Syntheses and Structures of Manganese(II) and Manganese(III) Nitrate Diaminosarcophagine Complexes

Abstract

The syntheses of [ Mn ((NH₃)₂sar)](NO₃)₄.H₂O and [ Mn ((NH₃)₂sar)](NO₃)₅.2H₂O, manganese(II) and manganese(III) complexes of the cage amine ligand diaminosarcophagine ( di-aminosarcophagine = (NH₂)₂sar = 1,8-diamino-3,6,10,13,16,19-hexaazabicyclo[6.6.6] icosane ) in its diprotonated form are recorded, together with their single-crystal X-ray structure determinations at c. 295 K. The monoclinic P2₁ array of the manganese(II) complex (a 12.386(5), b 12.431(4), c 8.598(4) Ǻ, β 93.89(4)°, V 1321(1) Ǻ³,Z 2) is archetypical for similar complexes of a wide variety of transition metals; for the present determination, R was 0.027 for 2013 'observed' (I > 3σ(I)) reflections. The manganese(III) complex is monoclinic C 2/c, a 10.744(2), b 13.294(4), c 20.462(9) Ǻ, β 102.38(3)°, Z 4; R was 0.055 for 1629 'observed' reflections. Both structures show the six secondary nitrogen atoms of the ligand to be bound to the manganese ion in a configuration approximately halfway between a trigonal prism and an octahedron. The ligand is in the lel₃ conformation. In the first complex, Mn -N distances, appropriate to high-spin manganese(II), range from 2.228(3) to 2.253(3) Ǻ, mean 2.23₈ Ǻ; in the second, surprisingly, the distances are even more closely ranged (unlike those of the sarcophagine analogue of the previous paper), 2.115(4)-2.127(4) Ǻ, the mean (2.12₂ Ǻ) being closely comparable to that recorded for the sar analogue, and show no appreciable variation attributable to the expected Jahn-Teller effect.