BridgedN-Heterocyclic/Mesoionic (NHC/MIC) Heterodicarbenes as Ligands for Transition Metal Complexes

Abstract

Following a copper catalyzed alkyne azide cycloaddition (CuAAC) and N-alkylation protocols, we report the preparation of a hybrid N-heterocyclic/mesoionic [NHC(H)-MIC(H)][2I] salt (1) in high yields. The treatment of salt 1 with CuO and KI yields a second hybrid NHC/MIC proligand featuring a tetraiodocuprate anion [NHC(H)-MIC(H)][CuI] (2). Through selective deprotonation and metalation, both salts 1 and 2 can generate either the chelate heterodicarbene complexes (3) with the rare [NHC·(M)·MIC][MX] general formula (M = Pd, Rh) or NHC-anchored/pendent triazolium species (4) [NHC·(M)-MIC(H)]. If the triazolium moiety of type 4 complexes is deprotonated with KHMDS in the presence of a second metal center, a series of heterobimetallic complexes of the type [NHC·(M)-MIC·(M')] (5) are achieved. Interestingly, the reaction of salt 2 with KHMDS yields the bimetallic copper heterodicarbene (6) which can be a useful transfer reagent for the preparation of type 3 complexes. A variety of synthetic routes for the preparation of complexes 3-5 and their full characterization in solution and in the solid state will be discussed.

Polymorphic Copper Iodide Anions: Luminescence Thermochromism and Mechanochromism of (PPh4)2[Cu2I4]

“…33 Another binuclear anion is [Cu2I4] 2which has been encountered in several associations with different organic and inorganic cations. 34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57,58,59,60,61,62,63,64,65,66 The photophysical properties of these compounds have been rarely characterized, [Cu2I4] 2being simply treated as an inorganic counter-anion and not as an emissive species by itself. In particular, with the tetraphenylphosphonium cation, the polymorphic structure of (PPh4)2[Cu2I4] has been reported but no photophysical characterization has been investigated.…”

Structural and Luminescent Properties of Homoleptic Silver(I), Gold(I), and Palladium(II) Complexes with nNHC-tzNHC Heteroditopic Carbene Ligands

“…21 The synthesis of heteroditopic carbene ligands, that is, ligands combining two types of N-heterocyclic carbenes, is appealing because, in principle, it should allow one to isolate original heterobimetallic species, taking advantage of the different acidity of the heterocyclic rings. 22−25 Moreover, the properties of a complex having a bidentate ligand with mixed donors might not be intermediate with respect to those of the corresponding homoditopic compounds. For example, a palladium(II) complex with a dicarbene ligand having two different NHC donors was found to display enhanced catalytic properties with respect to the corresponding complexes with the homodicarbene ligands; this was explained in terms of “electronic asymmetry” in the complex.…”

New palladium (II) complexes with 1‐phenyl‐1H‐tetrazole‐5‐thiol and diphosphine Synthesis, characterization, biological, theoretical calculations and molecular docking studies

“…The Pd − S bond lengths are in the range 2.27–2.28 A, which is in line with those of related triazolylidene–palladium complexes. [ 50 ] The Pd‐P bond distance 2.361–2.371 A, which is longer that of Pd − S. Compared with other carbenes, the Pd–N bond length, 1.94 A, shorter than nitrogen containing groups chelated complexes [ 51 ] indicating the stability of the resulting coordination. Here the ligands adopt a relative cis disposition [S(53)‐Pd(1)‐S(3) 92.298, S(54)‐Pd(1)‐S(15) 89.305, P(26)‐Pd(1)‐S(3) 93.846, P(27)‐Pd(1)‐S(15) 89.082, N(19)‐Pd(1)‐P(2) 91.022, N(7)‐Pd(1)‐P(3) 88.007, S(52)‐Pd(1)‐S(3) 92.211, S(53)‐Pd(1)‐S(52) 89.476, P(26)‐Pd(1)‐S(15) 88.820, P(27)‐Pd(1)‐S(15) 92.041, S(15)‐Pd(1)‐S(3) 87.573, P(27)‐Pd(1)‐P(26) 85.726, P(28)‐Pd(26)‐N(5) 89.015 and P(27)‐Pd(26)‐N(17) 91.768] for complexes 1‐5b respectively.…”