Phosphorus cations and bulky cyclopentadienyl ligands

xix, 164 leaves : ill. ; 29 cmIncludes abstract.Includes bibliographical references.The synthesis and characterisation of some ethynylphosphonium salts are described starting from 1-bromo-2-phenylacetylene and tertiary phosphines. Structural information for these molecules has been obtained using X-ray crystallography, and deviant reactivity was observed at elevated temperatures when the electron-rich tris(2,4,6-trimethoxyphenyl)phosphine was employed. A new approach to the corresponding 1,4-bis(ethynylphosphonium) salts was also developed by a similar reaction, and the first bis(ethynylphosphonium) salts were characterised using X-ray crystallography. Exploratory research into the synthesis of m-terphenyl substituted cyclopentadienyl ligands (Ter[superscript Mes]Cp and Ter[superscript Dipp]Cp) is also described. A new synthetic route is presented and is accomplished through the reaction of aryl lithium reagents with cobaltocenium salts, followed by oxidation of the intermediate cobalt(I) species to afford the corresponding cyclopentadiene. The preparation, structural, and spectroscopic properties of the alkali metal salts (Li–Cs) is described, and some preliminary coordination chemistry is presented

Crystal structure of 2-azido-1,3-bis(2,6-diiso- propylphenyl)-1,3,2-diazaphospholidine

Published VersionThe title compound, C26H38N5P, was synthesized by reacting 2-chloro-1,3- bis(2,6-diisopropylphenyl)-1,3,2-diazaphospholidine with sodium azide and a catalytic amount of lithium chloride in tetrahydrofuran. The title compound is the first structurally characterized 2-azido-1,3,2-diazaphospholidine and exhibits a P atom in a trigonal pyramidal geometry. The azide P—N bond length of 1.8547 (16) A ̊ is significantly longer than the P—N separations for the chelating diamine [P—N = 1.6680 (15) and 1.6684 (14) A ̊ ]. The sterically hindered 2,6- diisopropylphenyl groups twist away from the central heterocycle, with dihedral angles between the central heteocyclic ring and benzene rings of 76.17 (10) and 79.74 (9) . In the crystal, a weak C—H...N link to the terminal N atom of the azide group leads to [100] chains

Crystal structure of 2-chloro-1,3-bis(2,6-diiso- propylphenyl)-1,3,2-diazaphospholidine 2-oxide

Published versionThe title compound, C26H38ClN2OP, was synthesized by reacting phosphoryl chloride with N,N′-bis­(2,6-diiso­propyl­phen­yl)ethane-1,2-di­amine in the presence of N-methyl­morpholine which acted as an auxilliary base to quench the HCl released as a by-product. The resultant N-heterocyclic phosphine five-membered ring adopts a half-chair conformation and features a tetra­coordinate P atom ligated by the chelating di­amine [P—N = 1.6348 (14) and 1.6192 (14) Å], one double-bonded O atom [P1—O1 = 1.4652 (12) Å] and one Cl atom [P1—Cl1 = 2.0592 (7) Å]. The sterically hindered 2,6-diiso­propyl­phenyl (Dipp) groups twist away from the central heterocycle, with torsion angles of −75.66 (19) and 83.39 (19)° for the P—N—Car—Car links. A number of intra­molecular C—H...N, C—H...O and C—H...Cl close contacts occur. In the crystal, mol­ecules are linked by C—H...O hydrogen bonds to generate [010] chains. C—H...Π inter­actions are also observed

Highly ordered N-heterocyclic carbene monolayers on Cu(111)

EA and FG acknowledge funding from EPSRC grants (EA: EP/R512199/1; FG: EP/S027270/1). We thank the EaStCHEM for computational support via the EaStCHEM Research Computing facility. CMC thanks the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI) for funding of the work from her lab described in this article. AJV acknowledges NSERC for a Vanier scholarship and the Walter C. Sumner foundation for additional financial support. IS acknowledges Queen’s University for the RT Mohan Scholarship and the Ontario government for an Ontario Graduate Scholarship.The benzannulated N-heterocyclic carbene, 1,3-dibenzylbenzimidazolylidene (NHCDBZ) forms large, highly ordered domains when adsorbed on Cu(111) under ultrahigh vacuum conditions. A combination of scanning tunnelling microscopy (STM), high resolution electron energy loss spectroscopy (HREELS) and density functional theory (DFT) calculations reveals that the overlayer consists of vertical benzannulated NHC moieties coordinating to Cu adatoms. Long range order results from the placement of the two benzyl substituents on opposite sides of the benzimidazole moiety, with their aromatic rings approximately parallel to the surface. The organization of three surface-bound benzyl substituents from three different NHCs into a triangular array controls the formation of a highly ordered Kagome-like surface lattice. By comparison with earlier studies of NHCs on Cu(111), we show that the binding geometry and self-assembly of NHCDBZ are influenced by intermolecular and adsorbate-substrate interactions and facilitated by the flexibility of the methylene linkage between the N-heterocycle and the aromatic wingtip substituents.Publisher PDFPeer reviewe

Crystal Structure of Bis(2,4,6-trimethylphenyl)-phosphine Oxide

Published VersionThe single crystal structure of bis(2,4,6-trimethylphenyl) phosphine oxide has been determined. All interatomic distances and angles can be considered normal. The aryl substituents adopt an intermediate configuration when compared to both sterically unhindered (e.g., diphenylphosphine oxide) and congested (e.g., bis(2,4,6-tri-tert-butylphenyl)phosphine oxide) secondary phosphine oxides, illustrating the influence of steric congestion on the molecular structure

N-heterocyclic carbenes reduce and functionalize copper oxide surfaces in one pot

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.PostprintPeer reviewe

Using social media to assess the consumer nutrition environment: comparing Yelp reviews with a direct observation audit instrument for grocery stores

Objective To examine the feasibility of using social media to assess the consumer nutrition environment by comparing sentiment expressed in Yelp reviews with information obtained from a direct observation audit instrument for grocery stores. Design Trained raters used the Nutrition Environment Measures Survey in Stores (NEMS-S) in 100 grocery stores from July 2015 to March 2016. Yelp reviews were available for sixty-nine of these stores and were retrieved in February 2017 using the Yelp Application Program Interface. A sentiment analysis was conducted to quantify the perceptions of the consumer nutrition environment in the review text. Pearson correlation coefficients (ρ) were used to compare NEMS-S scores with Yelp review text on food availability, quality, price and shopping experience. Setting Detroit, Michigan, USA. Participants None. Results Yelp reviews contained more comments about food availability and the overall shopping experience than food price and food quality. Negative sentiment about food prices in Yelp review text and the number of dollar signs on Yelp were positively correlated with observed food prices in stores (ρ=0·413 and 0·462, respectively). Stores with greater food availability were rated as more expensive on Yelp. Other aspects of the food store environment (e.g. overall quality and shopping experience) were captured only in Yelp. Conclusions While Yelp cannot replace in-person audits for collecting detailed information on the availability, quality and cost of specific food items, Yelp holds promise as a cost-effective means to gather information on the overall cost, quality and experience of food stores, which may be relevant for nutrition outcomes

Mono- and bis-imidazolidinium ethynyl cations and the reduction of the latter to give an extended bis-1,4-([3]cumulene)-p-carbo-quinoid system

Sherpa Romeo yellow journal. This is the peer reviewed version. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived VersionsAn extended π-system containing two [3]cumulene fragments separated by a p-carbo-quinoid and stabilized by two capping N-heterocyclic carbenes (NHCs) has been prepared. Mono- and bis-imidazolidinium ethynyl cations have also been synthesized from the reaction of an NHC with phenylethynyl bromide or 1,4bis(bromoethynyl)benzene. Cyclic voltammetry coupled with synthetic and structural studies showed that the dication is readily reduced to a neutral, singlet bis-1,4-([3]cumulene)-p-carbo-quinoid due to the πaccepting properties of the capping NHCsYe

Crystal structure of 2-azido-1,3-bis(2,6-diisopropylphenyl)-1,3,2-diazaphospholidine

The title compound, C26H38N5P, was synthesized by reacting 2-chloro-1,3-bis(2,6-diisopropylphenyl)-1,3,2-diazaphospholidine with sodium azide and a catalytic amount of lithium chloride in tetrahydrofuran. The title compound is the first structurally characterized 2-azido-1,3,2-diazaphospholidine and exhibits a P atom in a trigonal pyramidal geometry. The azide P—N bond length of 1.8547 (16) Å is significantly longer than the P—N separations for the chelating diamine [P—N = 1.6680 (15) and 1.6684 (14) Å]. The sterically hindered 2,6-diisopropylphenyl groups twist away from the central heterocycle, with dihedral angles between the central heteocyclic ring and benzene rings of 76.17 (10) and 79.74 (9)°. In the crystal, a weak C—H...N link to the terminal N atom of the azide group leads to [100] chains

Crystal Structure of Bis(2,4,6-trimethylphenyl)-phosphine Oxide

The single crystal structure of bis(2,4,6-trimethylphenyl)phosphine oxide has been determined. All interatomic distances and angles can be considered normal. The aryl substituents adopt an intermediate configuration when compared to both sterically unhindered (e.g., diphenylphosphine oxide) and congested (e.g., bis(2,4,6-tri-tert-butylphenyl)phosphine oxide) secondary phosphine oxides, illustrating the influence of steric congestion on the molecular structure