. Can. J. Chem. 69, 121 (1991).The crystal and molecular structures of s n ( % t -B~)~ and [Sn(&i-Pr)4.H&i-Pr]2 have been determined by single-crystal X-ray diffracti9n. Sn(&t-Bu)40crystallizes in the monoclinic crystal system with space group C2/c, where a = 17.382(6) A, [Sn(&i-Pr)4.H&i-Pr]2 exhibits an edge-shared, bi-octahedral structure in the solid state that is distorted due to the presence of asymmetric hydrogen bonding between axially coordinated alcohol ligands and an isopropoxide ligand. I3C NMR and IR spectroscopic data have been recorded for Sn(&t-Bu)4 and S n ( & t -B~-d~)~ to establish criteria for unambiguous identification of solution structures of tin(1V) alkoxides. It is demonstrated that the two-bond 2~~j C -&~~9 s n coupling constant is larger for terminal alkoxide ligands than for k2-alkoxide bridges, and the v(Sn-0) stretching frequency has been assigned. The dynamic solution behaviour of [Sn(&i-Pr)4.H&i-Pr]2 has been studied using variable temperature 'H and I3C NMR spectroscopy. The data obtained are consistent with a process that involves rapid reversible dissociation of isopropanol at room temperature. Upon cooling, the equilibrium concentration of the species with coordinated alcohol increases, and the molecule undergoes rapid intramolecular proton transfer (AG* < 11.9 kcal mol-I). Upon further cooling, the I3C NMR data are consistent with a solution structure analogous to that found in the solid state.Key words: tin, alkoxide, NMR, dynamic, structure. travers deux liaisons 2~~lC-&ttssn, est plus grande pour les ligands alcoolates terminaux que pour les ponts alcoolates-k2; de plus, on a attribut la frtquence de,. Faisant appel a la rmn du 'H et du I3c, a temperature variable, on a ttudit le comportement dynamique du [Sn(%i-Pr).HO--i-Pr] en solution. Les donntes obtenues sont en accord avec un processus qui implique une dissociation reversible rapide de l'isopropanol, a la temptrature ambiante. Par refroidissement, la concentration de l'espkce avec de I'alcool isopropylique augmente et la moltcule subit un transfert intramoltculaire rapide de proton (AG* < 1 1,9 kcal mol-I). Si on continue le refroidissement, les donntes de la rmn du I3c obtenues sont en accord avec une structure en solution qui serait analogue a celle qui est trouvte a l'ttait solide.
ChemInform Abstract The reaction of the Cu halides (II) with the peptide ligands (I) which resemble part of the metal-chelating portion of the antitumor drug bleomycin affords the new title complexes (III) and (IV). (IIIa) crystallizes in P21/n with Z=4, (IVb) in P21/c with Z=4. In solution the compounds (III) dissociate into monomeric tetragonal Cu(II) complexes. Some magnetic properties of (III) and (IV) are discussed.
. Can. J. Chem. 68, 565 (1990) The structural data show a relatively short approach between the Rh centres (2.948 A) and between the bridging sulfur atoms (2.888 A). The implications of these structural features in terms of metal-metal and sulfur-sulfur bonding are discussed. In addition, the implications of these results with respect to the formation of thiolato-bridged, early-late heterobimetallics is considered.Key words: thiolate abstraction, rhodium thiolate bridged dimer.
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