CRYSTAL-STRUCTURES AND MAGNETIC-BEHAVIOR OF 2 NOVEL COPPER(II) HALIDE CHAINS - (C7H10N)4CU5CL14 AND (C5H14N)4CU5CL14 - MULTIPLE COPPER(II) HALIDE COORDINATION GEOMETRIES

The crystal structures of tetrakis(1,4-dimethylpyridinium) tetradecachloropentacuprate(II) ((1,4-DMP)4Cu5Cl14) and tetrakis-(ethyltrimethylammonium) tetradecachloropentacuprate(II) ((ETrMA)4Cu5Cl14) have been determined. For (1,4-DMP)4Cu5Cl14 the unit cell is triclinic P1 with a = 7.604 (1) Å, b = 9.986 (2) Å, c = 15.146 (2) Å, α = 94.84 (1)°, β = 97.24 (1)°, γ = 101.61 (1)°, and Z = 1. For (ETrMA)4Cu5Cl14 the unit cell is monoclinic P21/c with a = 15.499 (3) Å, b = 9.063 (2) Å, c = 15.687 (3) Å, β = 92.56 (2)°, and Z = 2. The structures refined to R = 0.0322 ((1,4-DMP)4Cu5Cl14) and R = 0.0526 ((ETr-MA)4Cu5Cl14). Both structures consist of chains of pentanuclear Cu5Cl144− clusters in which the copper(II) ions occur in one of the three different coordination geometries. In (1,4-DMP)4Cu5Cl14 the cluster configuration is bowtie-shaped: the central copper ion (Cu(1)) of the bowtie is tetragonally distorted octahedral, the copper ions on two opposite corners (Cu(2)) are distorted square pyramidal, and the copper ions on the other two opposite corners (Cu(3)) are distorted tetrahedral. In (ETrMA)4Cu5Cl14 the cluster configuration is linear: the central copper ion (Cu(1)) is in a tetragonally distorted octahedral configuration, the two copper ions (Cu(2)) on either side are 4 + 1 + 1 coordinate with a square-pyramidal distortion, and the terminal pair (Cu(3)) are distorted square pyramidal. The presence of multiple copper(II) halide geometries in these and other structures is rationalized by simple electrostatic arguments. Magnetic susceptibility data have been collected in the temperature range 2–100 K for (1,4-DMP)4Cu5Cl14 and 4.2–80 K for (ETrMA)4Cu5Cl14. The data have been fit to a Heisenberg, spin-1/2, “bowtie” cluster model with a mean field correction to account for the intercluster interaction: J13 = 0 K, J12/k = −34.1 (6) K, J23/k = −4.9 (3) K, θ = −7.0 (3) K, and g = 2.164 (7) for (1,4-DMP)4Cu5Cl14; J12 = J23 = 37.7 (9) K, J13 = 0 K, g = 2.05, and J′= −1.48 (3) K for (ETrMA)4Cu5Cl14. Fitting the region of the maximum in the (ETrMA)4Cu5Cl14 susceptibility to a one-dimensional spin-5/2 Heisenberg model gives JIC ≈ −10 K. The values found for the intracluster exchange can be explained in terms of simple atomic orbital arguments. The complicated pentacoordinate geometry of the copper ions in the intercluster bridges precludes a simple orbital explanation of the intercluster exchange. © 1990, American Chemical Society. All rights reserved.