STRUCTURAL CHEMISTRY OF GALLIUM(II1). CRYSTAL STRUCTURES OF K3[Ga(catecholate)3)]·1.5H2O AND [Ga(benzohydroxamate)3]·H2O·CH3CH2OH

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Abstract
Although Ga(III) has been used extensively as a substitute for Fe(III) in microbial iron chelating agents or their analogues, there are some striking differences in their in vivo behaviour. A search for a structural difference is reported here, in which the structures of K,[Ga(C & O)] 1.5 H, O, 1, and [Ga(C, H, NO)] .H, O.CH, CH,OH, 2, have been determined by single crystal X-ray diflraction. Colorless crystals of 1 are monoclinic, space group C2/cwitha= 20.679(1)° b= 15.868(1)A, c= 12.350(1)8, p= 91.90(1)″, V= 405ql)A. Foreight formulaunits per cell, dcOlc = 1.766, and dabs = 1.77(2) g cm-,. Refinement of268 variables on4181 reflections resulted in agreement factors of R = 3.24%, and R, = 3.87%. Crystals of 2 are triclinic, space group P1, and have a= 10.267(1)A, b= 11.388(2)%c= 13.027(1)8, a= 71.48(1)″),§= 73.32(1)″, y= 60.72(1)″, and V= 1243.6(3)A3. For two formula units of 2 per unit cell, dcarc = 1.448 g cm-' and dabs = 1.44(1) g cm-'. Of 5696 unique reflections. 3426 were used to refine307 variables, with the resultingagreement factors: R= 4.0% andR,= 5.4%. For1 the average Cia-0 distance is 1.984(6) Awith an average 0-Ga-On, angle of83.8(1)″. The twist angle is 48.8(1)″. For2 the average Cia-O(N) and Ga-O(C) distances are 1.952(10) A and 1.986 (13) A, respectively. The average OGa-On, angle is 81.7(1)″, and the twist angle is4ql)″. The structural similarities ofthe Fe(IIIO and Ga(1II) complexes do not point to any difference in stability or biological recognition.

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