Gas Chromatography of Various Dipivaloymethanato-metal Complexes

Abstract

The separability of 25 kinds of dipivaloylmethanato(DPM)-metal chelates by gas chromatography was invesgated and the effect, f the structure of metal chelates on the retention time were discussed.The retention time of various chelates is shown in Table 1. The gas chromatographic separation of Lu(DPM)3 and Yb(DPM)3 is the most difficult among rare earth metal chelates and a theoretical plate number as many as 11000 is necessary to make the peak resolution one. However, a column of only 650 theoretical Plates is necessary for the separation of Nd(DPM)3 and Pr(DPM)3.The structure of the chelate significantly affected their retention time. Among the divalent metal chelates of coordination number 4, the square planer chelate showed a much longer retention time than the tetrahedral chelate. The retention time depended greatly on the molecular volume. Among the spherical molecule, the octahedral chelate of coordination number 6 showed a much longer retention time than the tetrahedra1 chelate of coordination number 4. In the case of octahedral chelate, the reduction of the size of the central metal ion made the retention time shorter.