Bis(benzoylpyridin-p-toluensulfonylhydrazido)nickel Ni(BPSH)2 · H2O — Beziehungen zwischen Struktur und Redox- bzw. Extraktionsverhalten heterocyclischer Sulfonamidochelate

Bis(benzoylpyridin-toluensulfonylhydrazido)nickel Ni(BPSH)₂ · H₂O — Relations between Structure, Redox, and Extraction Properties of Heterocyclic Sulfonamido Chelates The crystal structure of Ni(BPSH)₂ · H₂O was determined by x-ray diffraction: monoclinic, space group P21/c (Nr. 14); a = 15.077(4) Å, b = 14.901(3) Å, c = 16.335(3) Å, β = 95.74(1)°. R = 0.047 for a total of 5564 observed reflexions. Ni(BPSH)₂ · H₂O has a distorted tetrahedral structure with two six-membered chelate rings, one of them with a boat from. The electron system of the building blocks CNN^? within the chelate rings approaches that of a diazallyl group. The result is a high electron density on the sp²-hybridized donor atom N^? and, as a consequence, a short Ni? N^?-distance (1.908 or 1.924 Å). The electronic properties of N^? also explain the high NH-acidity of the acid H(BPSH) (pk_s = 9,51 in 75 per cent dioxane) and the ligand field strength of BPSH^? which is low compared to that of other bidentate sulfonamido ligands and which is reflected in the paramagnetism of Ni(BPSH)₂ · H₂O. The redox behavior of metal chelates of the type, which is represented by Ni(BPSH)₂ · H₂O, is caused by a building block of the ligand which is also present in bipyridyl or in the 1,4-diaza-1,3-dienes. The central atoms M¹¹ have only the function of interference factors.