N. Kitanovski, L. Golič, A. Meden
Mar 24, 2005
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Journal
Croatica Chemica Acta
Abstract
By a selective exchange of ligand Br by Cl, a series of nonstoichiometric bromo-chloro-pyridine-molybdenum(III) octahedral compounds of the type (cat)[MoBr a Cl ( 4 - a ) py 2 ] (cat = pyH, a = 3-1 (1, 4, 7)); cat = [(C 2 H 5 ) 3 NH] a = 2.744 (2); cat = Rb, a = 2.278 (5); cat =[(C 6 H 5 ) 4 )As], a = 1.258 (8) and [MoBr a Cl ( 3 - a )py 3 ] (a = 2-1 (3, 6)) have been prepared and characterized. Owing to great similarity of the powder diffraction patterns and IR spectra of compounds mer-[MoBr a Cl ( 3 - a ) py 3 ] (a = 3-0) with the known monoclinic modification in the space group P2 1 /c and compounds [MoBr a Cl ( 3 - a ) py 3 ] (a = 2-1 (3, 6)), the same type of crystal lattice was confirmed. Isostructurality was observed also for the orthorhombic trans-(pyH)[MoBr 4 py 2 ] (Pnma) and compounds 1 and 4, while compound 7 is isostructural to trans-(pyH)[MoCl 4 py 2 ]. X-ray crystallographic analyses of 2, 5 and 8, obtained by recrystallization of (pyH)[MoBr a Cl ( 4 - a ) py 2 ] (a = 3-1) with different cations, were performed. In these compounds, Mo I I I is octahedrally coordinated with four halogenido ions at distances 2.4953(6)-2.5920(10) A and two pyridine molecules at distances 2.195(4)-2.220(4) A. Trans oriented pyridine rings in compounds 5 and 8 are co-planar, while deviation from co-planarity was noticed for compound 2 (8.9(3)°). The stoichiometry of four coordinated Br and Cl atoms in these compounds is not ideal, since the structure analysis results for 2, 5 and 8 show a mixed occupancy of crystallographic sites; thus, refined population parameters for both atoms (Br and Cl) were calculated.