Cobalt, as an essential element for human beings, exists almost exclusively as Co(II) or Co(III) in biological systems. These two predominant oxidation states allow its coordination complexes to exhibit different redox and magnetic properties and make them suitable for applications in biology and medicine. As a part of our ongoing research in elaborating biologically active cobalt-containing complexes a new heterometallic [Co2Y2(OH)2(ib)4(bdea)2(NO3)2]∙2MeCN (1) cluster has been synthesized by the reaction of Co(II) isobutyrate (Hiz = isobutyric acid) and Y(NO3)3∙ 6H2O with N-butyldiethanolamine (H2bdea) in MeCN.Figure 1. Structure of [Co2Y2(OH)2(ib)4(bdea)2(NO3)2] cluster in 1.Single-crystal X-ray structural analysis reveals that 1 is a tetranuclear compound (Figure 1) and crystallizes with two acetonitrile molecules in the P21/n space group of the monoclinic system with a = 14.727(3), b = 9.243(2), c = 19.002(4) Å,  = 99.06(3), V = 2554.3(9) Å3. Cluster 1 has a rhombic planar tetranuclear central core best described as a „butterfly” motif with the Y(III) ions ocupied the „body” positions and the Co(III) ions at the „wing” sites. The core is stabilized by two OH− groups, each of them bridges two Y(III) and one Co(III) ions. In this tetranuclear heterometallic cluster, peripheral ligation of four metal centers is provided by four isobutyrate groups and two additional doubly deprotonated bdea2− co-ligands. The Co−O and Co−N bond distances fall into range of 1.881(2)−1.964(2) and 1.967(2)−1.999(2) Å, and the Y−O bond distances are 2.248(2)–2.467(2) Å.