SYNTHESIS AND STRUCTURE OF TITANIUM TETRATHIOLATE AND TANTALUM PENTATHIOLATE COMPLEXES - METAL SULFUR BONDING IN EARLY TRANSITION METAL COMPOUNDS

摘要

The reaction of TiCl4 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 with a = 11.666(4), b = 19.417(5), c = 8.916(7) Angstrom, alpha = 97.09(2), beta = 110.30(2), gamma = 87.95(3)degrees, V = 1880(3) Angstrom(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) Angstrom. One of the thiolate groups has a very acute M-S-C angle of 86.5(5)degrees. The reaction of TaCl5 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, with a = 11.165(9), b = 11.890(5), c = 18.675(11) Angstrom, alpha = 90.87(4), beta = 101.83(6), gamma = 96.77(5)degrees, V = 2407(5) Angstrom(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) Angstrom and TaS-C-av angle is 116(7)degrees. structural comparisons of 1 and 2 with analogous phenolate complexes reveal large values for Delta[(MS)-(M-O)]. The extent of the S to M pi-bonding in these electron deficient early transition metal thiolates is considerably reduced compared to the O to M pi-bonding in phenolate analogs. The observation of the acute Ti-S-C angles suggests that the limited thiolate metal pi-bonding in 1 can not compensate for the strong electron deficiency of the Ti(IV) center. [References: 76]