A facile synthesis of Robinson’s NHC-stabilised diborane(4)

Reactions of bis(pinacolato)diboron (B2pin2) with [(IDip)AlH3] (IDip = (HCNDip)2C:, Dip = 2,6-iPr2C6H3) afforded both the new diborane [(IDip)BH2B(pin)] and the known compound [(IDip)BH2BH2(IDip)] in a facile one-pot procedure; the latter reaction is improved by the addition of free IDip. [(IDip)AlH3] transfers both IDip and hydride ligands to the diborane moiety in a halide-free approach. [(IDip)BH2B(pin)] was structurally and spectroscopically characterised and additional spectroscopic data for [(IDip)BH2BH2(IDip)] is reported.Publisher PDFPeer reviewe

Neutral dinuclear copper(I)-NHC complexes : synthesis and application in the hydrosilylation of ketones

The authors gratefully acknowledge the Royal Society (University Research Fellowship to C.S.J.C.) for funding.The synthesis of a class of highly stable neutral dinuclear Cu(I)-NHC complexes using 1,2,4-triazole as a bridging ligand is described. Various NHCs were used to generate a library of [Cu(μ-trz)(NHC)]2, complexes. Interestingly, [Cu(μ-trz)(IPr)]2 was found to be highly active in the hydrosilylation of ketones, without the need for an external base or any other additive. A wide range of aryl and alkyl ketones, as well as sterically hindered ketones, was successfully reduced to alcohols using the lowest catalyst loading reported to date.PostprintPeer reviewe

[Silver(I)(Pyridine-Containing Ligand)] complexes as unusual catalysts for A3-coupling reactions

Two original macrocyclic silver(I)(pyridine-containing ligand) complexes [Ag(I)(Pc-L)] were synthesized and characterized. Their ability to catalyze the coupling among aldehydes, terminal alkynes and amines (A3-coupling) was demonstrated. The reaction could be performed under conventional as well as dielectric heating. The catalysts were effective in both cases, but dielectric heating allowed a lower catalyst loading and reduced ratio among reaction partners in shorter reaction times. The reaction scope was broad, including aryl/alkyl aldehydes, aryl/alkyl acetylenes and secondary aliphatic amines. Some unprecedented propargylamines have been prepared. The new catalytic system was also tested with more challenging coupling partners such as aniline and ketones

Normal and abnormal NHC coordination in cationic hydride iodide complexes of aluminium

We thank the University of St Andrews and the EPSRC UK National Mass Spectrometry Facility (NMSF) at Swansea University.The mixed N-heterocyclic carbene (NHC) complexes NHCAlHxI3-x, where NHC is IDip or IMes ((HCNAr)2C:, Ar = 2,6-iPr2C6H3 = Dip (IDip); or 2,4,6-Me3C6H2 = Mes (IMes)), x = 1 or 2, were either prepared from NHCAlH3 and NHCAlI3 or by halogenation of NHCAlH3 with MeI. Reaction of [(IDip)AlHxI3-x], with x = 0-3, with another equivalent of a IDip afforded either fluxional equilibria in benzene solution for x = 0, no reaction for x = 3, or the new mixed normal-abnormal NHC-coordinated ionic complexes [(IDip)AlH2(aIDip)]I ( 9 ) and [(IDip)AlHI(aIDip)]I ( 10 ), where aIDip is the abnormal IDip carbene tautomer bonded through its 4-position. The molecular structures of 9 and 10 were determined and show slightly shorter Al–C(aIDip) than Al–C(IDip) distances. In addition, a complex containing [(IDip)AlI2(aIDip)]I ( 11 ) was structurally characterized though could not intentionally be synthesised. Possible formation mechanisms for 9 - 11 are discussed and the normal and abnormal IDip coordination to the aluminium(III) centre is believed to occur for steric reasons.PostprintPeer reviewe

Investigating the structure and reactivity of azolyl-based copper(I)-NHC complexes : the role of the anionic ligand

The authors gratefully acknowledge the Royal Society (University Research Fellowship to C.S.J.C.), the Spanish MINECO (CTQ2014-59832-JIN), and EU (FEDER fund UNGI08-4E-003) for funding.A family of copper(I)-NHC azolyl complexes was synthesized and deployed in the hydrosilylation of dicyclo-hexylketone to probe the role of the anionic ligand on catalytic performance. The azolyl ligand is shown to have a crucial role in catalytic activity without the need for additives, and this at very low catalyst loading.PostprintPeer reviewe

Simple Synthetic Routes to Carbene‐M‐Amido (M=Cu, Ag, Au) Complexes for Luminescence and Photocatalysis Applications

The development of novel and operationally simple synthetic routes to carbene‐metal‐amido (CMA) complexes of copper, silver and gold relevant for photonic applications are reported. A mild base and sustainable solvents allow all reactions to be conducted in air and at room temperature, leading to high yields of the targeted compounds even on multigram scales. The effect of various mild bases on the N−H metallation was studied in silico and experimentally, while a mechanochemical, solvent‐free synthetic approach was also developed. Our photophysical studies on [M(NHC)(Cbz)] (Cbz=carbazolyl) indicate that the occurrence of fluorescent or phosphorescent states is determined primarily by the metal, providing control over the excited state properties. Consequently, we demonstrate the potential of the new CMAs beyond luminescence applications by employing a selected CMA as a photocatalyst. The exemplified synthetic ease is expected to accelerate the applications of CMAs in photocatalysis and materials chemistry