Successive Protonation and Methylation of Bridging Imido and Nitrido Ligands at Titanium Complexes.

The reactions of nitrido complexes [{Ti(η-CMe)(μ-NH)}(μ-N)] () and [{Ti(η-CMe)}(μ-N)] () with electrophilic reagents ROTf (R = H, Me; OTf = OSOCF) in different molar ratios have allowed the structural characterization of a series of titanium intermediates en route to the formation of the ammonium salts [NR]OTf and [NR][Ti(η-CMe)(OTf)]. The treatment of the trinuclear imido-nitrido complex with 5.5 equiv of triflic acid in toluene at room temperature led to the dinuclear complex [Ti(η-CMe)(μ-N)(NH)(μ-OSOCF)(OTf)] () and [NH]OTf. Compound , along with the ammonium salts [NMe]OTf and [NMe][Ti(η-CMe)(OTf)] (), was also obtained in the reaction of with 8 equiv of methyl triflate in toluene at 100 °C. The trinuclear complex [Ti(η-CMe)(μ-N)(μ-NH)(μ-OSOCF)(OTf)] (), an intermediate in the formation of , was isolated in the treatment of with 4 equiv of MeOTf, although compound was prepared in better yield by treatment of with MeSiOTf (2 equiv). Addition of a large excess of MeOTf or HOTf reagents to solutions of resulted in the clean formation of ammonium salts [NR][Ti(η-CMe)(OTf)] (R = Me (), H ()). Treatment of the tetranuclear nitrido complex [{Ti(η-CMe)}(μ-N)] () with 1 equiv of ROTf in toluene afforded the precipitation of the ionic compounds [{Ti(η-CMe)}(μ-N)(μ-NR)][OTf] (R = H (), Me ()), while a large excess of HOTf led to the formation of [{Ti(η-CMe)}(μ-N)(μ-NH)][Ti(η-CMe)(OTf)(NH)] () by rupture of a fraction of tetranuclear molecules. Complex reacted with 1 equiv of [M(η-CH)(CO)H] (M = Mo, Cr) via hydrogenation of one nitrido ligand to give the molecular derivative [{Ti(η-CMe)}(μ-N)(μ-NH)] () and [{M(η-CH)(CO)}], while a second 1 equiv of [M(η-CH)(CO)H] produced the ionic compounds [{Ti(η-CMe)}(μ-N)(μ-NH)][M(η-CH)(CO)] (M = Mo (), Cr ()) by protonation of another nitrido group. The X-ray crystal structures of -, , , and were determined.