PREPARATION AND STEREOCHEMISTRY OF BIS-CHELATE CHROMIUM(II), MANGANESE(II), IRON(II), AND COBALT(II COMPLEXES OF TYPES M-O4 AND M-O2S2

A series of monomeric bis-chelate metal(II) complexes derived from the β-difunctional ligand 1 with X = Y = O and X = O, Y = S has been prepared and their stereochemistry has been established in the crystalline state and in solutions of noncoordinating solvents. The bis(dipivaloylmethanido) complexes Cr(dpm)2 and Mn(dpm)2 have been synthesized for the first time and are members of an extensive series of M(dpm)2 complexes, M = Cr(II)-Zn(II), of known structure. Cr(dpm)2 is shown to be planar. The monothio analogs Fe(Sdpm)2 and Co(Sdpm)2 have also been prepared. The former, like Fe(dpm)2, is tetrahedral but the latter is planar in the solid and exhibits a planar ⇌ tetrahedral equilibrium in chloroform solution, in contrast to the tetrahedral and planar structures of Co(dpm)2 and bis(dithioacetylacetonato)cobalt(II), respectively, in both phases. Several other bis(monothio-°-diketonato)cobalt(II) complexes are shown to be tetrahedral in both the solid and solution phases. Several stereochemical patterns of four-coordinate complexes which may be recognized from the results of this and other investigations are summarized. © 1969, American Chemical Society. All rights reserved.