Addition of Lappert's Stannylenes to Carbodiimides, Providing a New Class of Tin(II) Guanidinates

Reactions of bis­[bis­(trimethylsilyl)­amino]tin and the
dimer of
[bis­(trimethylsilyl)­amino]tin chloride with various carbodiimides
give pure corresponding tin­(II) guanidinates in essentially quantitative
yields. Heteroleptic bis­(trimethylsilyl)­amido ({R-NC­[N­(SiMe3)2]­N-R}­SnN­(SiMe3)2)- and chloro-substituted
({R-NC­[N­(SiMe3)2]­N-R}­SnCl) tin­(II) guanidinates
were obtained from reactions of N,N′-diisopropyl-, N,N′-dicyclohexyl-, N,N′-bis­(4-methylphenyl)-, and N-[3-(dimethylamino)­propyl]-N′-ethylcarbodiimides,
respectively. Homoleptic tin­(II) guanidinates {R-NC­[N­(SiMe3)2]­N-R}2Sn were obtained from the N,N′-bis­(4-methylphenyl)- and N-[3-(dimethylamino)­propyl]-N′-ethyl-substituted
carbodiimides. Similar reactions of N,N′-bis­(2,6-diisopropylphenyl)-
and N,N′-bis­(trimethylsilyl)­carbodiimide,
respectively, having the bulkiest substituents of the series, failed
to take place under various conditions. The complexes prepared were
characterized as monomers in solution by 1H, 13C, and 119Sn NMR spectroscopy in C6D6 and THF-d8. The solid-state NMR spectra
were recorded for structure comparison. X-ray diffraction studies
of one homoleptic monomer, two heteroleptic chloro complexes with
the structures of two different types of dimers, and the oxidation
product of the heteroleptic bis­(trimethylsilyl)­amido-substituted guanidinatea
centrosymmetric (guanidinato)­tin­(IV) oxidewere performed on
appropriate crystals. Attempts to prepare homoleptic types of isopropyl-
and cyclohexyl-substituted tin­(II) guanidinate complexes were unsuccessful.
The structures were also evaluated by DFT methods.