A facile and highly stereoselectiVe synthesis of noVel O,P,C-cage complexes Via thermal C-O ring opening of an oxaphosphirane W(CO) 5 complex is described. All compounds were unambiguously characterized by elemental analysis, multinuclear NMR, IR, MS, and single-crystal X-ray diffraction studies.

CP or CP? One‐electron oxidation of Li/Cl phosphinidenoid complexes led to the discovery of transient P‐chlorophosphanyl complexes 1. Subsequent cross‐coupling and rearrangement or elimination reactions yielded 2 and 3; the latter is the first structurally characterized phosphaquinomethane complex. ESR spectroscopy and DFT calculations support the existence of short‐lived P‐centered radicals.

Reactivity studies of Li/Cl phosphinidenoid W(CO) 5 complexes 2a,b toward various iodine compounds are reported. Transiently generated complexes 2a,b yielded no selective reactions with 3-, 9-, and 9,12-diiodo o-carbaboranes 3a-c, whereas clean transfer-iodination reaction occurred with C-iodo-substituted o-carbaboranes 3d,e, thus giving chloro(iodo)phosphane complex 6a in the case of 2a. Complex 2a was also reacted with iodo(phenyl)acetylene to yield complexes 6a, 8, and 9 in competing reactions. An independent pathway to chloro(iodo)phosphane complexes 6a,b was reaction of complexes 2a,b with elemental iodine at low temperature. All compounds were unambiguously characterized by elemental analysis, multinuclear NMR, IR, MS studies, and, in the case of 6a and 9, single-crystal X-ray diffraction.

The novel P,C-cage ligand in the dinuclear tungsten complex 3 was obtained by reaction of the Li/Cl phosphinidenoid complex 2, characterized by NMR spectroscopy, at low temperature; complex 3 was characterized by elemental analysis and NMR, IR, and MS studies and by single-crystal X-ray diffraction.Carbenoids I 1 and silylenoids II 2 are versatile reactive intermediates in organic synthesis (Scheme 1). In contrast, phosphinidenoids III are still unknown, although some authors had speculated 3 about their existence.Recently, we reported the generation of the first Li/Cl phosphinidenoid transition-metal complex (IV) and chemical evidence through various reactions. With methyl iodide the P-Me-substituted phosphine complex was selectively obtained, thus showing the nucleophilic reactivity of IV, while π-systems afforded three-membered heterocyclic complexes such as