Cyanoisocyanoarene Metal Complexes as Building Blocks for Coordination Polymers: Structural Nonrigidity of a Metal-Nitrile Linkage

The complexes trans-[PdI₂(CNR)₂], 1a-1e, (CNR = 3-CN-C₆H₄-CN (1a), 4-CN-3-C₂H₅-C₆H₃-CN (1b), c: 4-CN-3-Cl-C₆H₃-CN (1e), 4-CN-1,2-(NC)₂-C₆H₃ (1d), 4-CN-C₆H₄-CH₂CN (1e)), have been prepared. Complex 2a forms a coordination polymer, 3, with copperbis(hexafluoroacetylacetonate) in the ratio of 1:2. The crystal structures of compounds 2b, 2c, 2e, and 3 have been determined by X-ray crystallography. 2b: C₂₀H₁₆I₂N₄-Pd. monoclinic space group, P1 (no. 2), a = 4.630(2) Å, b = 8.365(4) Å, c = 14.835(5) Å, β= 98.03(2)°, Z = 1 1964 unique reflections, R = 0.038, R_w = 0.036. 2c: C₁₆H₆Cl₂I₂N₄Pd, monoclinic space group, P1 (no. 2), a = 7.569(1) Å, b = 8.229(1) Å, c = 9.114(2) Å, β= 77.21(1)°, Z = 1, 1633 unique reflections, R = 0.030, R_w = 0.028. 2e: C₁₈H₁₂I₂N₄Pd, monoclinic space group, C2/c (no. 15), a = 14.171(3) Å, b = 8.3781(7) Å, c = 18.096(4) Å, β = 103.41(1)°, Z = 4, 2198 unique reflections, R = 0.036, R_w = 0.023. 3: C₃₆H₁₂Cu₂F₂₄I₂N ₄₈Pd, monoclinic space group, p1 (no. 2), a = 10.946(2) Å, b = 11.315(3) Å, c = 12.261(3) Å, β = 99.39(1)°, Z = 1, 2698 unique reflections, R = 0.049, R_w = 0.057.