Mixed ligand complexes of cobalt(II) -: Synthesis, structure, and properties of Co4(thd)4(OEt)4

Synthesis, crystal structure, thermal stability, and magnetic properties of mixed-ligand complexes of cobalull) with Pdiketonato (thd = C11H19O2-) and alkoxides (OR mainly OMe = methoxide = CH3O- or OEt = ethoxide = C2H5O-) are reported. Direct reaction between Co(thd)(2) (1) and EtOH gives a new complex with the structural formula [Co-4(thd)(4)(OEt)(4)] (2) whereas MeOH correspondingly reacts to [Co-4(thd)(4)(OMe)(4)(MeOH)(4)] (3). The yield of these products decreases with increasing size of the R group owing to increased solubility of I in the alcohol. The structure of 2 is determined from single-crystal X-ray diffraction data. At 100 K 2 takes a monoclinic structure (space group C21c): a = 15.108(2), b = 19.428(2), c = 21.240(3) A, and P = 108.882(2)'. At 295 K 2 has transformed to a closely related orthorhombic structure (space group Fdda): a = 15.233(3), b = 19.712(3), c = 40.916(7) A. Protracted hydrolysis accompanied by oxygenation of complexes 2 and 3 in laboratory air (viz. simultaneous exposure to moisture and oxygen) leads to a new complex 4 with empirical formula corresponding to [Co(thd)(OH)(02)], Magnetic susceptibility data show that Co takes the valence state 11 in all complexes 1-4. For 4 this implies that dioxygen has to form an adduct-like association to the rest of the complex. Unfortunately complex 4 has hitherto only been obtained in the amorphous state, but all here produced evidences point at 4 as a distinct entity and that products of 4 obtained from 2 and 3 are chemically identical (but differ somewhat with regard to short- and longer-range order in the atomic arrangement). The interatomic distances in the crystal structure of complexes 1-3 are briefly discussed in terms of the bond-valence concept.