TERMINAL AND BRIDGING IMIDO COMPLEXES FROM TITANIUM TETRACHLORIDE ANDPRIMARY 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 com plex [TiCl2(NtBu)(NH(2)tBu)(2)](3) in 90% yield. Treatment of [TiCl2(N tBu)(NH(2)tBu)(2)](3) with tert-butylamine in chloroform or dichlorome thane affords [TiCl2(NtBu)(NH(2)tBu)(3)] in 87% yield as orange crysta ls. Solid [TiCl2(NtBu)(NH(2)tBu)(3)] evolves tert-butylamine upon stan ding 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 mixtur e of compounds. Sublimation of [TiCl2(NtBu)(NH(2)tBu)(3)] or [TiCl2(Nt Bu)(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 du ring the sublimation process. Other primary alkyl- and arylamines reac t with titanium tetrachloride in dichloromethane to afford complexes o f 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), t etramethylethylenediamine (TMEDA, 1 equiv per titanium), or N,N'-diiso propylethylenediamine (DIPEDA, 1 equiv per titanium) affords monomeric imido complexes of the formula [TiCl2(NtBu)L(2)] in 42-65% yields. Th ese complexes contain very short titanium-nitrogen triple bonds and po ssess essentially linear imido linkages. [TiCl2(NtBu)(TMEDA)] crystall izes 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).2.4tB uNH(2), [TiCl2(NnBu)(NH(2)nBu)(2)], and [TiCl2(NtBu)(TMEDA)] were stud ied in order to understand the types of gas phase species that might b e present during the chemical vapor deposition of titanium nitride fil ms from these precursors. In general, ions and fragments derived from [TiCl2(NtBu)](3), [TiCl2(NtBu)](2), [TiCl3(NHR)], and [TiCl2(NtBu)] we re observed. These results imply that monomeric and dimeric imido comp lexes are significant gas phase species derived from the above precurs ors, and such imido complexes are probably important intermediates in the deposition of titanium nitride films.