Synthesis and imido-group exchange reactions of tert-butylimidotitanium complexes

Titanium Imido Complexes of Cyclooctatetraenyl Ligands

“…This is probably the result of the electron-withdrawing nature of aryl groups, compared to the inductively electron-donating alkyl group, and is well precedented. [26] Presumably, this causes a difference in the availability of the N imido lone pair for donation to the metal.…”

“…[30] Results and Discussion Synthesis and characterisation of cyclooctatetraenyl titanium imido complexes: Titanium imido dichloride starting materials [Ti(NR)Cl 2 (py) 3 ] (R= tBu, 2,6-Me 2 C 6 H 3 , 2,6-iPr 2 C 6 H 3 and 2-tBuC 6 H 4 ) were prepared according to previously described routes. [21,26] Reaction of these with either K 2 [COT] (COT = C 8 H 8 ) or the more sterically bulky Li 2 -[COT'']·1.8 THF (COT'' = 1,4-bis(trimethylsilyl)-1,3,5,7-cyclooctatetraenyl) gave products that depended critically on the exact nature of both the imido and cyclooctatetraenyl ring substituents. Addition of one equivalent of either K 2 [COT] or Li 2 [COT'']·1.8 THF to [Ti(NtBu)Cl 2 (py) 3 ] in THF at À50 8C gave a dark red solution.…”

“…[6] A general entry point to new titanium imido chemistry is gained by way of the readily prepared synthons [Ti(NR)Cl 2 (py) 3 ] (R= tBu or aryl) and their homologues, from which straightforward metathesis reactions afford a wide range of derivatives. [26] We noticed that although cyclopentadienyl and to a lesser extent arene co-ligands have been widely used in transitionmetal imido chemistry, there has only been one report of imido complexes bearing cyclooctatetraenyl co-ligands, namely the dinuclear m-arylimido derivatives [M 2 (m-N-2,6-iPr 2 C 6 H 3 ) 2 (h 8 -COT) 2 ] (M= Zr, Hf). [27] Therefore, we were interested to see if using the smaller titanium congener would lead to a mononuclear derivative.…”

“…[26,29] This method was problematic because the ligand exchange was slow even at elevated temperatures and it was difficult to remove any trace excess arylamine from the product. However, the ligand-exchange method was successfully utilised to synthesise the ring-unsubstituted phenyl-imido complex [Ti 2 (m-NPh) 2 (COT'') 2 ] (8) [Eq.…”

Imidotitanium Complexes with Heteroallylic Ligands: Synthesis and Solid-State Structure

“…[35] The TiϪNϪC(tBu) angle [31] The tert-butylimido ligand can thus be assumed to act as four-electron donor towards titanium. crystallization from hexane, in which it is less soluble than the titanium complex 4.…”