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].

Halogen-substituted silylenes are an important building block for synthesizing silicon-based low-valent and multiple-bond species. However, the number of reports on heavier halosilylenes that contain bromine and iodine is still limited. Here, we present a convenient synthesis for bromo-and iodosilylenes supported by an iminophosphonamide ligand. The heavier halosilylenes [Ph 2 P( t BuN) 2 ]SiX (2: X = Br, 3: X = I) were successfully synthesized via the halogen-exchange reaction of chlorosilylene 1 with alkali halides in THF. As a demonstration of the reactivity of 2 and 3, oxidative addition reactions of 2 and 3 with elemental selenium in C 6 D 6 afforded the corresponding bromo-( 5) or iodosilylene-selone (6) as colorless crystals. The molecular structures of 2, 3, 5, and 6 were fully characterized by spectroscopic means and single-crystal X-ray diffraction analysis. Furthermore, the effects of the halogen atom on the electronic state of halosilylenes 1−3 and halosilylene−selones 4−6 were investigated using density functional theory (DFT) calculations.

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].

We report the reactions of an iminophosphonamido-silylene (1) with different palladium complexes. The reaction of 1 with [Pd(PPh3)4] furnished a homoleptic tris(silylene)-palladium(0) complex. In contrast, treatment of 1 with [PdMe2(tmeda)]...