- 1-AZA-5-STANNA-5,5-DIMETHYLBICYCLO1,5>OCTAN UND 1-AZA-5-STANNA-5-METHYLTRICYCLO1,5>UNDECAN, PENTAKOORDINIERTE TETRAORGANOZINNVERBINDUNGEN
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The synthesis of Me2Sn(CH2CH2CH2)2NMe and MeSn(CH2CH2CH2)3N is reported.The transannular Sn-N interaction is confirmed by 1H, 13C and 119Sn NMR spectroscopy.
- Jurkschat, K.,Tzschach, A.
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- Heterocyclic systems containing tin(IV) - XIII [1]. Possible ceasing or inversion of the structural trans influence during the course of a bimolecular nucleophilic attack of a donor group in a series of SnIV rings
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In the series of the heterocycles X[(CH2)3]2SnR2 (16 newly synthesized compounds and two taken from the literature) and in the germanium analog BuiN[(CH2)3]2GeCl2, the donor group X (= NMe, NBz, NBui, NPri, O, S) intramolecularly attacks the Lewis acidic atoms Sn or Ge. Eight structure determinations (and, in addition, 2 taken from the literature) are compared. The nucleophilic attack at Sn is stronger for the ligands R2 = Cl2 than for the more electronegative R2 = (OSiPh3)2. Overall the familiar trans influence holds: simultaneous approach of X and weakening of the ligand R(trans). In three cases of subtly graded donor strength a slight inversion or ceasing is observed: shorter distances X...Sn and simultaneously shorter distances Sn - R(trans). Also in a series of 8 compounds with O...Si-(Hal) interaction, taken from the literature, the dominant trans influence ceases to zero in the central part of the oxygen approach. Actually, the discussed ranges of inversion or ceasing of the trans influence are small and in terms of e.s.d.s at the borderline of statistical significance. Despite this objection, the existence of four alike cases is noticeable. As an explanation for this secondary effect, a bonding scheme is discussed in which the electronegativity of the ligands inhibits the nucleophilic attack and in which its drive originates from the π-basicity of the ligands into a σ*-LUMO at Sn or Ge. This bonding scheme is supported by semi-empirical MO calculations on the extended Hueckel level for the Ge compound and its tetrahedral analogue Cl2GeBun2. In addition, a qualitative discussion of 119Sn NMR chemical shifts is given, which uses the same line of arguments as applied above on the basis of interactions of frontier Orbitals.
- Beuter, Mike,Kolb, Ute,Zickgraf, Andrea,Braeu, Elmar,Bletz, Michael,Draeger, Martin
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p. 4005 - 4015
(2008/10/09)
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- Synthesis, spectroscopic investigations, and molecular structures of 1-elementa-5-stannabicyclo[3.3.01,5]octanes, RR′Sn(CH2CH2CH2)2E (E = NMe, O, S)
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The 1-elementa-5-stannabicyclo[3.3.01,5]octanes Cl2Sn(CH2CH2CH2)2E (E = NMe, O, S), Me(Cl)Sn-(CH2CH2CH2)2E (E = NMe, O), Me2Sn(CH2CH2CH2)2E (E = NMe, O), and t-Bu2Sn(CH2CH2CH2)2NMe and the stannacyclooctane Me2Sn(CH2CH2CH2)2CH 2 have been prepared by the reaction of the Grignard reagents E(CH2CH2CH2MgX)2 (X = Cl, Br) with tin tetrachloride or organotin halides. The molecular structures of Cl2Sn(CH2CH2CH2)2NMe (1), Cl2Sn(CH2CH2CH2)2O (5), and Cl2Sn(CH2CH2CH2)2S (8) were determined by X-ray analysis. 1 crystallizes in the monoclinic space group Cc (Z = 4) with a = 13.987 (5) ?, b = 7.668 (2) ?, c = 11.213 (3) ?, and β = 112.68 (2)°. The structure was refined to R = 0.027. 5 crystallizes in the monoclinic space group C2/c (Z = 8) with a = 23.034 (7) ?, b = 7.153 (2) ?, c = 13.944 (4) ?, and β = 114.09 (2)°. The structure was refined to R = 0.163. 8 crystallizes in the monoclinic space group P21/a (Z = 4) with a = 11.521 (1) ?, b = 13.869 (3) ?, c = 6.894 (1) ?, and β = 109.57 (1)°. The structure was refined to R = 0.072. As a result of the Sn-N (2.441 ?), Sn-O (2.384 ?), and Sn-S (2.851 ?) interaction, respectively, the tin atoms in 1, 5, and 8 exhibit distorted trigonal-bipyramidal configurations with the heteroatom in apical position. 1H, 13C, and 119Sn NMR studies in solution show conformational equilibria with dominating boat-chair (BC) and chair-chain (CC) conformations. The dynamic behavior of the compounds is interpreted in terms of a combined dissociation-inversion (DI) and ring inversion (RI) mechanism.
- Jurkschat, Klaus,Schilling, J?rgen,Mügge, Clemens,Tzschach, Alfred,Meunier-Piret, Jacqueline,Van Meerssche, Maurice,Gielen, Marcel,Willem, Rudolph
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