High Resolution Image Download MS PowerPoint Slide 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 P 2 motif, (PCP) (OC) Ir 2 (η 2, η 2;μ 2 -P 2) (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, PhMe 2 PCH 2, the photointermediate is intercepted, leading to a unique phosphavinyl complex, (PCP) Ir (P═CH 2) (4), in 60% spectroscopic yield. Complex 2 also reacts thermally with PhMe 2 PCH 2 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 CH 2 groups couple to a C 3 fragment in a new ylide, PhMe 2 PCHCOCH 3. Structural characterization, isotopic labeling, and IR and NMR spectroscopic studies, along with quantum simulations, unveil a rigid, π-bonded P═CH 2 − moiety in 4, having magnetically inequivalent hydrogens at room temperature. Complex 4 comprises a deprotonated ligand form of the elusive phosphaethylene molecule (HP═CH 2) 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═CH 2 − fragments, leading to a linear Ir═P═CH 2 transition geometry for this molecular switch. Lastly, we utilize the phosphavinyl ligand to form other rare π-constructs with an organic azide.
Tan et al. (Mon,) studied this question.