Ze-Ying Zhang

Synthesis, electrochemistry, and oxygen-atom transfer reactions of dioxotungsten(VI) and -molybdenum(VI) complexes with N2O2 and N2S2 tetradentate ligands

A series of N2O2 tetradentate ligands with a range of substituents attached to the nitrogen atoms have been prepared (H2Ln) (n = 1–9). Treatment of these ligands and the N2S2 tetradentate ligand H2L10 with [WO2Cl2(DME)] (DME = 1,2-dimethoxyethane) in the presence of triethylamine leads to the formation of cis-dioxotungsten(VI) complexes [WO2(Ln)] (n = 1–10). Reaction of the N2O2 tetradentate ligands H2Ln (n = 1, 3–7) with ammonium molybdate tetrahydrate and dilute hydrochloric acid gives the corresponding molybdenum(VI) analogs [MoO2(Ln)] (n = 1, 3–7). These compounds have been spectroscopically characterized and the molecular structures of [WO2(Ln)] (n = 1, 2, 9) and [MoO2(L5)] have been established by X-ray diffraction analysis. These high-valent compounds participate in oxygen-atom transfer reactions and can catalyze the oxidation of benzoin with dimethyl sulfoxide. The complex [WO2(L10)], which contains an S-donor ligand, has lower reduction potential and higher reactivity toward oxo-transfer reactions than analogous tungsten complexes having N2O2 ligands. The kinetics of these catalytic processes along with the structure and electrochemistry of these dioxotungsten and -molybdenum complexes are described and compared.

Synthesis and characterization of half- and full-sandwich lanthanacarboranes of the C2B9-carborane ligand. X-ray crystal structures of [LnCl2(THF)5][nido-C2B9H12] (Ln=Y, Yb)

Abstract Treatment of LnCl3(THF)x with one equivalent of Na2[nido-7,8-C2B9H11] in THF gave the half-sandwich lanthanacarborane chloride compound (η5-C2B9H11)Ln(THF)2(μ-Cl)2Na(THF)2 (Ln=Y (1), Er (2), Yb (3), Lu (4)). Recrystallization of 1 or 3 from a wet THF–toluene solution afforded the ionic compound [LnCl2(THF)5][nido-C2B9H12] (Ln=Y (5), Yb (6)). Reaction of 1 or 3 with Na2[nido-7,8-C2B9H11] in a molar ratio of 1:1 in THF generated the full-sandwich lanthanacarborane {(η5-C2B9H11)2Ln(THF)2}{Na(THF)2} (Ln=Y (7), Yb (8)). All of these new compounds were characterized by 1H-, 13C-, and 11B-NMR spectra and elemental analyses. The solid-state structures of 5 and 6 were further confirmed by single-crystal X-ray analyses.

Systematic studies on the reactions of lanthanide trichlorides with Na[1,3-bis(trimethylsilyl) cyclopentadienyl]. Crystal structures of [1,3-(Me3Si)2C5H3]3Ln (LnLa, Nd, Gd, Dy)

Abstract Reflux of LnCl3 with an excess amount of Na[(Me3Si)2C5H3] in THF and then in toluene gave two kinds of complexes dependent upon the size of the central metal, the tris ligand complexes of the type [(Me3Si)2C5H3]3Ln (LnLa, Nd, Sm, Gd or Dy) and the bis ligand complexes of the general formula [{(Me3Si)2C5H3}2LnCl]2 (LnGd, Dy, Y, Er or Yb). Neither THF coordinated nor THF ring-opened product was isolated. These compounds were fully characterized by elemental analyses. IR, MS and 1H NMR (for diamagnetic metals) spectroscopy. The structures of the tris ligand complexes of La, Nd, Gd and Dy have been further confirmed by single-crystal X-ray diffraction analyses. Each of the three (Me3Si)2C5H3 ligands is η5-bonded to the central lanthanide atom to form the trigonal planar geometry with an average (ring centroid)-metal-(ring centroid) bond angle of 120°. The variations in the metal-carbon bond distances are consistent with the phenomenon of lanthanide contraction.

Synthesis of novel ruthenium complexes of 2,2′-bis(diphenylphosphinomethyl)-1,1′-biphenyl and their catalytic hydrogenation reactions to α,β-unsaturated aldehydes

Three ruthenium complexes containing BISBI [2,2′-bis(diphenylphosphinomethyl)-biphenyl], RuCl2(PPh3)(BISBI) 1, RuHCl(CO)(PPh3)(BISBI) 2 and RuH2(CO)(PPh3)(BISBI) 3, had been prepared. Their compositions and structures were characterized by 31P{1H}-NMR, 1H-NMR and elemental analysis. Results of 31P{1H}-NMR showed that the PPh3 in complex 1 was completely dissociated and a dimer complex [RuCl2(BISBI)]2 was generated in CDCl3 and C6D6 solutions. Molecular structure of 3 was also confirmed by single-crystal X-ray diffraction, the crystal belonged to a monoclinic system, P21/n space group, a=16.771(3) A, b=20.688(4) A, c=17.139(3) A, β=106.03(3)°, V=5715(3) A3 and Z=4. The hydrogenation results revealed that the three complexes showed much higher activities and selectivities than their analogous triphenylphosphine complexes for the hydrogenation of CO bond in citral (3,7-dimethyl-2,6-octadienal) and cinnamaldehyde.

Metal–metal bond cleavage in the trinuclear clusters M3(CO)12-n(Ph2Ppy)n (M=Ru, n=3; Os, n=1; Ph2Ppy=2-(diphenylphosphino)pyridine) by Lewis acids

Abstract Reaction of M 3 (CO) 12- n (Ph 2 Ppy) n (M=Ru, n =3; M=Os, n =1) with HgX 2 (X=Br, Cl) gave cis -M(CO) 3 ( μ -Ph 2 Ppy)(HgX) 2 , (M=Ru, 1 ; M=Os, 2 ), and the reaction of Ru 3 (CO) 9 (Ph 2 Ppy) 3 with CdI 2 resulted in the formation of I(CO) 2 Ru( μ -Ph 2 Ppy) 2 Ru(CO) 2 I, 3, which demonstrate the cleavage of metal-metal bonds by Lewis acids. The crystal and molecular structures of 1 , 2 and 3· 0.5MeOH·H 2 O have been determined by X-ray analysis.

Synthesis and X-ray crystal structure of bis[η5-1,3-bis(trimethylsilyl)cyclopentadienyl] lanthanide and yttrium iodide complexes

Abstract Treatment of [{(Me3Si)2C5H3}2LnCl]2 with excess amounts of NaI in dry THF, or reaction of a mixture of LnCl3 and with two equivalents of [(Me3Si)2C5H3]Na in dry THF at room temperature, gave five new monomeric complexes [(Me3Si)2C5H3]2LnI(THF) (Ln = La (1), Sm (2), Y (3), Er (4), Lu (5)) in 50–69% yield. The mixed π-ligand complex [{(Me3Si)2C5H3}{(Me3Si)C5H4}]Lul(THF) (6) was also prepared in a similar manner. The compounds were fully characterized by elemental analyses, IR and MS spectroscopy, 1H NMR (for diamagnetic metals) and single-crystal X-ray diffraction studies (except 1). In each compound, the C5 ring centroids, the THF oxygen atom and iodide ligand describe a distorted tetrahedral geometry around the metal. The variations in the metal-iodide bond distances are not as predictable as those in metal-carbon and metal-oxygen bond distances.

SYNTHESIS AND X-RAY STRUCTURES OF TRIVALENT LANTHANIDE (+)-NEOMENTHYLCYCLOPENTADIENYL COMPLEXES

Abstract Trivalent lanthanide (+)-neomenthylcyclopentadienyl complexes [CpR2Ln(μ-Cl)]2 (Ln=Sm (1), Yb (2), Y (3), Lu (4); CpR=(+)-neomenthylcyclopentadienyl)] and CpRLnX2(THF)3 [X=Cl, Ln=Sm (6), Gd (7), Yb (8), Y (9), Lu (10); X=I, Ln=Sm (11), Yb (12)) have been prepared by metathetical reactions of lanthanide halide with appropriate alkali-metal (+)-neomenthylcyclopentadienyl complexes. X-ray structural analysis has revealed that compounds 1 and 3 are chloro-bridged dimers with the asymmetric plane described by Ln2Cl2 almost perpendicular to the plane described by the four cyclopentadienyl ring centroids. The monomeric compound CpRLnI2(THF)3 (11) adopts a pseudo-octahedral geometry with the two iodine atoms taking the trans-positions.

General synthesis of ferrocenylphosphine-bridged digold carboxylato complexes crystal and molecular structure of Au2(η1-CF3CO2)2(η-dppf) · C6H14 (dppf = Fe(C5H4PPh2)2)

Metathesis of Au 2 Cl 2 ( μ -dppf) with Ag(RCO 2 ) (R = CH 3 , CF 3 , C 2 H 5 and C 6 H 5 ) gives Au 2 ( η 1 -RCO 2 ) 2 ( μ -dppf) in 75–97% yields. Spectroscopic data are consistent with a common structure containing a ferrocenyl diphosphine bridging two moieties of Au(I) bearing carboxylates in a unidentate coordination mode. Similar reaction of Au 2 Cl 2 ( μ -dppm) with Ag(CF 3 CO 2 ) gives Au 2 ( η 1 -CF 3 CO 2 ) 2 ( μ -dppm) in 52% yield. X-ray single-crystal crystallographic diffraction analysis of Au 2 ( η 1 -CF 3 CO 2 ) 2 ( μ -dppf) · C 6 H 14 shows that in the centrosymmetric dinuclear molecule, the Au(I) geometry is approximately linear (∡ O-Au-P 177.1(1)°) and the trifluoroacetate ligand is unidentate (C(18)-O(1) 1.267(4)A and C(18)-O(2/2a) 1.212(4) A). An intermolecular Au…Au interaction of 3.254(1) A links the molecules into an infinite zigzag chain running parallel to the c axis. Crystal data: Au 2 ( η 1 -CF 3 CO 2 ) 2 ( μ -dppf) · C 6 H 14 , space group C 2/ c (No. 15), a = 15.325(3), b = 19.058(4), c = 15.373(3)A, b = 95.98(3)°, final R = 5.66% for 3784 observed reflections.