Search

We show that the N-heterocyclic carbene precursor employed has a significant influence on the purity of the resulting films prepared by vapour-phase deposition.

Herein, we describe the synthesis of a toroidal Au

The preparation of a novel Au6 cluster bearing a bidentate mixed carbene–thiolate ligand is presented. The length of linker between the central benzimidazole and thiolate has a strong effect on the formation of cluster products, with a C2 chain giving an Au6 cluster, while a C3 chain results in no evidence of cluster formation. Density functional theory analysis predicts a non-metallic cluster with a large HOMO–LUMO (3.2–3.6 eV) and optical gap.

The Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) are thanked for financial support of this work in terms of operating and equipment grants to CMC and JHH. AJV and MRN thank the Ontario government for OGS fellowships. AJV thanks NSERC for a Vanier Scholarship and also the Walter C. Sumner foundation for additional scholarship support. Benzimidazolium hydrogen carbonate salts have been shown to act as N-heterocyclic carbene precursors which can remove oxide from copper oxide surfaces and functionalize the resulting metallic surfaces in a single step. Both the surfaces and the etching products are fully characterized by spectroscopic methods. Analysis of surfaces before and after NHC treatment by X-ray photoelectron spectroscopy demonstrates the complete removal of copper(II) oxide. Using 13C-labelling, we determine that the products of this transformation include a cyclic urea, a ring-opened formamide and a bis-carbene copper(I) complex. These results illustrate the potential of NHCs to functionalize a much broader class of metals, including those prone to oxide treatment, greatly facilitating the preparation of NHC-based films on metals other than gold. Postprint

The preparation of a novel Au

The extremely bulky N-heterocyclic carbene (NHC), ITr, (ITr = [(HCNCPh3)2C:]) featuring sterically shielding umbrella-shaped trityl (-CPh3) substituents was prepared. This NHC features the highest percent buried volume (%Vbur) to date, and was used to form a thermally-stable quasi one-coordinate thallium(I) cation [ITr-Tl]+. This Tl(I) adduct and the corresponding lithium complex [ITr*Li(OEt2)]+ are versatile "all-in-one" transmetalation/ligation reagents for preparing low-coordinate inorganic species inaccessible via pre-existing routes.

Benzimidazolium hydrogen carbonate salts have been shown to act as N-heterocyclic carbene precursors which can remove oxide from copper oxide surfaces and functionalize the resulting metallic surfaces in a single step. Both the surfaces and the etching products are fully characterized by spectroscopic methods. Analysis of surfaces before and after NHC treatment by X-ray photoelectron spectroscopy demonstrates the complete removal of copper(II) oxide. Using 13C-labelling, we determine that the products of this transformation include a cyclic urea, a ring-opened formamide and a bis-carbene copper(I) complex. These results illustrate the potential of NHCs to functionalize a much broader class of metals, including those prone to oxide treatment, greatly facilitating the preparation of NHC-based films on metals other than gold.

Gold superatom nanoclusters stabilized entirely by N-heterocyclic carbenes (NHCs) and halides are reported. The reduction of well-defined NHC-Au-Cl complexes produces clusters comprised of an icosahedral Au

We introduce a large-scale synthesis of a sterically encumbered N-heterocyclic olefin (NHO) and illustrate the ability of its deprotonated form to act as an anionic four-electron bridging ligand. The resulting multicenter donating ability has been used to link two low oxidation state Ge(II) centers in close proximity, leading to bridging Ge-Cl-Ge and Ge-H-Ge bonding environments supported by Ge2C2 heterocyclic manifolds. Reduction of a dimeric [RGeCl]2 species (R = anionic NHO, [(MeCNDipp)2C═CH]-; Dipp = 2,6-iPr2C6H3) did not give the expected acyclic RGeGeR analogue of an alkyne, but rather ligand migration/disproportionation transpired to yield the known diorganogermylene R2Ge and Ge metal. This process was examined computationally, and the ability of the reported anionic NHO to undergo atom migration chemistry contrasts with what is typically found with bulky monoanionic ligands (such as terphenyl ligands).

N-Heterocyclic carbenes (NHCs) have become one of the most widely studied class of ligands in molecular chemistry and have found applications in fields as varied as catalysis, the stabilization of reactive molecular fragments, and biochemistry. More recently, NHCs have found applications in materials chemistry and have allowed for the functionalization of surfaces, polymers, nanoparticles, and discrete, well-defined clusters. In this review, we provide an in-depth look at recent advances in the use of NHCs for the development of functional materials.

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; line-height: 20.0px; font: 17.4px Helvetica; color: #000000; -webkit-text-stroke: #000000; background-color: #ffffff} span.s1 {font-kerning: none} span.s2 {font: 11.2px Helvetica; font-kerning: none} span.s3 {font-kerning: none; color: #000000} Magic number Au13 nanoclusters stabilized entirely by N-heterocyclic carbenes (NHCs) have been prepared by the bottom-up reduction of well-defined molecular NHC–Au–Cl complexes with sodium borohydride. The nature of the wingtip groups was shown to be critical in the preparation of stable clusters. The all NHC-clusters are prepared in high yield by this straight-forward method, display higher stability than related all phosphine clusters, and possess extremely high emission quantum yield. DFT analysis of these clusters based on the resolved crystal structure reveals their electronic structure as 8-electron superatoms.

Herein we detail the synthesis and characterisation of a series of zirconium compounds featuring the bis(amido)silyl ligand [(i)Pr2Si(NDipp)2](2-) (Dipp = 2,6-diisopropylphenyl). The functionalisation of bis(amido)silyl zirconium halide complexes with a variety of nucleophiles, such as LiNMe2, LiBH4 and MeLi, was explored and the resulting products showed a propensity to form anionic zirconate salts when the syntheses were carried out in THF. One of the zirconate products, [(i)Pr2Si(NDipp)2]Zr(NMe2)2·ClLi(THF)3, has the ability to catalyse the dehydrocoupling of primary and secondary amine-boranes at room temperature in aromatic solvents.

The synthesis and coordination chemistry of a series of dianionic bis(amido)silyl and bis(amido)disilyl, [NSiN] and [NSiSiN], chelates with N-bound aryl or sterically modified triarylsilyl (SiAr(3)) groups is reported. In order to provide a consistent comparison of the steric coverage afforded by each ligand construct, various two-coordinate N-heterocyclic germylene complexes featuring each ligand set were prepared and oxidative S-atom transfer chemistry was explored. In the cases where clean oxidation transpired, sulfido-bridged centrosymmetric germanium(IV) dimers of the general form [LGe(μ-S)](2) (L = bis(amidosilyl) ligands) were obtained in lieu of the target monomeric germanethiones with discrete Ge═S double bonds. These results indicate that the reported chelates possess sufficient conformational flexibility to allow for the dimerization of LGe═S units to occur. Notably, the new triarylsilyl groups (4-RC(6)H(4))(3)Si- (R = (t)Bu and (i)Pr) still offer considerably expanded degrees of steric coverage relative to the parent congener, -SiPh(3,) and thus the use of substituted triarylsilyl groups within ligand design strategies should be a generally useful concept in advancing low-coordination main group and transition-metal chemistry.

We present isolable examples of formal zinc hydride cations supported by N-heterocyclic carbene (NHC) donors, and investigate the dual electrophilic and nucleophilic (hydridic) character of the encapsulated [ZnH](+) units by computational methods and preliminary hydrosilylation catalysis.

A series of monomeric heterocyclic metallylenes [{(i)Pr(2)Si(NR)(2)}M:] (M = Ge and Sn; R = Dipp = 2,6-(i)Pr(2)C(6)H(3) or SiPh(3)) have been prepared. Preliminary atom-transfer chemistry involving the new low-valent germylenes with the chalcogen sources Me(3)NO and S(8) yielded the corresponding dimeric oxo- and sulfido complexes (e.g., [{(i)Pr(2)Si(NDipp)(2)}Ge(μ-E)](2); E = O and S). Structural analyses of the metallylenes and their oxidized products reveal that incorporation of the umbrella-shaped triarylsilyl groups (SiPh(3)) within the NSiN chelate confers additional steric protection about the group 14 centers relative to a Dipp group. The inclusion of sterically modifiable -SiAr(3) (Ar = aryl) units as part of a bis(amido) ligand array represents a new approach in this field and holds considerable promise with regard to attaining increasingly higher degrees of steric bulk.

The synthesis of a series of N-heterocyclic carbene (NHC) complexes involving zinc, cadmium, and the heavy Group 14 elements germanium, tin, and lead is reported. The direct reaction between the bulky carbene IPr (IPr = (HCNDipp)2C:, Dipp = 2,6-iPr2C6H3) and the Group 14 halide reagents GeCl4 and SnCl4 afforded the 1 : 1 complexes IPr·ECl4 (E = Ge and Sn) in high yield; similarly, ZnI2 interacted with IPr in THF to give the THF-bound complex IPr·ZnI2·THF. CdCl2 underwent divergent chemistry with IPr and the major product isolated was the imidazolium salt [IPrH][IPr·CdCl3], which could be converted into IPr·CdCl2·THF upon treatment with Tl[OTf]. In addition, the stable PbII amide adduct, IPr·PbBr(NHDipp), was prepared. Each of the new carbene–element halide adducts was treated with the hydride sources Li[BH4] and Li[HBEt3] in order to potentially access new element hydride adducts and/or clusters. In most instances scission of the element–carbene bonds transpired, except in the case of IPr·ZnI2·THF, which reacted with two equivalents of Li[BH4] to yield the thermally stable bis(borohydride) zinc complex IPr·Zn(BH4)2.