title: Preparation and characterization of asymmetric alpha-alkoxy dipyrrin ligands and their metal complexes.
abstract: Asymmetric alpha-substituted dipyrrins have been synthesized and characterized. The compounds were formed by a metal mediated reaction involving a single alkoxy group substituted into the alpha-position of an alpha,beta-unsubstituted dipyrrin. An alpha-methoxy dipyrrin, 5-(4-cyanophenyl)-1-methoxydipyrrin (alpha-OMe-4-cydpm), was prepared from 5-(4-cyanophenyl)-4,6-dipyrromethane. Methoxy, ethoxy, and propoxy derivatives (alpha-OMe-4-mecdpm, alpha-OEt-4-mecdpm, alpha-OPr-4-mecdpm) of 5-(4-methoxycarbonylphenyl)-4,6-dipyrromethane have also been prepared. A homoleptic, bis(1-methoxy)dipyrrinato zinc(II) complex, [Zn(alpha-OMe-4-mecdpm)(2)], has been synthesized, as has a heteroleptic cobalt(III) complex with one alpha-OMe-4-cydpm ligand and two unsubstituted 5-(4-cyanophenyl)dipyrrin (4-cydpm) ligands ([Co(alpha-OMe-4-cydpm)(4-cydpm)(2)]). The rotational barrier of the meso-aryl substituent of [Zn(alpha-OMe-4-mecdpm)(2)] was found to be 17.3 kcal mol(-1) by variable-temperature NMR spectroscopy. The compounds alpha-OMe-4-cydpm and [Zn(alpha-OMe-4-mecdpm)(2)] have also been characterized by X-ray diffraction. The formation of the new dipyrrin derivatives is shown to be general and can be performed on dipyrrins with various meso-aryl substitutents, with a variety of alcohols, and can be promoted by several metal salts.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, Calfornia 92093-0358, USA.
authors.forename: Sara R
authors.initials: SR
authors.lastname: Halper
authors.forename: Jay R
authors.initials: JR
authors.lastname: Stork
authors.forename: Seth M
authors.initials: SM
authors.lastname: Cohen
mesh_terms: D000438:Alcohols; D003035:Cobalt / Q000737:chemistry; D018360:Crystallography, X-Ray; D007202:Indicators and Reagents; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D016877:Oxidants / Q000737:chemistry; D011758:Pyrroles / Q000737:chemistry*; D012996:Solutions; D012997:Solvents; D021241:Spectrometry, Mass, Electrospray Ionization; D015032:Zinc / Q000737:chemistry
chemical_list: D000438:Alcohols; D007202:Indicators and Reagents; D008024:Ligands; D008670:Metals; D009942:Organometallic Compounds; D016877:Oxidants; D011758:Pyrroles; D012996:Solutions; D012997:Solvents; D003035:Cobalt; D015032:Zinc