Formation and properties of unstable intermediates containing multiple p.pi.-p.pi. bonded Group 4B metals

Gusel’nikov, L. E.; Nametkin, N. S.

doi:10.1021/cr60322a004

Cited by 299 publications

(63 citation statements)

References 79 publications

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“…The bond strengthenings for BeH2 and MgH2 are explained in Section 3. 4 and those for other compounds in Section 3.6. Similar trends are found in the bond lengths1691.…”

Section: Bonding Energies Of Monohydrides Xh and "Saturated" Hydridesmentioning

confidence: 99%

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Chemical Bonding in Higher Main Group Elements

Kutzelnigg

1984

Angew. Chem. Int. Ed. Engl.

937

584

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Many concepts used for a qualitative description of chemical bonding that originated in the early days of theoretical chemistry have been vindicated recently by quantum chemical calculations, at least as far as first row elements are concerned. However, many concepts that have been justified for first row elements (Li to Ne) cannot-contrary to widespread belief-be generalized to the higher main group elements. This applies particularly to the concept of hybridization, which should be viewed with considerable caution. The essential difference between the atoms of the first and higher rows is that the cores of the former contain only s-AOs, whereas the cores of the latter include at least s-and p-AOs. As a consequence, the s and p valence AOs of first row atoms are localized in roughly the same region of space, while the p valence AOs of higher row atoms are much more extended in space. This has the consequence that for the light main group elements both lone-pair repulsion and isovalent hybridization play a greater role than for the heavy main group elements. Furthermore, this implies that single bonds between first row elements are weak and multiple bonds are strong, whereas for the second or higher row elements single bonds are strong and multiple bonds weak. The "extended valence" (violation of the octet rule) observed in compounds of higher main group elements has very little to do with the availability of d-AOs but is due rather to the size of these atoms and thus to the reduced steric hindrance between ligands and, to a lesser extent, also to the lower electronegativity of the heavy atoms. A model based on the concept of electron-rich multicenter bonds is certainly closer to reality than one involving hybrids with the participation of d-AOs. The XO bonds in phosphane oxides, sulfoxides, 0x0 acids and related compounds are better formulated as semipolar rather than as true double bonds, even if they behave in some respects like double bonds.-The growing interest of theorists in compounds of higher main group elements parallels new and, in some instances, spectacular results of experimental research on the chemistry of these elements.

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“…The bond strengthenings for BeH2 and MgH2 are explained in Section 3. 4 and those for other compounds in Section 3.6. Similar trends are found in the bond lengths1691.…”

Section: Bonding Energies Of Monohydrides Xh and "Saturated" Hydridesmentioning

confidence: 99%

“…What is perhaps more interesting is that they found a barrier of only ca. 4 kcal/mol, which suggests that the thermal dimerization is no longer symmetry-forbidden, unlike that of ethene.…”

Section: S I C and Sio Double Bondsmentioning

confidence: 99%

Chemical Bonding in Higher Main Group Elements

Kutzelnigg

1984

Angew. Chem. Int. Ed. Engl.

937

584

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“…All silenes thus formed react with various trapping agents, such as alcohols, [10][11][12][13][14][15][16][17] carbonyl compounds, [18][19][20][21] alkenes, [22][23][24][25][26][27][28][29] and alkynes 30 to give the addition products and in the absence of such trapping agents, dimerization products of silene intermediates were obtained. 31,32 The photolysis of the aromatic compounds having two pentamethyldisilanyl groups, such as 1,2-, 1,3-, 1,4-bis(pentamethyldisilanyl)-benzenes, 33 1,4-, 1,5-bis(pentamethyldisilanyl)naphthalenes 34 also affords the silene intermediates but in the case of 4,4'-bis(pentamethyldisilanyl)biphenyl, 35 the photoproducts from the silene intermediate were not obtained.…”

Section: Introductionmentioning

confidence: 99%

Photoreactions of 2-(Pentamethyldisilanyloxy)phenylpentamethyldisilane

2008

Bulletin of the Korean Chemical Society

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Photolysis of 2-(pentamethyldisilanyloxy)phenylpentamethyldisilane 1 in methanol provides five photoproducts 3, 4, 5, 6, and 7. Compounds 3 and 4 were probably formed from the methanol addition reactions of silene intermediate 2 and the formation of 5, 6, and 7 can best be explained by the nucleophilic attack of methanol to silicon atom in pentamethyldisilanyloxy or pentamethyldisilanyl group of the photoexcited state of 1. Irradiation of 1 in n-hexane gives a photoproduct 6 via silyl radical intermediate 8 and a novel intramolecular cyclization photoproduct 11 via silene 9 and silyl radical intermediate 10. Irradiation of 1 in deaerated methylene chloride in the presence of acetone affords a novel photoproduct 11 and phenol 7 but the expected photoproducts from the reaction of the silene intermediate with acetone were not obtained.

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“…This amply reviewed field (1,11,20,21,24,25,86,87,88) would not benefit from yet another review, so an overview of the most general methods of silene generation and common reactions of silenes will be presented with limited commentary. Table 5 shows some common methods of silene generation.…”

Section: Methodsmentioning

confidence: 99%

“…This thesis is concerned with the utilization of divalent silicon species (silylenes) (10) and (p-p) rr silicon-carbon bonds (silenes) (11) to generate molecules which are of theoretical interest, such as 1 and 2. These molecules have proved themselves to be difficultly accessible by more common means.…”

Section: Introductionmentioning

confidence: 99%

The synthesis of carbacyclic silanes via organosilicon reactive intermediates

Vuper

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Formation and properties of unstable intermediates containing multiple p.pi.-p.pi. bonded Group 4B metals

Cited by 299 publications

References 79 publications

Chemical Bonding in Higher Main Group Elements

Chemical Bonding in Higher Main Group Elements

Photoreactions of 2-(Pentamethyldisilanyloxy)phenylpentamethyldisilane

The synthesis of carbacyclic silanes via organosilicon reactive intermediates

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