Association of Dicyanodiphenylacetylenes with Silver(I) Salts in Solution and Solid State: Electrospray Ionization Mass Spectrometry Samples Aggregates at Subsaturated Concentrations

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• 作者：Keith A. Hirsch ; Scott R. Wilson ; and Jeffrey S. Moore
• 刊名：Journal of the American Chemical Society
• 出版年：1997
• 出版时间：October 29, 1997
• 年：1997
• 卷：119
• 期：43
• 页码：10401 - 10412
• 全文大小：262K
• 年卷期：v.119,no.43(October 29, 1997)
• ISSN：1520-5126

文摘

Complexes of 2,3'-dicyanodiphenylacetylene (2,3'-DCPA,1), 2,2'-dicyanodiphenylacetylene (2,2'-DCPA,2), and 2,4'-dicyanodiphenylacetylene (2,4'-DCPA,3) with silver(I) salts have been characterized in thesolid stateby single-crystal X-ray analysis. In addition, aggregates ofcompounds 1-3 and silver(I)ions have been identifiedin solution by electrospray ionization mass spectrometry (ESI-MS).The topology of the structures in the solid state,namely finite versus infinite, is found to depend on the substitutionpattern of nitrile groups on diphenylacetylene.For 2,3'-DCPA (1), crystallization with silver(I)triflate (AgCF₃SO₃), silver(I)perchlorate hydrate (AgClO₄·xH₂O,x~ 1), or silver(I) hexafluoroantimonate (AgSbF₆)produces cyclic dimers of composition[Ag(1)(X)]₂ (X =CF₃SO₃^-(4) or ClO₄^- (5)) and{[Ag(1)](SbF₆)}₂(6). For these structures, 2,3'-DCPA coordinates tosilver(I) ions in a cisoidconformation with respect to the orientation of nitrile groups.Significant deformations of the cyclic dimers areobserved as a function of the counterion employed. In contrast tothe finite structures involving 2,3'-DCPA,crystallization of 2,2'-DCPA (2) withAgCF₃SO₃ yields the infinite chainstructure [Ag(2)(CF₃SO₃)](7). 2,2'-DCPAcoordinates to silver(I) in a transoid conformationresulting in a "half-bow-tie" motif for the chains.Crystallizationof 2,4'-DCPA (3) with AgCF₃SO₃produces the infinite, undulating sheet structure[Ag(3)(CF₃SO₃)](8) in whichhelical chains of 2,4'-DCPA coordinated to silver(I) ions arebridged by triflate counterions. Positive ion ESI-MSof solutions of 2,3'-DCPA (1) andAgCF₃SO₃,AgClO₄·H₂O, or AgSbF₆ in acetoneor acetonitrile show a distributionof aggregates including[Ag₂(1)₂(X)]⁺ (X =CF₃SO₃^-,ClO₄^-, or SbF₆^-).The composition of these species correspondsto that of the cyclic dimers of complexes4-6 minus one counterion, X.With 2,2'-DCPA (2) andAgCF₃SO₃ inacetone or acetonitrile, the aggregates[Ag(2)]⁺ and[Ag(2)₂]⁺ are observed andhigher adducts are noted to bepresent in much lower abundance. It is believed that thepredominance of adducts involving one silver(I) ion isdueto the formation of chelated species in solution in which 2,2'-DCPAcoordinates to a silver(I) ion in a cisoidconformation. Molecular modeling suggests that such species areviable. ESI-MS of 2,4'-DCPA (3) andAgCF₃SO₃ in acetone or acetonitrile shows the existence of[Ag(3)]⁺ as well as higher aggregateswhich are less prevalent.For a given ligand, aggregation at concentrations of the ligandand silver(I) salt of ca. 10^-3 M issignificant inacetone, however, it is largely disrupted in acetonitrile due to thepredominance of acetonitrile·Ag(I) adducts.Analysisof the ESI-MS data for all three ligands withAgCF₃SO₃ in acetone or acetonitrile showsthat the aggregate[Ag₂(L)₂(CF₃SO₃)]⁺is most abundant for L = 2,3'-DCPA (1). It ispostulated that the relatively high abundance of[Ag₂(1)₂(CF₃SO₃)]⁺is indicative of the formation of a cyclic dimer in solution thatresembles complex 4. Similarly,it is believed that cyclic dimers exist in solution withClO₄^- and SbF₆^- aswell.