The heterospin mixed ligand complex [Ni 6 (OH) 4 Piv 4 (hfac) 4 (NIT Ph) 2 ] (1) (NIT Ph is 4,4,5,5 tetramethyl 2 phenyl 4,5 dihydro 1H imidazol 1 oxyl 3 oxide, hfac is hexafluoro acetylacetonate, and Piv is pivalate) was synthesized. The method for the synthesis of complex 1 is based on the replacement of acetone molecules in the hexanuclear complex containing the hexafluoroacetylacetonate and pivalate ligands [Ni 6 (OH) 4 Piv 4 (hfac) 4 (Me 2 CO) 4 ] by NIT Ph molecules. Two monodentate NIT Ph molecules replace four acetone molecules, because the coordination of the O atom of the nitroxide group results in the blocking of one of the positions in the coordination environment of Ni II the access to which is hindered by the phenyl ring of NIT Ph. As a result, these ions are in a square pyramidal environment unusual of Ni II . In the low temperature range, the dependence of the magnetization of 1 on the magnetic field is described by the Brillouin function. The reaction of [Ni 6 Piv 4 (hfac) 4 (OH) 4 (Me 2 CO) 4 ] with the nitronyl nitroxide radicals 4,4,5,5 tetramethyl 2 (4 pyridyl) 4,5 dihydro 1H imidazol 1 oxyl 3 oxide (NIT p Py) or 4,4,5,5 tetramethyl 2 (1 methyl 1H imidazol 5 yl) 4,5 dihydro 1H imidazol 1 oxyl 3 oxide (NIT Iz) containing the pyridine or 1 methylimidazol 5 yl substituent, respectively, in the side chain is accompanied by the decomposition of the polynuclear frag ment and affords the mononuclear complexes Ni(hfac) 2 (NIT p Py) 2 and Ni(hfac) 2 (NIT Iz) 2 , respectively. The reaction of 4,4,5,5 tetramethyl 2 (1 methyl 1H imidazol 5 yl) 4,5 dihyd ro 1H imidazol 1 oxyl (Im Iz), which is the imine analog of NIT Iz, with [Ni 6 Piv 4 (hfac) 4 (OH) 4 (Me 2 CO) 4 ] afforded the decanuclear complex [Ni 10 (OH) 8 Piv 4 (hfac) 8 (Im Iz) 2 (H 2 O) 6 ]. The molecular and crystal structures of all heterospin compounds were determined, and the magnetic properties of all compounds were investigated in the 2-300 K temperature range.The interactions of polynuclear metal compounds with nitroxides serve as an efficient method for the synthesis of multispin compounds. 1-5 In solid phases, some of these compounds exhibit bulk magnetization. 1,4 However, what often complicates implementation of this synthetic ap proach is poor solubility of the starting polynuclear com plexes in organic solvents, due to which they cannot be introduced into reactions with nitroxides. In addi tion, the metal ions of the polynuclear fragment should possess high electron withdrawing ability to coordi nate weak donors such as the O atoms of the nitrox ide groups. Finally, the starting polynuclear fragment should contain easily replaceable terminal ligands. The recently described 6 mixed ligand hexanuclear complex [Ni 6 (OH) 4 Piv 4 (hfac) 4 (Me 2 CO) 4 ], meets theses require ments. Thus the pivalate anions (Piv) that are present in this complex provide the solubility in organic solvents, the hexafluoroacetylacetonate anions (hfac) enhance the elec tron withdrawing properties of the Ni II ions, and acetone molecules serve as easily replace...