METAL-COMPLEXES OF STERICALLY HINDERED PYRAZOLYLPYRIDINES - THE SINGLE-CRYSTAL X-RAY STRUCTURE OF [CU(L-1)(2)]BF4(L-1 = 1-(PYRID-2-YL)-3-(2',5'-DIMETHOXYPHENYL)PYRAZOLE)

Reaction of potassium 3{5}-(3',4'-dimethoxyphenyl)pyrazolide with 2-br omopyridine in diglyme at 130 degrees C for 3 days followed by an aque ous quench, affords 1-{pyrid-2-yl}-3-{3',4'-dimethoxyphenyl} pyrazole (L-2) in 69% yield after recrystallisation from hot hexanes. Complexat ion of [Cu(NCMe)(4)]BF4 by 2 molar equivalents of 1-{pyrid-2-yl}-3-(2' ,5'-dimethoxyphenyl) (L-1) or L-2 in MeCN at room temperature, followe d by concentration and crystallisation with Et2O, gives [Cu(L)(2)]BF4( L = L-1, L-2) in good yields. Treatment of AgBF4 with L-1 or L-2 in h MeNO2 similarly gives [Ag(L)(2)]BF4 (L = L-1, L-2); reaction of AgBF4 with L-2 in MeCN gives a product of stoichiometry [Ag(L-2)(NCMe)]BF4. The H-1 NMR spectra of the [M(L)(2)]BF4 complexes show peaks arising f rom a single coordinated ligand environment. The single crystal X-ray structure of [Cu(L-1)(2)]BF4 shows a tetrahedral complex cation with C u-N = 2.011(8), 2.036(8), 2.039(8), 2.110(8) Angstrom. The Cu-1 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)degrees. Complexation of hydrated Cu(BF4)(2) by L-2 in M eCN at room temperature yields [Cu(L-2)(2)](BF4)(2). The cyclic voltam mograms of the three Ag-1 complexes in MeCN/0.1 M Bu-4(n) NPF6 are sug gestive of extensive ligand dissociation in this solvent. (C) 1997 Els evier Science Ltd.