A study by (^31)P N.M.R. of phosphorus compounds and complexes in liquid hydrogen chloride

Abstract

The oxidation and exchange reactions of simple phosphorus compounds and the behaviour of a range of low valent triphenylphosphine complexes of the transition metals in liquid hydrogen chloride at room temperature were studied by (^31)P nuclear magnetic resonance spectroscopy. When oxidation did occur, the phosphorus was oxidised from the +3 to the +5 oxidation state. In general, five co-ordinate fluorine containing phosphorus(V) species were produced from the oxidation of phosphorus(III) fluoride and four co-ordinate species of type PBr(_x)C1(_4-x)(^+) (O ≤ x ≤ 4) from the oxidation of phosphorus(ill) bromide or chloride. The (^31)P n.m.r. chemical shifts of the complete series PBr(_x)C1(_4-x)(^+) (O ≤ x ≤ 4) were recorded in solution for the first time, stabilised by tetrachloroborate anions in liquid hydrogen chloride. The protonation of a series of oxygen containing phosphorus (V) compounds in the solvent at room temperature was investigated using P n.m.r. spectroscopy. A measure of the "acidity" of liquid hydrogen chloride was obtained from comparison of chemical shift values with values for the protonated species in other acidic room temperature solvents. The behaviour of the boron trihalides and tetrahaloborate ions in the solvent at room temperature was studied by (^11)B n.m.r. spectroscopy. The behaviour of low valent triphenylphosphine complexes of iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, iridium, platinum31and gold in the solvent was investigated using (^31)P n.m.r., and where appropriate (^11)B n.m.r., spectroscopy. Protonation of the iron(O)complexes Fe(CO)(_5-x)(Ph(_3)P)(_x)(x = 1,2) in the presence of the Lewis acid BC1(_3) was observed. Oxidative addition reactions took place between the iridium(l) and rhodium(l) complexes (Ph(_3)P)(_2)M(CO)C1 (M = Ir,Rh) and the solvent. Finally, the oxidation of platinum(O) to platinum(II) in reactions between tris- and tetrakis (triphenylphosphine)platinum(0) and liquid hydrogen chloride was observed. Products were characterised by elemental analysis, Raman and infrared, and (^31)P and (^11)B nuclear magnetic resonance spectroscopy.