139697-84-0Relevant articles and documents
Gold(III) NHC Complexes for Catalyzing Dihydroalkoxylation and Hydroamination Reactions
Nair, Ashwin G.,McBurney, Roy T.,Gatus, Mark R. D.,Binding, Samantha C.,Messerle, Barbara A.
, p. 12067 - 12075 (2017)
A gold(III) complex of an N-heterocyclic carbene based hemilabile ligand with two pendant pyrazole arms (1,3-bis((1H-pyrazol-3-yl)methyl)-2,3-dihydro-1H-imidazole, LH) was synthesized. Complex [LAu(III)Cl3] is an excellent catalyst for promoting dihydroalkoxylation at room temperature, even catalyzing this reaction at 0 °C. [LAu(III)Cl3] is one of the most efficient catalysts reported to date for the spirocyclization of alkynyl diols. Furthermore, [LAu(III)Cl3] catalyzed intra- and intermolecular hydroamination reactions, achieving good to excellent conversions. [LAu(III)Cl3] is a more efficient catalyst than a gold(I) analogue, [LAu(I)Cl]. The dependence of the quantity of weakly coordinating anion [BArF4]- ((3,5-trifluoromethyl)phenyl borate) present on catalysis efficiency was probed for the dihydroalkoxylation reaction. X-ray diffraction analysis of single crystals demonstrated the solid-state structure of gold complexes [LAu(III)Cl3] and [LAu(I)Cl], which displayed the expected square-planar and linear coordination geometries, respectively.
Cooperativity in bimetallic dihydroalkoxylation catalysts built on aromatic scaffolds: Significant rate enhancements with a rigid anthracene scaffold
Ho, Joanne H. H.,Choy, Sandra W. S.,MacGregor, Stuart A.,Messerle, Barbara A.
, p. 5978 - 5984 (2011)
This work describes investigations into metal-catalyzed sequential reactions using a series of single metal and bimetallic Rh(I) and/or Ir(I) pyrazolyl complexes. Monometallic complexes with bis(1-pyrazolyl)methane (bpm) ligands [M(CO)2(bpm)]BArF 4 (1), bimetallic complexes [M2(CO)2(Lscaffold)][BArF 4]2 (2-4) where M = Rh(I) or Ir(I) bearing bitopic ligands Lscaffold = bis(1-pyrazolyl)methane-derived ligands, p-C 6H4[CH(pz)2]2 (Lp), m-C6H4[CH(pz)2]2 (Lm), and anthracene-bridged 1,8-C14H8[CH(pz)2] 2 (LAnt), [M2(CO)4(L p)]-[BArF 4]2 (2), [M 2(CO)4(Lm)][BArF 4] 2 (3), and [M2(CO)4(LAnt)][BAr F 4]2 (4) were used as catalysts. The efficiency of the complexes as catalysts was tested for the dihydroalkoxylation of a series of alkyne diol substrates, 2-(6-hydroxyhex-1-ynyl)benzyl alcohol (5), 1-methyl-3-heptyne-1,7-diol (6), 2-(5-hydroxypent-1-ynyl)benzyl alcohol (7), and 2-(4-hydroxybut-1-ynyl)benzyl alcohol (8), forming spiroketals. All complexes tested were highly effective catalysts for the intramolecular dihydroalkoxylation reaction. The homobimetallic complexes 2-4 showed significant enhancement in activity and selectivity relative to the single metal catalysts (1). The order of catalytic activity of the bimetallic complexes was found to be [M2(CO)4(LAnt)][BArF 4]2 > [M2(CO)4(L m)][BArF 4]2 > [M 2(CO)4(Lp)][BArF 4] 2 for all substrates, and the bimetallic cooperativity index was established for each reaction.
The advantages of covalently attaching organometallic catalysts to a carbon black support: Recyclable Rh(I) complexes that deliver enhanced conversion and product selectivity
Tregubov, Andrey A.,Walker, D. Barney,Vuong, Khuong Q.,Gooding, J. Justin,Messerle, Barbara A.
, p. 7917 - 7926 (2015)
Pure carbon black (CB) was covalently attached to a bidentate nitrogen coordination motif with a carbon-carbon bond by spontaneous reaction with an in situ generated ligand precursor. The functionalized support was treated with [Rh(CO)2(μ-Cl)]2 to form a heterogeneous carbon-based support covalently linked to a well defined Rh(i) coordination complex. The hybrid material was characterized using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), Infrared (IR) spectroscopy and inductively coupled plasma mass spectrometry (ICP-MS). The CB-supported Rh(i) catalyst was active in both hydroamination and dihydroalkoxylation reactions achieving turnover numbers approaching 1000 and was readily recycled. The selectivity of an intramolecular dihydroalkoxylation reaction was significantly improved by covalently anchoring the catalyst to the CB surface.
Simple and reactive Ir(i) N-heterocyclic carbene complexes for alkyne activation
Gatus, Mark R. D.,Pernik, Indrek,Tompsett, Joshua A.,Binding, Samantha C.,Peterson, Matthew B.,Messerle, Barbara A.
, p. 4333 - 4340 (2019)
Two simple unsymmetrical monometallic Ir(i) complexes with an N-heterocyclic carbene ligand and an analogous bimetallic Ir(i) complex were synthesised. These complexes were found to be extremely active catalysts for a range of C-X (X = N or O) and Si-N bond forming reactions involving alkyne and imine activation for dihydroalkoxylation, hydroamination and hydrosilylation reactions. These catalysts exhibited reaction rates far exceeding those of other Rh(i) and Ir(i) complexes previously reported. In addition, a small change to the ligand design (phenyl vs. mesityl) substantially affected both the reactivity and product selectivity of the catalyst. The Ir(i) complex bearing a mesitylene wingtip provided unprecedented regioselectivity in the dihydroalkoxylation reaction and a new kinetic product from the typical hydrosilylation protocol of 2-benyzlpyrroline to produce an N-silylaminoalkene. Our mechanistic studies indicated that this transformation proceeded via a dehydrogenative coupling mechanism.
Highly versatile heteroditopic ligand scaffolds for accommodating group 8, 9 & 11 heterobimetallic complexes
Gatus, Mark R. D.,Bhadbhade, Mohan,Messerle, Barbara A.
, p. 14406 - 14419 (2017)
Two highly versatile xanthene scaffolds containing pairs of heteroditopic ligands were found to be capable of accommodating a range of transition metal ions, including Au(i), Ir(i), Ir(iii), Rh(i), and Ru(ii) to generate an array of heterobimetallic complexes. The metal complexes were fully characterised and proved to be stable in the solid and solution state, with no observed metal-metal scrambling. Heterobimetallic complexes containing the Rh(i)/Ir(i) combinations were tested as catalysts for the two-step dihydroalkoxylation reaction of alkynediols and sequential hydroamination/hydrosilylation reaction of alkynamines.
Enhancements in catalytic reactivity and selectivity of homobimetallic complexes containing heteroditopic ligands
Gatus, Mark R. D.,McBurney, Roy T.,Bhadbhade, Mohan,Messerle, Barbara A.
, p. 7457 - 7466 (2017/07/10)
Rh(i) and Ir(i) homobimetallic complexes were synthesised using a heteroditopic ligand system on a xanthene scaffold containing a monodentate N-heterocyclic carbene ligand and a bidentate bis(pyrazol-1-yl)methane ligand. The complexes were tested as catalysts for the two-step dihydroalkoxylation and two-step hydroamination/hydrosilylation reactions. This is the first known report of an organometallic group 9 complex, Ir(i) bimetallic complex, 13, to selectively favour the opposite spirocyclisation product from that reported in the literature, 14cvs.14b. The Ir(i) homobimetallic complex catalyses the intramolecular hydroamination reaction of alkynamines efficiently and proved to be a highly active catalyst for promoting the subsequent hydrosilylation of the pyrrolines; completing the hydrosilylation reactions in less than 40 seconds. A chloro-bridged bimetallic species was observed in the solid state, revealing that the COD co-ligands present underwent an oxidation.
