Addition of Lappert's stannylenes to carbodiimides, providing a new class of tin(II) guanidinates

Article abstract of DOI:10.1021/om201118m

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.