113978-91-9Relevant articles and documents
An acidity scale of tetrafluoroborate salts of phosphonium and iron hydride compounds in [D2]dichIoromethane
Li, Tianshu,Lough, Alan J.,Morris, Robert H.
, p. 3796 - 3803 (2008/02/08)
Equilibrium constants (K) for reactions between acids and the conjugate base forms of a number of phosphonium salts, [HPR3][BF4], and iron hydrides, [Fe(CO)3H(PR3)2][BF 4], in CD2Cl2 have been determined by means of 31P and 1H NMR spectroscopy at 20°C. The anchor compound chosen for pKCD2Cl2 determinations was [HPCy 3][BF4] with a pKCD2Cl2 value of 9.7, as assigned by literature convention (Cy: cyclohexyl). A continuous scale of pKCD2Cl2 values covering the range from 9.7 to -3 was created and correlated with the ΔH values reported by Angelici and co-workers and literature pKa values. The pKCD2Cl2 values for 15 other hydride or dihydrogen complexes of the iron group elements and of diethyl ether were also placed on this scale. The crystal structures of [Fe(CO) 3H(PCy2Ph)2][BF4] and [Fe(CO) 3(PCy2Ph)2] revealed that the frans-oriented, bulky, unsymmetrical phosphane ligands distort the equatorial plane of the complexes. The acidity of iron carbonyl hydrides is an important feature of the reactions of iron hydrogenase enzymes.
Air-stable trialkylphosphonium salts: simple, practical, and versatile replacements for air-sensitive trialkylphosphines. Applications in stoichiometric and catalytic processes.
Netherton,Fu
, p. 4295 - 4298 (2007/10/03)
Trialkylphosphines furnish unusual, sometimes unique, reactivity in a range of transformations. Unfortunately, their utility is compromised by their sensitivity to oxidation. We have examined a simple but powerful strategy for addressing this problem: convert air-sensitive trialkylphosphines into air-stable phosphonium salts via protonation on phosphorus. These robust salts serve as direct replacements for the corresponding phosphines (simple deprotonation under the reaction conditions by a Bronsted base liberates the trialkylphosphine) in a diverse set of applications. [reaction: see text]