Reactivity of acyclic diaminocarbene ligands

Experimental and computational tuning of metalla-N-heterocyclic carbenes at palladium(ii) and platinum(ii) centers

“…Transition metal complexes with heteroatom-stabilised carbenes, i.e. N-heterocyclic carbenes (NHCs) 1 and acyclic diaminocarbenes (ADCs), 2 underpin a broad range of applications in the catalysis of organic processes; 1 a ,2 a ,3 they are studied as emissive materials in optoelectronics 4 and potential anticancer drugs. 2 a ,5 The ligand properties of diaminocarbenes are manifested through the formation of the M–C carbene σ-bond by transferring a pair of nonbonding electrons from the nucleophilic σ-orbital of the carbene carbon atom to the metal atom M. At the same time, the formation of a π-bond is also possible as a result of the interaction of a vacant electron-deficient pπ-orbital of a carbene carbon atom with a metal, whose orbital symmetry is suitable.…”

Tuning the luminescence of transition metal complexes with acyclic diaminocarbene ligands

“…28,49,56,57 Another important observation regarding metal-ADCs is their synthetic availability since several strategies for their preparation are established and widely used. [58][59][60][61][62] Valuable properties of complexes of transition metals with diaminocarbene ligands associated with their photophysical applications are determined by the characteristics of the metal centre, as well as by the balance between donor and steric properties of the diaminocarbene ligand. Each application requires complexes and, therefore, ligands with a different set of parameters, that are screened empirically, imposing stringent requirements on the method of their synthesis.…”

“…At the same time, the most widespread approach is based on nucleophilic addition to metal-bound isocyanides and leading to the production of diminocarbene metal complexes without the release of free carbene. [58][59][60][61][62][63] This approach is stoichiometric, atom-efficient and high-yielding as a rule allowing for an easy variation of the periphery of ADCs, thus ensuring high synthetic flexibility (Scheme 1). The elegance of this approach consisting basically of one step and leading to diverse well-defined metaldiaminocarbene species is in sharp contrast to the strategies for the generation of custom-made N-heterocyclic carbenes 64 and cyclic alkylaminocarbenes, 39 where only the ligand synthesis may require several consecutive steps.…”

“…those featuring one or two NH wingtips, possess Brønsted acidity, being able to act as donors of hydrogen bonding. 62 For Au i –ADC complexes, aurophilic interactions arise alongside the hydrogen bonding and their synergetic interactions make these complexes capable of luminescence. As an example, complex [Au{C(NMe 2 )(NHMe)} 2 ](PF 6 ) 135 bearing a sole NH proton on the ADC moiety is non-emissive in both the solution and in the solid state.…”

Current Developments of N-Heterocyclic Carbene Au(I)/Au(III) Complexes toward Cancer Treatment

“…NHC gold carbene complexes have become state of the art over the last decade, with numerous applications in the medicinal field [ 150 ]. Acyclic carbene (ACC) ligands, on the other hand, present a promising alternative due to their synthetic versatility, and they provide a variety of methods to improve solubility, cell uptake, and selectivity of cytotoxicity [ 151 , 152 , 153 ]. Some of the first examples of this category are the acyclic carbene adducts of gold; however, their biological impact is as yet hardly explored [ 148 , 154 ].…”