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In this study, a modification combining densification and heat treatment of poplar wood (Populus tomentosa Carr.) was carried out, and the machining properties of theunmodified poplar wood (control) and the heat treated densified wood (HTD)were tested and evaluated. Inaddition, the water-based UV paint was covered on the control and HTD respectively, and thesurface coating properties of them were evaluated. The results showed that: (1)Themachining properties of poplar wood were improved after theheat treatment-densification modification. The score of comprehensive machining properties of the HTD was 45 (excellent grade), while the score of the control was 36 (good grade). (2)The abrasion resistance, hydrophobicity and adhesion were improved after heat treatment-densification modification. Therefore, the modification combining densification and heat treatment played asignificant role in enhancing thevalue of wood.

The reaction of [Ir(cod)(μ-Cl)]2 (cod = 1,5-cyclooctadiene) with 2 equiv of the ketophosphine Ph2PCH2C(O)Ph in the presence of TlPF6 afforded the hydrido, phosphino-enolate Ir(III) complex [IrH(cod){Ph2PCH ··· C( ··· O)Ph,κP,κO}{Ph2PCH2C(O)Ph,κP}]PF6 (4), which results from the room temperature activation of a C–H bond from the PCH2 moiety. The distorted octahedral coordination environment around the metal centre in 4 contains the cod ligand, the P atom of the monodentate ketophosphine and the P,O donor atoms of a chelating phosphino-enolate ligand acting as a 3-electron donor. The hydride ligand was located on the difference Fourier map obtained by single-crystal X-ray diffraction studies and is trans to the enolate oxygen and cis to the two, mutually cis P atoms. The reaction of this complex with NaH in THF led to the isolation of the Ir(I) complex [Ir(cod){Ph2PCH ··· C( ··· O)Ph,κP,κO}{Ph2PCH2C(O)Ph,κP}] (5). The penta-coordination environment around the metal centre in 5 includes the cod ligand, one 3-electron donor P,O chelating phosphino-enolate ligand and a P-bound Ph2PCH2C(O)Ph ligand containing an uncoordinated ketone function. The structures of 4·CH2Cl2 and 5·C7H8 have been determined by X-ray diffraction analysis.

Three types of hybrid phosphorus-imidazolium salts, 1-methyl-3-(3-((diphenylphosphino)methyl)benzyl)-1H-imidazol-3-ium hexafluorophosphate (2·PF6), 1-methyl-3-(3-(di-tert-butylphosphinooxy)phenyl)imidazolium iodide (8a), and 3-(3-((diphenylphosphoryl)methyl)phenyl)-1-methyl-1H-imidazol-3-ium iodide (11) have been prepared and used as precursors to phosphine-NHC, phosphinite-NHC, and phosphoryl-NHC metal complexes, respectively. The structure of 11 has been determined by X-ray diffraction. The Ag(I) and Ir(I) complexes of the phosphine-NHC ligand, [Ag(μ-P-NHC,κC,κP)]2(PF6)2 (3) and [Ir(cod)(μ-P-NHC,κC,κP)]2(PF6)2 (4), were obtained and characterized by NMR, ESI-MS, elemental analysis, and X-ray diffraction. Both complexes are dinuclear and dicationic, with two P-NHC ligands bridging the two metal centers. The presence of the P donor led for 3 to an unprecedented structure compared to that of related Ag(I) complexes with trans spanning bis-NHC ligands. Complex 4 is the first example of a dinuclear iridium complex with a hybrid P-NHC ligand. The new hydrido, Ir(III) pincer-type complex [IrH(CNHCCCNHC)(MeCN)]PF6 (7) is suggested to have a square-pyramidal structure. The tetranuclear Ag(I) complex with the phosphinite-NHC ligand, [Ag2(μ3-I)(μ-PO-NHC,κP,κCNHC)]2 (9a) has a cubane-type structure, with alternating silver and iodine apexes and two PO-NHC ligands bridging opposite edges of the Ag4 tetrahedron. The Ir(III) pincer complexes [IrH(I)(PO-NHC,κP,κC,κCNHC)(Me)] (10a) and [IrH(I)(PO-NHC,κP,κC,κCNHC)(n-Bu)] (10b), with Me or n-Bu substituents on the nitrogen atom, respectively, have been prepared and characterized. Ag(I) and Cu(I) complexes with the phosphoryl-NHC ligand are reported and the centrosymmetric structure of the latter, [Cu(OP-NHC,κCNHC)2(μ-I){Cu(μ-I)}]2 (13), was established by X-ray diffraction and consists of a central Cu2(μ-I)2 rhombus connected by single iodide bridges to two Cu(OP-NHC,κCNHC)2 moieties. The Ir(III) hydride pincer complexes 10a,b were tested as catalyst precursors for the C-H bond activation of alkanes. Although their efficiency was significantly lower for transfer dehydrogenation from cyclooctane (coa) to t-butylethylene (tbe) than that of known PCP-Ir systems, these results represent the first attempts to study the catalytic properties of hybrid P-NHC iridium pincer complexes.

New Cu(I) and Ag(I) complexes containing a chelating bis(N-heterocyclic carbene) ligand, in which an aryl group acts as a spacer between the NHC donor groups, have been prepared by deprotonation of the bis-imidazolium salt 1,1′-((4,6-dimethyl-1,3-phenylene)bis(methylene))bis(3-methyl-1H-imidazol-3-ium) bis(hexafluorophosphate) ((H2L)(PF6)2). Their structures, determined by X-ray diffraction, reveal a short separation (2.611(4) A (Cu) and 2.747(7) A (Ag), respectively) between the metal center and the C2 arene carbon of the ligand, whose metalation would result in pincer-type complexes. However, DFT calculations indicate that these distances do not correspond to C–H–M bonding interactions. Furthermore, whereas Ag(I) NHC complexes are typically used as transmetalation reagents, we report here an unusual example of the reverse situation consisting of a Cu(I) to Ag(I) transfer of NHC ligands.

A novel heterodifunctional phosphinite imidazolium salt was synthesized and reacted with Ag(I) to afford an unusual tetrasilver cubane-type cluster with two P-NHC ligands bridging between the Ag(I) centres of opposite Ag(2)I(2) faces.