Depending on the nature of the substituents and the experimental conditions used, transient or stable phosphinocarbenes are generated from the corresponding-diazophosphines. Of particular interest thermolysis of (trimethylsilyl)[bis (diisopropylamino) phosphino] diazomethane (1), at 250 C under vacuum, leads to the corresponding stable phosphinocarbene 2 (bp 75-80 C/10" 2 mmHg). According to NMR data (, 13C, 31P, 29Si), 2 possesses a phosphorus-vinyl ylide or a X5-phosphaacetylene structure. A [2+ 3] cycloaddition, typicalfor multiple-bond behavior, is observed when 2 is treated with trimethylsilyl azide, but pyrolysis of 2 leads tofive-membered rings 22 probably through carbene insertion into a CH bond of a phosphorus substituent.

In the fifties, the possibility of synthesizing a low coordinated heavier main group element was questionable. 1 However, in the last few years, molecules featuring pT-p, double bonds, involving silicon, germanium, phosphorus, arsenic, and sulfur havebeen reported. 2 The next challenge was to prepare triply-bonded derivatives, and, up to now, only thiazyltrifluoride (F3S-N) 3 and a few phospha4 and arsaalkynes5 are known tobe stable at room temperature. It is well established that aminonitrene, 6 sulfe-nylnitrene, 3 sulfmylnitrene, 7 and phosphinonitrene8 can be regarded as diazene, thiazyne, oxathyazyne, and phosphonitrile, respectively, due to delocalization of the lone pair. We wanted to find out if the generation of a carbenoid species next to a heteroatom, bearing both a lone pair and a vacant p or d orbital, is a general method for obtaining “triple-bonded-like” derivatives. Here we want to