Complexes formés par addition d'éthers-couronnes aux énolates de Na<sup>+</sup> et K<sup>+</sup> de l'acétylacétate d'éthyle: structures cristallines et système d'équilibres en solution dans le THF et le DMSO

. Can. J. Chem. 69,687 (1991). The crystal structures of three crown ether complexes (cyclohexano-15-crown-5.2LiOPh (I): Li207C26H36, Mr = 474.45, h(CuKa)filt. = 1.5418 A; cyclohexano-15-crown-5.2NaOPh (2): Na207C26H36, MI = 504.54, h(CuKa)filt. = 1.5418 A; and 15-crown-5.2NaOPh (3): Na207C22H30, MI = 452.46, h(CuKa)mono. = 1.5418 A) have been determined by X-ray diffraction at room temperature (T = 298 K). Complex 1 crystallizes in space group P2,/n with a = 15.032(5), b = 13.332(2), c = 13.533(3) A, P = 106.28(2)", V = 2603.2 A3, andZ = 4. Complex 2 crystallizes in space group P2Jn with a = 15.94(1), b = 12.194(7), c = 14.068(7) A, P = 102.84(5)", V = 2666.3 A3, andZ = 4. Complex 3 crystallizes in space group P2,/c with a = 12.451(3), b = 17.263(3), c = 12.659(6) A, P = 1 15.74(3)", V = 2450.8 A3, and Z = 4. The three structures were solved by direct methods and refined by full-matrix least-squares calculations to residuals, R, of 0.080,0.069, and 0.081 for complexes 1, 2, and 3, respectively. In each structure the macrocycle forms a 1:2 host-guest complex with the alkali metal. Each structure exhibits a dimer of the general form (MAC.2MOPh)2 where M = Li+ and Na+ for structures 1 and 2, respectively, and MAC = cyclohexano-15-crown-5, while M = Na+ and MAC = 15-crown-5 for structure 3. In each case the two metals of the monomeric unit have different crystallographic and chemical environments. In structures 1 and 3 one alkali metal is coordinated to all five oxygens of the macrocycle and to one of the phenoxide oxygens, while the other alkali metal is coordinated to only one oxygen of the macrocycle and to three phenoxide oxygens. In structure 2, one alkali metal is coordinated to only four of the five oxygens of the macrocycle and to two of the phenoxide oxygens, while the other alkali metal is coordinated to only one oxygen of the macrocycle and to three phenoxide oxygens (as in 1 and 3).Key words: crown ether, host-guest complexes, X-ray crystallography Dans chacune des structures, le macrocycle forme un complexe 1 : 2 hBte-invitC avec le mCtal alcalin. Chaque structure comporte un dimkre de la forme gCnCrale (MAC.2MOPh)2; pour les structures 1 et 2, MAC = cyclohexano-15-couronne-5 et M = Li+ et Na' respectivement alors que M = Na+ et MAC = 15-couronne-5 pour la structure 3. Dans chaque cas, les deux mCtaux de l'unitC monomkre sont dans des environnements cristallographiques et chimiques diffkrents. Dans les structures 1 et 3, un mCtal alcalin est coordinC aux cinq oxygknes du macrocycle et un oxygkne phenolique alors que l'autre metal alcalin est coordinC 2i un seul oxygkne macrocyclique et i trois oxygknes phenoliques. Dans la structure 2, un metal alcalin est coordinC 2 seulement quatre des cinq oxygknes du macrocycle et i deux oxygknes phCnoliques alors que l'autre metal alcalin est coordinC a seulement un oxygkne du macrocycle et i trois oxygknes phCnoliques.

Section: Cyclohexano-15-crown-52naoph (2)mentioning

confidence: 94%

Section: Cyclohexano-15-crown-52naoph (2)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Crown ether complexes exhibiting unusual 1:2 macrocycle salt ratios: X-ray crystal structures of cyclohexano-15-crown-5•2LiOPh, cyclohexano-15-crown-5•2NaOPh, and 15-crown-5•2NaOPh

Watson¹,

Fortier²,

Murchie³

et al. 1991

“…There are numerous other examples of formation of crown-and cryptand-complexed ion pairs in nonpolar (27) and dipolar aprotic solvents (28), as well as in the solid state (29).…”

Section: Reactivities Of Free Ions and Ion Pairsmentioning

confidence: 99%

Metal ion catalysis in nucleophilic displacement reactions at carbon, phosphorus, and sulfur centers. III. Catalysis vs. inhibition by metal ions in the reaction of p-nitrophenyl benzenesulfonate with ethoxide

Pregel¹,

Dunn²,

Buncel³

1990

Thispaper is dedicated to Professor Ross Stewart on the occasion of his 65th birthday MARKO J. PREGEL, EDWARD J. DUNN, and ERWIN BUNCEL. Can. J. Chem. 68, 1846 (1990). The rate of the nucleophilic displacement reaction of p-nitrophenyl benzenesulfonate (I) with alkali metal ethoxides in ethanol at 25°C has been studied by spectrophotometric techniques. For lithium ethoxide, sodium ethoxide, potassium ethoxide, and cesium ethoxide, the observed rate constants increase in the order LiOEt < NaOEt < CsOEt < KOEt. The effect of added crown ether and cryptand complexing agents was also investigated. Addition of complexing agent to the reaction of KOEt results in the rate decreasing to a minimum value corresponding to the reaction of free ethoxide. Conversely, addition of complexing agent to the reaction of LiOEt results in the rate increasing to a maximum value that is identical to the minimum value seen in the reaction of KOEt in the presence of excess complexing agent. In complementary experiments, alkali metal ions were added in the form of umeactive salts. Addition of a K' salt to the reaction of KOEt increases the reaction rate, while addition of a ~i + salt to the reaction of LiOEt decreases the rate. The involvement of metal ions in the reaction of 1 is proposed to occur via reactive alkali metal -ethoxide ion pairs. The kinetic data are analyzed in terms of an ion pairing treatment that allows the calculation of second-order rate constants for free ethoxide and metal-ethoxide ion pairs; the rate constants increase in the order LiOEt < EtO-< NaOEt < CsOEt < KOEt. Thus, ~i ' is an inhibitor of the reaction of ethoxide with 1 , while the other metals ions studied are all catalysts. Equilibrium constants for the association of the various metal ions with the transition state are calculated using a thermodynamic cycle, and are compared to association constants in the ground state. Consistent with the observed kinetic results, Li+ is found to stabilize the ground state more than the transition state, while Na', K + , and Cs' all stabilize the transition state more than the ground state. The trend in the magnitude of the transition state stabilization is interpreted in terms of interactions of the transition state with bare or solvated metal ions. It is concluded that the transition state for the reaction of 1 with ethoxide forms solvent separated ion pairs with alkali metal ions. Analogous data were available for the reaction of p-nitrophenyl diphenylphosphinate (2) with ethoxides, where Li', Na+, K' , and Cs+ all function as catalysts, and the results are analyzed as above. In contrast to the sulfonate system, it is proposed that the phosphinate transition state forms contact ion pairs with alkali metal ions. The difference is attributed to a greater localization of negative charge in the phosphinate transition state, leading to stronger interactions with metal ions, which overcome metal ion -solvent interactions.Key words: nucleophilic substitution at sulfur, alkali metal ion catalysis.MARKO J. PREGEL, EDWARD J. D...

“…The original pioneering work of Pedersen (1) described the synthesis of benzo-15-crown-5 and subsequently a series of articles have appeared dealing with the crystal structure (2) and complexation features of this molecule (3)(4)(5)(6)(7)(8)(9), as well as 15-crown-5 ether itself (10)(11)(12)(13)(14). Also the solid phase 13C NMR features of benzo-15-crown-5 have been reported (15).…”

Section: Introductionmentioning

confidence: 99%

Dibenzo-15-crown-5 ether and its sodium thiocyanate complex. X-ray crystallographic and NMR studies in the solid phase and in solution

Buchanan¹,

Mathias²,

Lear³

et al. 1991

Can. J. Chem. 69,404 (1991). For the title systems, single crystal X-ray data indicate the presence of totally asymmetric structures. These features are reflected in the multiplicity of resonances in the solid phase I3C NMR spectra. Some of the I3c chemical shift trends are analyzed in terms of torsional angle influences. In solution, resonance assignments have been made with the aid of 2D methods. Stereochemical inferences are drawn from NOESY spectra and 'H-'H couplings. Low temperature solution experiments indicate that conformational interconversions in both the free ligand and the NaNCS complex are rapid on the NMR timescale down to 163 K.