Contributions to the chemistry of halosilane adducts

Kummer, D.; Chaudhry, S. C.; Seifert, J.; Deppisch, B.; Mattern, G.

doi:10.1016/0022-328x(90)80212-i

Cited by 34 publications

(5 citation statements)

References 16 publications

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“…In 10g and 10j the 29 Si resonance changes to high field as the temperature increases . This temperature dependence suggests an increase in the coordination number or strength with increasing temperature, a phenomenon reported previously in the case of solvent-driven ionic dissociation in hexacoordinate, as well as in pentacoordinate, − silicon complexes. It is thus likely, in analogy with the previous reports, that the temperature dependence is associated with the ionic dissociation shown in eq : I − IV represent canonical structures describing collectively the charge distribution in the zwitterionic compounds 10 .…”

Section: Resultssupporting

confidence: 74%

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

et al. 2009

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O-Trimethylsilylated hydrazides with Schiff-base derivatives at the terminal nitrogen atoms-[RC(OSiMe 3 )dNNdCR 0 R 00 ] react with chloro(chloromethyl)dimethylsilane [ClCH 2 SiMe 2 Cl] in a regioselective manner, forming either five-membered or zwitterionic six-membered chelate complexes with pentacoordinate silicon. The type of product is determined by the size of the acidsubstituent R: bulky R groups (Ph, t-Bu) lead to exclusive formation of the six-membered product, whereas with the less bulky groups (Me, PhCH 2 ) only the five-membered product is obtained. Upon mild heating, the six-membered chelate complex transforms into its five-membered isomer, through a Wawzonek-type rearrangement. This facile transformation is remarkable in comparison to previously reported Wawzonek reactions that take place only at elevated temperatures. † Dedicated to Prof. Gerhard Roewer on the occasion of his 70th birthday.

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Section: Resultssupporting

confidence: 74%

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

et al. 2009

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“…The six-membered chelate rings in 5 and in 9b are nearly equal, in the sense that the bond lengths in 5 (C−O = 1.321 Å, C(O)−N = 1.289 Å, O−Si = 1.788 Å) almost equal the corresponding bond lengths in 9b (Table ). The striking difference between these two chelates is in the Si−Cl bond lengths (Si−Cl = 2.624 Å in 5 ), which is ∼0.3 Å longer in 5 than in 9b . It may be concluded that while in 5 the Si−Cl bond is essentially dative (as implied by structure IV ), it is mostly covalent in 9b , in accord with structure III .…”

Section: Resultsmentioning

confidence: 86%

Irreversible Rearrangement in Hexacoordinate Silicon Complexes: From Neutral Bis(N→Si) Chelates to Mono(N→Si) Zwitterionic λ⁶-Silicates

et al. 2000

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The reaction of (chloromethyl)trichlorosilane (7) with O-trimethylsilylated N,N-dimethylhydrazides yields initially under kinetic control, in nearly quantitative yields, a neutral hexacoordinate bis(NfSi) chelate, bis(N-(dimethylamino)acylimidato-N,O)chloro(chloromethyl)silicon(IV) (8a-c). Upon heating, the octahedral complexes 8 are quantitatively and irreversibly converted to the isomeric hexacoordinate chelates zwitterionic λ 6 -silicates 9a-c, (N-(dimethylamino). This molecular rearrangement is rather unusual, since it involves chelatering expansion from the common five-membered ring to a six-membered ring in the thermodynamically favored product 9. 8b and 9b were characterized by X-ray crystal analyses and in solution by their 1 H, 13 C, and 29 Si NMR spectra. The analogous compounds 8a,c and 9a,c were characterized by the respective analogy of their NMR spectra. Both 8b and 9b have slightly distorted octahedral geometries around the central silicon atom. Both series of chelates 8 and 9 undergo ligand-site exchange processes, observed by the coalescence of signals due to diastereotopic N-methyl and/or CH 2 groups. Each compound (of both series) undergoes two consecutive rate processes: in 8 this sequence of exchange processes is analogous to previously reported stereomutations through a bicapped-tetrahedral intermediate or transition state; in 9 the first (lower barrier) process is a nitrogen-silicon dissociationrecombination, and the high-barrier process is an inversion of configuration at the silicon center.We have recently utilized the reaction of O-(trimethylsilyl)-N,N-dimethylhydrazides (1) with polyhalosilanes as a convenient method for the synthesis of a variety of different penta-and hexacoordinate silicon complexes with NfSi coordination (eq 1). 1-9 1 functions as a precursor for five-membered NfSi chelate rings.On the other hand, when 1 was allowed to react with (chloromethyl)dimethylchlorosilane (4; eq 2), OfSi coordinated complexes with five-and six-membered chelate cycles (6 and 5, respectively) were obtained. 10-13 † Ben-Gurion University. Kalikhman, I.; Krivonos, S.; Stalke, D.; Kottke, T. J. Am. Chem. Soc. 1998, 120, 4209. (7) Mozzhukhin, A. O.; Antipin, M. Yu.; Struchkov, Yu. T.; Gostevskii, B. A.; Kalikhman, I. D.; Pestunovich, V. A.; Voronkov, M. G. Bannikova, O. B.; Petuchov, L. P.; Pestunovich, V. A.; Voronkov, M. G. Dokl. Akad. Nauk SSSR 1986, 287, 870. (11) Kalikhman, I. D.; Pestunovich, V. A.; Gostevskii, B. A.; Bannikova, O. B.; Voronkov, M. G. J. Organomet. Chem. 1988, 338, 169. (12) Macharashvili, A. A.; Shklover, V. E.; Struchkov, Yu. T.; Gostevskii, B. A.; Kalikhman, I. D.; Bannikova, O. B.; Voronkov, M. G.; Pestunovich, V. A.

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“…Free rotation and isomerisation about the exocyclic N=C bond is not initially expected, partly because of reported short N À C bond lengths in a related conjugate acid, [51] and also because the steric bulk of R 1 and R 2 should drive the formation of a single isomer. With respect to steric factors, some comparison can be made with NHCs that also contain N substituents that point in the general direction of the metal, whereas substituents such as tertiary phosphanes project away from the metal, although rotation about the E À C (E= N or P) bonds increases the effective bulk of the ligand.…”

Section: Introductionmentioning

confidence: 98%

“…The angle between the planes defined by C(2)-C(1)-N(1) and C(1)-N(1)-C(7) for 11 is essentially equal (~6.88) to that in compound 7, and collectively, the structural features of 11 are similar to a related compound 1-methyl-2-(2'-pyridyl)-aminopyridinium chloride. [51] The 1 H NMR spectroscopic investigation shows four signals for the heterocycle that are significantly downfield from precursors 1, 5, and 9, respectively, whereas compound 11, for example, gives signals at 6 ), which are upfield from a typical unsubstituted pyridinium group such as N-methylpyridinium iodide. [57] A broad signal at 6.53 ppm is observed for the NÀ H(1) proton, however, the solubility of 12 and 13 restricted the solvents that could be used to obtain the NMR spectra to D 2 O or CD 3 OD, preventing the observation of analogous NH signals.…”

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confidence: 97%

Synthesis, Coordination Chemistry and Bonding of Strong N‐Donor Ligands Incorporating the 1H‐Pyridin‐(2E)‐Ylidene (PYE) Motif

Qiu

Thatcher

Slattery

et al. 2009

Chemistry A European J

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A range of N-donor ligands based on the 1H-pyridin-(2E)-ylidene (PYE) motif have been prepared, including achiral and chiral examples. The ligands incorporate one to three PYE groups that coordinate to a metal through the exocyclic nitrogen atom of each PYE moiety, and the resulting metal complexes have been characterised by methods including single-crystal X-ray diffraction and NMR spectroscopy to examine metal-ligand bonding and ligand dynamics. Upon coordination of a PYE ligand to a proton or metal-complex fragment, the solid-state structures, NMR spectroscopy and DFT studies indicate that charge redistribution occurs within the PYE heterocyclic ring to give a contribution from a pyridinium-amido-type resonance structure. Additional IR spectroscopy and computational studies suggest that PYE ligands are strong donor ligands. NMR spectroscopy shows that for metal complexes there is restricted motion about the exocyclic C-N bond, which projects the heterocyclic N-substituent in the vicinity of the metal atom causing restricted motion in chelating-ligand derivatives. Solid-state structures and DFT calculations also show significant steric congestion and secondary metal-ligand interactions between the metal and ligand C-H bonds.

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Contributions to the chemistry of halosilane adducts

Cited by 34 publications

References 16 publications

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

Irreversible Rearrangement in Hexacoordinate Silicon Complexes: From Neutral Bis(N→Si) Chelates to Mono(N→Si) Zwitterionic λ⁶-Silicates

Synthesis, Coordination Chemistry and Bonding of Strong N‐Donor Ligands Incorporating the 1H‐Pyridin‐(2E)‐Ylidene (PYE) Motif

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Contributions to the chemistry of halosilane adducts

Cited by 34 publications

References 16 publications

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

Regioselective Intramolecular Chloride Displacement Leading to Five- or Six-Membered Chelate-Ring Closure and Pentacoordinate Silicon Complexes: A Facile Wawzonek Rearrangement

Irreversible Rearrangement in Hexacoordinate Silicon Complexes: From Neutral Bis(N→Si) Chelates to Mono(N→Si) Zwitterionic λ6-Silicates

Synthesis, Coordination Chemistry and Bonding of Strong N‐Donor Ligands Incorporating the 1H‐Pyridin‐(2E)‐Ylidene (PYE) Motif

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Irreversible Rearrangement in Hexacoordinate Silicon Complexes: From Neutral Bis(N→Si) Chelates to Mono(N→Si) Zwitterionic λ⁶-Silicates