Structural studies on clathro-chelate complexes. Part III. Trigonal prismatic co-ordination of d7 cobalt(II) in orthorhombic crystalline [{FB(ONCHC5H3N)3P}CoII+][BF4–],MeCN and a single-crystal transformation of unsolvated monoclinic [{FB(ONCHC5H3N)3P}CoII+][BF4–]

Abstract

{Fluoro-[6,6′,6″-phosphinidynetris-(pyridine-2-carbaldehyde oximato)(3–)]borato(1–)}cobalt(1+) tetrafluoro-borate-acetonitrile (I) crystallizes in the noncentrosymmetric space group Aba2 with a= 23·408(19), b= 17·494(15), c= 12·090(8)Å, and Z= 8. A single-crystal X-ray diffraction study by Patterson and Fourier methods from diffractometer data has led to the location of all non-hydrogen atoms, with R 10·5% for 1126 independent non-zero reflections. The cation has approximate C_3v symmetry, with the central Co^II atom co-ordinated to six nitrogen atoms, mean Co^–N(aldoximo) 2·063(18) and Co^–N(pyridyl) 2·118(38) A. The co-ordination sphere of the cobalt(II) atom defines a slightly tapered trigonal prism, with N(aldoximo)⋯ N(aldoximo) 2·738(25)–2·822(29), N(pyridyl)⋯ N(pyridyl) 2·917(30)–3·050(29)Å, and the N(aldoximo)⋯ N(pyridyl)‘bite’ 2·512(30)–2·598(29)Å. The triangle defined by the three aldoximo-nitrogen atoms is rotated by only 0·89° relative to that defined by the three pyridyl nitrogens.

The unsolvated species [{FB(ONCHC₅H₃N)₃P}Co^II+][BF₄^–](II) crystallizes in the monoclinic space group P2₁/c with a= 13·262(12), b= 17·967(4), c= 10·656(16)Åβ= 108·87(12)°, and Z= 4. An attempted X-ray crystallographic study of this complex was thwarted by an apparently hydrolytic single-crystal transformation to an unknown species.