Coordination and reactivity study of titanium phenoxo complexes containing a bulky bidentate imino-N-heterocyclic carbene ligand

Larocque, Timothy G.; Lavoie, Gino G.

doi:10.1016/j.jorganchem.2012.05.018

Cited by 15 publications

(4 citation statements)

References 35 publications

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“…Chelating NHC ligands found in the known titanium(IV) complexes include bidentate alkoxy-NHC, aryloxy-NHC, imido-NHC, tridentate NHC-amide-NHC, NHC-aryl-NHC, aryloxy-NHC-aryloxy, as well as cyclopentadienyl-NHC ligands. [153][154][155][156][157]161,163,165 The wide use of oxygen-based anion-functionalized NHCs is likely due to the well-known oxophilicity of early transition metals.…”

Section: Complexes Of Titaniummentioning

confidence: 99%

“…Chelating NHCs, particularly those having anionic donors, can bind tightly with titanium(IV) centers, which can alleviate the lability of Ti(IV)–C(carbene) bonds. Chart lists some examples of the reported titanium(IV)–NHC complexes. − The known titanium(IV) NHC complexes display very rich structural diversity (Figure ). Both inorganic ligands (e.g., halides, alkoxides, aryloxides, amides, carboxylates, azides, and imides) and organometallic hydrocarbyl ligands ,,,, (e.g., benzyl and methyl , ) are compatible with NHCs in the coordination sphere of titanium(IV).…”

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

“…Chart lists some examples of the reported titanium(IV)–NHC complexes. − The known titanium(IV) NHC complexes display very rich structural diversity (Figure ). Both inorganic ligands (e.g., halides, alkoxides, aryloxides, amides, carboxylates, azides, and imides) and organometallic hydrocarbyl ligands ,,,, (e.g., benzyl and methyl , ) are compatible with NHCs in the coordination sphere of titanium(IV). Chelating NHC ligands found in the known titanium(IV) complexes include bidentate alkoxy-NHC, aryloxy-NHC, imido-NHC, tridentate NHC-amide-NHC, NHC-aryl-NHC, aryloxy-NHC-aryloxy, as well as cyclopentadienyl-NHC ligands. − ,,, The wide use of oxygen-based anion-functionalized NHCs is likely due to the well-known oxophilicity of early transition metals.…”

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

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

et al. 2018

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High-oxidation-state 3d metal species have found a wide range of applications in modern synthetic chemistry and materials science. They are also implicated as key reactive species in biological reactions. These applications have thus prompted explorations of their formation, structure, and properties. While the traditional wisdom regarding these species was gained mainly from complexes supported by nitrogen- and oxygen-donor ligands, recent studies with N-heterocyclic carbenes (NHCs), which are widely used for the preparation of low-oxidation-state transition metal complexes in organometallic chemistry, have led to the preparation of a large variety of isolable high-oxidation-state 3d metal complexes with NHC ligation. Since the first report in this area in the 1990s, isolable complexes of this type have been reported for titanium(IV), vanadium(IV,V), chromium(IV,V), manganese(IV,V), iron(III,IV,V), cobalt(III,IV,V), nickel(IV), and copper(II). With the aim of providing an overview of this intriguing field, this Review summarizes our current understanding of the synthetic methods, structure and spectroscopic features, reactivity, and catalytic applications of high-oxidation-state 3d metal NHC complexes of titanium to copper. In addition to this progress, factors affecting the stability and reactivity of high-oxidation-state 3d metal NHC species are also presented, as well as perspectives on future efforts.

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Section: Complexes Of Titaniummentioning

confidence: 99%

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

Section: High-oxidation-state 3d Metal Complexes With Nhc Ligationmentioning

confidence: 99%

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

et al. 2018

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“…However, their dissociation from oxophilic metals was partially prevented by designing multidentate anionic carbon, nitrogen, and oxygen-functionalized NHC ligands [ 5 , 13 , 15 , 16 , 17 ]. Anchoring such functionalized NHC ligands to oxophilic metals has proved to be a successful approach for developing catalysts, notably of group 4 metals, for the (oligo-)polymerization of olefins [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ], hydroamination/cyclization of aminoalkenes [ 30 , 31 , 32 , 33 , 34 , 35 , 36 ], controlled ring-opening polymerization of rac -lactide [ 37 , 38 , 39 , 40 ], and more recently, for the copolymerization of epoxides with CO 2 [ 41 , 42 , 43 , 44 , 45 ].…”

Section: Introductionmentioning

confidence: 99%

Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2

et al. 2020

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Tridentate, bis-phenolate N-heterocyclic carbenes (NHCs) are among the ligands giving the most selective and active group 4-based catalysts for the copolymerization of cyclohexene oxide (CHO) with CO2. In particular, ligands based on imidazolidin-2-ylidene (saturated NHC) moieties have given catalysts which exclusively form polycarbonate in moderate-to-high yields even under low CO2 pressure and at low copolymerization temperatures. Here, to evaluate the influence of the NHC moiety on the molecular structure of the catalyst and its performance in copolymerization, we extend this chemistry by synthesizing and characterizing titanium complexes bearing tridentate bis-phenolate imidazol-2-ylidene (unsaturated NHC) and benzimidazol-2-ylidene (benzannulated NHC) ligands. The electronic properties of the ligands and the nature of their bonds to titanium are studied using density functional theory (DFT) and natural bond orbital (NBO) analysis. The metal–NHC bond distances and bond strengths are governed by ligand-to-metal s- and p-donation, whereas back-donation directly from the metal to the NHC ligand seems to be less important. The NHC p-acceptor orbitals are still involved in bonding, as they interact with THF and isopropoxide oxygen lone-pair donor orbitals. The new complexes are, when combined with [PPN]Cl co-catalyst, selective in polycarbonate formation. The highest activity, albeit lower than that of the previously reported Ti catalysts based on saturated NHC, was obtained with the benzannulated NHC-Ti catalyst. Attempts to synthesize unsaturated and benzannulated NHC analogues based on Hf invariably led, as in earlier work with Zr, to a mixture of products that include zwitterionic and homoleptic complexes. However, the benzannulated NHC-Hf complexes were obtained as the major products, allowing for isolation. Although these complexes selectively form polycarbonate, their catalytic performance is inferior to that of analogues based on saturated NHC.

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Characteristics of Cyclometalation Reactions for Organometallic Intramolecular-Coordination Five-Membered Ring Compounds

Omae¹

2013

Cyclometalation Reactions

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Coordination and reactivity study of titanium phenoxo complexes containing a bulky bidentate imino-N-heterocyclic carbene ligand

Cited by 15 publications

References 35 publications

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

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

Unsaturated and Benzannulated N-Heterocyclic Carbene Complexes of Titanium and Hafnium: Impact on Catalysts Structure and Performance in Copolymerization of Cyclohexene Oxide with CO2

Characteristics of Cyclometalation Reactions for Organometallic Intramolecular-Coordination Five-Membered Ring Compounds

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