Chiu-Mine Hung

Coordination chemistry of Group 12 metals with phosphorodiselenoates: syntheses, structures and VT 31P NMR study of monomer–dimer exchange equilibrium

The reactions of diselenophosphates, [dsep, (RO)2PSe2-; R = Et, (n)Pr and (i)Pr] with cadmium(II) and mercury(II) perchlorates in a 2 : 1 molar ratio formed compounds of stoichiometry M[Se2P(OR)2]2{M = Cd, R = Et (1), (n)Pr (2), (i)Pr (3); Hg, Et(4), (n)Pr (5), (i)Pr (6)}, and with zinc(II) perchlorates, chalcogen centered tetranuclear clusters, [Zn4(micro4-E){Se2P(OR)2}6]{E = Se, R = Et (7), (n)Pr (8), (i)Pr (9); E = O, R = Et (10), (n)Pr (11), (i)Pr (12)} were formed. All these complexes have been characterized with the help of analytical data, X-ray crystallography (1, 3, 6, 10, 11 and 12), and FAB-mass spectrometry (7-12). Compound 1 is a linear double-chain polymer, in which each pair of Cd atoms is bridged by two dsep ligands; the mercury 6 polymer has a helical chain structure, in which two Hg atoms are bridged by one dsep ligand, and the other ligand chelates the Hg atom. The chelating dsep ligands lie on either side of the helical chain. Compound 3 exists as a dimer in which two cadmium atoms are connected by two bridging dsep ligands, and each cadmium atom is further chelated by a dsep ligand. The metal atoms in 1, 3 and 6 are each coordinated by four selenium atoms in a distorted tetrahedral geometry. Clusters 10-12 have tetrahedral array of zinc atoms with an oxygen atom in the center with edge-bridging dsep ligands. Positive FAB-mass spectra support the formation of selenium-centered clusters,7-9, of which the cluster 8 was structurally confirmed earlier. The solution state behavior of compounds 1-12 has been studied by using multinuclear NMR spectroscopy. Dimer 3 in CD2Cl2 showed monomer-dimer exchange equilibrium in the temperature range 20 to -90 degrees C and the free energy of activation is calculated from the coalescence temperature as DeltaG++(223 K)= 38.5 kJ mol(-1). Polymer undergoes depolymerization in CDCl3 and exhibits monomer-dimer exchange equilibrium in the temperature range 20 to -60 degrees C.

Characterization of Cu11(μ9-Se)(μ3-I)3[Se2P(OR)2]6 (R = Pr, Pri) by X-ray diffraction and multinuclear NMR

Two types of products were isolated from the reaction of NH4Se2P(OR)2 (R = Pr, Pri), Cu(CH3CN)4PF6, and Bu4NI in a 3 ∶ 2 ∶ 2 molar ratio in diethyl ether. The formulation of 1, Cu8(μ8-Se)[Se2P(OR)2]6, and 2, Cu11(μ9-Se)(μ3-I)3[Se2P(OR)2]6, was confirmed by elemental analyses, positive FAB mass spectrometry, multinuclear NMR (1H, 31P, and 77Se), and X-ray diffraction (1a and 2b). The geometry in 1 can be described as a selenide-centered, slightly distorted Cu8 cube with each edge of the cube being bridged by a selenium atom of the diselenophosphato (dsep) ligands . The sx dsep ligands, each capped on the square face of the cube, adopt a tetrametallic tetraconnective coordination pattern. The eleven copper atoms in 2 adopt the geometry of a 3,3,4,4,4-pentacapped trigonal prism with a selenium atom in the center. The coordination geometry for the central selenium atom is tricapped trigonal prismatic. In addition, the central core (Cu11Se in 2) is further stabilized by three iodides and six dsep ligands. A unique 77Se NMR pattern for the dsep ligands clearly indicates that local C3h symmetry was retained in solution. Moreover, the octacoordinated and nonacoordinated selenium atoms in 1 and 2 are unequivocally characterized by the 77Se NMR spectra, whose resonance frequencies are centered around −1150 and −1200 ppm, respectively.

A novel nonacoordinate bridging selenido ligand in a tricapped trigonal- prismatic geometry. X-Ray structure of Cu11(μ9-Se)(μ3-Br)3[Se2P(OPri)2]6

The first nonacoordinate bridging selenido ligand in a tricapped trigonal prismatic geometry, Cu11(μ9-Se)(μ3-Br)3[Se 2P(OPri)2]6, is prepared along with closed-shell ion-centered CuI8 cubes, Cu8(μ8-Se)[Se2P(OPri)2 ]6 and Cu8(μ8-Br)[Se2P(OPri)2 ]6(PF6), from the reaction of NH4Se2P(OPri)2, Cu(CH3CN)4PF6, and Bu4NBr in CH2Br2 at 0 °C.

Ag8Cl2[Se2P(OEt)2]6: A rare example containing a combination of discrete clusters and chains

The novel halide-centered Ag(I)8 cubic clusters containing diethyl diselenophosphato ligands are prepared and their solid state structures, a discrete unit or a one-dimensional chain, are dictated by the counter anions.

Novel silver diselenophosphate clusters: structures of Ag10(μ10-Se)[Se2P(OEt)2]8 and {Ag[Se2P(OPri)2]}6

Two types of clusters, [Ag(Se2P(OR)2)]n (R = Et, n = ∞, 1a; R = Pri, n = 6, 1b) and Ag10(μ10-Se)[Se2P(OR)2]8 (2a, 2b) were obtained from the reaction of stoichiometric amounts of Ag(CH3CN)4PF6 and NH4Se2P(OR)2 in (C2H5)2O at −20 °C. These new silver(I) clusters containing diselenophosphate (dsep) ligands were characterized by elemental analysis, NMR spectroscopy, fast-atom bombardment mass spectrometry (FAB-MS) for 2, and, in the case of 1b, and 2a, by X-ray crystallography. The structure of 1b reveals a hexameric aggregate {Ag[Se2P(OPri)2]}6 where six silver atoms are located at the corners of a pseudohexagonal prism alternating with selenium atoms in two Ag3Se3 rings interconnected vertically by the P–Se bridges of the dsep ligands but not by additional Ag–Se bonding. The dsep ligands are organized in a paddle-wheel fashion about an Ag6Se6 pseudohexagonal prismatic core. The decasilver clusters 2 contain an encapsulated selenium atom in a distorted, cis-bicapped trapezoidal-prismatic geometry and are surrounded by eight dsep ligands having three different types of coordination pattern. Furthermore, the hypercoordinated selenide ion, Se2−, in 2 was unequivocally identified by the solution 77Se{1H} NMR spectrum with a chemical shift centered at −1396 ppm.