Silver(I)–3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine coordination polymers: a diversity of chain motifs

The influence of solvent and anion on the formation of coordination polymers between silver(I) and 3,6-bis(pyridin-3-yl)-1,2,4,5-tetrazine (3,3′-pytz), a bridging ligand that can adopt both cisoid and transoidconformations, is reported. Reaction of AgPF6 in MeCN with 3,3′-pytz in CH2Cl2 gives ([{Ag(NCMe)2}(μ-3,3′-pytz)][PF6]·MeCN)∞, 1, of AgPF6 in MeNO2 and 3,3′-pytz in CH2Cl2 gives ([{Ag2(μ-3,3′-pytz)2}(μ-3,3′-pytz)][PF6]2·4MeNO2)∞, 2, and of AgCF3SO3 in MeCN and 3,3′-pytz in CH2Cl2 gives {[Ag(μ-3,3′-pytz)]CF3SO3}∞, 3. These cationic coordination polymers exclusively form chain structural motifs. That in 1, ([{Ag(NCMe)2}(μ-3,3′-pytz)]+)∞, has a castellated construction with each tetrahedral silver(I) center coordinated by two solvent molecules as well as two linking transoid-oriented 3,3′-pytz bridges (Ag⋯Ag 13.210 A) in a 1:1 polymeric chain. That in 2, ([{Ag2(μ-3,3′-pytz)2}(μ-3,3′-pytz)]2+)∞, is novel. It is the first coordination polymer to exhibit both cisoid and transoid conformations of a bridging ligand coordinated to the same metal center. Pairs of silver(I) centers are linked by pairs of cisoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 11.695 A) to form [Ag2(μ-3,3′-pytz)2] motifs, which are bridged, in turn, by transoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 13.318 A) to form a 3:2 ligand:metal infinite polymeric zigzag chain. That in 3, {[Ag(μ-3,3′-pytz)]+}∞, has a zigzag architecture despite being based on linear silver(I) centers. Transoid-oriented 3,3′-pytz molecules link silver(I) centers (Ag⋯Ag 13.225 A) to give a 1:1 ligand:metal infinite polymeric zigzag chain. The chains aggregate in parallel pairs linked by weak Ag⋯Ag contacts (Ag⋯Ag = 3.220 A), which are supported by (μ2-κO,κO′) bridging CF3SO3− anions.