950595-40-1Relevant academic research and scientific papers
Synthesis of a new bidentate NHC-Ag(I) complex and its unanticipated reaction with the Hoveyda-Grubbs first generation catalyst
Occhipinti, Giovanni,Jensen, Vidar R.,T?rnroos, Karl Wilhelm,Fr?ystein, Nils ?ge,Bj?rsvik, Hans-René
, p. 7186 - 7194 (2009)
A new sterically demanding bidentate imidazolium bromide has been prepared and used as ligand precursor for the synthesis of the corresponding NHC-silver(I) complex. The X-ray analysis of the silver(I) complex revealed a rare Ag4O4 c
Catalytic Transfer of Magnetism Using a Neutral Iridium Phenoxide Complex
Ruddlesden, Amy J.,Mewis, Ryan E.,Green, Gary G. R.,Whitwood, Adrian C.,Duckett, Simon B.
supporting information, p. 2997 - 3006 (2015/06/30)
A novel neutral iridium carbene complex Ir(κC,O-L1)(COD) (1) [where COD = cyclooctadiene and L1 = 3-(2-methylene-4-nitrophenolate)-1-(2,4,6-trimethylphenyl)imidazolylidene] with a pendant alkoxide ligand has been prepared and characterized. It contains a strong Ir-O bond, and X-ray analysis reveals a distorted square planar structure. NMR spectroscopy reveals dynamic solution-state behavior commensurate with rapid seven-membered ring flipping. In CD2Cl2 solution, under hydrogen at low temperature, this complex dominates, although it exists in equilibrium with a reactive iridium dihydride cyclooctadiene complex. 1 reacts with pyridine and H2 to form neutral Ir(H)2(κC,O-L1)(py)2, which also exists in two conformers that differ according to the orientation of the seven-membered metallocycle, and while its Ir-O bond remains intact, the complex undergoes both pyridine and H2 exchange. As a consequence, when placed under para-hydrogen, efficient polarization transfer catalysis (PTC) is observed via the signal amplification by reversible exchange (SABRE) approach. Due to the neutral character of this catalyst, good hyperpolarization activity is shown in a wide range of solvents for a number of substrates. These observations reflect a dramatic improvement in solvent tolerance of SABRE over that reported for the best PTC precursor IrCl(IMes)(COD). For THF, the associated 1H NMR signal enhancement for the ortho proton signal of pyridine shows an increase of 600-fold at 298 K. The level of signal enhancement can be increased further through warming or varying the magnetic field experienced by the sample at the point of catalytic magnetization transfer. (Chemical Equation Presented).
