Tuning the Si–N Interaction in Metalated Oligosilanylsilatranes

Abstract

Most known silatrane chemistry is concerned with examples where the attached silatrane substituent atom is that of an element more electronegative than silicon. The current study features silylated silatranes with a range of electropositive elements attached to the silyl group. The resulting compounds show different degrees of electron density on the silatrane-substituted silicon atom. This directly affects the Si–N interaction of the silatrane which can be monitored either by 29Si NMR spectroscopy or directly by single crystal XRD analysis of the Si–N distance. Within the sample of study the Si–N distance is increased from 2.153 to 3.13 Å. Moreover, the bis(trimethylsilyl)silatranylsilyl unit was studied as a substituent for disilylated germylene adducts.

Chemistry of a 1,5-Oligosilanylene Dianion Containing a Disiloxane Unit

“…Silylated lanthanides are an interesting field of research pioneered by Schumann and co-workers. 49,50 Oligosilylated examples are still investigated by us 31−34 and others. 51−54 As mentioned, we initially devised the synthesis of oligosilanylene diide 2 to employ it as a ligand for Ln(II)-silyl complexes.…”

Oligosilanylated Silocanes

“…The signals of 3 (+3.5 ppm) and 8 (+19.5 ppm) reflect the downfield shift associated with the change of an alkoxy substituent for either a methyl or oligosilanyl group. One unusual feature of the silatranyloligosilanide NMR spectroscopy was the unusually strong downfield shift of the silatranyl Si signal upon silanide formation [ 3 , 5 ]. Starting from a resonance for the silatranyl silicon atom of tris(trimethylsilyl)silylsilatrane of δ Si = −52.8 ppm, the respective silanides obtained by abstraction of a trimethylsilyl group resonated at −11.8 ppm, yielding a ∆δ Si of +40.8 ppm.…”

“…Compound 12 is special as it has the substitution pattern of (MeO) 3 Si Si(SiMe 3 ) 2 K or silatranyloligosilanide (RO) 3 Si Si(SiMe 3 ) 2 K. The silocanyl Si 1 resonance of δ Si 1 = −13.9 ppm is very close to the respective silatrane [ 3 , 5 ] and even the strong upfield shift of the silanide signal at δ Si 2 = −210.2 ppm ( Table 1 ) is something we also observed for the silatranyloligosilanide cases [ 3 , 5 ].…”

“…Extending our previous work on oligosilanylated silatranes [ 3 , 4 , 5 , 6 , 7 ], we have chosen to study the chemistry of a related system with a less constrained geometry. For this reason we decided to turn to the family of silocanes, which can be regarded as silatranes with one of the bridging arms between nitrogen and silicon missing.…”

“…Nowadays, a number of compound classes featuring hypercoordination are well-investigated. Especially, the cage-type atrane molecules of heavier group 14 elements have received much attention [ 1 , 2 ] and recently we have contributed to these investigations by some studies of oligosilanyl-substituted silatranes [ 3 , 4 , 5 , 6 , 7 ].…”