Unusually Coordinated Phosphorus Compounds; 36.¹ Phosphavinyldiazoalkane/1,2,4-Diazaphosphole Cyclization

In the reactions of bis(trimethylsilyl)methylenechlorophosphine (7) and chloro(phenyltrimethylsilylmethylene)phosphine (16) with metalated diazomethane derivatives (N₂=C(M)R), the primarily formed substituted phosphavinyldiazoalkanes[methylene(1-diazoalkyl)phosphines] (13a, b and 17) can only, if at all, be isolated and characterized spectroscopically at - 78°C. At the latest during thawing, they undergo [1,5] cyclization reactions to furnish the 1H-1, 2,4-diazaphospheles 15 or 18. The silyl groups bonded to the nitrogen atoms in the latter compounds can be readily cleaved hydrolytically to give the corresponding N-unsubstituted 1H-1,2,4-diazaphospholes 11 and 19. (Diazotrimethylsilylmethyl)phenyltrimethylsilylmethylene)phosphine (17) takes part in a 1,3-dipolar cycloaddition reaction with (2,2-dimethylpropylidyne) phosphine (20) to produce 3-tert-butyl-1-trimethylsilyl-5-(phenyltrimethylsilylmethylene) phosphino-1-H-1,2,4-diazaphosphole (23).