Phosphinidene Reactivity of a Transient Vanadium P≡N Complex.

Toward the preparation of a coordination complex of the heterodiatomic molecule PN, P≡N-V(N[Bu]Ar) (1, Ar = 3,5-MeCH), we report the use of ClPA (A = CH, anthracene) as a formal source of phosphorus(I) in its reaction with Na[NV(N[Bu]Ar)] (Na[4]) to yield trimeric cyclo-triphosphane [PNV(N[Bu]Ar)] (3) with a core composed exclusively of phosphorus and nitrogen. In the presence of NapS (peri-1,8-naphthalene disulfide), NapSP-NV(N[Bu]Ar) (6) is instead generated in 80% yield, suggesting trapping of transient 1. Upon mild heating, 3 readily fragments into dimeric [PNV(N[Bu]Ar)] (2), while in the presence of bis(trimethylsilyl)acetylene or cis-4-octene, the respective phosphirene (Ar[Bu]N)VN-PC(SiMe) (7) or phosphirane (Ar[Bu]N)VN-P(CH) (8) compounds are generated. Kinetic data were found to be consistent with unimolecular decay of 3, and [2+1]-cycloaddition with radical clocks ruled out a triplet intermediate, consistent with intermediate 1 reacting as a singlet phosphinidene. In addition, both 7 and 8 were shown to reversibly exchange cis-4-octene and bis(trimethylsilyl)acetylene, serving as formal sources of 1, a reactivity manifold traditionally reserved for transition metals.