Competitive or sequential reaction of an electrophilic terminal phosphinidene metal(0) complex with allyl halides? [2+1]-cycloaddition vs. C-X bond insertion.

The transiently generated electrophilic terminal phosphinidene complex [(CO)5WPCH(SiMe3)2] reacted with allyl halides (X = F, Cl, Br) in toluene resulting in the formation of stable C-X insertion products 3a-c and diastereomeric phosphirane complexes 4a,a',b,b' as well as methylenephosphirane complex 5 as observed by 31P{1H} NMR spectroscopy. DFT calculations revealed that a novel rearrangement of transient phosphirane complexes is responsible involving C → P X atom transfer.