Relation between magnetic and structural anisotropy in the Ni23Se12(PEt3)13 cluster compound

We have measured the magnetic properties of the cluster compound Ni23Se12(PEt3)13, where PEt3 is triethyl phosphine, by dc magnetization (1.5–300 K) and ac susceptibility (0.280–4 K). We observe a small, almost temperature-independent, magnetic moment of only ~2μB/cluster indicating the presence of two unpaired spins in the cluster. Despite the large shape anisotropy of the molecule, we find no preferred magnetic axis. We interpret this as the result of delocalization of the valence electrons due to covalent Ni-Se bonding.

Cr6Te8(PEt3)6 and a Molecule-Based Synthesis of Cr3Te4

The molecular cluster compound Cr6Te8(PEt3)6 (1) is formed by the reaction of TePEt3 with either (Et3P)2Cr(allyl)2 or Cr(2,4-dimethylpentadienyl)2. This compound can be converted to the extended inorganic solid state compound Cr3Te4 by simple thermolysis. We have determined the structure of the title compound crystallographically (monoclinic; a = 13.076(5) Å, b = 21.194(7) Å, c = 23.694(7) Å, β = 105.21(5)°, V = 6276(10) Å3, Z = 4). The molecule is formed by a Cr6 octahedron, a Te8 cube, and a (PEt3)6 octahedron, all of which are concentric. We compare and contrast the structure and properties of the cluster with those of related solid-state compounds.

Effect of Diverse Ligands on the Course of a Molecules-to-Solids Process and Properties of Its Intermediates

We have been studying chemical processes that use discrete molecular reagents to form extended solid inorganic materials. The goals of this program have been to determine how best to design and implement these molecular precursor reactions and to discover what chemical intermediates lie on the molecules-to-solids paths. In this manuscript we report studies of the reactions of the low-valent iron complex Fe(C8H8)2 with low-valent tellurium compounds of the form TePR3 (R = various hydrocarbon groups) that lead ultimately to the exclusively inorganic extended solid compounds FexTey. We have found four Fe/Te cluster types that are chemical intermediates in this process: Fe4Te4(PEt3)4, 1; Fe4Te4(PiPr3)4, 2; Fe6Te8(PMe3)6, 3; (dmpe)2FeTe2, 4; (depe)2FeTe2, 5; Fe4Te6(dmpe)4, 6. (Here iPr = CHMe2, dmpe = Me2PCH2CH2PMe2, and depe = Et2PCH2CH2PEt2.) The different clusters form when different supporting phosphine ligands are employed. We report the syntheses, structures, and properties of these intermediates and the comparisons and contrasts between these molecular intermediates and the extended solid products. We note that when larger ligands are used smaller clusters are formed. We also note what features of the molecular structures lead to ferromagnetic versus antiferromagnetic coupling of the distinct Fe centers. We have determined the structures of the following materials crystallographically: 2 (C36H84Fe4Te4P4; tetragonal, P421c; a = 14.0469(7) Å, c = 13.5418(9) Å; Z = 2); 3 (C18H54Fe6Te8P6; trigonal, R3; a = 11.859(2) Å, c = 26.994(5) Å; Z = 3); dmpe·2Te (C6H16Te2P2; monoclinic, P21/c; a = 6.0890(4) Å, b = 10.7934(7) Å, c = 9.8200(5) Å, β = 104.63(7)°; Z = 2); 5 (C20H48FeTe2P4; orthorhombic, Pbnn; a = 10.997(3) Å, b = 14.157(3) Å, c = 18.345(4) Å; Z = 4); 6 (C24H64Fe4Te6P8; orthorhombic, Abaa; a = 12.056(3) Å, b = 17.725(5) Å, c = 21.403(8) Å; Z = 4).