SYNTHESIS AND IDENTIFICATION OF PENTACHLOROPYRIDINEMOLYBDATE(III) AND PENTABROMOPYRIDINEMOLYBDATE(III) - CRYSTAL-STRUCTURES OF [NH2(CH3)(2)](2)[MOPYCL(5)] AND [N(CH3)(4)](2)[MOPYCL(5)] (PY=PYRIDINE)

The first reaction product between (pyH)(3)[MoX(6)] (X=Cl,Br) and diluted pyridine at 20 degrees C or lower is (pyH)(2)[MopyX(5)]. M(2)(I)[MopyX(5)] with different cations (M(I)=NH2(CH3)(2)(+), N(CH3)(4)(+) and others) can be prepared from concentrated aqueous ammonia solutions of (pyH)(2)[MopyX(5)]. M(2)(I)[MopyX(5)] reacts further with pyridine; depending on the reaction conditions the products are cis- or trans-M(I)[Mopy(2)X(4)] or mer-Mopy(3)X(3) (X=Cl,Br). The compounds were characterised by chemical analysis, infrared spectroscopy, conductivity measurements, magnetic measurements at room temperature, and X-ray powder diffraction, and two of them-[NH2(CH3)(2)](2)[MopyCl(5)] (A) and [N(CH3)(4)](2)[MopyCl(5)] (B)-were characterised by single-crystal X-ray analysis. A and B crystallize in the monoclinic C2/c space group, with Z=4. Molybdenum is octahedrally coordinated by 5 chlorine atoms and pyridine. The average Mo-Cl and Mo-N(pyridine) distances are 2.44(1) and 2.20(1) Angstrom.