Compounds containing linked, multiply-bonded dimetal units. 3. Preparation, molecular structure and magnetic properties of a compound containing tetrakis (μ-6-chloro-2-hydroxopyridinato)-diosmium (II,III) cations linked axially by pyrazine

Abstract

The compounds [Os 2(chp) 4py]BF 4(hexane) 2 and [{Os 2(chp) 4} 2(pyz)](BF 4) 2(CH 2Cl 2) 2(pyz) 2, whe chp=anion of 6-chloro-2-hydroxypyridine, py=pyridine and pyz=pyrazine, have been prepared, crystallographically characterized and their magnetic properties measured in the range 2–300 K. All Os 2(chp) 4 units have all their chp units aligned in the same direction and have the py or pyz ligand axially bound to the Os atom with the four chp oxygen atoms. In the second case the pyz molecule bridges the two Os 2 units. The Os-Os distances are 2.336(1) and 2.334(1) Å, respectively. The magnetic data are consistent with quarter ground states based on a σ 2π 4δ 2δ ∗π ∗2 configuration, but detailed interpretation of the temperature dependence was not accomplished. The py compound forms crystals in space group P 1 with a=13.651(3), b=16.216(3), c=9.229(1) A ̊ , α=105.36(1), β=98.95(2), γ=78.54(2)°, V=1919(1) A ̊ 3, Z=2 . The pyz compound forms monoclinic crystals in space group P2 1/c with a=12.441 (5), b=16.189(5), c=17.695(8) A ̊ , β=98.01(4)°, V=3529(3) A ̊ 3, Z=2 .