in tetrahydrofuran byproducts: H2, HP(O2C6H4)2; absence of air and moisture; pptn. on mixing Nb-complex with 2 equiv. ofphosphine; decantation;

in diethyl ether absence of air and moisture; pptn. on standing for some d, decantation, drying (vac.);

in toluene absence of air and moisture; pptn. on mixing Nb-complex with 2 equiv. ofphosphine; decantation, crystn. (room temp., 1 week), decantation, drying (vac.); elem. anal.;

in tetrahydrofuran; diethyl ether byproducts: HP(t-Bu)2; absence of air and moisture; stirring Nb-complex (in ether) with 1 equiv. of phosphine (in THF) for 30 min; decantation, solvent removal (vac.), dissoln. in PhMe;