Synthesis of Imidazole-Based Functionalized Mesoionic Carbene Complexes of Palladium: Comparison of Donor Properties and Catalytic Activity toward Suzuki–Miyaura Coupling

Three different backbone-monofunctionalized imidazolium salts have been synthesized using the metal–halogen exchange procedure, and their corresponding mesoionic carbene complexes with palladium were prepared via oxidative addition without protection of the C2 position. The donor properties were evaluated with ³¹P NMR spectroscopy of the respective palladium complexes. The catalytic activity of these complexes toward Suzuki–Miyaura coupling of aryl bromides was also explored. Also, in one case, a comparison of donor properties was made with those of a “normal” carbene with similar steric bulk

Synthesis, Structure, and Coordination Chemistry of Phosphine-Functionalized Imidazole/Imidazolium Salts and Cleavage of a C–P Bond in an NHC–Phosphenium Salt using a Pd(0) Precursor

A simple method involving metal–halogen exchange reaction(s) to prepare various phosphine-functionalized imidazole/imidazolium salts and their coordination chemistry with different metal precursors has been described. Interestingly, the reaction of 1,3-dimethyl-2-(diphenylphosphino)-4-iodoimidazolium iodide (<b>6</b>) with Pd₂(dba)₃ in the presence of triphenylphosphine affords a Pd­(II)–NHC complex which involves the cleavage of a C–P bond presumably occurring via oxidative addition of Pd(0) to a C–I bond to afford an in situ generated Pd­(II) species, which subsequently reacts with another 1 equiv of <b>6</b> through the phosphine center to form an adduct followed by a dephosphinylation reaction

Backbone Thio-Functionalized Imidazol-2-ylidene–Metal Complexes: Synthesis, Structure, Electronic Properties, and Catalytic Activity

A new synthetic route to prepare imidazolium salts with heteroatom-containing functional groups at the backbone has been reported. Accordingly, the first example of a backbone bis-thiofunctionalized imidazolium salt (<b>4</b>) was prepared by sequential metal–halogen exchange reaction of 1-methyl-4,5-diiodoimidazole (<b>1</b>) followed by a quaternization reaction with methyl iodide. The metal–carbene complexes <b>6</b>, <b>8</b>, and <b>10</b> were synthesized conveniently through three different routes, namely, (a) an in situ generated carbene route, (b) a transmetalation method, and (c) direct reaction with a basic metal precursor, and structurally characterized. Subsequently the electronic properties of the newly prepared 1,3-dimethyl-4,5-bis­(phenylthio)-imidazol-2-ylidene ((SPh)₂IMe) was studied by measuring the carbonyl stretching frequency of the corresponding [Ir­{(SPh)₂IMe}­(CO)₂(Cl)] complex. In addition, the air-stable palladium–NHC complex <b>10</b> was found to be catalytically active in Suzuki–Miyaura coupling reactions of aryl bromides

Backbone Thio-Functionalized Imidazol-2-ylidene–Metal Complexes: Synthesis, Structure, Electronic Properties, and Catalytic Activity

A new synthetic route to prepare imidazolium salts with heteroatom-containing functional groups at the backbone has been reported. Accordingly, the first example of a backbone bis-thiofunctionalized imidazolium salt (<b>4</b>) was prepared by sequential metal–halogen exchange reaction of 1-methyl-4,5-diiodoimidazole (<b>1</b>) followed by a quaternization reaction with methyl iodide. The metal–carbene complexes <b>6</b>, <b>8</b>, and <b>10</b> were synthesized conveniently through three different routes, namely, (a) an in situ generated carbene route, (b) a transmetalation method, and (c) direct reaction with a basic metal precursor, and structurally characterized. Subsequently the electronic properties of the newly prepared 1,3-dimethyl-4,5-bis­(phenylthio)-imidazol-2-ylidene ((SPh)₂IMe) was studied by measuring the carbonyl stretching frequency of the corresponding [Ir­{(SPh)₂IMe}­(CO)₂(Cl)] complex. In addition, the air-stable palladium–NHC complex <b>10</b> was found to be catalytically active in Suzuki–Miyaura coupling reactions of aryl bromides