Simple Silylhydrazines as Models for Si-Nβ-Donor Interactions in SiNN Units

Abstract

Two simple silylhydrazines, H 3 SiMeNNMe 2 and (H 3 Si) 2 NNMe 2 , have been prepared by the reaction of bromosilane with the corresponding NH-functional hydrazine in the presence of a base and the appropriate lithiated hydrazine. The intermolecular attractive interactions (b-donor ± acceptor interaction) between the silicon and b-nitrogen atoms of H 3 SiMeNNMe 2 and (H 3 Si) 2 NNMe 2 has been demonstrated by low-temperature X-ray crystallography and ab initio calculations (MP2/6-311 G). The contributions to the strength of this two-bond interaction are discussed in the light of a new series of calculations on RSiH 2 NR'NR '' 2 molecules (R H, F; R' H, Me, SiH 3 ; R'' H, Me), which show electronegative substituents at the silicon acceptor center to exert the largest effect, while the electronic nature of the substituent at the b-nitrogen atom is also important. As the resulting structures cannot be described satisfactorily by either the VSEPR concept or Bartells two-bond radius model, a two-bond interatomic attraction has to be taken into account in addition; this leads to an extension of the common models for empirical structure prediction.

Extremely bulky secondary phosphinoamines as substituents for sterically hindered aminosilanes

“…4 Molecular structures of 8, 9 and 10 with the thermal ellipsoid plots at the 25% probability level. 23 The two higher silanes 9 and 10 show a different involvement of their phosphorus lone pairs. Selected structural parameters are given in Table 2. of 5 and 8, showed the conversion of the -SiCl 3 moiety to the an -SiH 3 unit only slightly affects the molecular geometry of the compounds.…”

“…Moreover, the N-Si bond length in 8 (1.713(2) Å) compares well with that found for the known silylhydrazine H 3 SiMeNNMe 2 (1.693(1) Å). 23 The two higher silanes 9 and 10 show a different involvement of their phosphorus lone pairs. In 9 the two phenyl groups at the phosphorus are turned towards the bulky Ar † group, allowing a weak interaction between P1 and Si2.…”

Two Successive Steps of Hypercoordination at Tin: The Gas-Phase and Solid-State Structures of (N,N-Dimethylaminoxy)trimethylstannane

“…Recently we have established the occurrence of donor bonds for SiON and SiNN linkages. The most extreme case in our hands is ClH 2 SiONMe 2 , which adopts a SiON angle of only 79.7(1)° in the crystal, but does not undergo even weak intermolecular interactions as detected in related systems such as ClH 2 SiNMe 2 .…”

Are There Structurally Relevant Attractive Interactions between Nitrogen Atoms and Group 14 Elements in Their Aminomethyl Compounds?

“…Recently we have systematically studied isoelectronic compounds containing E−N−N and E−O−N fragments and found attractive interactions between the nitrogen and group 14 centers. In addition to these hydrazinosilanes and aminoxysilanes our studies included also aminoxygermanes and -stannanes .…”