Nitrogen titanium complex having general formula: wherein: - R 1 represents a hydrogen atom; or is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; - R 2, R 3, R 4 and R 5, identical or different, represent a hydrogen atom; or are selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted, nitro groups, hydroxyl groups, amino groups; - Y represents a NH-R 6 group wherein R 6 represents a hydrogen atom, or is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; or a N-R 7 group wherein R 7 is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; - X 1, X 2, X 3 and X 4, identical or different, represent a halogen atom such as chlorine, bromine, iodine, preferably chlorine; or are selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, -OCOR 8 groups or groups - OR 8 wherein R 8 is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15; or one of X 1, X 2 and X 3 is selected from ethers such as diethylether, tetrahydrofuran, dimethoxyethane, preferably is tetrahydrofuran; - n is 1 in the case wherein Y represents a NH-R 6 group wherein R 6 has the same meanings reported above; or is 0 in the case wherein Y represents a N-R 7 group wherein R 7 has the same meanings reported above, or in the case wherein one of X 1, X 2 and X 3 is selected from ethers. - R 1 represents a hydrogen atom; or is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; - R 2, R 3, R 4 and R 5, identical or different, represent a hydrogen atom; or are selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted, nitro groups, hydroxyl groups, amino groups; - Y represents a NH-R 6 group wherein R 6 represents a hydrogen atom, or is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; or a N-R 7 group wherein R 7 is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, optionally halogenated, cycloalkyl groups optionally substituted, aryl groups optionally substituted; - X 1, X 2, X 3 and X 4, identical or different, represent a halogen atom such as chlorine, bromine, iodine, preferably chlorine; or are selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15, -OCOR 8 groups or groups - OR 8 wherein R 8 is selected from linear or branched C 1 -C 20 alkyl groups, preferably C 1 -C 15; or one of X 1, X 2 and X 3 is selected from ethers such as diethylether, tetrahydrofuran, dimethoxyethane, preferably is tetrahydrofuran; - n is 1 in the case wherein Y represents a NH-R 6 group wherein R 6 has the same meanings reported above; or is 0 in the case wherein Y represents a N-R 7 group wherein R 7 has the same meanings reported above, or in the case wherein one of X 1, X 2 and X 3 is selected from ethers.