Preparation of Ti(IV) Fluoride N-Heterocyclic Carbene Complexes

1,3,4,5-Tetramethylimidazol-2-ylidene (LMe) and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (L iPr) readily form complexes of trans-TiF4(LMe)2 (1) and of trans-TiF4(L iPr)2 (4) with TiF4 in THF, respectively. Complex 1 has been used as a precursor for preparing the Ti(IV) fluoride carbene complexes [{TiF2(LMe)(NEt2)}2(μ-F)2] (2) and (TiF4(LMe)2)(NacNacLi) (3) (NacNac = HC(CMeN(2,6-iPr2C6H3))2). Complex 2 was prepared from the reaction of 1−3 equiv of 1 and 1 equiv of Ti(NEt2)4 or by reacting TiF4 with Ti(NEt2)4 and LMe in toluene. Complex 3 has been prepared from 1 and NacNacLi in toluene. Reaction of 1 and AlMe3 in toluene results in ligand transfer and formation of AlMe3(LMe). Complex 4 is unstable in solution at room temperature and degrades with formation of [HL iPr][TiF5(L iPr)] (5). Complexes 1, 2·2CH2Cl2, 4, and 5 were characterized by single crystal X-ray structural analysis, elemental analysis, IR and NMR spectroscopy, and mass spectrometry. The relative basicities of LMe, L iPr, and the donor ligands THF, pyridine, DMSO, and H2O as well as [Cl]− and [F]− toward the Ti(IV) pentafluoride anion were established by NMR and confirmed by density functional theory (DFT) calculations. LMe and L iPr are more basic than the mentioned molecular donors and more basic than chloride, however less basic than fluoride.