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[^<i>t</i>Bu]­Ar)₃ (<b>1</b>, Ar = 3,5-Me₂­C₆H₃), we report the use of ClP<b>A</b> (<b>A</b> = C₁₄H₁₀, anthracene) as a formal source of phosphorus­(I) in its reaction with Na­[NV­(N­[^<i>t</i>Bu]­Ar)₃] (Na­[<b>4</b>]) to yield trimeric cyclo-triphosphane [PNV­(N­[^<i>t</i>Bu]­Ar)₃]₃ (<b>3</b>) with a core composed exclusively of phosphorus and nitrogen. In the presence of NapS₂ (<i>peri</i>-1,8-naphthalene disulfide), NapS₂P-NV­(N­[^<i>t</i>Bu]­Ar)₃ (<b>6</b>) is instead generated in 80% yield, suggesting trapping of transient <b>1</b>. Upon mild heating, <b>3</b> readily fragments into dimeric [PNV­(N­[^<i>t</i>Bu]­Ar)₃]₂ (<b>2</b>), while in the presence of bis­(trimethyl­silyl)­acetylene or <i>cis</i>-4-octene, the respective phosphirene (Ar­[^<i>t</i>Bu]­N)₃­VN-PC₂­(SiMe₃)₂ (<b>7</b>) or phosphirane (Ar­[^<i>t</i>Bu]­N)₃­VN-P­(C₈H₁₆) (<b>8</b>) compounds are generated. Kinetic data were found to be consistent with unimolecular decay of <b>3</b>, and [2+1]-cycloaddition with radical clocks ruled out a triplet intermediate, consistent with intermediate <b>1</b> reacting as a singlet phosphin­idene. In addition, both <b>7</b> and <b>8</b> were shown to reversibly exchange <i>cis</i>-4-octene and bis­(trimethyl­silyl)­acetylene, serving as formal sources of <b>1</b>, a reactivity manifold traditionally reserved for transition metals