Reaction of Cp(2)TiCl(2) with donor ligands such as imidazole or PMe(3) proceeds to a relatively small extent to induce reduction of Ti(IV)yielding the Ti(III) species Cp(2)TiCI(L) (3) with concurrent loss of a chlorine radical. Subsequent reaction of 3 with 1 equiv of 1,3-propanedithiol gives [Cp(2)TiCl]2(SCH2CH2CH2S) (4). In the presence of excess dithiol the known species [Cp(2)Ti(SCH2CH2CH2S)](2) (1a) is formed. Related reactions of CpTiCl(3) have been studied. Reaction of CpTiCl(3) with PMe(3) or PHEt(2) yields the Ti(IV) adducts CpTiCl(3)(L) (L = PMe(3) (5a), PHEt(2) (5b)). The complex 5a crystallizes in the space group P2(1)/n with a = 8.777(9) Angstrom, b = 13.033(3) Angstrom, c = 11.350(4) Angstrom, beta = 98.14(7)degrees, V = 1285(3) Angstrom(3), and Z = 4. The complex 5b crystallizes in the space group P2(1)/n with a = 7.502(3) Angstrom, b = 16.723(6) Angstrom, c 10.961(2) Angstrom, beta = 92.55(2)degrees, V = 1374(1) Angstrom(3), and Z = 4. Also generated in these reactions are small quantities of the reduced species CpTiCl(2)(L)(2) (L = PMe(3) (7a), PHEt(2) (7b)), which were characterized by EPR spectroscopy. In similar reactions the reduced species CpTiCl(2)(L)(2) (L = imidazole (7c), methylimidazole (7d) are isolated. The compound 7d crystallizes in the space group C2(1)/c with a = 12.715(5) Angstrom, b = 9.594(2) Angstrom, c = 14.428(4) Angstrom, beta = 115.00(2)degrees, V = 1595(2) Angstrom(3), and Z = 4. Reaction of 7d with 1,2-ethanedithiol give the species [CpTiCl(SCH2CH2S)](2) (8), which crystallizes in the space group P2(1)/a with a = 12.991(7) Angstrom, b = 8.582(3) Angstrom, c = 17.681(7) Angstrom, beta = 105.75(4)degrees, V = 1898(3) Angstrom(3), and Z = 4. Similarly, reaction of 7d with 1,3-propanedithiol gives the known species CpTiCl(SCH2CH2CH2S) (9). Reaction of 8 with a donor (imidazole or PMe(3)) and (PhS)(2) gives the product [CpTi(SCH2CH2S)(SPh)](2) (10). This complex crystallizes in the space group P (l) over bar with a = 9.459(4) Angstrom, b = 10.931(3) Angstrom, c = 9.258(3) Angstrom, alpha = 106.12(2)degrees, beta = 114.50(3)degrees, gamma = 95.01(3)degrees, V = 814.1(5) Angstrom(3), and Z = 1. In a similar reaction, 9 reacts with PMe(3) to generate the Ti(III) species CpTi(SCH2CH2CH2S)(PMe(3))(2) (11), which undergoes subsequent reaction with (PhS)(2) to give the known product CpTi-(SCH2CH2CH2S)(SPh) (12). The reactivity, structural, and electrochemical data presented herein suggest that a radical mechanism is operative in the formation of 1, 4, 8-10, and 12. Such a mechanistic proposal does offer an explanation for the previously observed "base dependence" of thiolate substitution reactions at Ti(IV).