Neutral Pentacoordinate Halogeno‐ and Pseudohalogenosilicon(IV) Complexes with an SiSONCX Skeleton (X=F, Cl, Br, I, N, C): Synthesis and Structural Characterization in the Solid State and in Solution

Abstract

A series of neutral pentacoordinate silicon(IV) complexes with an SiSONCX skeleton (X=F, Cl, Br, I, N, or C) was synthesized and structurally characterized by multinuclear solution-state and solid-state NMR spectroscopy and single-crystal X-ray diffraction. These compounds contain an identical tridentate dianionic S,N,O ligand, a monodentate (pseudo)halogeno ligand (F, Cl, Br, I, NCS, N(3), or CN), and a monodentate organyl ligand (methyl, phenyl, 4-(trifluoromethyl)phenyl, or pentafluorophenyl). For most of these compounds, a dynamic equilibrium between the pentacoordinate silicon(IV) complex and two isomeric tetracoordinate silicon species in solution was observed. Most surprisingly, comparison of two series of analogous compounds containing fluoro, chloro, bromo, or iodo ligands demonstrated that pentacoordination in these series of silicon(IV) complexes is favored in the rank order I approximately Br>Cl>F; i.e., increasing the softness of the halogeno ligand favors pentacoordination.

Neutral Pentacoordinate Halogeno‐ and Pseudohalogenosilicon(IV) Complexes with a Tridentate Dianionic O,N,O or N,N,O Ligand: Synthesis and Structural Characterization in the Solid State and in Solution

“…Most of the penta‐ and hexacoordinate silicon(IV) compounds reported in the literature contain hard ligand atoms such as fluorine, chlorine, oxygen, nitrogen, and carbon atoms 1. Recently, quite new perspectives for the chemistry of higher‐coordinate silicon have been generated by introducing soft chalcogen ligand atoms (sulfur, selenium, tellurium) into the coordination sphere of the hard silicon(IV) coordination center 2b,2f,2m,3. In this context, we have recently reported on the syntheses, structures, and properties of the neutral pentacoordinate silicon(IV) complexes 1a – 1g 2f,3f.…”

Neutral Pentacoordinate Silicon(IV) Complexes with a Tridentate Dianionic O,N,O or N,N,O Ligand, an Anionic PhX Ligand (X = O, S, Se), and a Phenyl Group: Synthesis and Structural Characterization in the Solid State and in Solution

“…Recently, we have reported on the synthesis and characterization of the neutral pentacoordinate silicon(IV) complexes 1a – g 1,2. These compounds contain a tridentate dianionic S , N , O ligand, an (pseudo)halogeno ligand, and a phenyl group.…”

Bis[N,N′‐diisopropylbenzamidinato(−)]silicon(II): A Silicon(II) Compound with Both a Bidentate and a Monodentate Amidinato Ligand

“…[1][2][3][4] Silylenes with two-coordinate silicon have been studied extensively, [2] while higher-coordinate silicon(II) species are still relatively rare. [4] In continuation of our systematic studies on highercoordinate silicon(IV) complexes, [5] we have succeeded in synthesizing the six-coordinate bis(amidinato)silicon(IV) complex 1 (Scheme 1). [4] In continuation of our systematic studies on highercoordinate silicon(IV) complexes, [5] we have succeeded in synthesizing the six-coordinate bis(amidinato)silicon(IV) complex 1 (Scheme 1).…”

“…[3,4] In this context, three-and four-coordinate amidinato-substituted silicon(II) compounds should be mentioned. [4] In continuation of our systematic studies on highercoordinate silicon(IV) complexes, [5] we have succeeded in synthesizing the six-coordinate bis(amidinato)silicon(IV) complex 1 (Scheme 1). [6] Inspired by a recent study by Roesky et al, [4d] we transformed 1 into the three-coordinate silicon(II) species 2 by using a reductive HCl elimination.…”

“…[8] The silicon coordination polyhedron of 2 ( Figure 2) is best described as a distorted pseudo-tetrahedron, with the lone pair as the fourth ligand. The two N-Si-N angles amount to 102.63 (5) and 102.29(6)8, respectively. The SiÀN bond length of the monodentate ligand (1.7885 (12) ) is significantly shorter than those of the bidentate ligand (1.9065(12) and 1.9026(12) ), clearly reflecting the different coordination modes of the two amidinato ligands.…”