Carbene complexes, bis(imido) complexes, and titanium alkyne hydroamination catalysts

Several new chelating dipyrrolyl ligands based on N,N-di(pyrrolyl-alpha-methyl)- N-methylamine (dpma) have been synthesized, including a compound containing a norborn-enyl group (H2dpna) and a compound containing a chiral menthyl group (H2dpCHIRA). Dipyrrolylmethane derivatives have also been investigated as chelating dipyrrolyl ligands for metal complexes.;The group-6 complexes M(NBut)2(dpma), where M = Cr, Mo, and W, have been synthesized and characterized by single-crystal x-ray diffraction, which shows that the axial imido ligand is significantly bent compared to the linear imido group. Variable temperature 1H NMR indicates that the imido ligands remain inequivalent from -80°C to +80°C. 1H, 13C, and 14N NMR data have been used to investigate the imido group inequivalencies. DFT calculations have been performed to determine the energies associated with straightening the axial (bent) imido ligand, and indicate that the spectroscopic differences between the two imido ligands is due to the different chemical environments (axial versus equatorial).;The dpma ligand has been incorporated into several different molybdenum and ruthenium alkylidene species. These five-coordinated complexes do not perform metathesis reactions, probably due to steric and electronic effects imposed by the dpma ligand. Another complex containing the 5,5-dimethyldipyrrolylmethane ligand (dmpm), shows metathesis activity at elevated temperatures, but decomposition of the complex at these temperatures prohibits the use of this complex as a metathesis catalyst.;The first group-6 imido self-tethered alkylidene has been prepared. The tethered complex shows no sign of ring strain. The complex is unstable to alkoxide substitution.;Cyclooctyne has been found to react in a [2+2] manner with molybdenum and tungsten bis(imido) dichloride complexes. The alkylidene product isolated in both cases contains two equivalents of cyclooctyne, and is stable to metathesis conditions. Chemical and thermal decomposition of these complexes results in a novel pyrrole containing the two cyclooctyne molecules. The tungsten complex reacts with 50% aqueous sulfuric acid to yield a dinuclear mu-oxo oxide complex containing the inserted cyclooctyne molecules.;Titanium complexes containing the dpma and dmpm ligands, as well as Ti(NMe 2)4, have been found to be active catalysts for the hydroamination of alkyne with amines. These catalysts exhibit different selectivity, indicating that the active catalysts in each case is different.