Silane tetrahedral form

The bi- and tridentate phosphines dppp (l,3-bis(diphenylphosphino)propane) and dppep (bis (2-diphenylphosphinoethyl)phenylphosphine) have been complexed with Co and their divalent four- and five-coordinated thiophenolate complexes Co(dppp)(SPh)2 and Co(dppep)(SPh)2 have been isolated and structurally characterized.379 Somewhat related to dppp is the bidentate silane Ph2PCH2SiMe2CH2PPh2, which forms high-spin, pseudo-tetrahedral dihalocobalt(II) complexes.380... 

All halides EX4 form tetrahedral molecules. Mixed halides are known, as well as fully or partially halogen-substituted catenated alkanes, silanes and germanes (e.g., Ge2Cl6). Unlike the carbon... 

Semiempirical MNDO calculations indicate that the difference in energy between the tetrahedral and planar forms of bis(ethylenedioxy)silane and bis(o-phenyl-enedioxy)silane is considerably smaller than that for the corresponding carbon... 

Monodisperse oligo(phenylenevinylene)s are assembled to three-dimensional scaffolds in convergent three- or fourfold Homer reactions of a silane core and stilbenoid aldehydes in moderate to good yields. The central silane is sensitive toward nucleophilic attack. Tetrahedral compounds with short side chains form stable amorphous films but trigonal-pyramidal shaped assemblies tend to recrystallize. The connection of the chromophores to a central silicon atom results in a stabilization of the excited states an intense blue-green fluorescence is emitted from solution as well as from transparent films. 

Silicon atom belongs to group IV of the periodic table and its orbitals consist of Is 2s 2p 3s 3p similar to carbon. The outer electrons form covalent tetrahedral sp and octahedral sp d hybrid orbital with other atoms such as silane and potassium silicone hexafluoride respectively, but no stable sp or sp hybrid orbitals are found. Since the electronegativity of Si atom is smaller than that of carbon, the bond between Si and... 

All halides EX4 form tetrahedral molecules (point group Td). Mixed halides are known, as well as fully or partially halogen-substituted catenated alkanes, silanes and germanes (e.g. Ge2Cl6). Unlike the carbon compounds, halides of Si and Ge are Lewis acids and readily form complexes such as [SiF6]. Attack by Lewis bases often leads to decomposition, and thus rapid hydrolysis in water,... 

The main difference from C, N, and O is that Si, P, and S can form more bonds than the first row elements. This is because they have more orbitals the five 3d orbitals added to the 3s and three 3p orbitals. Silicon forms tetrahedral silanes, rather like alkanes, but also forms stable five-valent anions. Phosphorus forms phosphines, rather like amines, but also tetrahedral phosphine oxides. Sulfur can have any coordination number horn zero to seven, forming sulfides, like ethers, and tetrahedral sulfones with six bonds to sulfur. And it is with sulfur that we start. 

Increased functionality of the organometallic moiety will lead to more intricate supramolecular assemblies. A suggestive organometallic example is provided by tetra(p-cyanophenyl)silane, Si(C6H4CN-p)4, which forms a three-dimensional self -organized supramolecular network of interpenetrating double layers by coordination with silver ions [27] and a layered supramolecular structure with TiCU [28], both imposed by the directionality of tetrahedral silicon centers. Supramolecular assemblies are defined as "extended polymolecular arrays presenting a more or less... 

Si coordination spheres have been reported (with weak S Si interactiOTis indicated by interatomic separations of 3.05-3.48 A), thiocarbamate was shown to form a noticeably shorter Si—S bond in 186 (2.70 A) and the animi of the thiourea derivative methimazole was shown to be capable of forming a trisilane (187) with two adjacent octahedral Si coordination spheres, one of which comprises four Si—S bonds (with separations ranging between 2.35 and 2.48 A). Notably, this trisilane with a central Si(Si2S4) skeleton is one out of only few crystallographically characterized hexacoordinated Si compounds which are devoid of first and second row elements in the octahedral Si coordination sphere of one of their Si atoms (further examples can be found with P and Cl in the coordination sphere, vide infra). The kind of tetrahedral capping by rather long Si S separations of about 3.17-3.50 A is encotmtered with various methimazolyl-substituted silanes such as 188 [349]. 

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