Crystallographic studies of the biuret reaction. I. Potassium bis-biuret cuprate(II) tetrahydrate, K₂[Cu(NHCONHCONH)₂].4H₂O

[Biuretato(2–)-N 1,N 5](ethylenediamine)copper(II)

“…The bond lengths and angles of the biuret ligand are essentially the same as those found for dipotassium bis[biuretato(2-)-NI,N 5]cuprate(II) tetrahydrate (Freeman, Smith & Taylor, 1961) and dipotassium di-phydroxo-bis{ [biuretato(2-)-N1,NSlcopper(ll) } tetrahydrate (Birker & Beurskens, 1974) ( (14), O(12),N(14) planes are 7.7 (7) and 5.9 (6) °, respectively.…”

Crystallographic studies of the biuret reaction. II. Structure of bis-biuret-copper(II) dichloride, Cu(NH2CONHCONH2)2C12

“…Within the accuracy of the determination, the bond lengths and angles of the biuret molecule in this complex are entirely consistent with those found in biuret hydrate (Hughes, Yakel & Freeman, 1961;Craven, Freeman & Sabine, 1966) and in its complexes with zinc (Nardelli, Fava & Giraldi, 1963), cadmium (Cavalca, Nardelli & Fava, 1960) and copper at high pH (Freeman, Smith & Taylor, 1961). From these structure analyses there are now available five sets of dimensions for biuret molecules (reviewed by Nardelli, Fava & Giraldi, 1963) and nine sets of dimensions for crystallographically distinct -NH-CO-NH2 groups.…”

“…4H20, is formed by the reaction of alkaline biuret with copper(II). In this complex the biuret molecules act as bidentate chelates, the deprotonated amide nitrogen atoms being the ligand atoms (Freeman, Smith & Taylor, 1961). Under neutral conditions a blue-green complex, [Cu(NH2CONHCONH2)2]C12, can be isolated.…”

Solution of the phase problem in centrosymmetric structures with heavy atoms in special positions

“…The probability of correct sign determination is generally reduced as the absolute value of I Uh'l decreases, but we can The presence of further heavy atoms in the structure influences the probability P+ unfavourably. We can compare the structure of Cu2C24NI2012H56 considered above with the structure of Cu2CaN12016H2sK2 (Freeman, Smith & Taylor, 1961). Both F(000)=422 and 2ncu=0"178 of the latter structure are comparable to corresponding values of the first structure, but the value of e differs considerably (e = 0.0097).…”