COORDINATION-COMPOUNDS OF MOLYBDENUM(II), DERIVATIVES OF THE OCTAHALODIMOLYBDATE(II) ION .4. SYNTHESIS AND CRYSTAL-STRUCTURES OF 2 NEUTRAL COMPOUNDS WITH 4-METHYLPYRIDINE

Mo2Cl4Pic4·CHCl3 (A) (Pic=4-methylpyridine) and Mo2Br4Pic4 (B) crystallize in the monoclinic space group. A in C2/c (No. 15) with a=15.175 (4), b=10.847 (2), c=19.946 (6) Å and β=104.52 (2)°;Do=1.71 (2), Dc=1.72 gcm-3 for Z=4. B in P2l/n (No. 14) with a=9.270 (3), b=16.614 (5), c=9.305 (3) Å and β=91.96 (5)°;Do=2.03 (3), Dc=2.05 gcm-3 for Z=2. Two halogens and 4-methylpyridines of the Mo X2Pic2 group are in the trans position. Mo-Mo bond lengths are 2.153 96) for A and 2.150 92) Å for B. Both molecules are situated on the inversion center resulting in the eclipsed configuration of the ligands around the molybdenum pair. The structure of B has been refined to the conventional R factors of 0.08 and 0.098. Disorder on the part of 4-methylpyridines and chloroform molecules stopped the refinement of A at the end R value of 0.175. Mean Mo-X and Mo-N bonding distances are 2.40 (2), 2.25 (5) Å for A and 2.53 (3), 2.25 (1) Å for B. © 1979 Springer-Verlag.