Caught in the trap: Two different routes to the thermally unstable phosphinidenoid complex I are described, and chemical evidence for this novel intermediate is provided through selective reactions. For example, methyl iodide, dimethylcyanamide, or butyraldehyde furnished complexes II, III, and IV (see scheme) under very mild conditions.

Isolation and characterisation of the first Li/halogen phosphinidenoid transition-metal complex as well as low-temperature solution NMR, MAS-NMR experiments, DFT structures and calculated NMR chemical shifts are reported.

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Synthesis of the first N-lithiated cyanophosphanide complexes 5a-c was achieved via reaction of complex 1 with t BuLi/12-crown-4, NaN(SiMe 3 ) 2 /15-crown-5, or KO t Bu/18-crown-6 at low temperature. Compounds 5a-c were isolated and fully characterized by NMR and IR spectroscopy and elemental analysis. The structure of complex 5a, as established by X-ray diffraction studies, revealed that the lithium is coordinated to nitrogen and the oxygen centers (of the crown ether unit). This geometry of 5a is best described as a phosphanide complex isomeric to a phosphinidenoid complex. A phosphinidenoid-like behavior of 5a was observed in the melt, evidenced by formation of cyclotriphosphane 4 via LiCN elimination and decomplexation. In solution 5a reacted with methyl iodide (or methyl triflate) like a phosphanide, thus leading to P-methyl complex 8.