Neutral Hexacoordinate Silicon Tris-Chelates:  Structure and Stereodynamics

Kalikhman, I. D.; Kingston, Vijeyakumar; Girshberg, and Olga; Kost, Daniel

doi:10.1021/om010465d

Cited by 18 publications

(3 citation statements)

References 23 publications

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“…Upon heating, it rearranges quantitatively to 45 . The two chloro ligands in 45 have been utilized to bind a third chelate, forming a complex with three different chelate rings ( 46 ) …”

Section: Reactivitymentioning

confidence: 99%

“…13 The two chloro ligands in 45 have been utilized to bind a third chelate, forming a complex with three different chelate rings (46). 35 Finally, the reactions of di(chloromethyl)dichlorosilane (47) were investigated. 36 A double ring expansion takes place when 47 reacts with 1 (R ) CF 3 ), forming a neutral hexacoordinate dichelate with two of the less common six-membered chelate rings (48, eq 20).…”

Section: Rearrangement Of Hydrido Ligandmentioning

confidence: 99%

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Hypercoordinate Silicon Complexes Based on Hydrazide Ligands. A Remarkably Flexible Molecular System

Kost

Kalikhman

2008

Acc. Chem. Res.

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Though only one row apart on the periodic table, silicon greatly differs from carbon in its ability to readily form five- and six-coordinate complexes, termed "hypercoordinate silicon compounds". The assorted chemistry of these compounds is varied in both structures and reactivity and has generated a flurry of innovative research endeavors in recent years. This Account summarizes the latest work done on a specific class of hypercoordinate silicon compounds, specifically those with two hydrazide-derived chelate rings. This family is especially interesting due to the ability to form multiple penta- and hexacoordinate complexes, the chemical reactivity of pentacoordinate complexes, and the observation of intermolecular ligand crossovers in hexacoordinate complexes. Pentacoordinate complexes in this family exhibit marked structural flexibility, as demonstrated by the construction of a complete hypothetical Berry-pseudorotation reaction coordinate generated from individual crystallographic molecular structures. Although hexacoordinate complexes generally crystallize as octahedra, with a decrease in the ligand donor strength the complexes can crystallize as bicapped tetrahedra. Hexacoordinate complexes bearing a halogen ligand undergo a solvent-driven equilibrium ionic dissociation, which is controlled by solvent, temperature, counterion, and chelate structure and has been directly demonstrated by conductivity measurements and temperature-dependent (29)Si NMR. Hexacoordinate silicon complexes can also undergo reversible neutral nonionic dissociation of the N-Si dative bond. Ionic pentacoordinate siliconium salts react readily via methyl halide elimination, initiated by their own counterion acting as a base. Pentacoordinate complexes can also undergo intramolecular aldol condensations of imines, which may find potential as a template for organic synthesis. In addition, these complexes are capable of performing an uncatalyzed intramolecular hydrosilylation of imine double bonds. Perhaps the most striking manifestations of flexibility are the facile and complete intermolecular ligand crossovers. Crossovers have been observed between different hexacoordinate complexes, and between complex molecules and their differently substituted precursors, and take place within minutes. Although the precise mechanisms of these transformations remain elusive, NMR and single-crystal X-ray diffraction measurements have shed light on these interesting phenomena. A profusion of crystallographic data and careful NMR experimentation has led to an improved understanding of penta- and hexacoordinate hydrazide-based silicon dichelates. The diverse chemical reactivity of these complexes demonstrates both the scope and complexity of silicon chemistry. Future exploration into the structures and chemistry of hypercoordinate silicon will continue to enhance our understanding and appreciation of this unique element.

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“…Upon heating, it rearranges quantitatively to 45 . The two chloro ligands in 45 have been utilized to bind a third chelate, forming a complex with three different chelate rings ( 46 ) …”

Section: Reactivitymentioning

confidence: 99%

Section: Rearrangement Of Hydrido Ligandmentioning

confidence: 99%

Hypercoordinate Silicon Complexes Based on Hydrazide Ligands. A Remarkably Flexible Molecular System

Kost

Kalikhman

2008

Acc. Chem. Res.

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“…The synthesis of compound 9, with its three different bidentate ligands, was also very challenging (in this context, see also ref. 6).…”

Section: Introductionmentioning

confidence: 99%

Novel neutral hexacoordinate benzamidinatosilicon(iv) complexes with SiN3OF2, SiN3OCl2, SiN3OBr2, SiN5O and SiN3O3 skeletons

et al. 2011

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The neutral pentacoordinate monoamidinatosilicon(IV) complex 1 (SiN(2)Cl(3) skeleton) and the neutral hexacoordinate monoamidinatosilicon(IV) complexes 2-9 (SiN(3)OF(2), SiN(3)OCl(2), SiN(3)OBr(2), SiN(5)O and SiN(3)O(3) skeletons) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 1) and NMR spectroscopy in the solid state and in solution. Compounds 2-9 contain one bidentate monoanionic N,N'-diisopropylbenzamidinato ligand, one bidentate monoanionic ligand derived from 8-hydroxyquinoline and (i) two identical monoanionic ligands (F, Cl, Br, N(3), NCO, NCS, OSO(2)CF(3)) or (ii) one bidentate dianionic benzene-1,2-diolato ligand. The dynamic behavior of 2-4 (SiN(3)OX(2) skeleton; X = F, Cl, Br) and 9 (SiN(3)O(3)) in solution was studied by multinuclear variable-temperature NMR experiments. Compound 1 was synthesised by reaction of SiCl(4) with the corresponding lithium amidinate, and compound 2 was obtained by reaction of 1 with 8-hydroxyquinoline and triethylamine. Compound 2 served as the starting material in the syntheses of 3-9, in which the two chloro ligands of 2 were substituted by two identical (pseudo)halogeno ligands, two trifluoromethanesulfonato ligands or one benzene-1,2-diolato ligand. Compounds 3 and 4 contain the novel SiN(3)OBr(2) and SiN(3)OF(2) skeletons, while compounds 5-7 are the first neutral hexacoordinate silicon(IV) complexes with an SiN(5)O skeleton.

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Dynamic Stereochemistry of Penta‐ and Hexacoordinate Germanium(IV) Complexes

and¹,

Korlyukov²

2023

Organogermanium Compounds

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Neutral Hexacoordinate Silicon Tris-Chelates: Structure and Stereodynamics

Cited by 18 publications

References 23 publications

Hypercoordinate Silicon Complexes Based on Hydrazide Ligands. A Remarkably Flexible Molecular System

Hypercoordinate Silicon Complexes Based on Hydrazide Ligands. A Remarkably Flexible Molecular System

Novel neutral hexacoordinate benzamidinatosilicon(iv) complexes with SiN3OF2, SiN3OCl2, SiN3OBr2, SiN5O and SiN3O3 skeletons

Dynamic Stereochemistry of Penta‐ and Hexacoordinate Germanium(IV) Complexes

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