Pentacoordinate silicon complexes synthesis

Scheme 4. The synthesis of the novel pentacoordinate silicon complexes 6 -11.

Synthesis of pentacoordinate silicon complexes from Si02. Nature. 353 642-644. Longloilert, R., Chaisuwan, T., Luengnaruemitchai, A., and Wongkasemjit, S. 2011. Synthesis of MCM-48 from sUatrane via sol-gel process. J. Sol-Gel ScL Technol. 58(2) 427-435. 

The synthesis of pentacoordinate silicon complexes with enamine-functionalized salen ligands is easily performed by the addition of MeSiCls and diethylamine to a salen ligand (eq 22). ... 

Summary The synthesis of the first silicon complexes with the tridentate diketoamine HN[CH2C(rBu)=0]2 (1) is described. The reaction of YSiXs (X = Cl, Br Y = H, Cl, Br, Ph, Vinyl) with 5-aza-2,2,8,8-tetramethylnonane-3,7-dione (1) in the presence of NEtj as an auxiliary base furnished the unusual dinuclear silicon complexes (6-11) having pentacoordinate silicon centers. Theoretical calculations (B3LYP/6-31G ) carried out for the monomeric chloro-substituted silane 7A are consistent with a folded structure and a relatively short and highly polarized Si-N bond (1.742 A Charge Si 0.96 N -0.53). The calculated value for the dimerization energy of 7A is -29 kcal/mol, reflecting the presence of a partial Si-N it-bond. Thus, the novel dimeric silicon compound 7 is the result of a head-to-tail dimerization of formally two Si=N bonds in 7A. 

Summary Our investigations on silicon compounds of etfaylene-MiV"-bi (2 -hydroxyacetophenoneiminate) led to the synthesis and X-ray structure analysis of a new kind of salen complex — hypervalent silicon compounds with a threefold deprotonated salen ligand and an enamine structure. This stmctural unit provides access to new routes for synthesizing hypercoordinate silicon complexes. Addition reactions between various Brpnsted acids and these new pentacoordinate silicon compounds were carried out to precipitate complexes bearing hexacoordinate silicon atoms. 

The reaction conditions for the synthesis of [Si2(pz )g] and [Si(pz )4] have been investigated in detail in order to obtain suitable precursor compoxmds for the synthesis of the hitherto unknown Janus-head ligand tris(3,5-dimethylpyrazolyl) silanide ([Si(pz )3] [241]. The X-ray stmctures of several pentacoordinated disilanes of type 95 with X = Cl or 3,5-dimethylpyrazolyl have been presented in this work. The chemistry of 3,5-dimethylpyrazolyl silicon complexes has been further explored. Although pyrazolide is an anionic substituent, its second N atom (the imine N atom of N-silylated pyrazole) also coordinates to silicon, thus exhibiting features of a neutral nitrogen donor as well. 

Evans and coworkers62 described the synthesis and structural study of a series of pentacoordinate bis(catecholate) complexes of silicon(IV). The crystal structure of the anion of [Et3NH][SiMe(3,5-dncat)2] [H2(3, 5-dncat) = 3, 5-dinitrocatechol] is reported (Figure 7). 

The main methods for the synthesis of hexacoordinate silicon compounds are similar to those for pentacoordinate complexes and were outlined in a recent review6. These methods include (a) addition of nucleophiles (neutral or anionic) to tetracoordinate silanes (b) intermolecular or intramolecular coordination to an organosilane (c) substitution of a bidentate ligand in a tetrafunctional silane. The following discussion focuses mainly on new complexes, reported since the recent reviews6,7 were published. 

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