TERMINAL AND BRIDGING IMIDO COMPLEXES FROM TITANIUM TETRACHLORIDE AND PRIMARY AMINES - IMPLICATIONS FOR THE CHEMICAL-VAPOR-DEPOSITION OF TITANIUM NITRIDE FILMS

Reaction of titanium tetrachloride with tert-butylamine (greater than or equal to 5 equiv) in dichloromethane affords the trimeric imido complex [TiCl2(NtBu)(NH(2)tBu)(2)](3) in 90% yield. Treatment of [TiCl2(NtBu)(NH(2)tBu)(2)](3) with tert-butylamine in chloroform or dichloromethane affords [TiCl2(NtBu)(NH(2)tBu)(3)] in 87% yield as orange crystals. Solid [TiCl2(NtBu)(NH(2)tBu)(3)] evolves tert-butylamine upon standing at 23 degrees C for 12-24 h to reform [TiCl2(NtBu)(NH(2)tBU)(2)](3). In solution, [TiCl2(NtBu)(NH(2)tBu)(3)] exists as a complex mixture of compounds. Sublimation of [TiCl2(NtBu)(NH(2)tBu)(3)] or [TiCl2(NtBu)(NH(2)tBu)(2)](3) affords the hexameric imido complex {[TiCl2(NtBu)](3)}(2).2.4tBuNH(2), in which most of the tert-butylamine was lost during the sublimation process. Other primary alkyl- and arylamines react with titanium tetrachloride in dichloromethane to afford complexes of the general formula [TiCl2(NR)(NH(2)R)(2)]. Treatment of [TiCl2(NtBu)(NH(2)tBu)(3)], [TiCl2(NtBu)(NH(2)tBu)(2)](3), or {[TiCl2(NtBu)](3)}(2).2.4tBuNH(2) with triphenylphosphine oxide (2 equiv per titanium), tetramethylethylenediamine (TMEDA, 1 equiv per titanium), or N,N'-diisopropylethylenediamine (DIPEDA, 1 equiv per titanium) affords monomeric imido complexes of the formula [TiCl2(NtBu)L(2)] in 42-65% yields. These complexes contain very short titanium-nitrogen triple bonds and possess essentially linear imido linkages. [TiCl2(NtBu)(TMEDA)] crystallizes in the space group P2(1)/n with a = 16.355(9) Angstrom, b = 8.794(3) Angstrom, c = 23.052(6) Angstrom, beta = 92.97(4)degrees, V = 3311(2) Angstrom(3), and Z = 4. [TiCl2(NtBu)(DIPEDA)] crystallizes in the space group P2(1)/c with cell dimensions a = 8.113(2) Angstrom, b = 12.049(3) Angstrom, c = 18.598(5) Angstrom, beta = 99.48(2)degrees, V = 1793.2(8) Angstrom(3), and Z = 4. The mass spectra of [TiCl2(NtBu)(NH(2)tBu)(3)], [TiCl2(NtBu)(NH(2)tBu)(2)](3), {[TiCl2(NtBU)](3)}(2).2.4tBuNH(2), [TiCl2(NnBu)(NH(2)nBu)(2)], and [TiCl2(NtBu)(TMEDA)] were studied in order to understand the types of gas phase species that might be present during the chemical vapor deposition of titanium nitride films from these precursors. In general, ions and fragments derived from [TiCl2(NtBu)](3), [TiCl2(NtBu)](2), [TiCl3(NHR)], and [TiCl2(NtBu)] were observed. These results imply that monomeric and dimeric imido complexes are significant gas phase species derived from the above precursors, and such imido complexes are probably important intermediates in the deposition of titanium nitride films.