Metal complexes of sterically hindered pyrzolylpyridines. The single crystal X-ray structure of [Cu(L)2]BF4 (L = 1-{pyrid-2-yl}-3-{2′,5′-dimethoxyphenyl}pyrazole) |
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Authors: | Malcolm A. Halcrow Natalie L. Cromhout Paul R. Raithby |
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Affiliation: | Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CD2 1EW, U.K. |
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Abstract: | Reaction of potassium 3{5}-(3′,4′-dimethoxyphenyl)pyrazolide with 2-bromopyridine in diglyme at 130°C for 3 days followed by an aqueous quench, affords 1-{pyrid-2-yl}-3-{3′,4′-dimethoxyphenyl}pyrazole (L2) in 69% yield after recrystallization from hot hexanes. Complexation of [Cu(NCMe)4]BF4 by 2 molar equivalents of 1-{pyrid-2-yl}-3-{2′,5′-dimethoxyphenyl}pyrazole (L1) or L2 in MeCN at room temperature, followed by concentration and crystallisation with Et2O, gives [Cu(L)2]BF4 L = L1, L2) in good yields. Treatment of AgBF4 with L1 or L2 in MeNO2 similarly gives [Ag(L)2]BF4 L = L1, L2); reaction of AfBF4 with L2 in MeCN gives a product of stoichiometry [Ag(L2)(NCMe)]BF4. The 1H NMR spectra of the [M(L)2]BF4 complexes show peaks arising from a single coordinated environment. The single crystal X-ray structure of [Cu(L1)2]BF4 shows a tetrahedral complex cation with Cu---N = 2.011(8), 2.036(8), 2.039(8), 2.110(8) Å. The CuI centre is close to tetrahedral, the dihedral angle between the least-squares planes formed by the Cu atom and the N donor atoms of the two ligands being 88.3(3)°. Complexation of hydrated Cu(BF4)2 by L2 in MeCN at room temperature yields [Cu(L2)2](BF4)2. The cyclic voltammograms of the three AgI complexes in MeCN/0.1 M Bu4n NPF6 are suggestive of extensive ligand dissociation in this solvent. |
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Keywords: | copper silver pyrazolylpyridine crystal structure |
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