A new hexakis(isocyanato)silicate(IV) and the first neutral Lewis-base adducts of silicon tetraisocyanate

Abstract

The new silicates K2Si(NCE)6, E = O, S (1a,b) were synthesised directly by reaction of silicon tetrachloride with potassium cyanate or thiocyanate. 1a,b can be converted to the salts (PPN)2[Si(NCE)6] (2a,b) with bulky cations (PPN+ = N(PPh3)2+), which contain isolated silicate dianions. Reaction of 1a with diimines affords the hexacoordinate complexes Si(NCO)4L, L = bpy (3), phen (4), which are the first isolated neutral adducts to Si(NCO)4. The compounds were characterised by a combination of IR and NMR spectroscopies, MS, TGA, DSC and X-ray diffraction.

Novel neutral hexacoordinate silicon(iv) complexes with two bidentate monoanionic benzamidinato ligands

“…The main focus of this study was the synthesis and structural characterisation of novel neutral hexacoordinate silicon(IV) complexes with SiN 4 X 2 skeletons (X = F, Cl, Br, C, N, S, Se). In this context, compounds 5-7 (SiN 6 skeletons), 8 (SiN 4 S 2 ), 9 (SiN 4 SSe) and 10 (SiN 4 Se 2 ) were of particular interest: To the best of our knowledge, neutral hexacoordinate silicon(IV) complexes with an SiN 6 skeleton have not yet been reported, except for a quite recently published phenanthroline adduct of Si(NCO) 4 , 4 and hexacoordinate silicon(IV) complexes with SiN 4 S 2 , SiN 4 SSe and SiN 4 Se 2 skeletons were even totally unknown. Furthermore, compounds 9 and 10 are the first hexacoordinate silicon(IV) complexes with Si-Se bonds, whereas pentacoordinate silicon(IV) complexes with Si-Se bonds have been reported quite recently.…”

Syntheses, Structures, and Infrared Spectra of the Hexa(cyanido) Complexes of Silicon, Germanium, and Tin

“…The PPN 2 E­(CN) 6 compounds are moderately air sensitive and dissolve readily in polar aprotic solvents without noticeable dissociation or linkage isomerization of the E­(CN) 6 2– complex anions. The synthetic methodologies applied to these hypercoordinate complexes are partially based on those used previously for the N 3 , NCS and NCO analogues. ,, However, more forcing conditions are required for the final reaction step E­(CN) 5 Cl 2– + CN – → E­(CN) 6 2– + Cl – , the reasons for which were identified with the help of systematic DFT and coupled cluster calculations. According to these calculations it is primarily the reduction in the net-loss of electronic energy in the reaction involving tin and, presumably, the similarity in Sn–CN and Sn–Cl bond strengths which cause the supposed reaction equilibrium to lie on the side of the starting material.…”

Cyanidosilikate – Synthese und Struktur

“…[Me 3 SiF(CN)] − ‐Ionen wurden als starke nukleophile Cyanidquelle für S N 2‐Reaktionen diskutiert, während [Me 3 Si(CN) 2 ] − und [Me 3 Si(CN)Cl] − als reaktive Spezies in enantioselektiven Cyanosilylierungen von Aldehyden und Ketonen beschrieben wurden . Erstaunlicherweise sind keine Salze mit dem Hexacyanidosilikatdianion [Si(CN) 6 ] 2− bekannt, während die analogen Hexapseudohalogenidosilikate des Azids, (Iso‐)Cyanats und Thiocyanats isoliert wurden. Darüber hinaus haben Fehlhammer et al.…”