structure of titanium tetrathiolate and tantalum pentathiolate complexes. Metal-sulfur bonding in early transition metal compounds☆

Abstract The reaction of TiCl 4 with potassium 2,3,5,6-tetramethylbenzenethiolate (KS-2,3,5,6-Me 4 C 6 H) in THF gives [Ti(S-2,3,5,6-Me 4 C 6 H) 4 ] ( 1 ) in 50% yield. Compound 1 crystallizes in the triclinic space group P 1 with a = 11.666(4), b = 19.417(5), c = 8.916(7)A, α = 97.09(2), β = 110.30(2), γ = 87.95(3)°, V =1880(3), A 3 , Z = 2. The monomeric [Ti(S-2,3,5,6-Me 4 C 6 H) 4 ] has a distorted tetrahedral structure with TiS bonds of 2.292(6) A. One of the thiolate groups has a very acute MSC angle of 86.5(5)°. The reaction of TaCl 5 with excess (LiS-2,3,5,6-Me 4 C 6 H) in hexane gives [Ta(S-2,3,5,6-Me 4 C 6 H) 5 ] ( 2 ). Compound 2 crystallizes in the triclinic space group, P 1 with a = 11.165(9), b = 18.675(11) A, α = 90.87(4), β = 101.83(6), γ = 96.77(5)°, V = 2407(5) A 3 with Z = 2. [Ta(S-2,3,5,6-Me 4 C 6 H) 5 ) is a monomeric compound with a distorted five-coordinate geometry. The average TaS bond distance is 2.37(3) A and TaSC av angle is 116(7)°. Structural comparisons of 1 and 2 with analogous phenolate complexes reveal large values for Δ[(MS)−(MO)]. The extent of the S to M gp -bonding in these electron deficient early transition metal thiolates is considerably reduced compared to the O to M π -bonding in phenolate analogs. The observation of the acute TiSC angles suggests that the limited thiolate metal π -bonding in 1 can not compensate for the strong electron deficiency of the Ti(IV) center.