Silver(I) Coordination Chemistry of 2,6-Diarylpyrazines. π-Stacking, Anion Coordination, and Steric Control

The silver(I) coordination chemistry of 2,6-diarylpyrazines is reported. Discrete coordination complexes and two-dimensional coordination networks were characterized. The substitution pattern on the pendant aryl groups controlled
the type of coordination chemistry involved. Thus, o-methyl-substituted aryl groups held the aryl groups orthogonal
to the central pyrazine ring, opening the “hindered” nitrogen atoms to complexation, and polymeric networks were
characterized. In the absence of the o-methyl groups, discrete coordination complexes were characterized. Thus,
a dimeric 2:1 ligand−silver(I) complex was isolated and characterized on reaction of 2,6-bis(3‘,5‘-dimethylphenyl)pyrazine with silver(I) trifluoroacetate in acetonitrile solvent, while a 2:2 complex was isolated from dichloromethane
solvent. Two trifluoroacetate ligands bridge two silver cations in both complexes. Reaction of the same pyrazine
ligand with silver(I) tetrafluoroborate yielded a discrete 2:1 complex. A 2:1 complex was isolated on reaction of
2,6-diphenylpyrazine with silver(I) nitrate. These complexes were interlinked by weakly coordinating nitrate anions
to form interwoven one-dimensional ribbons. Two-dimensional networks were obtained on reaction of silver(I)
trifluoroacetate with either 2,6-bis(2‘,6‘-dimethylphenyl)pyrazine or 2-(2‘,6‘-dimethylphenyl)-6-(3‘,5‘-dimethylphenyl)pyrazine. The networks comprised pyrazine−silver(I) strands cross-linked with complex bridged silver(I) trifluoroacetates.