Synthesis and P-P cleavage reactions of [P(X)X']2; X-ray structures of [Co[P(X)X'](CO)3] and P4[P(X)X']2[X = N(SiMe3)2, X'= NPri2

Treatment of P(X)(X')Cl with KC8 gave the crystalline diphosphine P(X)X']2 (1) which dissociated reversibly into the phosphinyl radical *P(X)X' (2), a plausible intermediate in the reaction of with Cr(CO)6], Co(NO)(CO)3] or P4, yielding CrP(X)X']2(CO)3] (3), CoP(X)X'](CO)3] (4), or 1,4-P4P(X)X']2 (5); the P(X)X' substituent is pyramidal at P in but planar in X = N(SiMe3)2, X'= NPri2].