Reaction of sulfur diimides with organoboranes — studied by multinuclear magnetic resonance in solution

Abstract

Reactions between sulfur diimides R(NSN)R′ (RR′ tBu ( 1a), SiMe 3 ( 1b), SnMe 3 ( 1c); R tBu, R′SnMe 3 ( 1d); RSiMez 3, R′SnMe 3 ( 1e)) and various organoboranes were studied, and the products were characterized by multinuclear magnetic resonance data ( 1H, 11B, 13C, 15N, 29Si and 119Sn NMR). Tetraalkyldiboranes(6) (Et 2BH 2BEt 2 ( 2), dimeric 9-borobicyclo[3,3.1]nonane ( 3)) react with 1a and 1b by 1,3-hydroboration to give the N-sulfanyl-dialkylaminoboranes 4 and 5 which are instable with respect to eliminatio of short-lived [RNS]. Trialkylboranes (Et 3B ( 8)) react only sluggishly with 1a, but more readily with 1b mainly via S-ethylation, formally a 1,2-ethyloboration, to give the diethylborylamido-imino-ethanesulfinic acid 9b decomposes slowly at room temperature via ethene elimination to give 4b, followed by further decomposition via [RNS] elimination. The compounds 9 can be prepared independently from the reaction between the N-lithio-imino-ethanesulfinic acid amide 10 and diorganoboron halides. The molecular structure of the lithium amide 10a (RR′tBu) was determined by X-ray analysis as a dimer in which the four nitrogen, two sulfur and two lithium atoms adopt a boat conformation, in contrast with other known derivatives of this type. If the sulfur diimides bear at least one trimethylstannyl group ( 1c-e), their reactions with Et 3B ( 8), iPr 3B ( 12) or 9-iso-butyl-9-borabicyclo[3,3,1]nonane ( 13) lead to the novel aminoboranes 14–16. These are products of a 1,1,-organoboration, since the Me 3Sn group moves from one nitrogen atom to the other, and both the boryl and an alkyl group end up at the same nitrogen atom.