Synthesis and P–P cleavage reactions of [P(X)X′] 2 ; X-ray structures of [Co{P(X)X′}(CO) 3 ] and P 4 [P(X)X′] 2 [X = N(SiMe 3 ) 2 , X′ = NPr i 2 ]

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 [Cr[P(X)X']2(CO)3] (3), [Co[P(X)X'](CO)3] (4), or 1,4-P4[P(X)X']2 (5); the P(X)X' substituent is pyramidal at P in but planar in [X = N(SiMe3)2, X'= NPri2].