Recent progress on NHC-stabilized early transition metal (group 3–7) complexes: Synthesis and applications

Abstract

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Tridentate complexes of group 4 bearing bis-aryloxide N-heterocyclic carbene ligand: Structure, spin density and charge states

“…These values fairly also fall within the range of C-TM bond distances found for group 4 NHC complexes thus far X-ray characterized according to the CCDC database recently reported in Ref. [14] the TM and the O sites of the carbene ligand increase in the charged system. Conversely, no significant changes were observed in the distance between the metal center and the C atom of the carbene ligand, which turns out to be insensitive to the charge state of the complex.…”

“…However, results concerning the use of oxophilic and electropositive early transition metal species supported by NHC carbene have been much less investigated as opposed to the rich literature on late transition metal NHC complexes. [7,6,13,14] This is mainly due to the difficulty in synthesizing complexes sufficiently stable to be manipulated and used in catalytic reactions without giving rise to dissociation or disassembling of the NHC system. As a consequence, also quantum chemical investigations into this type of systems have been so far rather limited.…”

“…[20] Among the NHCs ligands documented so far, NHCincorporating pincer-type chelating tridentate ligands is receiving increasing attention thanks to their chemical robustness, stability and versatility in catalytic performance. [21,22,23,19,14] In particular, the bis-aryloxide N-heterocyclic carbene tridentate ligand tBu (OCO) 2− has been shown to be suitable to host early transition metals, with a high versatility ranging from group 3 to group 7 TM. [21] The tBu (OCO) 2− ligand features a central NHC donor flanked on each side by an orthoand para-substituted phenolate moiety in which the tBu groups provide a high degree of steric protection that allows an unprecedented ability in coordinating Ti, Zr and Hf in a very stable way, thus providing highly robust [ tBu (OCO)]MR 2,3 (with R = Cl, THF, O i Pr) complexes displaying exceptional catalytic performances.…”

Silver (I) N-Heterocyclic Carbene Complexes: A Winning and Broad Spectrum of Antimicrobial Properties

“…Metal-NHC complexes have been primarily used in catalytic chemistry [ 10 , 11 ]. However, more recently NHC ligands have been applied as carrier molecules for metals in anticancer applications [ 12 ].…”

On the Origin of E-Selectivity in the Ring-Opening Metathesis Polymerization with Molybdenum Imido Alkylidene N-Heterocyclic Carbene Complexes

“… 9 By contrast, neutral, pentacoordinated and cationic, tetracoordinated Mo imido alkylidene N -heterocyclic carbene (NHC) complexes show improved stability not only toward oxygen, water, and protic substrates but also toward high temperatures without sacrificing reactivity and productivity. 10 − 13 Indeed, these catalysts are characterized by an impressive functional group tolerance and allow for olefin metathesis reactions with hydroxyl-, carboxyl-, aldehyde-, ether-, and amine-containing substrates. 14 Apart from their high activity 15 , 16 they also show remarkable stereoselectivity in ring-opening metathesis polymerization (ROMP), allowing the synthesis of highly tactic polymers.…”