Coordination complexes of TiX4 (X=F, Cl) with a bulky N-heterocyclic carbene: Syntheses, characterization and molecular structures

Flexible Structural Features of Pentafulvene Titanium Derivatives: Isolation and Characterization of NHC Complexes

“…The chemical shifts of the NHC carbene atoms in 3 are found at higher field ( 13 C{ 1 H} NMR, δ = 3 a : 197.5, 3 b : 190.9, 3 c : 191.8 ppm) compared with 2 ( δ =213.7 ppm). A similar behaviour is found also for titanium NHC adducts (e.g., NHC‐TiCl 4 δ =188.8 or [Cp 2 TiCH 3 (NHC)] + δ =178.2 ppm). For the exocyclic fulvene carbon atoms in 3 ( 13 C{ 1 H} NMR, δ = 3 a : 108.4, 3 b : 116.7, 3 c : 116.2 ppm) a characteristic high field shift is observed compared with the corresponding free pentafulvene ligand ( 13 C{ 1 H} NMR, δ = a : 164.8, b : 151.7, c : 152.2 ppm).…”

“…As imilar behaviour is found also for titanium NHC adducts (e.g.,N HC-TiCl 4 d = 188.8 [9] or [Cp 2 TiCH 3 (NHC)] + d = 178.2 ppm [10] ). For the exocyclic fulvene carbon atoms in 3 Scheme2.Reactionofp entafulvenetitanium complexes 1a-1c with 1,3,4,5-tetramethylimidazole-2-ylidene (2)t oN HC titanium adducts 3a-3c.…”

“…The Ti1ÀC1 bond length (3a:2 .342(2) ) is comparable to the titanium(0)N HC complex of [Ti(h 6 -C 6 H 6 ) 2 ] (2.323(3) ). [17] On the other hand, NHC complexes of titanium in highero xidation states are characterized by shorter TiÀC bonds( NHC!TiCl 4 2.198(6) , [9] [NHC!TiCl 3 (m-O)] 2 2.20 (av.) [18] ).…”

A structurally-characterized NbCl5–NHC adduct

“…5a On the other hand, the carbene atom in 2a displays CÁ Á ÁCl contacts with the four equatorial Cl-ligands [3.14-3.36 Å] which are within the sum of the van der Waals radii of the respective atoms [sum = 3.45 Å]. 13 An analogous situation was previously observed in a range of d 0 transition metal-chloride NHC complexes, 6 including VOCl 3 (IMes) 14 and TiCl 4 (IPr) 2 , 15 and was attributed to some p interaction between the Cl-lone pairs and the p-orbital of the carbenic carbon. Such an interaction has been considered to be a form of back-bonding donation, made possible by the electron density on the Cl-ligands, in spite of the formal absence of electrons at the metal centre.…”

High-Oxidation-State 3d Metal (Ti–Cu) Complexes withN-Heterocyclic Carbene Ligation

“…The . 167 Bellemin-Laponnaz and Dagorne showed that the treatment of [Ti(CH 2 Ph) 4 ] with imidazolinium chloride gave the unexpected rearranged dimer product that might come from the migration of the benzyl group from the titanium center to the carbene carbon (Scheme 2). 152 In addition, the moisture-sensitive nature of titanium(IV)−NHC complexes may result from hydrolysis of the Ti(IV)− C(carbene) bonds to give imidazolium salts.…”