4 research outputs found
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 <sup>31</sup>P
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 Pd<sub>2</sub>(dba)<sub>3</sub> in the
presence of triphenylphosphine affords a PdÂ(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 PdÂ(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-bisÂ(phenylthio)-imidazol-2-ylidene ((SPh)<sub>2</sub>IMe) was studied by measuring the carbonyl stretching frequency
of the corresponding [IrÂ{(SPh)<sub>2</sub>IMe}Â(CO)<sub>2</sub>(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-bisÂ(phenylthio)-imidazol-2-ylidene ((SPh)<sub>2</sub>IMe) was studied by measuring the carbonyl stretching frequency
of the corresponding [IrÂ{(SPh)<sub>2</sub>IMe}Â(CO)<sub>2</sub>(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