An Iminophosphonamido‐Chlorosilylene as a Strong σ‐Donating NHSi Ligand: Synthesis and Coordination Chemistry.

The N‐heterocyclic silylene (NHSi) [Ph2P(tBuN)2]SiCl (1), supported by an iminophosphonamide ligand, was obtained from the dehydrochlorination of [Ph2P(tBuN)2]SiHCl2 (2) with LiN(SiMe3)2. NHSi 1 contains an extremely high‐energy HOMO level and consequently displays unique coordination behavior toward RhI complexes. When 1 was treated with 1/4 of an equivalent of [RhCl(cod)]2 (cod=1,5‐cyclooctadiene), the 14‐electron Y‐shaped bis(chlorosilylene) RhI complex 5 was obtained as dark purple crystals. The reaction of 1 with 1/6 of an equivalent of [RhCl(cod)]2 yielded the cationic tris(silylene)‐RhI complex [6]+⋅Cl− as red crystals, wherein a two‐coordinated silylene ligand engages in a Si=Rh double bond. A structural analysis of 5 and [6]+⋅Cl− revealed that the central rhodium atoms adopt trigonal and square‐planar coordination geometries, respectively, with considerably shortened Si‐Rh bonds [5: 2.1605(5) Å; [6]+: 2.133(1) Å]. [ABSTRACT FROM AUTHOR]