Crystal structure of the orthorhombic basic copper nitrate, Cu₂(OH)₃NO₃

Abstract

The crystal structure of the orthorhombic copper salt Cu₂(OH)₃NO₃ (natural gerhardtite) has been determined from X-ray diffractometer data by means of three-dimensional Patterson and Fourier syntheses, and refined by difference Fourier syntheses and least-squares methods to a finalR index of 0.097 for 532 reflections. Crystals of Cu₂(OH)₃NO₃ are orthorhombic:a=6.087(2),b=13.813(4),c=5.597(2) Å,Z=4, space groupP2₁2₁2₁. The Cu atoms form deformed hexagonal pseudocells (010). Each Cu(1) ion is surrounded by an approximately square planar arrangement of four OH ions at 1.929, 1.952, 1.993 and 1.998 Å and by two O (of NO₃ ions) at 2.359 and 2.480 Å, completing a deformed coordination octahedron; each Cu(2) ion is similarly coordinated by four OH at 1.989, 1.997, 2.009 and 2.018 Å, one OH at 2.309 Å, and one O at 2.384 Å. The structure involves layers of such deformed octahedra, of theC6-type, linked together by hydrogen bonds through the NO₃ ions. Similarities to and differences from the structure of the monoclinic polymorphous form are discussed.