Sensitivity of Silver(I) Complexes of a Pyrimidine–Hydrazone Ligand to Solvent, Counteranion, and Metal-to-Ligand Ratio Changes

Metal complexation studies were performed with AgSO3CF3 and AgBF4 and the ditopic pyrimidine–hydrazone
ligand 6-(hydroxymethyl)­pyridine-2-carboxaldehyde (2-methylpyrimidine-4,6-diyl)­bis­(1-methylhydrazone)
(1) in both CH3CN and CH3NO2 in a variety of metal-to-ligand ratios. The resulting complexes
were studied in solution by NMR spectroscopy and in the solid state
by X-ray crystallography. Reacting either AgSO3CF3 or AgBF4 with 1 in either CH3CN or CH3NO2 in a 1:1 metal-to-ligand ratio
produced a double helicate in solution. This double helicate could
be converted into a linear complex by increasing the metal-to-ligand
ratio; however, the degree of conversion depended on the solvent and
counteranion used. Attempts to crystallize the linear AgSO3CF3 complex resulted in crystals with the dimeric structure
[Ag21(CH3CN)2]2(SO3CF3)4 (2), while
attempts to crystallize the AgSO3CF3 double
helicate from CH3CN resulted in crystals of another dimeric
complex, [Ag21(SO3CF3)­(CH3CN)2]2(SO3CF3)2·H2O (3). The AgSO3CF3 double helicate was successfully crystallized
from a mixture of CH3CN and CH3NO2 and had the structure [Ag212]­(SO3CF3)2·3CH3NO2 (4). The linear AgBF4 complex could not
be isolated from the double helicate in solution; however, crystals
grown from a solution containing both the AgBF4 double
helicate and linear complexes in CH3CN had the structure
[Ag21(CH3CN)2]­(BF4)2 (5). The AgBF4 double
helicate could only be crystallized from CH3NO2 and had the structure [Ag212]­(BF4)2·2CH3NO2 (6).