Synthesis and characterisation of an N-heterocyclic carbene with spatially-defined steric impact

Abstract

The synthesis and co-ordination chemistry of a new 'bulky yet flexible' N-heterocyclic carbene ("IPaul") is reported. This carbene has spatially-defined steric impact; steric maps show that two quadrants are very bulky while the other two are quite open. The electronic properties of this carbene are very similar to those of other 1,3-diarylimidazol-2-ylidenes. Copper, silver, iridium, and nickel complexes of the new ligand have been prepared. In solution, the ligand adopts two different conformations, while X-ray crystallographic analyses of the transition metal complexes suggest that the syn-conformer is preferred in the solid state due to intermolecular interactions. The copper(i) chloride complex of this new ligand has been shown to be highly-active in the hydrosilylation of carbonyl compounds, when compared to the analogous IPr, IMes, IPr* and IPr*(OMe) complexes.

Phosphine Functionalized NHC Ligands and Their Cyclopentadienide Nickel(II) Complexes

“…As expected, the bond parameters around the nickel(II) atoms are in complete agreement with the complexes described above (Ni‐NHC, Ni‐Cp) and with the data of other CpNiCl complexes , . The nickel(II) complex 4d is rather insoluble in all common solvents.…”

Coinage metal complexes of selenoureas derived from N-heterocyclic carbenes

“…Two new selenoureas were prepared from Glorius's IBioxMe4 ligand (11) 22 and from the recently-reported IPaul ligand (12), 23 and characterised by methods including NMR spectroscopy (Scheme 1). The IPaul derivative exists as a mixture of two rotamers, with δSe values (51, 64 ppm) lying midway between those for IMes (27 ppm) and IPr* (106 ppm), consistent with the structure of IPaul as an IMes/IPr* hybrid.…”

An N‐Heterocyclic Carbene with a Saturated Backbone and Spatially‐Defined Steric Impact

“…The synthesis of the target ligand was achieved straightforwardly from diimine 5 (Scheme ) . The reduction of 5 with aluminium hydride reagent 6 led to the diamine 7 in good yield.…”

“…General: Unless otherwise stated, all materials were obtained from commercial sources and used as supplied. Compound 5 and IPaul · HCl ( 1 ) were prepared according to literature procedures . Anhydrous solvents were obtained from an Innovative Technologies PureSolv solvent drying system.…”