Twisting the arm: structural constraints in bicyclic expanded-ring N-heterocyclic carbenes.

A series of diaryl, mono-aryl/alkyl and dialkyl mono- and bicyclic expanded-ring N-heterocyclic carbenes (ER-NHCs) have been prepared and their complexation to Au(i) investigated through the structural analysis of fifteen Au(NHC)X and/or [Au(NHC)2]X complexes. The substituted diaryl 7-NHCs are the most sterically encumbered with large buried volume (%VB) values of 40-50% with the less flexible six-membered analogues having %VB values at least 5% smaller. Although the bicyclic systems containing fused 6- and 7-membered rings (6,7-NHCs) are constrained with relatively acute NCN bond angles, they have the largest %VB values of the dialkyl derivatives reported here, a feature related to the fixed conformation of the heterocyclic rings and the compressional effect of a pre-set methyl substituent.

[1]  M. Whittlesey,et al.  Copper-NHC-Mediated Semihydrogenation and Hydroboration of Alkynes: Enhanced Catalytic Activity Using Ring-Expanded Carbenes , 2018, Organometallics.

[2]  N. C. Kasuga,et al.  Syntheses, Structures, and Antimicrobial Activities of Gold(I)- and Copper(I)- N-Heterocyclic Carbene (NHC) Complexes Derived from Basket-Shaped Dinuclear Ag(I)-NHC Complex. , 2018, Inorganic chemistry.

[3]  Wenqin Wu,et al.  Ring-expanded N-heterocyclic carbenes as ligands in iron-catalysed cross-coupling reactions of arylmagnesium reagents and aryl chlorides. , 2018, Chemical communications.

[4]  P. D. Newman,et al.  Ring‐Expanded N‐Heterocyclic Carbenes for Copper‐Mediated Azide–Alkyne Click Cycloaddition Reactions , 2018, ChemCatChem.

[5]  David Zahner,et al.  A Structure‐Based Activity Study of Highly Active Unsymmetrically Substituted NHC Gold(I) Catalysts , 2018 .

[6]  Rebecca L. Melen,et al.  Amidine functionalized phosphines: tuneable ligands for transition metals. , 2017, Dalton transactions.

[7]  A. Slawin,et al.  Expedient Syntheses of Neutral and Cationic Au(I)–NHC Complexes , 2017 .

[8]  M. Kappes,et al.  Defined tetranuclear coinage metal chains. , 2017, Chemical communications.

[9]  F. Glorius,et al.  Privileged chiral N-heterocyclic carbene ligands for asymmetric transition-metal catalysis. , 2017, Chemical Society reviews.

[10]  A. Slawin,et al.  Inner-sphere versus outer-sphere coordination of BF4- in a NHC-gold(I) complex , 2017 .

[11]  B. Skelton,et al.  Stable AuIII complexes with four N-heterocyclic carbene groups can be prepared in high yield directly from KAuCl4. , 2017, Dalton transactions.

[12]  U. Flörke,et al.  Reactivity of Grubbs–Hoveyda II Complexes Including Extended N-Heterocyclic Carbenes with a Bicyclic Camphor-Based Framework , 2017, Synthesis.

[13]  D. Murphy,et al.  Influence of Ring-Expanded N-Heterocyclic Carbenes on the Structures of Half-Sandwich Ni(I) Complexes: An X-ray, Electron Paramagnetic Resonance (EPR), and Electron Nuclear Double Resonance (ENDOR) Study. , 2016, Inorganic chemistry.

[14]  Jeffrey M. Farrell,et al.  Chiral carbene-borane adducts: precursors for borenium catalysts for asymmetric FLP hydrogenations. , 2016, Dalton transactions.

[15]  A. Slawin,et al.  Synthesis of AuI- and AuIII-Bis(NHC) Complexes: Ligand Influence on Oxidative Addition to AuI Species , 2016 .

[16]  P. D. Newman,et al.  Mono- and dimeric complexes of an asymmetric heterotopic P,CNHC,pyr ligand. , 2016, Dalton transactions.

[17]  L. Cavallo,et al.  SambVca 2. A Web Tool for Analyzing Catalytic Pockets with Topographic Steric Maps , 2016 .

[18]  M. Ingleson,et al.  Three-Coordinate Iron(II) Expanded Ring N-Heterocyclic Carbene Complexes , 2016 .

[19]  F. Rominger,et al.  Synthesis of Different Classes of Six-Membered Gold(I) NHC Complexes by the Isonitrile Route , 2016 .

[20]  L. De Cola,et al.  A Bis(Diphosphanyl N-Heterocyclic Carbene) Gold Complex: A Synthon for Luminescent Rigid AuAg2 Arrays and Au5 and Cu6 Double Arrays. , 2016, Angewandte Chemie.

[21]  J. Bacsa,et al.  Synthesis and Reactivity of New Copper(I) Hydride Dimers , 2016 .

[22]  U. Siemeling,et al.  Ferrocene-Based N-Heterocyclic Carbenes with Functionalised Benzyl Substituents: Ferrocene-Based N-Heterocyclic Carbenes , 2015 .

[23]  B. Kirchner,et al.  Stretch Out or Fold Back? Conformations of Dinuclear Gold(I) N-Heterocyclic Carbene Macrocycles. , 2015, Inorganic chemistry.

[24]  G. Sheldrick.  Crystal structure refinement with SHELXL , 2015, Acta crystallographica. Section C, Structural chemistry.

[25]  S. Tabassum,et al.  Synthesis of New Camphor-Based Carbene Ligands and Their Application in a Copper-Catalyzed Michael Addition with B2Pin2 , 2014, Synthesis.

[26]  S. Aldridge,et al.  Expanded-ring N-heterocyclic carbenes for the stabilization of highly electrophilic gold(I) cations. , 2014, Chemistry.

[27]  Xingbang Hu,et al.  Gold-catalyzed hydroarylation of alkenes with dialkylanilines. , 2014, Journal of the American Chemical Society.

[28]  A. Bond,et al.  Expanded ring N-heterocyclic carbene adducts of group 15 element trichlorides: synthesis and reduction studies. , 2014, Dalton transactions.

[29]  I. Riddlestone,et al.  Use of ring-expanded diamino- and diamidocarbene ligands in copper catalyzed azide-alkyne "click" reactions , 2014 .

[30]  F. Glorius,et al.  An overview of N-heterocyclic carbenes , 2014, Nature.

[31]  K. Cavell,et al.  Pd–PEPPSI-Type Expanded Ring N-Heterocyclic Carbene Complexes: Synthesis, Characterization, and Catalytic Activity in Suzuki–Miyaura Cross Coupling , 2014 .

[32]  V. Ananikov,et al.  Expanded-ring N-heterocyclic carbenes efficiently stabilize gold(I) cations, leading to high activity in π-acid-catalyzed cyclizations. , 2014, Chemistry.

[33]  S. Aldridge,et al.  Probing the limits of ligand steric bulk: backbone C-H activation in a saturated N-heterocyclic carbene. , 2014, Chemistry.

[34]  M. Cokoja,et al.  Chemistry of iron N-heterocyclic carbene complexes: syntheses, structures, reactivities, and catalytic applications. , 2014, Chemical reviews.

[35]  B. Kariuki,et al.  N-alkyl functionalised expanded ring N-heterocyclic carbene complexes of rhodium(I) and iridium(I): structural investigations and preliminary catalytic evaluation. , 2013, Dalton transactions.

[36]  G. Bertrand,et al.  Anti-Bredt N-heterocyclic carbene: an efficient ligand for the gold(I)-catalyzed hydroamination of terminal alkynes with parent hydrazine. , 2013, Chemical communications.

[37]  K. Cavell,et al.  Zerovalent [Pd(NHC)(Alkene)1,2] Complexes Bearing Expanded-Ring N-Heterocyclic Carbene Ligands in Transfer Hydrogenation of Alkynes , 2013 .

[38]  P. D. Newman,et al.  Monovalent chiral-at-copper complexes: halide-controlled diastereoselectivity. , 2012, Chemical communications.

[39]  B. Kariuki,et al.  Gold(I) Complexes Bearing Sterically Imposing, Saturated Six- and Seven-Membered Expanded Ring N-Heterocyclic Carbene Ligands , 2012 .

[40]  U. Monkowius,et al.  Syntheses, crystal structures, reactivity, and photochemistry of gold(III) bromides bearing N-heterocyclic carbenes. , 2011, Dalton transactions.

[41]  S. Nolan.  The development and catalytic uses of N-heterocyclic carbene gold complexes. , 2011, Accounts of chemical research.

[42]  A. Trzeciak,et al.  N-Heterocyclic carbene–rhodium complexes as catalysts for hydroformylation and related reactions , 2011 .

[43]  F. Rominger,et al.  Synthesis, Reactivity, and Electrochemical Studies of Gold(I) and Gold(III) Complexes Supported by N-Heterocyclic Carbenes and Their Application in Catalysis , 2010 .

[44]  P. D. Newman,et al.  Metal Complexes of Chiral NHCs Containing a Fused Six- and Seven-Membered Central Ring , 2010 .

[45]  S. Nolan,et al.  Percent buried volume for phosphine and N-heterocyclic carbene ligands: steric properties in organometallic chemistry. , 2010, Chemical communications.

[46]  V. Catalano,et al.  Luminescent copper(I) halide butterfly dimers coordinated to [Au(CH3imCH2py)2]BF4 and [Au(CH3imCH2quin)2]BF4. , 2009, Inorganic chemistry.

[47]  Yi‐Hung Liu,et al.  N-Heterocyclic Carbene Transfer from Gold(I) to Palladium(II) , 2009 .

[48]  S. Tabassum,et al.  New enantiopure NHCs derived from camphor. , 2009, Chemical communications.

[49]  S. Nolan,et al.  N-heterocyclic carbenes in late transition metal catalysis. , 2009, Chemical reviews.

[50]  B. Kariuki,et al.  Synthesis and Structural Features of Rhodium Complexes of Expanded Ring N-Heterocyclic Carbenes , 2009 .

[51]  Amitabha Bhattacharyya,et al.  Coinage metal-N-heterocyclic carbene complexes. , 2009, Chemical reviews.

[52]  D. Dixon,et al.  13C NMR spectroscopy of "Arduengo-type" carbenes and their derivatives. , 2009, Chemical reviews.

[53]  James C. Knight,et al.  Novel Expanded Ring N-Heterocyclic Carbenes: Free Carbenes, Silver Complexes, And Structures , 2008 .

[54]  M. Buchmeiser,et al.  Copper (I) 1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R=mesityl, 2-propyl): synthesis, X-ray structures, immobilization and catalytic activity , 2005 .

[55]  V. Catalano,et al.  Pyridine substituted N-heterocyclic carbene ligands as supports for Au(I)-Ag(I) interactions: formation of a chiral coordination polymer. , 2004, Inorganic chemistry.

[56]  S. Berners‐Price,et al.  Dinuclear gold(I) complexes of bridging bidentate carbene ligands: synthesis, structure and spectroscopic characterisation. , 2004, Dalton transactions.

[57]  Johnathan N. Brantley,et al.  1,6‐Enyne Cyclizations Catalyzed by N‐Heterocyclic Carbene Supported Gold Complexes: Deconvoluting Sterics and Electronics , 2014 .

[58]  G. Sheldrick.  A short history of SHELX. , 2008, Acta crystallographica. Section A, Foundations of crystallography.