Eric Brenner

Resorcinarene‐Functionalised Imidazolium Salts as Ligand Precursors for Palladium‐Catalysed Suzuki–Miyaura Cross‐Couplings

Three imidazolium salts based on a rigid resorcinarene platform (1–3) were synthesised and used as catalyst precursors in the Suzuki–Miyaura cross‐coupling of aryl halides with phenylboronic acid. In these pro‐carbene ligands, the heterocyclic moiety has one N atom connected to a C2 atom of a resorcinolic ring, and the other is substituted by an alkyl group (R=n‐propyl, iso‐propyl, benzyl). The methinic C atoms of the macrocyclic core are all substituted by a pentyl group. The best catalytic performances were obtained by using an imidazolium/Pd ratio of 1:1. The catalytic systems displayed high activities, which increased in the order R=n‐propyl (1)

Hummingbird behaviour of N-heterocyclic carbenes stabilises out-of-plane bonding of AuCl and CuCl units.

An N-heterocyclic carbene substituted by two expanded 9-ethyl-9-fluorenyl groups was shown to bind an AuCl unit in an unusual manner, namely with the AuX rod sitting out of the plane defined by the heterocyclic carbene unit. As shown by X-ray studies and DFT calculations, the observed large pitch angle (21°) arises from an easy displacement of the gold(I) atom away from the carbene lone-pair axis, combined with the stabilisation provided by weak CH⋅⋅⋅Au interactions involving aliphatic and aromatic H atoms of the NHC wingtips. Weak, intermolecular Cl⋅⋅⋅H bonds are likely to cooperate with the H⋅⋅⋅Au interactions to stabilise the out-of-plane conformation. A general belief until now was that tilt angles in NHC complexes arise mainly from steric effects within the first coordination sphere.

The calixarene cavity – binding site or refuge?

Consideration of the Hirshfeld surfaces for some simple inclusion complexes of p-t-butyltetrathiacalix[4]arene and a number of its metal ion derivatives indicates that a bound metal ion can significantly influence the nature of the interactions between the included molecule and the cavity. These interactions do, however, vary with the degree of deprotonation of the calixarene, the particular nature of the bound metal ion and, in some cases, with the extent of exo-cavity interactions of the included species. The possible influences of inclusion interactions on the catalytic activity of metallocalixarenes are assessed. Hirshfeld surfaces can be used to discern differences in the interactions of included solvents with the cavity of p-t-butyltetrathiacalix[4]arene in various derivatives of the calixarene.

Crystal structure of trans-dichlorido[1,3-bis(9-methyl-9H-fluoren-9-yl) benzimidazol-2-ylidene](pyridine)palladium(II) – a compound with anagostic CH–Pd interactions, C40H31Cl2N3Pd

Abstract C40H31Cl2N3Pd, orthorhombic, Pnma (no. 62), a = 16.7821(7), b = 14.1436(8), c = 11.1431(5) Å, V = 3205.9(2) Å3, Z = 4, Rgt(F) = 0.0394, wRref(F2) = 0.0817, T = 150 K.

Crystal structure of 5-(imidazol-1-yl)-25,26,27,28-tetrabenzyloxy- calix[4]arene (cone), C59H50N2O4

C59H50N2O4, monoclinic, P2(1)/n (no. 14), a = 19.028(3) angstrom, b = 12.605(1) angstrom, c = 20.943(3) angstrom, beta = 114.91(2)degrees, V = 4555.9 angstrom(3), Z = 4, R(F) = 0.043, wR(ref)(F-2) = 0.085, T = 140 K.