Ling-Kang Liu

Substituted metal carbonylsXVIII. rhenium 1,1′-bis(diphenylphosphino)ferrocene (DPPF) complexes derived from [Re2(CO)9]. Crystal structures of two isomorphous pentametallic [M2(CO)9]2(μ-dppf) (M Mn, Re) and trimetallic Re2(CO)9(dppfO) complexes

Abstract Amine oxide-assisted decarbonylation of Re2(CO)10 in the presence of 1,1′-bis(diphenylphosphino)ferrocene (dppf) produces, under different conditions, [Re2(CO)9]2 (μ-dppf) (1), Re2(CO)9(1-dppf) (5) and its oxidation product Re2(CO)9(1-dppfO) (7). 1 undergoes an oxidative bridge-scission with Me3NO to give 7. X-ray crystallographic analysis of 1 and [Mn2(CO)9]2(μ-dppf) (2), included for comparison, revealed that the two molecules are isomorphous, each taking the form of an open and “linear” tetranuclear complex supported alternately by M M bonds and a “half eclipsed” dppf bridge. Complex 7, which is trimetallic, consists of dppf (mono)oxide coordinated to [Re2(CO)9] through the phosphine site. X-ray Photoelectron Spectra revealed the existence of the chemically inequivalent Re and P sites within the same molecule. The chemically distinct Re centres in 1, 5, 7 and Re2(CO)9(CH3CN) are differentiable by their Re(4f7/2) and Re(4f5/2) binding energies.

Substituted metal carbonyls XV. Crystal and molecular structures of two isomorphous singly diphosphine-bridged complexes (OC)5M(μ-dppf)M(CO)5·CH2Cl2 (M = Cr, Mo; dppf = (Ph2PC5H4)2Fe)☆

Abstract The crystal structures of two dinuclear compounds (OC) 5 M(μ-dppf)M(CO) 5 ·CH 2 Cl 2 (M = Cr, Mo; dppf = (Ph 2 PC 5 H 4 ) 2 Fe), determined by single-crystal X-ray diffraction studies, were found to be isomorphous. (Crystal data: (OC) 5 Cr(μ-dppf)Cr(CO) 5 , space group C 2/ c , a 16.659(3), b 15.350(5), c 18.877(2) A, β 112.43(2)°, Final R 0.046 for 2999 observations. (OC) 5 Mo(μ-dppf)Mo(CO) 5 , space group C 2/ c , a 16.705(4), b 15.545(4), c 19.091(3) A, β 111.92(2)°, Final R 0.037 for 3332 observations). The diphosphine serves as a single bridge between two essentially unperturbed metal carbonyl spheres. The iron was located on a two-fold axis as required crystallographically. The relationship between the phosphinoferrocenyl geometry and the stability of this type of “open” complexes is described together with the solid-state decomposition data from Thermogravimetric (TG) and Differential Scanning Calorimetric (DSC) analyses.

Mixed sulphur and phosphorus ylide complexes of palladium formed by phase-transfer catalysis. X-Ray crystal structure of [Pd{(CH2)2S(O)Me}{Ph2PCH2PPh2CHC(O)Ph}]I·CH2Cl2·H2O

Phosphorus ylide complexes [PdBr2{Ph2P(CH2)nPPh2CHC(O)R}](n= 1 or 2; R = Me, Ph, or OEt), and mixed sulphur and phosphorus ylide complexes [Pd{(CH2)2S(O)Me}{Ph2P(CH2)n-PPh2CHC(O)R}]I, have been synthesized by the phase-transfer technique. The presence of the phase-transfer catalyst has only a marginal effect in the preparation of phosphorus ylide-containing complexes. The mixed ylide compounds have both a chelated double sulphur ylide and a C,P-chelated phosphorus ylide. A mixed-ylide complex [Pd{(CH2)2S(O)Me}{Ph2PCH2-PPh2CHC(O)Ph}]I·CH2Cl2·H2O has been investigated by means of X-ray crystallography. The Pd–C bond length of 2.183 5)A for the phosphorus ylide co-ordination is longer than that for the sulphur ylide co-ordination [2.094(3)A(average)].

Molecular structures of 1,1′bis(diphenylphosphino) ferrocene oxide and sulphide and their thermal properties

Abstract The crystal and molecular structure of anhydrous 1,1′-bis(diphenylphosphino) ferrocene sulphide, Fe[C 5 H 4 P(S)Ph 2 ] 2 (dppf S 2 ), is reported and compared with the hydrated oxide analogue, Fe[C 5 H 4 P(O) Ph 2 ] 2 · 2H20 (dppfO 2 · 2H20). It consists of two phosphoryl cyclopentadienyl rings [P-S = 1.938(2) A] sandwiching an Fe II centre. With four molecules per cell, the molecule is crystallographically required to sit on an inversion centre and hence the two rings are staggered. The thermal properties of [Fe(C 5 H 4 PPh 2 ) 2 ] (dppf), dppfO 2 · 2H20 and dppfS 2 were studied together with Fe(Cp) 2 and Ph 3 PO · H2O by TGA and DSC. The thermal stability decreases in the order dppFO 2 > dppf > dppf S 2 . The hydrogen-bonded hydrate in dppfO 2 · 2H20 is removed upon heating to 110–160°C.

Nanocomposite for methanol oxidation: synthesis and characterization of cubic Pt nanoparticles on graphene sheets

Abstract We present our recent results on Pt nanoparticles on graphene sheets (Pt-NPs/G), a nanocomposite prepared with microwave assistance in ionic liquid 2-hydroxyethanaminiumformate. Preparation of Pt-NPs/G was achieved without the addition of extra reductant such as hydrazine or ethylene glycol. The Pt nanoparticles on graphene have a cubic-like shape (about 60 wt% Pt loading, Pt-NPs/G) and the particle size is 6 ± 3 nm from transmission electron microscopy results. Electrochemical cyclic voltammetry studies in 0.5 M aqueous H2SO4 were performed using Pt-NPs/G and separately, for comparison, using a commercially available electrocatalyst (60 wt% Pt loading, Pt/C). The electrochemical surface ratio of Pt-NPs/G to Pt/C is 0.745. The results of a methanol oxidation reaction (MOR) in 0.5 M aqueous H2SO4 + 1.0 M methanol for the two samples are presented. The MOR results show that the ratios of the current density of oxidation (If) to the current density of reduction (Ib) are 3.49 (Pt-NPs/G) and 1.37 (Pt/C), respectively, with a preference by 2.55 times favoring Pt-NPs/G. That is, the tolerance CO poisoning of Pt-NPs/G is better than that of commercial Pt/C.

Synthesis and characterizations of Ni-NiO nanoparticles on PDDA-modified graphene for oxygen reduction reaction

We are presenting our recent research results about the Ni-NiO nanoparticles on poly-(diallyldimethylammonium chloride)-modified graphene sheet (Ni-NiO/PDDA-G) nanocomposites prepared by the hydrothermal method at 90°C for 24 h. The Ni-NiO nanoparticles on PDDA-modified graphene sheets are measured by transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and selected area electron diffraction (SAED) pattern for exploring the structural evidence to apply in the electrochemical catalysts. The size of Ni-NiO nanoparticles is around 5 nm based on TEM observations. The X-ray diffraction (XRD) results show the Ni in the (012), (110), (110), (200), and (220) crystalline orientations, respectively. Moreover, the crystalline peaks of NiO are found in (111) and (220). The thermal gravimetric analysis (TGA) result represents the loading content of the Ni metal which is about 34.82 wt%. The electron spectroscopy for chemical analysis/X-ray photoelectron spectroscopy (ESCA/XPS) reveals the Ni0 to NiII ratio in metal phase. The electrochemical studies with Ni-NiO/PDDA-G in 0.5 M aqueous H2SO4 were studied for oxygen reduction reaction (ORR).

The intramolecular blue-shifting C–H⋯F–C hydrogen bond: crystal structure of [4,4′-bis(HCF2CF2CF2CF2CH2OCH2)-2,2′-bpy]MCl2 where M = Pt, Pd

In the solid state, the two fluorous ponytails in [4,4′-bis(HCF2CF2CF2CF2CH2OCH2)-2,2′-bpy]MCl2 (M = Pt 2; Pd 3) reveal one with a transoidal HCF2CF2CF2CF2CH2– chain on carbon backbone, similar to that with a normal fluorous alkyl group, and the other with a cisoidal HCF2CF2CF2CF2CH2– chain on a carbon backbone, exhibiting an intramolecular blue-shifting C–H⋯F–C hydrogen-bond. With the contraction of C–H bond, the increase in C–H stretch and the short H⋯F distance, these two examples are among the blue-shifting hydrogen bonds as defined by Hobza et al. The calculated C–H stretches using periodic density functional theory (DFT) are in good agreement with IR observations.

The reaction of CpFe(CO)2X(X Cl, Br, I) with phosphines catalyzed by [CpFe(CO)2]2: evidence for an electron transfer chain catalysis mechanism

Abstract The catalytic substitution of phosphines for halide on CpFe(CO)2X(X  Cl, Br, I) has been shown to proceed through an electron transfer chain catalysis mechanism. The reaction may be initiated by CpFe(CO)2(PR3) generated by photochemical or thermal cleavage of [CpFe(CO)2]2 or by addition of catalytic amounts of other strong reductants.

Substituted metal carbonyls. Part 25: Unidentate, intramolecular, and intermolecular bridging modes of 1,1′-bis(diphenylphosphino)ferrocene inM3S2(CO)9 (M = Fe, Ru) cluster derivatives

Carbonyl exchange of Fe3(μ3-S)2(CO)9 wioth1,1′-bis(diphenylphosphino)ferrocene (dppf) in refluxing THF gives a cluster ligand with a pendant phosphine moiety, Fe3(μ3-S)2(CO)8 (gn1-Ph2PlC5H4)Fe(C5H4)P4 MePh2)]1−,4. Addition of 1 to AuCl(SMe2) gives ClAu(μ-dppf) Fe4(μ3-S)2(CO)8,8 (45%). Spectroscopic evidence is also obtained for (OC)8 (μ3-S)2Fe3(μ-dppf) Os3(CO)11,7 and PdCl2[(μ-dppf)Fe3(μ3-D)2(CO)8]2,9, from1 and Os3(CO)11(CH3CN) and PdCl2CN)2, respectively. Crystal data dor3: space group P21/n,a = 10.891(3) Å,b = 19.939(3) Å,c = 20.443(2) Å,β 100.17(2)°.Z = 4, 3917 reflections,R = 0.049.

Phase-transfer catalyzed base hydrolysis of Pt(Ph2PCH2PPh2)Cl2. Synthesis and crystal structure of the trinuclear compound [Pt3(μ3-O)(μ-η2-PPh2O)3((PPh2Me)3]PF6·CHCL3

Abstract Base hydrolysis of Pt(dppm)Cl2, (dppm = Ph2PCH2PPh2), under phase-transfer catalysis (PTC) conditions gave the triplatinum compound [Pt3(μ3-O)(μ-η2-PPh2O)3(PPh2Me)3]PF6. This trinuclear compound can be transformed to {Pt(PPh2Me)[PPh2(OH)]Cl2}, which upon treating with aqueous NaOH under PTC conditions produced a dimeric compound [Pt(μ-O)(PPh2Me)(PPh2O)]2. The trinuclear compound has been characterized by various specroscopic methods and X-ray crystallography.