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Relevant academic research and scientific papers

Cyclometalation of aryl-substituted phosphinines through C-H-bond activation: A mechanistic investigation

A series of 2,4,6-triarylphosphinines were prepared and investigated in the base-assisted cyclometalation reaction using [Cp*IrCl2] 2 (Cp=1,2,3,4,5-pentamethylcyclopentadienyl) as the metal precursor. Insight in the mechanism of the C-H bond activation of phosphinines as well as in the regioselectivity of the reaction was obtained by time-dependent 31P{1H}NMR spectroscopy. At room temperature, 2,4,6-triarylphosphinines instantaneously open the Ir-dimer and coordinate in an η1-fashion to the metal center. Upon heating, a dissociation step towards free ligand and an Ir-acetate species is observed and proven to be a first-order reaction with an activation energy of ΔE A=56.6kJ mol-1 found for 2,4,6-triphenylphosphinine. Electron-donating substituents on the ortho-phenyl groups of the phosphorus heterocycle facilitate the subsequent cyclometalation reaction, indicating an electrophilic C-H activation mechanism. The cyclometalation reaction turned out to be very sensitive to steric effects as even small substituents can have a large effect on the regioselectivity of the reaction. The cyclometalated products were characterized by means of NMR spectroscopy and in several cases by single-crystal X-ray diffraction. Based on the observed trends during the mechanistic investigation, a concerted base-assisted metalation-deprotonation (CMD) mechanism, which is electrophilic in nature, is proposed. Finely tuned: A series of substituted 2,4,6-triarylphosphinines were prepared and investigated in a base-assisted cyclometalation reaction using [Cp*IrCl 2]2 (Cp=1,2,3,4,5-pentamethylcyclopentadienyl) as the metal precursor M (see figure). Insight into the mechanism of the C-H bond activation of phosphinines as well as into the regioselectivity of the reaction was obtained by using time-dependent 31P{1H}NMR spectroscopy and single-crystal X-ray diffraction. Copyright

Phosphabenzene compounds and their use in hydroformylation

Phosphabenzene compounds of the formula (I) where the radicals R1to R13are, independently of one another, hydrogen, COOM, SO3M, NR3X, NR2, OR, COOR or SR (where M=hydrogen, NH4or alkali metal, X=anion, R=hydrogen or C1-C6-alkyl), or C1-C12-alkyl, C6-C12-aryl, C7-C12-aralkyl, C7-C12-alkaryl or C3-C6-heteroaromatics, where the alkyl, aryl, alkaryl and aralkyl radicals may bear the abovementioned radicals as substituents and two or more of the radicals may be joined to form aliphatic or fused-on rings, where at least one of the radicals R4and R8and at least one of the radicals R9and R13is not hydrogen, can be used for preparing hydroformylation catalysts.