REACTION OF [NI(PH2PCH2CH2PPH2)(2)] WITH DCL - CONTROLLING THE FORMATION OF HD AND D-2

The reaction between anhydrous DCl and [Ni(Ph2PCH2CH2PPh2)(2)] in dich loromethane produced mixtures of HD and D-2. The relative amounts of t he dihydrogen isotopomers produced depends on the concentration of aci d. Mechanistic investigations showed that the reaction involves initia l formation of [NiD(Ph2PCH2CH2PPh2)(2)](+). This deuteriation labilise s the nickel to phosphine dissociation. At low concentrations of acid, phosphine chelate ring opening produces [NiCl2(Ph2PCH2CH2PPh2)] (conf irmed by X-ray crystallography) and free (PhPCH2CH2PPh2)-P-2 together with HD(65 +/- 5) and D-2 (35 + 5%). The hydrogen atom of HD originate s from a phosphine ligand. At high concentrations of acid the rate of attack of DCl at [NiD(Ph2PCH2CH2PPh2)(2)](+) becomes faster than phosp hine chelate ring opening and results in the formation of [Ni((PhPCH2C H2PPh2)-P-2)(2)]Cl-2 and predominantly D-2. Experimentally, the highes t concentration of DCl that can be used without appreciable decomposit ion of the complex is 0.2 mol dm(-3). At this concentration of acid th e dihydrogen isotopomer distribution is HD (35 +/- 5) and D-2 (65 +/- 5%); however, analysis of the product distribution indicates that at m uch higher acid concentrations D-2 could be the exclusive isotopomer.