ADDITION OF TRANSITION-METAL DIHALIDES TO ACETYLACETONATES OF DIVALENT METAL-IONS

Transition metal dihalides (a)M(II)X2 (FeCl2, CoCl2 NiBr2 etc.) are added by the chelates M(II)(acac)2 under formation of binuclear complexes (THF)2M(II)(acac)2((a)M(II)X2). The octahedral and the tetrahedral centre of these compounds are connected by tridentate oxygen atoms of the two acetylacetonato ligands which are simultaneously included in four-membered rings (M(II)O2(a)M(II)). The addition is combined with a deformation of the octahedral centre, as a prerequisite of a closest package of the atoms within the M(II)O2(a)M(II)-ring. In the trinuclear complex (THF)2Ni(acac)2(HgCl2)2 III the interaction between the three coordination centres is weak. No structural change of the octahedral centre (THF)2Ni(acac)2 is found, but the HgCl2-groups diverge slightly from linearity (Cl-Hg-Cl 171.1-degrees). No binuclear complexes with a central ion of the oxidation state III in the octahedral centre were obtained. One reason is the lowered donor strength of the bidentate Lewis base function of the otahedral centre [(THF)2M(n+)(acac)2]n-2 with M+3 as a centralatom. Reacting systems with di- and trivalent ions prefer ionic complexes, as it is shown by the formation of [(THF)2V(acac)2][(THF)CoCl3] IV from VCl3 and Co(acac)2. The crystal structures of (THF)2Co(acac)2CoCl2 II and [(THF)2V(acac)2][(THF)CoCl3] IV were determined by x-ray diffraction. II: orthorhombic-primitive; space group P2(1)2(1)2(1), Z = 4; a = 967.4(2), b = 1 453.4(3), c = 1715.9(4) pm; R = 0.049 for 3084 observed reflections. IV: triclinic; space group P1, Nr.2; Z = 2; a = 871.5(2), b = 930.6(3); c = 1865.6(6) pm; alpha = 101.70(2), beta = 92.45(2), gamma = 91.06(2)-degrees; R = 0.060 for 4221 observed reflections.