Yong-Hua Li

Multinuclear palladium compounds containing palladium centers ligated by five silicon atoms

Palladium (Pd) generally prefers low oxidation states. So far, no stable Pd compound with a +5 oxidation state is known. Here, we report two multinuclear Pd compounds containing Pd centers ligated by five silicon (Si) atoms. A thermal condensation reaction of [{1,2-C6H4(SiMe2)(SiH2)}PdII(Me2PCH2CH2PMe2)] (Me = methyl) afforded two stereoisomers of dinuclear PdII compounds and a trinuclear Pd compound as major products and a tetranuclear Pd compound as a minor product. The structures of the four Pd compounds were confirmed by single-crystal x-ray structure analysis. The dinuclear Pd compounds have a dimeric structure of [{1,2-C6H4(SiMe2)(SiH)}PdII(Me2PCH2CH2PMe2)] connected through a Si–Si single bond formed by dehydrogenation of two molecules of the starting compound. The trinuclear and tetranuclear Pd compounds proved to have Pd centers bonded to five Si atoms with normal Pd–Si single-bond distances. Theoretical calculations of the trinuclear and tetranuclear Pd compounds accurately reproduced their x-ray structures and suggested that all of the Pd–Si bonds of the central Pd atoms have a relatively high single-bond character.

Proton-transfer supramolecular salts resulting from 3,5-dinitrobenzoic acid and aminomethyl pyridine

Three hydrogen-bonding three-dimensional (3D) networks of ammonium carboxylate salts formed between 3,5-dinitrobenzoic acid and aminomethyl pyridine (2-, 3-, 4-) are described here. During solution crystallization, the hydrogen atom transfers from the carboxylic acid to the amine to yield ammonium carboxylate salts, which feature three charge-separated N+–H⋯O− hydrogen bonds to afford two types of one-dimensional (1D) hydrogen-bonding columns. Of the three structures, ((2-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (1) shows a hydrogen-bonding column which consists of alternating R12(4) and R24(8) rings whereas ((3-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (2) results in a hydrogen-bonding column which comprises repeating R34(10) rings. ((4-pyridylmethyl)ammonium) (3,5-dinitrobenzoate) (3) bears a unique shape of Chinese knot among four cations instead of the column constructed by rings. From this we can gather information about the possible position effects of functional groups on the overall packing.

Inorganic anion-assisted supramolecular assemblies of bent dipyridines: effects of anionic geometries on hydrogen-bonding networks

A series of inorganic acids were introduced into the self-assembly with the bent 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (4-bpo), yielding seven anion-assisted supramolecular salts, i.e. [(4-H2bpo2+)·(NO3−)2]·2H2O (1), (4-H2bpo2+)·(HPO42−) (2), [(4-H2bpo2+)2·(4-Hbpo+)·(I3−)3·(I−)2]·2H2O (3), [(4-Hbpo+)2·(PF6−)2]·H2O (4), [(4-H2bpo2+)·(BF4−)2]·H2O (5), [(4-Hbpo+)·(BF4−)] (6) and (4-H2bph2+)·(SO42−) (7). Structural analyses indicate that different inorganic anions (e.g. spherical, linear, trigonal planar, tetrahedral and octahedral) can induce the formation of diverse supramolecular architectures, influencing the crystallization ratio, the protonated number and the final structure. The anions are hydrogen bonded to the angular dipyridine, which offers a sufficient driving force for the directed assembly of supramolecular hydrogen-bonding frameworks. Thereto, various hydrogen-bonding motifs are observed in all these cases (1–7) and the nitrogen atoms of pyridines are protonated apart from salt 6. Among them, salts 1, 3, 4 and 5 crystallize with water molecules but the others do not. Interestingly, appealing substructures have been generated by anions and water molecules in 1, 3 and 5 but not in 4. HPO42− dimers form in 2 despite there being no assistance from solvent water. BF4− anions facilitate the formation of the helical chain in 6. Unexpectedly, the oxadiazole ring opened via the in situ hydrolysis under hydrothermal conditions during crystallization with H2SO4, producing salt 7.

Supramolecular assemblies through host–guest interactions of 18-crown-6 with ammonium salts: geometric effects of amine groups on the hydrogen-bonding architectures

A series of ammonium salts were introduced into the self-assembly with the same host 18-crown-6, yielding five supramolecular salts, that is [(C4H6N3)·(18-crown-6)2]+·() (1), [(C6H14N)·(18-crown-6)]+·() (2), [(C6H14N)·(18-crown-6)]+·() (3), [(C6H10N2)·(18-crown-6)]2+·()2 (4) and [(C6H8NO2)·(18-crown-6)]+·[(C7H3N2O6)− ]2 (5). Structural analysis indicates that different kinds of guest amines, ranging from chain-like aliphatic amine, annular aliphatic amine to aromatic amine, have a great impact on host–guest interactions and supramolecular architectures. The major driving force in host–guest systems is found to be the strong N–H…O or/and weak C–H…O hydrogen-bonding interactions, with various ring motifs and interesting substructures such as the butterfly-like trimer in 1 and the rotator–stator assembly in 2–5. By analysing and summing up, we can come to the conclusion that the group in 4 exhibits an optimum value of around 0.755 Å from the O-plane and the 18-crown-6 macrocycle displays the minimum distortion. On the whole, ammonium cations show control over supramolecular assemblies, but counter anions that easily form hydrogen bonds will affect crystal structures, for instance, anion in 4 facilitates the formation of the 3D hydrogen-bonding network and helical hydrogen-bonding sheets while deprotonated 3,5-dinitrobenzoic acid assists the formation of discrete subunits.

Effects of Weak Hydrogen-Bonding Interactions on Supramolecular Assemblies of N,N-Dimethyl-1-admantylamine

AbstractThe reaction of N,N-dimethyl-1-admantylamine (ada) and inorganic acids or trivalent metal chlorides in the hydrochloric acid medium yields four new supramolecular salts, i.e. (adaH+)3·(SbCl3)·(SbCl4−)·(SbCl52−) (1), (adaH+)·(FeCl4−) (2), (adaH+)·(ClO4−) (3), and (adaH+)·(I3−) (4), respectively. Compound 5, (dtaH+)2·(I3−)·I− (dta = N,N-dimethyl-2,4,6-trimethylaniline) was also prepared for comparison with 4. Structural analyses reveals that the weak hydrogen-bonding interactions play a crucial role in the formation of various hydrogen-bonding networks. 3D supramolecular architectures are observed in 3, independent 1D infinite hydrogen-bonded chain structures are observed in 1, and discrete structures are observed in 2, 4 and 5. Surprisingly, due to the coexistence of SbCl3, [SbCl4]− and [SbCl5]2−, compound 1 proves to be a unique example according to the Cambridge Structure Database (CSD).Graphical AbstractStructural analysis reveals that the weak hydrogen-bonding interactions play a crucial role in the formation of various hydrogen-bonding networks. 3D supramolecular architectures are observed in 3, independent 1D infinite hydrogen-bonding chain structures are observed in 1 and discrete structures are observed in 2, 4 and 5.

Effects of Anionic Geometries on Hydrogen-Bonding Networks of 1-(4-pyridyl) Piperazine

A series of new salts have been obtained by the self-assembly of 1-(4-pyridyl) piperazine and inorganic ions or metal chloride in the hydrochloric acid medium, i.e. (C9H15N32+)·(Cl−)2 (1) (C9H15N32+)·(NO3−)2 (2), (C9H15N32+)·(CuCl42−) (3), (C9H15N32+)·(CoCl42−) (4), (C9H15N32+)·(ZnCl42−) (5), {(C9H15N32+)·[Mn(H2O)2Cl42−]}·H2O (6), (C9H14N3+)·(Sb2Cl7−) (7) and (C9H15N32+)·(PbCl42−) (8). Structural analyses indicate that different anionic structure (e.g. spherical, trigonal planar, tetrahedral, octahedral, polyhedral and chain) can induce the formation of diverse architectures, influencing the crystallization ratio, the protonated number and the final structures. Extensive intermolecular interactions have been utilized for the self-assembly of diverse frameworks, ranging from strong X–H···Y (X=O, N; Y=Cl, O) hydrogen bonds to weak C–H···M (M=O, Cl) interactions. Among them, 3D hydrogen-bonding architectures are observed in 1–7 but only a 2D hydrogen-bonding architecture is observed in 8. Salt 6 crystallizes with water molecules but the others do not. Interestingly, the anions of salts 7 and 8 are dinuclear and 1D complex ions, respectively.Graphical AbstractA series of supramolecular salts have been obtained by the self-assembly of 1-(4-pyridyl) piperazine and inorganic acids or metal chloride in the hydrochloric acid medium. Structural analyses indicate that different anionic structure (e.g. spherical, trigonal planar, tetrahedral, octahedral, polyhedral and chain) can induce the formation of diverse supramolecular architectures, influencing the crystallization ratio, the protonated number and the final structures.

Synthesis, structural characterization‚ and reactivity of a bis(phosphine)(silyl) platinum(II) complex

Treatment of 1,2-C6H4(SiMe2H)(SiH3) (1) with Pt(dcpe)(PEt3)2 (dcpe = Cy2PCH2CH2PCy2) in dry toluene at room temperature in the ratio of 1 : 1 leads to {1,2-C6H4(SiMe2)(SiH2)}PtII(dcpe) (2), which can react with sterically unhindered alcohol to form a dimethoxy substituted silyl platinum(II) compound (3). There are only five examples of bis(silyl) platinum(II) complexes prepared from this silyl ligand with such structural features registered in the Cambridge Structural Database. The structures of 2 and 3 were unambiguously determined by single-crystal X-ray analysis and multinuclear NMR spectroscopic studies.

An unusual (3,4)-connected cubic-C3N4 type network constructed with [FeIII(Tp)(CN)3]− (Tp− = hydrotris(pyrazolyl)borate)

By using a pre-designed anionic precursor [FeIII(Tp)(CN)3]− (Tp− = hydrotris(pyrazolyl)borate) as a structural building unit, a novel cyanide-bridged metal–organic framework (MOF), [(Tp)6FeII4FeIII2(CN)18Zn5(H2O)3.25·(CH3CN)4.75(C4H10O)2.125(H2O)2]n (1), has been synthesized and characterized by single crystal X-ray diffraction. There are two kinds of secondary building units (SBUs), cube and trigonal bipyramid (TBP) in complex 1. The cubic SBU contains a Zn4Fe4(CN)12 core. Each cube connects to four TBPs and each TBP binds three cubes through its equatorial bonds giving rise to an unprecedented cyanide-bridged (3,4)-connected cubic-C3N4 type network.

CCDC 809498: Experimental Crystal Structure Determination

Related Article: Hongyun Fang, Yoong-Kee Choe, Yonghua Li, S.Shimada|2011|Chem.Asian J.|6|2512|doi:10.1002/asia.201100085