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Stabilization of Triorganotin Cations — Competition between Intramolecular Coordinative O, S or NSn Bonds and Side‐on π Coordination to CC Bonds
Author(s) -
Wrackmeyer Bernd,
Kundler Sabine,
Milius Wolfgang,
Boese Roland
Publication year - 1994
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19941270209
Subject(s) - chemistry , intramolecular force , moiety , tin , stereochemistry , cationic polymerization , double bond , coordination complex , crystallography , medicinal chemistry , polymer chemistry , metal , organic chemistry
Abstract Di‐1‐alkynyltin compounds 1 of the type Me 2 Sn(CC U L) 2 [L U = 2‐pyridyl ( a ), Me 2 NCH 2 ( b ), MeOCH 2 ( c ), MeOCHCH ( d ), EtSCH 2 ( e )] were prepared and the 1,1‐organoboration of 1 with triethyl‐ ( 2a ) and triisopropylborane ( 2b ) has been studied. The first detectable intermediates were in all cases zwitterionic compounds 3 (from Et 3 B) and 4 (from i Pr 3 B) with a cationic triorganotin fragment, stabilized by coordinative s̀ LSn bonds and by side‐on coordination to the CC bond of an alkynylborate moiety. The nature of this stabilization has been established by three X‐ray analyses ( 3b, 4b , and 4d ) in the solid state and by multinuclear NMR ( 1 H‐, 11 B‐, 13 C‐, 15 N‐, 119 Sn NMR) in solution. The comparison of the molecular structure of 3b, 4b , and 4d with that of intermediates without functional groups shows that the distance of the tin atom to the CC bond is elongated. However, the planar arrangement of all relevant atoms proves that the side‐on coordination of the tin atom to the CC bond is still present. These intermediates 3 and 4 rearrange to stannoles 5, 6 and/or to 1‐stanna‐4‐bora‐2,5‐cyclohexadienes 9, 10 . In the case of 3b and 3e , 119 Sn NMR indicates that dialkenyltin compounds 7b and 7e are also formed as minor products. In the case of 3e , the 3‐stannolene 8e is one of the final products. In the stannoles 5 and 6 a coordinative LB bond is evident, and there is NMR spectroscopic evidence of a weak coordinative L—Sn bond.