New phases containing tetrameric and pentameric mesitylcopper have been isolated from ether solvents and characterized with single-crystal X-ray diffraction. Mesitylcopper crystallized from toluene, which is a widely used reagent, has been found to contain one lattice solvent molecule. On the basis of these findings and cryoscopic molecular weight determinations, an equilibrium between a tetramer and pentamer in both etheral and aromatic solutions is proposed.

The crystal structures of [Pr(dbm)3H2O] (1), [Sm(dbm)3H2O] (2), and [Er(dbm)3H2O] (3) have been determined (dbm=dibenzoylmethane). They display seven-coordinate propeller-shaped molecules, which are chiral and crystallize as conglomerates in space group R3. Analysis of the crystal structures reveals supramolecular interactions, including formation of a quadruple helix, which explain how stereochemical information can be transferred between stacks of molecules. A method to quantify the ee in bulk samples of stereochemically labile compounds by using solid-state CD spectroscopy is described. Using this method, it has been shown that compounds 1-3 undergo total spontaneous resolution directly after synthesis, forming a microcrystalline reaction product that is essentially enantiopure. The resolution of bulk quantities of seven-coordinate complexes (without chiral or polydentate ligands) is thus reported for the first time. Because the crystallization starts without seeding, the overall preparation may be regarded as absolute asymmetric synthesis.

The reaction between Ti(0-i-Pr)4 and [Pb(0-i-Pr)2]= or Pb40(0-z-Pr)6 offers the mixed-metal oxoalkoxide Pb2-Ti2(M4-0)(M3-0-i-Pr)2(M-0-i-Pr)4(0-z-Pr)4 (1) which has been characterized by crystallography at -120 °C. 1 belongs to the monoclinic space group P2\ln with a = 10.286( 14) k,b = 22.564(4) Á, c = 18.709(5) Á, ß = 97.93(5), V = 4301(6) Á* 123, and Z = 4. Compound 1 represents the first example of a structurally characterized "single-source" precursor having a Pb:Ti stoichiometry appropriated for PbTiOg. The 1:1 stoichiometry between the metals is retained by reaction between 1 and acetic acid or acetylacetone (1:2 molar ratio), Pb2Ti20(0Ac)2(0i-Pr)g (2) and Pb2TÍ20(acac)2(0-z-Pr)8 (3) being obtained respectively. All compounds have been isolated in high yields and were characterized by microanalysis, FT-IR and NMR ( , 13C, and 207Pb). Hydrolysiscondensation reactions of the various species giving lead titanate have been achieved.

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The reaction between Mg(viph)2 (viph = o-vinylphenyl) and copper(I) chloride has been found to be the best way of preparing the homoleptic tetramer [Cu4(viph)4]. The MgR2 reagent crystallizes as monomeric [Mg(THF)2(viph)2] from a THF solution. In the reaction between the Grignard reagent (viph)MgBr and copper(I) chloride, two unstable mixed halide/aryl intermediates, [Mg(THF)6][Cu5(viph)2Br4]2·THF (3) and [Mg(THF)5Cl][Cu5(viph)4Br2]·THF (4), were isolated and found to reduce the yield of [Cu4(viph)4] markedly. The crystal structures of 3 and 4 were determined and were found to exhibit unusual coordination geometries for copper(I) and provide mechanistic information. Compound 3 was found to react with excess triphenylphosphine in THF, yielding [Cu(PPh3)3Br]·THF. It is suggested that [Cu4(viph)4], which is not π-coordinated in the solid state or in THF solution, may have important precursor qualities for the preparation of new organocopper compounds.