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

Abstract

1,3,4,5-Tetramethylimidazol-2-ylidene (L(Me)) and 1,3-diisopropyl-4,5-dimethylimidazol-2-ylidene (L(iPr )) readily form complexes of trans-TiF4(L(Me))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(L(Me))(NEt 2)}2(mu-F)2] (2) and (TiF4(L(Me))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 L(Me) 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(L(Me)). 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 L(Me), 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. L(Me) and L(iPr ) are more basic than the mentioned molecular donors and more basic than chloride, however less basic than fluoride.

Synthesis and Characterization of N‐heterocyclic Carbene Complexes of Titanium(IV) and Titanium(III)

“…The solvents (THF, toluene, and n ‐hexane) were purified with the M‐Braun solvent drying system. IPr 16, Ti(NMe 2 ) 2 Cl 2 8, and TiCl 3 (thf) 3 17 were synthesized according to the published procedures. Other chemicals were of analytical grade and were used as received.…”

Medium and high oxidation state metal/non-metal fluoride and oxide–fluoride complexes with neutral donor ligands

“…, probably formed by trace hydrolysis, with the novel cations stabilised by the large fluorotitanate(IV) anion. 39 39 Using the criteria described above 60 places alkyl phosphines as donors towards TiF 4 somewhere near to OPR 3 , showing the effects of the hard/soft mismatch in these systems À towards softer transition metal centres, alkyl phosphines are extremely strong donors. 3 The only established complex derived from TiF 3 , seems to be the green [NMe 4 ][Ti III F 2 (H 2 O) 4 ][Ti IV F 6 ] obtained from TiCl 3 and [NMe 4 ]F in aqueous ethanol, the structure showing a trans octahedral [TiF 2 (H 2 O) 4 ] + cation.…”

Taking TiF4 complexes to extremes - the first examples with phosphine co-ligands

“…[5][6][7][8][9] . The latter include cis-[TiF 4 (Ph 3 PO) 2 ], 10 cis-[TiF 4 (dmso) 2 ], 11 [{TiF 4 } 2 (18crown-6)], 12 [{TiF 4 (PhCN)} 3 ], 13 [TiF 4 (MeCN) 2 ], 13 a series of Nheterocyclic carbene (NHC) adducts, 14 and a range of cationic species [TiF 3 (MeCN) 3 ] + and [TiF 2 (crown)] 2+ (crown = 15-crown-5 or 18-crown-6), obtained using SbF 5 for fluoride abstraction. 15 Organotitanium fluorides have attracted much interest in their own right and as catalyst precursors for olefin polymerisation and enantioselective synthesis.…”