Syntheses and structures of dinuclear rhodium(I) complexes and 1-D zigzag-chain rhodium(I) co-ordination polymers bridged by rod-like bidentate nitrogen ligands†

Abstract

Novel dinuclear rhodium(I) complexes, [Rh₂(2-bpbd)₂(cod)₂]X₂ (X = BF₄ 1a, PF₆ 1b or ClO₄ 1c; cod = cycloocta-1,5-diene) and 1-D rhodium(I) co-ordination polymers with the linkage of square-planar rhodium(I) centers, {[Rh(4-bpbd)(cod)]X}_n (X = BF₄ 2a, PF₆ 2b or ClO₄ 2c) and {[Rh(4-bpe)(cod)]X}_n(X = BF₄3a, PF₆ 3b or ClO₄ 3c), were systematically synthesized using 1,4-bis(2-pyridyl)butadiyne (2-bpbd), 1,4-bis(4-pyridyl)butadiyne (4-bpbd) and trans-1,2-bis(4-pyridyl)ethylene (4-bpe). The structures of 1a, 2a, 2b and 3a were crystallographically characterized. In 1a each Rh atom is bridged by two N atoms of 2-bpbd to afford a unique dinuclear structure with an 18-membered Rh₂N₄C₁₂ framework. In 2a, 2b and 3a, each Rh atom is bonded to two N atoms of 4-bpbd (2a and 2b) or 4-bpe (3a) and two CC bonds of cod in a square-planar geometry. The square-planar centers are in turn linked by 4-bpbd or 4-bpe ligands to form a 1-D zigzag-chain structure. The zigzag chains are located in parallel 9.6, 9.9 and 10.7 Å apart in 2a, 2b and 3a, respectively, and no effective intermolecular interactions were found.