Framework dimensionality of copper(i) coordination polymers of 4,4′-bipyrimidine controlled by anions and solvents

Abstract

The reaction of [Cu(C2H4)n]NO3 with 4,4′-bipyrimidine (bpm) in Me2CO under C2H4 afforded a polymeric Cu(I)–bpm/C2H4 adduct [Cu2(bpm)(C2H4)(NO3)2]n (1) with an infinite 1-D zigzag chain structure. Similar reactions of [Cu(C2H4)n]ClO4 or [Cu(MeCN)4]BF4 with bpm in Me2CO under C2H4 afforded Cu(I)–bpm/C2H4 adducts {[Cu3(bpm)2(C2H4)2](ClO4)3}n (2) and {[Cu3(bpm)2(C2H4)2]–(BF4)3}n (3), respectively, which have an infinite 1-D zigzag ladder structure. It is interesting that two disordered ClO4− or BF4− anions are accommodated in the inside cavity of the ladder chains. In contrast, the reaction of [Cu(MeCN)4]BF4 with bpm in MeOH under C2H4 afforded a Cu(I)–bpm/C2H4 adduct {[Cu4(bpm)3(C2H4)3(MeOH)](BF4)4·2H2O·3MeOH}n (4). Three Cu atoms are bridged by three bpm ligands to form a metallacalix[3]arene structure with three legs of C2H4. Furthermore, these metallacalix[3]arenes are linked through another Cu atom in the terminal N atom of bpm to produce a chiral 2-D sheet structure with space groupP63. One BF4− anion is accommodated in the small triangular Cu3 cavities, whereas three disordered BF4− anions are encapsulated in the large triangular Cu3 cavities. In contrast to complex 4, [Cu(MeCN)4]BF4 was reacted with bpm in MeOH under Ar, and C2H4 gas was then bubbled into the resultant brown suspensions. The reaction solution was allowed to come to room temperature, and Cu(I)–bpm complex {[Cu3(bpm)3](SiF6)1.5}n (5) was collected. The tetrahedral Cu atom is coordinated by two N atoms in the chelate site of bpm and two N atoms in the terminal sites of two other bpm ligands to form two racemic metallacalix[3]arene structures. It is noteworthy that these metallacalix[3]arenes are joined through the bpm ligands to afford a 3-D cage structure consisting of two right-handed and left-handed helix networks. One disordered SiF62− anion is accommodated in the inside cavity between two opposite metallacalix[3]arene structures. On the basis of these results, it has been concluded that BF4−, PF6−, ClO4− and SiF62− anions can serve as anion templates to self-assemble polymeric Cu(I) C2H4 adducts and a cage compound in complexes 2–5. The NO3− anion is ineffective as an anion template, as indicated by the higher coordination ability of the NO3− anion in complex 1. Additionally, solvent-dependent effects have been observed in the formation process: Me2CO can preferentially induce polymeric 1-D chain and 1-D ladder structures in complexes 1–3, whereas MeOH can produce 2-D sheet and 3-D cage structures by the linkage of metallacalix[3]–arene structures in complexes 4 and 5.