Mercury(II) Complexes of Anionic N-Heterocyclic Carbene Ligands: Steric Effects of the Backbone Substituent

Abstract

Mercury(II) complexes (Me-maloNHCDipp)HgCl (1b), (t-Bu-maloNHCDipp)HgCl (2b) and (t-Bu-maloNHCDipp)HgMe (2c) supported by anionic N-heterocyclic carbenes have been obtained in good yields from the reaction of the potassium salt of N-heterocyclic carbene ligand precursors and mercury(II) salts, HgCl2 and MeHgI. These molecules have been characterized by 1H-NMR, 13C-NMR and IR spectroscopy and elemental analysis. X-ray crystal structures of 1b and 2b are also presented. Interestingly, complex 1b is polymeric {(Me-maloNHCDipp)HgCl}n in the solid state, as a result of inter-molecular Hg-O contacts, and features rare three coordinate mercury sites with a T-shaped arrangement, whereas the (t-Bu-maloNHCDipp)HgCl (2b) is monomeric and has a linear, two-coordinate mercury center. The formation of T-shaped structure and the aggregation of complex 1b is attributable to the reduced steric demand of the N-heterocyclic carbene ligand backbone substituent.

Luminescent Copper(I)‐Complexes with an Anionic NHC obtained via a Coordination Polymer as Versatile Precursor**

“…The NHC bridges the central Cu I ions with its carbene‐carbon and backbone‐oxygen atoms, respectively. This coordination mode of the NHC ligand has previously been observed in a polymeric structure containing Hg II Cl moieties [15] . [1 ⋅ Cu] n is easily available, serves as a versatile starting material for a wide range of heteroleptic complexes and is, to the best of our knowledge, the first report on the synthetic use of a coordination polymer only consisting of an NHC and a metal ion.…”

“…This coordination mode of the NHC ligand has previously been observed in a polymeric structure containing Hg II Cl moieties. [15] [1 • Cu] n is easily available, serves as a versatile starting material for a wide range of heteroleptic complexes and is, to the best of our knowledge, the first report on the synthetic use of a coordination polymer only consisting of an NHC and a metal ion. Its application circumvents the aforementioned problems of the formation of inorganic byproducts during the synthesis of the final complexes, which are depicted in Scheme 1.…”

Carbon Ligands: From Fundamental Aspects to Applications

“…The NHCs which constitute the most developed family of neutral carbon ligands have been approached from two main directions by the different contributors, namely, from a synthetic point of view with the preparation of new carbenic structures, and for their applications either in catalysis or in biology. In the first direction, while Kunz et al described the fascinating coordination chemistry of a strongly donor macrocyclic C,N,C -pincer ligand exhibiting pentamethylene tethered NHC donor ends [ 12 ], Dias et al were interested in the design of Hg(II) complexes bearing anionic maloNHC ligands [ 13 ], and Santini et al in the chemistry of zwitterionic imidazolium borate species [ 14 ]. Regarding catalytic applications, Grela et al reported the preparation of a family of nitro-activated Ru(II)-based olefin metathesis catalysts while evaluating the influence of the NHC ligand [ 15 ].…”