The oxidation of [(Me3tacn)TiIIIBr3] (where Me3tacn is 1,4,7-trimethyl-1,4,7-triazacyclononane) in water with Na2[S2O8] yields upon addition of NaClO4 yellow-orange [(Me3tacn)TiIVBr3]ClO4 (1). The series [(Me3tacn)TiIVBrx(OCH3)(3-x)]+ (x = 2 (2); x = 1 (3); x = 0 (4)) has been synthesized by oxidation reactions of [(Me3tacn)TiBr3] with air in acetonitrile/methanol mixtures and methanol as solvents. Complexes 1, [(Me3tacn)-TiBr(OCH3)2](ClO4) (3), and [(Me3tacn)Ti(OCH3)3]BPh4 (4) have been structurally characterized by X-ray crystallography. Crystal data : for 1, monoclinic P2(1)/n, a = 11.146(6) angstrom, b = 12.640(5) angstrom, c = 12.871(5) angstrom, beta = 91.19(4)degrees, V = 1812.9 (14) angstrom3, Z = 4; for 3, monoclinic P2(1)/c; a = 11.837 (3) angstrom, b = 12.63 5 (3) angstrom, c = 13.044(2) angstrom, beta = 92.34(2)degrees, V = 1949.2(9) angstrom3, Z = 4; for 4, monoclinic P2(1)/n, a = 10.394(2) angstrom, b = 21.483(4) angstrom, c = 15.741(3) angstrom, beta = 90.30(3)degrees, V = 3514.8(12) angstrom3, Z = 4. Two orange-red peroxotitanium(IV) complexes [(Me3tacn)Ti(O2)(NCO)2] (5) and [(Me3tacn)Ti(O2)Cl2] (6) have been isolated from acetonitrile solutions of [(Me3tacn) 2Ti2III(NCO)4(mu-O)] and [(Me3tacn)TiCl3] Which had been exposed to air and H2O2, respectively. Crystal data for 5 : monoclinic P2(1)/n, a = 8.602(3) angstrom, b = 12.478(5), c = 14.671(4) angstrom, beta = 91.18(3)degrees, V = 1574.4(12) angstrom3, Z = 4. Complexes 5 and 6 contain an eta2-O2(2-) ligand. Three new octahedral titanyl complexes, [(Me3tacn)-Ti(O)Cl2] (7), [(tiptacn)Ti(O)(NCS)2] (8), and [(tiptacn)Ti(O)(NCO)2] (9), were obtained from acetonitrile solutions of [(Me3tacn)TiCl3], [(tiptacn)Ti(NCS)3], and [(tiptacn)Ti(NCO)2(OCH3)] by interaction with oxygen where tiptacn represents 1,4,7-isopropyl-1,4,7-triazacyclononane. Crystal data for 7 : monoclinic P2(1)/a, a = 12.815-(3) angstrom, b = 7.829(2) angstrom, c = 15,146(6) angstrom, beta = 114.67(3)degrees, V = 1380.9(10) angstrom3, Z = 4. The Ti=O distance was found to be 1.637(3) angstrom. All new compounds have been studied by infrared and Raman spectroscopy in solution and in the solid state.