Chi-Rung Lee

Structural relationship of various squarates

This work illustrates the structural relationship between three types of metal squarates as well as the ligand in its acid form and in its monoanion salt. Squaric acid, H2C4O4, is known to have a polymeric layer structure with planar molecules connected through intermolecular hydrogen bonds. The interlayer distance is only 2.649 A. The crystal of H2NMe2[H3(C4O4)2] is found to contain columns of [H3(C4O4)2-] repeating units, again connected by intermolecular hydrogen bonds. Within the repeated unit, there is a symmetric hydrogen bond connected to two HC4O4 moieties. A new type of metal squarate with M(HC4O4)2(H2O)4 M = MnII, FeII both belong to space group P, Z = 1, a = 5.194 (3), b = 7.454 (2), c = 8.901 (2) A, = 67.07 (2), = 77.26 (3), = 74.46 (4)°, for MnII is shown to have a layer-type structure, where all [HC4O4] units are bonded into infinite chains via symmetric hydrogen bonds, each (HC4O4)22- ligand bridging two metal ions (-2) in a trans fashion. The structurally most well understood metal squarate M(C4O4)(H2O)4 (M = MnII, FeII, CoII, NiII and ZnII, space group C2/c, Z = 4) is again a polymeric chain with C4O42- serving as a bridging ligand between two metal ions (-2) in trans positions. A three-dimensional polymeric structure is found to have the formula M(C404)(H2O)2, where C4O42- is a bridging ligand between four metal ions (-4). Due to the slight difference in packing, there are two structure types in this category: one is in space group R [M = FeII, a = 11.440 (2), c = 14.504 (3) A, Z = 9], the other is in Pnn [M = CoII, a = 16.255 (3) A, Z = 24]. The structural relationship between all these structures relies heavily on the understanding of intra- and intermolecular hydrogen bonds. The interesting building blocks of each compound will be illustrated. There are tunnels of various sizes in all these structures.

Copper(I)–Anilide Complex [Na(phen)3][Cu(NPh2)2]: An Intermediate in the Copper‐Catalyzed N‐Arylation of N‐Phenylaniline

Complex [Na(phen)(3)][Cu(NPh(2) )(2)](2), containing a linear bis(N-phenylanilide)copper(I) anion and a distorted octahedral tris(1,10-phenanthroline)sodium counter cation, has been isolated from the catalytic C-N cross-coupling reaction with the CuI/phen/tBuONa (phen=1,10-phenanthroline) catalytic system. Complex 2 can react with 4-iodotoluene to produce 4-methyl-N,N-diphenylaniline (3 a) with 70.6 % yield. In addition, 2 can work as an effective catalyst for C-N coupling under the same reaction conditions, thus indicating that 2 is the intermediate of the catalytic system. Both [Cu(NPh(2))(2)](-) and [Cu(NPh(2))I](-) have been observed by in situ electron ionization mass spectrometry (ESI-MS) under catalytic reaction conditions, thus confirming that they are intermediates in the reaction. A catalytic cycle has been proposed based on these observations. The molecular structure of 2 has been determined by single-crystal X-ray diffraction analysis.

Charge-density and X-ray absorption studies on heterobimetallic phosphido-bridged Mo and W complexes

411 and so on. For example, in the case of polyoxymethylene, synchrotron X-ray diffraction gave us the observed reflections more than 700, from which t h e d e t a i l s o f t h e c h a i n c o n f o r m a t i o n a n d c h a i n packing mode were derived accurately. The 2-dimensional n e u t r o n d i f f r a c t i o n d a t a collected for both of Hand D-polyoxymethylene samples allowed us to extract the H and D atomic positions exactly as shown in Figure. The similar results were obtained also for the other polymers listed above.