Bis(1-benzyl-3-methyl­imidazolium-κC 2)mercury(II) bis­(hexa­fluoridophosphate)

The asymmetric unit of the title complex, [Hg(C11H12N2)2](PF6)2, consists of one bis­(1-benzyl-3-methyl­imidazolium)mercury(II) cation, one half of the cation and an additional HgII atom, which lies on an inversion centre, and three hexa­fluorido­phosphate anions. The HgII atoms exist in a linear coordination geometry [C—Hg—C = 178.9 (2) and 180°] formed by two carbene C atoms from the imidazole rings. In the crystal, the cations and anions are connected via C—H⋯F hydrogen bonds, forming a three-dimensional network

3,5-Bis(3-methyl­imidazolium-1-ylmeth­yl)toluene bis­(hexa­fluoro­phosphate)

The asymmetric unit of the title N-heterocyclic carbene compound, C17H22N4 2+·2PF6 −, consists of one N-heterocyclic carbene dication and two hexa­fluoro­phosphate anions. The two imidazole rings are twisted away from but to the same side of the central toluene ring, making dihedral angles of 76.69 (7) and 78.03 (7)° with the central ring. In the crystal, the components are linked by C—H⋯F interactions, generating a three-dimensional network

1,3-Bis(2-cyano­benz­yl)imidazolium bromide

In the title salt, C19H15N4 +·Br−, the central imidazole ring makes dihedral angles of 83.1 (2) and 87.6 (2)° with the terminal benzene rings. The dihedral angle between the terminal benzene rings is 6.77 (19)°; the cyanide substituents have an anti orientation. In the crystal, the cations and anions are linked via C—H⋯N and C—H⋯Br hydrogen bonds, forming sheets lying parallel to the ac plane

1,3-Bis[(6-methyl-2-pyrid­yl)meth­yl]imidazolium bromide

The title compound, C17H19N4 +·Br−, is built up from 1,3-bis­[(6-methyl-2-pyridin­yl)meth­yl]imidazolium cations and bromide anions. Each of two 6-methyl-2-pyridyl rings is rotated out of the imidazole plane, making dihedral angles of 79.90 (9) and 86.40 (9)°. The packing is consolidated by aromatic π–π inter­actions between the pyridine rings of neighbouring mol­ecules [centroid–centroid distance = 3.554 (2) Å] and by weak C—H⋯N and C—H⋯Br hydrogen bonds

Palladium complexes of o-xylyl-linked alkoxybenzimidazolin-2-ylidenes: interesting structural conformations and application as pre-catalysts

New PdBr2-bis(N-heterocyclic carbene) complexes derived from 4,7-dibutoxybenzimidazole and 5,6-dibutoxybenzimidazole have been synthesized and structurally and spectroscopically characterized.The complexes show much greater solubility compared to the parent complex derived from benzimidazole, and interesting structural characteristics dependent on the position of the butoxy substituents. The complexes display high activities in the coupling of aryl iodides in the Mizoroki-Heckreaction and moderate activities in the Suzuki-Miyaura coupling of inactivated aryl bromides at low catalyst loadings, although activity differences between pre-catalysts has been observed. Structuralstudies suggest electronic effects within the complexes to be strongly affected by steric interactions between the hydrogen atoms of the o-xylyl bridges and the benzimidazole components and their substituents

Synthesis, structures and photoluminescence properties of silver complexes of cyclic (alkyl)(amino)carbenes

Silver complexes of cyclic (alkyl)(amino)carbenes (CAACs), (RL)nAgX (n = 1, X = Cl, Br, I; n = 2, X = OTf; R = Me2, Et2, or adamantyl) are accessible in high yields by reacting free carbenes with silver salts. The smaller carbene ligand Me2L leads to the formation of a mixture of neutral (Me2L)AgCl and cationic [(Me2L)2Ag]+ products. The transmetallation of (AdL)AgCl with copper and gold halides gives the corresponding copper and gold compounds (AdL)MCl (M = Cu and Au) in a clean and quantitative reaction. Whereas (Me2L)AgCl is monomeric in the solid state, (Et2L)AgCl crystallizes as a Cl-bridged dimer. None of the compounds show metal-metal interactions. The complexes show blue photoluminescence, which consists of a fluorescence component with a lifetime of several nanoseconds, as well as a long-lived emission in the microsecond regime

Silver(I) and mercury(II) complexes of meta- and para-xylyl linked bis(imidazol-2-ylidenes)

Mononuclear silver and mercury complexes bearing bis-N-heterocyclic carbene (NHC) ligands withlinear coordination modes have been prepared and structurally characterised. The complexes form metallocyclic structures that display rigid solution behaviour. A larger metallocycle of the form [L2Ag2]2+ [where L = parabis(N-methylimidazolylidene)xylylene] has been isolated from the reaction of para-xylylene-bis(N-methylimidazolium) chloride and Ag2O. Reaction of silver- and mercury-NHC complexes with Pd(NCCH3)2Cl2 affords palladium-NHC complexes via NHC-transfer reactions, the mercury case being only the second example of a NHC-transfer reaction using a mercury-NHC complex

R-Allyl Nickel(II) Complexes with Chelating N-Heterocyclic Carbenes: Synthesis, Structural Characterization, and Catalytic Activity

The N-heterocyclic carbene (NHC) nickel complexes [(L)Ni(NHC)][BArF4] (ArF = 3,5-bis(trifluoromethyl)- phenyl; L = allyl (1), methylallyl (2); NHC = 1-(2-picolyl)-3-methylimidazol-2-ylidene (a), 1-(2-picolyl)-3-isopropylimidazol-2-ylidene (b), 1-(2-picolyl)-3-n-butylimidazol-2-ylidene (c), 1-(2-picolyl)-3-phenylimidazol-2-ylidene (d), 1-(2-picolyl)-3- methylbenzoimidazol-2-ylidene (e), 1-(2-picolyl)-4,5-dichloro-3-methylimidazol-2-ylidene (f)) have been obtained in high yields and characterized by NMR spectroscopy. Furthermore, 1d was unambiguously characterized by single-crystal X-ray crystallography. Complexes 1a−f/2a−f have shown catalytic activity toward dimerization and hydrosilylation of styrenes. In particular, 1a proved to be the most efficient catalyst in the dimerization of styrene derivatives in the absence of cocatalyst. Also, complexes 1a,d showed high selectivity and moderate to good yields in hydrosilylation reactions

Synthesis, characterization and a reactivity study of some allyl palladium complexes bearing bidentate hemi-labile carbene or mixed carbene/PPh3 ligands

With the aim at synthesizing novel allyl complexes that can potentially act as catalysts in the Tsuji-Trost catalyzed reaction, we have synthesized and characterized some allyl and 2-Meallyl palladium derivatives with one hemilabile bidentate or two strong mono-coordinating spectator ligands. The hemilabile ligands are constituted by one nitrogen heterocyclic carbene (NHC) fragment acting as the pivot bearing a labile wing with a pyridine nitrogen or sulfur atom as the second stabilizing atom. One of two monodentate ligands is in all cases PPh3 whereas the other is a mono- or partially coordinated hemilabile carbene. The complexes were characterized by standard spectroscopic methods and elemental analysis and in two cases by SC-XRD technique.The reactivity of two selected complexes toward the Tsuji-Trost reaction was tested by stoichiometric allyl amination carried out with piperidine and the results of such a mechanistic investigation integrated by a computational study are also reported in this paper. (C) 2016 Elsevier Ltd. All rights reserved