Synthesis and structural characterization of new organo-diimido and organo-imido niobium and titanium complexes

Abstract

The organo-diimido complexes [{Nb(L₂)Cl₃}₂(μ-1,4-NC₆H₄N)], L = CH₃CN 1a or 4-^tBupy 2a, [{Nb(L₂)Cl₃}₂(μ-1,3-NC₆H₄N)], L = CH₃CN 1b or 4-^tBupy 2b, and [{Nb(L₂)Cl₃}₂(μ-1,2-NC₆H₄N)], L = CH₃CN 1c or 4-^tBupy 2c were isolated by treating NbCl₅ in the presence of CH₃CN or 4-^tBupy with the appropriate amount of the corresponding aniline N,N,N′,N′-tetrakis(trimethylsilyl)-1,4-, -1,3-, or -1,2-phenylenediamine, respectively. Compound 1a reacts with appropriate alkylating reagents to give the corresponding alkyl complexes, namely [{NbLR₃}₂(μ-1,4-NC₆H₄N)], L = CH₃CN, R = CH₂SiMe₃3a; or CH₂CMe₃3b; L = THF, R = CH₂SiMe₃4a or CH₂CMe₃4b. The crystal structure determination of 3a was carried out. Reaction of [Ti(py)₃Cl₂(N^tBu)] with N,N,N′,N′-tetramethyl-1,4-phenylenediamine, in 2∶1 or 1∶1 stoichiometric ratio, afforded the organo-imido complexes [Ti(py)_nCl₂(1,4-NC₆Me₄NH₂)], n = 3 (5a) or 2 (5b), while analogous reactions with 1,4- or 1,3-phenylenediamine give intractable mixtures of products. Organo-imido and organo-diimido titanium complexes were easily prepared by treating TiCl₄ with the appropriate N,N,N′,N′-tetrakis(trimethylsilyl)phenylenediamines in CH₂Cl₂ in 1∶1 and 2∶1 molar ratios in the presence of 4-tert-butylpyridine or N,N,N′,N′-tetramethylethylenediamine (TMEDA). The compounds prepared in this way are [Ti(4-^tBupy)₂Cl₂{1,4-NC₆H₄N(SiMe₃)₂}] 6a, [Ti(TMEDA)Cl₂{1,4-NC₆H₄N(SiMe₃)₂}] 6b, [Ti(TMEDA)Cl₂{1,3-NC₆H₄N(SiMe₃)₂}] 7b, [{Ti(4-^tBupy)₂Cl₂}₂(μ-1,4-NC₆H₄N)] 8a, [{Ti(TMEDA)Cl₂}₂(μ-1,4-NC₆H₄N)] 8b, [{Ti(4-^tBupy)₂Cl₂}₂(μ-1,3-NC₆H₄N)] 9a and [{Ti(TMEDA)Cl₂}₂(μ-1,3-NC₆H₄N)] 9b. Finally, the same reaction with N,N,N′,N′-tetrakis(trimethylsilyl)-1,2-phenylenediamine, in the presence of 4-^tBupy or TMEDA, gives the diamido complexes [Ti(4-^tBupy)₂Cl₂{1,2-C₆H₄(NH)₂}] 10a and [Ti(TMEDA)Cl₂{1,2-C₆H₄(NH)₂}] 10b. The structures of the different families of complexes were determined by spectroscopic methods.