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

Abstract

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 AgPF 6 in MeCN with 3,3′-pytz in CH 2Cl 2 gives ([{Ag(NCMe) 2}(μ-3,3′-pytz)][PF 6]·MeCN) ∞, 1, of AgPF 6 in MeNO 2 and 3,3′-pytz in CH 2Cl 2 gives ([{Ag 2(μ-3,3′-pytz) 2}(μ-3,3′-pytz)][PF 6] 2·4MeNO 2) ∞, 2, and of AgCF 3SO 3 in MeCN and 3,3′-pytz in CH 2Cl 2 gives {[Ag(μ-3,3′-pytz)]CF 3SO 3} ∞, 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 Å) in a 1:1 polymeric chain. That in 2, ([{Ag 2(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 Å) to form [Ag 2(μ-3,3′-pytz) 2] motifs, which are bridged, in turn, by transoid-oriented 3,3′-pytz molecules (Ag⋯Ag = 13.318 Å) 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 Å) 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 Å), which are supported by (μ 2-κO,κO′) bridging CF 3SO 3 − anions.