Solution and structural investigations of ligand preorganization in trivalent lanthanide complexes of bicyclic malonamides.

This report describes an investigation into the coordination chemistry of trivalent lanthanides in solution and the solid state with acyclic and preorganized bicyclic malonamide ligands. Two experimental investigations were performed: solution binding affinities were determined through single-phase spectrophotometric titrations and the extent of conformational change upon binding was investigated with single-crystal X-ray crystallography. Both experimental methods compare the bicyclic malonamide (BMA), which is designed to be preorganized for binding trivalent lanthanides, to an analogous acyclic malonamide.

Regioselective formation of beta-alkyl-alpha-phenyliridabenzenes via unsymmetrical 3-vinylcyclopropenes: probing steric and electronic influences by varying the alkyl ring substituent.

The synthesis of unsymmetrical (Z)-1-alkyl-3-(2-iodovinyl)-2-phenyl-1-cyclopropenes (R=Me (8 a), Et (8 b), iPr (8 c), and tBu (8 d)) and their reactions with Vaska's complex [Ir(CO)Cl(PPh3)2] and its trimethylphosphine analogue [Ir(CO)Cl(PMe3)2] were investigated. Iridabenzvalene (13/20), iridabenzene (14/21), and/or eta(5)-cyclopentadienyliridium complexes (15/22) were obtained in modest yields and were fully characterized by spectroscopic means. X-ray structural data was secured for iridabenzvalene 13 d and iridabenzenes 14 a,b,d.

K2[HCr2AsO10]: redetermination of phase II and the predicted structure of phase I.

Our prediction that phase II of dipotassium hydrogen chromatoarsenate, K(2)[HCr(2)AsO(10)], is ferroelectric, based on the analysis of the atomic coordinates by Averbuch-Pouchot, Durif & Guitel [Acta Cryst. (1978), B34, 3725-3727], led to an independent redetermination of the structure using two separate crystals. The resulting improved accuracy allows the inference that the H atom is located in the hydrogen bonds of length 2.

Phase transitions in K2Cr2O7 and structural redeterminations of phase II.

Crystals of phase II K2Cr2O7, potassium dichromate, space group P1 , grown from aqueous solution undergo a first-order transition to phase I, space group reportedly P21/n, at a phase-transition temperature, TPT, of 544 (2) K on first heating; the corresponding transition on cooling is at 502 (2) K. The endotherm on subsequent heatings occurs reproducibly at TPT = 531 (2) K. Mass loss between ca 531 and 544 K, identified as included water, is rapid and continues more slowly to higher temperatures for a total loss of ca 0.

Experimental and theoretical investigation of the coarctate cyclization of (2-Ethynylphenyl)phenyldiazenes.

A new route to substituted 2-phenyl-2H-indazoles through the cyclization of (2-ethynylphenyl)phenyldiazenes is presented. A coarctate reaction pathway forms the isoindazole carbene under neutral conditions, at moderate temperatures, and without the requirement of a carbene stabilizer. A wide variety of previously unknown diazene precursors was synthesized and cyclized.