Synthesis, molecular structure, and solution stereochemistry of hypercoordinated bis(3-(dimethylamino)propyl)tin compounds. Dissociative (nonregular)and nondissociative (regular) isomerization pathways

The syntheses of [Me2N(CH2)(3)](2)Sn(EAr)(2) (1, E = O Ar = C6H5; 2 E O Ar p-t-BuC6H4 3, E = O, Ar = p-NO2CsH4; 4, E = O, Ar = o-FC6H4; 7, E = S, A = C6H5), [Me2N(CH2)(3)](2)-Sn(o-O2C6H3R-3) (5, R = H; 6, R = OCH3), and {[Me2 N(CH2)(3)](2)SnPh}I-+(-) (8) are reported. X-ray diffraction analyses revea l distorted-octahedral geometries for the tin atoms in compounds 1-7 with, except for the stannaindane derivative 5, the carbon atoms in mutually tran s positions, while the nitrogen and oxygen atoms are cis. In compound 5, th e carbon atoms are cis, whereas the nitrogen atoms are trans. Compound 8, i n contrast, is ionic and consists of an intramolecularly pentacoordinated t riorganotin cation and an iodide anion. Variable-temperature H-1, C-13, and Sn-119 NMR investigations reveal the compounds to have similar structures in solution. The coalescence phenomena observed in the H-1 and C-13 NMR spe ctra are explained both in terms of Sn-O bond cleavage (1-4) and chirality inversion through a sequence of five intramolecular Berry-type pseudorotati ons (1-4, 8), interconverting the enantiomers with propeller-like geometry. The dynamic behavior in solution of the stannaindane derivatives 5 and 6 a nd of the thiophenolate derivative 7 is interpreted in terms of intramolecu lar Sn-N bond dissociation.