Coordination Chemistry ofN-Alkylbenzamide-2,3-dithiolates as an Approach to Poly(dithiolate) Ligands:  1,4-Bis[(2,3-dimercaptobenzamido)methyl]benzene and Its Chelate Complex with the (C₅H₅)Ti Fragment

The bidentate dithiolate ligands N,N-diethyl-2,3-dimercaptobenzamide (H(2)-1), bis(N,N-diethyl-2,3-dimercaptoterephthalamide (H(2)-2), and 1,4-bis(hydroxymethyl)-2,3-dimercaptobenzene (H(4)-3) were synthesized from 2,3-dimercaptobenzoic acid or 2,3-dimercaptoterephthalic acid. The air-sensitive ligands form metallocene complexes of the type [(eta(5)-C(5)H(5))(2)Ti(1)] (13), [(eta(5)-C(5)H(5))(2)Mo(1)] (15), [(eta(5)-C(5)H(5))(2)Ti(3)] (16), and [(eta(5)-C(5)H(5))(2)Ti(2)] (17). Complexes 15 and 16 were characterized by X-ray diffraction. Selected crystallographic details for 15 are as follows: formula C(21)H(23)MoNOS(2); M = 465.49; Pbca; a = 12.536(3), b = 14.313(3), c = 22.463(3) Å; V = 4031(2) Å(3); Z = 8; R = 3.56 and R(w) = 4.49 for 2111 structure factors (F(o)(2) >/= 3sigma(F(o)(2))) and 254 refined parameters. The molybdenum complex 15 shows an almost planar Mo(-S)(2)C(2) chelate ring. Selected crystallographic details for 16 are as follows: formula C(18)H(18)O(2)S(2)Ti; M = 378.35; P; a = 10.1778(11), b = 11.5806(14), c = 22.967(3) Å; alpha = 96.42(1), beta = 101.74(1), gamma = 108.82(1) degrees; V = 2462.3(5) Å(3); Z = 6; R = 4.79 and R(w) = 13.27 for 5426 structure factors (I >/= 2sigma(I)) and 766 refined parameters. All titanocene derivatives assume the envelope conformation. The free activation energy for the flip around the S-S axis was determined for 13 to be 69 kJ/mol. The bis(dithiolate) ligand 1,4-bis[(2,3-dimercaptobenzamido)methyl]benzene (H(4)-4) was prepared from 2,3-dimercaptobenzoic acid and converted into the dinuclear air-stable titanocene complex [{(eta(5)-C(5)H(5))(2)Ti}(2)(4)] (19). Complex 19 reacts with HCl/CHCl(3) with liberation of free H(4)-4 while reaction with NMe(4)Cl results in an intramolecular dithiolate shift under formal liberation of [(C(5)H(5))(3)TiCl] and formation of the square-pyramidal chelate complex (NMe(4))[(eta(5)-C(5)H(5))Ti(4)], (NMe(4))[20]. Crystallographic details for (NMe(4))[20].CH(2)Cl(2) are as follows: formula C(32)H(35)Cl(2)N(3)O(2)S(4)Ti; M = 740.67; P; a = 11.579(4), b = 12.210(4), c = 14.016(4) Å; alpha = 112.28(2), beta = 94.46(3), gamma = 104.22(3) degrees; V = 1744.9(10) Å(3); Z = 2; R = 5.35 and R(w) = 12.84 for 2870 structure factors (I >/= 2sigma(I)) and 397 refined parameters. The chelate rings in [20](-) assume an endo/exo conformation.