Metallaphosphinidenes, [M–P], contain open-shell single-atomic phosphorus but typically display uncontrollable reactivity, preventing their utilization to selectively construct elusive functional groups. Here, we report an iridium phosphaethynolate complex, [(PCP)Ir(PCO)] (2), in a halide metathesis with Na(OCP). Photolysis of 2 leads to a bimetallic, side-on bound {P2} motif, [{(PCP)(OC)Ir}2(η2,η2;μ2-P2)] (3), via the intermediacy of a putative, triplet iridium phosphinidene, [(PCP)Ir(P)(CO)] (A), probed computationally. When 2 is instead photolyzed in the presence of a phosphorus ylide, PhMe2PCH2, the photointermediate is intercepted, leading to a unique phosphavinyl complex, [(PCP)Ir(P═CH2)] (4), in 60% spectroscopic yield. Complex 2 also reacts thermally with PhMe2PCH2 to form 4. Tracking of the extruded CO fragment uncovers a divergent reactivity landscape; in the photolytic pathway, a carbonyl complex, [(PCP)Ir(CO)](PCO), forms, whereas in the thermal pathway, one CO and two CH2 groups couple to a [C3] fragment in a new ylide, PhMe2PCHCOCH3. Structural characterization, isotopic labeling, and IR and NMR spectroscopic studies, along with quantum simulations, unveil a rigid, π-bonded [P═CH2]− moiety in 4, having magnetically inequivalent hydrogens at room temperature. Complex 4 comprises a deprotonated ligand form of the elusive phosphaethylene molecule (HP═CH2) but possesses a much lower isomerization barrier (15.9(5) kcal mol–1) than classical phosphaalkenes (>40 kcal mol–1), owing to an interplay between the [(PCP)Ir]+ and [P═CH2]− fragments, leading to a linear {Ir═P═CH2} transition geometry for this molecular switch. Lastly, we utilize the phosphavinyl ligand to form other rare π-constructs with an organic azide.
}}, author = {{Tan, Mattias and Sandoval-Pauker, Christian and Takacs, Zoltan and Reinholdt, Anders}}, issn = {{0002-7863}}, language = {{eng}}, month = {{06}}, number = {{24}}, pages = {{25096--25106}}, publisher = {{The American Chemical Society (ACS)}}, series = {{Journal of the American Chemical Society}}, title = {{Metallaphosphinidene Coupling with a Phosphorus Ylide to Form a Phosphavinyl [P═CH2]− Ligand}}, url = {{http://dx.doi.org/10.1021/jacs.6c06304}}, doi = {{10.1021/jacs.6c06304}}, volume = {{148}}, year = {{2026}}, }