Preparative and structural studies of trans-tetrachloro and tetrabromodipyridinemolybdate(III) and tungstate(III)

The first products of reactions between (PyH)3MoX6 (PyH = pyridinium, C5H6N+; X = Cl, Br) and pyridine are trans-(PyH)MoCl4Py2 and trans-(Py)2HMoBr4Py2. Trans-(Py)2HMoCl4Py2 can be obtained from the cold solution of trans-(PyH)MoCl4Py2 in yridine. Four trans-(Py)2HMX4Py2 compounds are isostructural and three of them crystallize in the triclinic unit cell. Pairs of trans-(PyH)MCl4Py2 and (PyH)MBr4Py2 have nearly equal sequence of interplanar spacings. Crystal structure of trans-(Py)2HWCl4Py2 has been solved. The compound has a triclinic P1 space group with: a = 9.373(3), b = 9.563(3), c = 15.009(6) A, α = 78.21(1), β = 77.94(2), γ = 78.63(2)0 and Z = 2. Two independent WCl4Py2- groups are located on the symmetry center. Average W-Cl and W-N (pyridine) bond lengths are 2.435(5) and 2.18(2) A. The cation (Py)2H+ contains a hydrogen bond between pyridinium ion and pyridine. The N-N distance is 2.76 A. (author)