Mixed-ligand tris-chelates

However, a number of tris-chelate mixed ligand Cr(III) complexes do exhibit a correlation of the same signs between the lowest frequency 2E component and the major 4E component.119,120,122,123 This relation has been verified by examining the CD for diastereomers of [Cr(en)x(diamine)3 x]3 + (x = 0, 1, 2), c/i-[Cr(NH3)2 (diamine)2]3 +, where the diamines used were (R)- or (5)-propylenediamine and (IR,2R)- or (15,250-1,2-traras-cyclohexanediamine. The differences in CD patterns between each pair of the diastereomers were accounted for by separability and additivity of the configurational and conformational CD contributions. The CD in the spin-allowed 4T2 <— 4A2 transitions shows a positive major component (4E) for the configurational contribution and a minor negative (4Ai) and major positive (4E) components from the lower frequency side for the conformational contribution as shown in Figure 5.30. 

The sensitivity of the method can be increased by addition of gelatine (e = 7.5-10 ) [51]. Hafnium has been extracted with CHCI3 from HCl medium as the chelate complex with N-tolyl-p-methoxybenzohydroxamic acid, and the XO added has given a mixed-ligand complex (e = 8.4-10 ) [52]. In a similar way Zr was determined with the use of tri-n-butylacetohydroxamic acid [53]. 

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