Xiaobo Shi

Binary icosahedral clusters: Atom and electron counting rules

The first part of this paper deals with the enumeration of all possible stereoisomers (or polytypes) of a binary (two‐colored) icosahedron (either noncentered or centered) via Polya’s theorem. The numbers of achiral and chiral structures for each combination of the two types of atoms (or colors) A and B are determined. In cluster chemistry, A and B may represent two different kinds of atoms (e.g., main‐group elements vs transition metals) in a heteronuclear cluster, two different ligand environments in a homonuclear cluster, or atoms and holes (vacant sites) in an icosahedral cluster with missing vertices. The second part deals with the electronic requirements of binary icosahedral clusters where A and B may represent main‐group elements and transition metals, or, atoms and holes. Significantly different electron counts are observed for centered vs noncentered icosahedral clusters, depending upon the nature of the interstitial atom. Thus, icosahedral clusters can be classified into four broad categories a...

Abrusoside A: a new type of highly sweet triterpene glycoside

The structure and stereochemistry are reported for abrusoside A (1), an intensely sweet glycosidic constituent of Abrus precatorius leaves, based on the cycloartenol carbon skeleton.

Rotamerism and roulettamerism of vertex-sharing biicosahedral supraclusters: Synthesis and structure of [(Ph3P)10Au13Ag12Cl8](SbF6)

The relative rotation of two centered icosahedra of a vertex-sharing biicosahedral supracluster about the pentagonal symmetry axis gives rise to cluster “rotamerism” while the relative rotation of the satellite ring of six bridging halide ligands around the “equator” with respect to the metal framework gives rise to cluster “roulettamerism”; the latter is exemplified by the structures of [(Ph3P)10Au13Ag12X8]+X=Cl (this work) or Br.

Cluster rotamerism of a 25-metal-atom cluster [(Ph3P)10Au13Ag12Br8]+ monocation: a molecular rotary unit

Crystallographic studies of the title cluster in two crystal forms containing different anions [SbF6– and Br–(this work)] revealed two distinct rotamers with different metal configurations —ses and sss.

Cluster of clusters: structure of a novel 38-atom cluster (p-tolyl3P)12Au18Ag20Cl14

The X-ray crystal structure of a novel 38-atom cluster (p-tolyl3P)12Au18Ag20Cl14, the largest Au–Ag cluster known to date, is reported.

Bimetallic derivatives of the [M(en)3]3+ ion (M=Cr and Co): A series of compounds with unusual magnetic and structural properties (abstract)

The crystal structure and magnetic susceptibility of a series of [M(en)3]3+ (M=Cr or Co) derivatives are described. In particular, the crystalline structures of (1) [Cr(en)3]3[FeCl6]Cl6⋅H2O, (2) [Co(en)3]3[FeCl6]Cl6⋅H2O, and (3) [Cr(en)3][FeCl6]⋅11H2O are reported. Structural data, in A, for these compounds are as follows: (1) space group R3, a=15.447(4), c=21.060(6), Z=3; (2) space group R3, a=15.346(3), c=20.880(5), Z=3; (3) space group P3c1, a=11.654(3), c=15.508(4), Z=2. The main structural feature of the first two isomorphous materials is that they consist of a three‐dimensional network of triangular antiprisms formed by the [M(en)3]3+ (M=Cr or Co) ions and connected with each other by sharing corners. An [FeCl6]3− ion is placed at the center of each antiprism. Compound (3) contains a sc arrangement of [Cr(en)3]3+ and [FeCl6]3− octahedra. In addition, the magnetic susceptibilities of the above‐mentioned isomorphous compounds and of [M(en)3][FeCl6] (M=Cr and Co) and [Cr(en)3][InCl6] are reported. Whil...