Unusual Spin−Spin Interactions across the Coordination Bond in Hexacoordinate Silicon Complexes:  Crystal-Structure Coupling Relationship

Kalikhman, I. D.; Krivonos, Sonia; Kottke, Thomas; Kost, Daniel

doi:10.1021/om970327h

Cited by 38 publications

(23 citation statements)

References 11 publications

(9 reference statements)

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“…[15] The Si±F distance in 3 corresponds well with bond lengths found in other hypervalent silicon compounds (1.60±1.73 A Ê ) [15,16]. The distances Si±O and Si±N are remarkably short compared to other hexacoordinate silicon compounds [15].…”

Section: Resultssupporting

confidence: 63%

Hexacoordinate Silicon-Azomethine Complexes: Synthesis, Characterization, and Properties

Mucha¹,

Haberecht²,

Böhme³

et al. 1999

Monatshefte fuer Chemie

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N,N H -Ethylene-bis(2-hydroxyacetophenoneimine) salen*H 2 and N,N H -ethylenebis(3,5-di-tert-butyl-salicylideneimine) salen z H 2 react both with SiCl 4 under formation of hexacoordinate silicon compounds ((salen H )SiCl 2 , salen H salen* or salen z ). The analogous¯uoro derivatives (salen H )SiF 2 have been prepared by reaction of (salen H )SiCl 2 with ZnF 2 . X-ray structure analysis of (salen*)SiF 2 clearly demonstrates the octahedral coordination of silicon. Salen* acts as a tetradentate chelating ligand, two halogen atoms remaining at the silicon atom. The reduction of (salen*)SiCl 2 by alkaline metal affords polysilanes containing main chain hexacoordinate silicon. Coupling with acetylides results in polycarbosilanes with a Si±C:C±Si backbone.

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Section: Resultssupporting

confidence: 63%

Hexacoordinate Silicon-Azomethine Complexes: Synthesis, Characterization, and Properties

Mucha¹,

Haberecht²,

Böhme³

et al. 1999

Monatshefte fuer Chemie

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“…(a) Crystallographic Structures. The preparation of complexes of the series 6 − 11 was described previously. , Figure depicts the single-crystal X-ray structures for compounds 10 and 11 . These structures have the same near-octahedral geometry reported previously for members of this series, and hence the octahedron is a characteristic geometry for this series, in contrast to 1 − 4 with the bicapped tetrahedral structure.…”

Section: Resultsmentioning

confidence: 99%

“…The structure and chemistry of hexacoordinate silicon chelates have been the focus of a number of recent studies. − However, only a few structural and stereodynamic studies have been reported, and they have been described as being still in an “embryonic stage” . Within the few known crystal structures of neutral bis(N→Si) chelates, the structural diversity is rather large: most of the reported crystal structures feature a “bicapped tetrahedral” geometry ( 1 − 4 , Figure ), in which the basic tetrahedral structure around silicon is retained, with two donor nitrogens coordinated opposite two faces of the tetrahedron. − By contrast, crystal structures of nearly octahedral bis(N→Si) complexes have also been reported recently ( 5 , 6 , 7 , 8 , 9 ). The factors responsible for the solid-state structures of these complexes are not yet understood.…”

mentioning

confidence: 99%

Crystal Structures and Stereodynamics of Neutral Hexacoordinate Silicon Chelates: Use of an Optically Active Ligand for Assignment of an Intramolecular Ligand Exchange Process

et al. 1998

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Crystal structures determined for several neutral hexacoordinate bis(N→Si) chelates revealed in all cases near octahedral geometries with the nitrogen ligands in relative trans and the monodentate ligands in cis positions. To assign the two consecutive intramolecular ligand-site exchange processes (reported earlier), a bis-chelate was prepared containing a chiral carbon center in each of the chelate rings (14). By means of a phase sensitive NOESY NMR spectrum it was possible to conclude that the lower-barrier process involved exchange of diastereotopic groups only within each diastereomer, and not between them, resulting in the assignment of this process to the direct nondissociative interchange of the monodentate ligands (X, Y). The Si−Cl bond lengths were found to inversely correlate with the lower of the activation barriers. Dissociation−recombination of the N→Si dative bond was also observed by the high-temperature NMR spectra. Lack of correlation between Si−N distances in the crystals and activation barriers led to the conclusion that Si−N dissociation was not involved in the measured rate processes, but followed, at slightly higher temperature, the epimerization at the silicon center by exchange of the two oxygen sites.

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“…In DMSO- d 6 , the temperature-independent 29 Si NMR resonances for 9 and 10 appear at −141.3 and −135.2 ppm, respectively, supporting their hexacoordinate geometries. Evidence for fluoride coordination in both complexes is given by coupling with fluorine ( 1 J SiF (∼250 Hz) and 2 J CF (∼45 Hz)), which was maintained at high temperature . The NMR spectra of 9 and 10 at room temperature are more complex than those of 3 and 4 and display more than two closely spaced peaks of some of the carbon resonances of the OPO ligands.…”

Section: Synthesismentioning

confidence: 98%

Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

Koch¹,

Brennessel

Kraft

2017

Organometallics

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A series of spirocyclic monoorganosilicon compounds of the form RSi(OPO) 2 Cl [R = phenyl (1 1); p-tolyl (2 2); benzyl (3 3); Me (4 4); t Bu (5 5); thexyl (6 6)] (OPO = 1-oxo-2-pyridinone) was synthesized and characterized by 1 H , 13 C, and 29 Si NMR spectroscopy, X-ray crystallography, and elemental analysis. In the solid state, complexes 1 1, 2 2, and 3 3 are neutral and possess cis-OPO ligands in an octahedral arrangement, and complexes 4 4, 5 5, and 6 6 are cationic and possess effectively trans-OPO ligands in nearly ideal square pyramidal geometries along the Berry-pseudorotation coordinate. In 4-6 4-6, chloride dissociation is attributed to the additive effect of multiple intermolecular C-H•••Cl interactions in their crystals. In DMSO-d 6 solution, compounds 1 1-6 6 form cationic hexacoordinate DMSO adducts with trans-OPO ligands, all of which undergo dynamic isomerization with energy barriers of ~18-19 kcal/mol. Compounds with better leaving groups, (p-tolyl)Si(OPO) 2 X [X = I (7 7); X = triflate (8 8)], exhibit identical solution NMR spectra as 2 2, supporting anion dissociation in each. The fluoride derivatives RSi(OPO) 2 F [R = benzyl (9 9); Me (10 10)] exhibit hexacoordinate geometries with cis-OPO ligands in the solid state and exhibit dynamic isomerization in solution. Overall, these studies indicate, in both the solid and solution states, that the trans-OPO ligand arrangement is favored when anions are dissociated and a cis-OPO ligand arrangement when anions are coordinated.

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Unusual Spin−Spin Interactions across the Coordination Bond in Hexacoordinate Silicon Complexes: Crystal-Structure Coupling Relationship

Cited by 38 publications

References 11 publications

Hexacoordinate Silicon-Azomethine Complexes: Synthesis, Characterization, and Properties

Hexacoordinate Silicon-Azomethine Complexes: Synthesis, Characterization, and Properties

Crystal Structures and Stereodynamics of Neutral Hexacoordinate Silicon Chelates: Use of an Optically Active Ligand for Assignment of an Intramolecular Ligand Exchange Process

Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

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