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The synthesis and structure of the cationic, four-coordinate, ten-electron bismuth(III) complex [BiPh2(HMPA)2]+ (HMPA = hexamethylphosphoramide) is reported. The coordination geometry around the bismuth centre is that of a trigonal bipyramid with one equatorial site vacant and with phenyls in the other equatorial positions and the HMPA ligands in axial sites.  相似文献   
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DFT computations reveal that cis-trans preferences in [PtX2(PR3)2] species are due to a combination of electrostatics, pi-backbonding, antisymbiosis, and solvation effects.  相似文献   
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The crystallographically determined bond length, valence angle, and torsion angle information in the Cambridge Structural Database (CSD) has many uses. However, accessing it by means of conventional substructure searching requires nontrivial user intervention. In consequence, these valuable data have been underutilized and have not been directly accessible to client applications. The situation has been remedied by development of a new program (Mogul) for automated retrieval of molecular geometry data from the CSD. The program uses a system of keys to encode the chemical environments of fragments (bonds, valence angles, and acyclic torsions) from CSD structures. Fragments with identical keys are deemed to be chemically identical and are grouped together, and the distribution of the appropriate geometrical parameter (bond length, valence angle, or torsion angle) is computed and stored. Use of a search tree indexed on key values, together with a novel similarity calculation, then enables the distribution matching any given query fragment (or the distributions most closely matching, if an adequate exact match is unavailable) to be found easily and with no user intervention. Validation experiments indicate that, with rare exceptions, search results afford precise and unbiased estimates of molecular geometrical preferences. Such estimates may be used, for example, to validate the geometries of libraries of modeled molecules or of newly determined crystal structures or to assist structure solution from low-resolution (e.g. powder diffraction) X-ray data.  相似文献   
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The reactions between either BiBr2Ph and Na/K[Mo(CO)3(η? C5H5)], [BiPh{Mo(CO)3(η? C5H5)}2] and BiBr2Ph, or BiBr3 and BiPh3 and [Bi{Mo(CO)3(η? C5H5)}3] afford the complex [BiBrPh{Mo(CO)3(η? C5H5)}] 1 which has been characterised by X-ray crystallography. Complex 1 comprises a bismuth centre bonded to a bromine atom, a phenyl group and a Mo(CO)3(η? C5H5) fragment together with a longer secondary intermolecular interaction between a bromine from an adjacent molecule which results in a one-dimensional polymeric structure. Addition of a source of bromide anion to 1 affords the anionic complex [BiBr2Ph{Mo(CO)3(η? C5H5)}]? 3 ? although prolonged reaction results in the complex [BiBr2{Mo(CO)3(η? C5H5)}2]? 5 ? which was characterised by X-ray crystallography as its [Ph4P]+ salt. Complex 5 ? comprises a mononuclear bismuth centre bonded to two bromine atoms and two Mo(CO)3(η? C5H5) fragments in a geometry which lies between equatorially vacant trigonal bipyramidal and tetrahedral. The complex [PPN]2[Bi2Cl6{Mo(CO)3(η? C5H5)}2] 8 has also been synthesised and characterised by X-ray crystallography. A dimeric dianion is observed which can be viewed as two edge-shared square-based pyramids with chlorine atoms in the basal planes and Mo(CO)3(η? C5H5) fragments in the apical positions on opposite sides of the Bi2Cl6 plane.  相似文献   
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