Coordination chemistry of N-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(hydro xymethyl)-2,3-dimercaptobenzene (H-4-3) were synthesized from 2,3-dimercapt obenzoic acid or 2,3-dimercaptoterephthalic acid. The air-sensitive Ligands form metallocene complexes of the type [(eta(5)-C5H5)(2)Ti(1)] (13), [(eta (5)-C5H5)(2)Mo(1)] (15), [(eta(5)-C5H5)(2)Ti(3)] (16), and [(eta(5)-C5H5)(2 )Ti(2)] (17). Complexes 15 and 16 were characterized by X-ray diffraction. Selected crystallographic details for 15 are as follows: formula C21H23MoNO S2; M = 465.49; Pbca; a = 12.536(3), b = 14.313(3), c = 22.463(3) Angstrom; V = 4031(2) Angstrom(3); Z = X; R = 3.56 and R-w = 4.49 for 2111 structure factors (F-o(2) greater than or equal to 3 sigma(F-o(2))) and 254 refined parameters. The molybdenum complex 15 shows an almost planar Mo(mu-S)(2)C-2 chelate ring. Selected crystallographic details for 16 are as follows: for mula C18H18O2S2Ti; M = 378.35; <P(1)over bar>; a = 10.1778(11), b = 11.5806 (14), c = 22.967(3) Angstrom; alpha = 96.42(1), beta = 101.74(1), gamma = 1 08.82(1)degrees; V = 2462.3(5) Angstrom(3); Z = 6; R = 4.79 and R-w = 13.27 for 5426 structure factors (I greater than or equal to 2 sigma(I)) and 766 refined parameters. All titanocene derivatives assume the envelope conform ation. The free activation energy for the flip around the S-S axis was dete rmined for 13 to be 69 kJ/mol. The bis(dithiolate) ligand 1,4-bis[(2,3-dime rcaptobenzamido)methyl]benzene (H-4-4) was prepared from 2,3-dimercaptobenz oic acid and converted into the dinuclear air-stable titanocene complex [{( eta(5)-C5H5)(2)Ti}(2)(4)] (19). Complex 19 reacts with HCl/CHCl3 with liber ation of free H-4-4 while reaction with NMe4Cl results in an intramolecular dithiolate shift under formal liberation of [(C5H5)(3)TiCl] and formation of the square-pyramidal chelate complex (NMe4)[(eta(S)-C5H5)Ti(4)], (NMe4)[ 20]. Crystallographic details for (NMe4)[20]. CH2Cl2 are as follows: formul a C32H35Cl2N3O2S4Ti; M = 740.67; <P(1)over bar>; a = 11.579(4), b = 12.210( 4), c = 14.016(4) Angstrom; alpha = 112.28(2), beta = 94.46(3), gamma = 104 .22(3)degrees; V = 1744.9(10) Angstrom(3); Z = 2; R = 5.35 and R-w = 12.84 for 2870 structure factors (I greater than or equal to 2 sigma(I)) and 397 refined parameters. The chelate rings in [20](-) assume an endo/exo conform ation.