Markus Hummert

One- and Two-Electron-Transfer Reactions of (dpp-Bian)Sm(dme)3

The reduction of 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian) with an excess of samarium in 1,2-dimethoxyethane (dme) affords the Sm(II) complex (dpp-Bian)Sm(dme)(3) (1). The reaction of 1 with 0.5 mol equiv of 1,2-dibromostilbene proceeds with the formation of the dimeric Sm(III) complex [(dpp-Bian)SmBr(dme)](2) (2). Oxidation of both the metal and the dpp-Bian ligand takes place if 1 is reacted with equimolar amounts of 1,2-dibromostilbene or iodine, yielding the monomeric Sm(III) derivatives (dpp-Bian)SmBr(2)(dme) (3) and (dpp-Bian)SmI(2)(THF)(2) (4; THF = tetrahydrofuran), respectively. The reaction of 1 with 0.5 mol equiv of iodine followed by 0.5 mol equiv of tetramethylthiuram disulfide gives the Sm(III) complex (dpp-Bian)SmI[SC(S)NMe(2)](dme) (5). Compound 4 and tBuOK react with the formation of the iodine-bridged dimer [(dpp-Bian)SmI(OtBu)(THF)](2) (6). Complexes 1 and 2 have been characterized by (1)H NMR spectroscopy and complexes 2-6 by their molecular structures, which were determined by single-crystal X-ray diffraction.

Oxidation by oxygen and sulfur of Tin(IV) derivatives containing a redox-active o-amidophenolate ligand.

Oxidation of tin(IV) o-amidophenolate complexes [Sn(ap)Ph(2)] (1) and [Sn(ap)Et(2)(thf)] (2) (ap=dianion of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (ImQ)) with molecular oxygen and sulfur in toluene solutions was investigated. The reaction of oxygen with 1 at room temperature forms a paramagnetic derivative [Sn(isq)(2)Ph(2)] (3) (isq=radical anion of ImQ) and diphenyltin(IV) oxide [{Ph(2)SnO}(n)]. Interaction of 1 with sulfur gives another monophenyl-substituted paramagnetic tin(IV) complex, [Sn(ap)(isq)Ph] (4), and the sulfide, [Ph(3)Sn](2)S. The oxidation of 2 with oxygen and with sulfur proceeds through the derivative [Sn(isq)(2)Et(2)] (7), which undergoes alkyl elimination to give two new tin(IV) compounds, [Sn(ap)(isq)Et] (5) and [Sn(ap)(EtImQ)Et] (6) (EtImQ=2,4-di-tert-butyl-6-(2,6-diisopropylphenylimino)-3-ethylcyclohexa-1,4-dienolate ligand), respectively, along with the corresponding alkyltin(IV) oxide and sulfide. Complexes 3-5 and 7 were studied by EPR spectroscopy. The structures of 3, 4 and 6 were investigated by X-ray analysis.

Magnetic properties and molecular structures of binuclear (2-pyrazinecarboxylate)-bridged complexes containing Re(IV) and M(II) (M = Co, Ni)

Three novel Re(iv) compounds, the mononuclear complex Bu(4)N[ReBr(5)(Hpyzc)] (1) and the heterobimetallic complexes [ReBr(5)(mu-pyzc)M(dmphen)(2)].2CH(3)CN [M = Co (2), Ni (3)] (Hpyzc = 2-pyrazinecarboxylic acid, dmphen = 2,9-dimethyl-1,10-phenanthroline), have been synthesized and their crystal structures determined by single-crystal X-ray diffraction. The structure of 1 consists of [ReBr(5)(Hpyzc)](-) complex anions and tetrabutylammonium cations, Bu(4)N(+). The Re(iv) is surrounded by five bromide anions and a N-donor Hpyzc monodentate ligand, in a distorted octahedral environment. The structures of 2 and 3 consist of dinuclear units [ReBr(5)(mu-pyzc)M(dmphen)(2)], with the metal ions linked by a pyzc bridge ligand, being bidentate toward M(II) and monodentate toward Re(IV). The environment of Re(IV) is the same as in 1, whereas M(II) is six-coordinate, being surrounded by four nitrogen atoms of two bidentate dmphen ligands and one oxygen atom and one nitrogen atom of the pyzc anion. The magnetic properties of 1-3 were investigated in the temperature range 2.0-300 K. 1 shows the expected magnetic behavior for a mononuclear Re(IV) complex with a weak intermolecular antiferromagnetic coupling at low temperatures. The bimetallic complexes exhibit an intramolecular ferromagnetic coupling between Re(IV) and the M(II) ion (Co, Ni).

Organometallic Compounds of the Lanthanides 182 (1). Calcium and Neodymium Complexes Containing the dpp-BIAN Ligand System: Synthesis and Molecular Structure of ((dpp-BIAN)CaI(THF) 2 ) 2 and ((dpp-BIAN)NdCl(THF) 2 ) 2

Oxydation of (dpp-BIAN)Ca(THF)4 with 0.5 equiv. of I2 in THF yields [(dpp-BIAN)CaI(THF)2]2 (1). A corresponding neodymium compound [(dpp-BIAN)NdCl(THF)2]2 (2) has been obtained by reaction of (dpp-BIAN)Na2 with NdCl3 in THF. The X-ray single crystal structure analyses show 1 and 2 to be isostructural dimers containing octahedrally coordinated metal atoms bridged by the respective halides. The chelating dpp-BIAN ligand acts as a radical anion in the Ca2+ complex 1 and as a dianion in the Nd3+ complex 2, respectively.

New Synthetic Routes for 1-Benzyl-1,4,7,10-tetraazacyclododecane and 1,4,7,10-Tetraazacyclododecane-1-acetic Acid Ethyl Ester, Important Starting Materials for Metal-coded DOTA-Based Affinity Tags

Two improved routes to synthesize 1-benzyl-1,4,7,10-tetraazacyclododecane (6) and 1,4,7,10- tetraazacyclododecane-1-acetic acid ethyl ester (11) are described as well as the synthesis of 1-{2-[4-(maleimido-N-propylacetamidobutyl)amino]-2-oxoethyl}-1,4,7,10-tetraazacyclododecane- 4,7,10-triacetic acid (17) and its Y, Ho, Tm, and Lu complexes. The 1H and 13C NMR spectra of the new compounds as well as the single crystal X-ray structure analyses of the intermediates 4-benzyl-1,7-bis(p-toluenesulfonyl)diethylenetriamine (3) and 1,4,7-tris(p-toluenesulfonyl)diethylenetriamine (7) are reported and discussed. The rare earth complexes of 17 have been characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry.

Solvent dependent reactivity: solvent activation vs. solvent coordination in alkylphosphane iron complexes

The pyridine-derived tetrapodal tetraphosphane C5H3N[CMe(CH2PMe2)2]2 is susceptible to selective protonolysis of a phosphorus-carbon bond in the presence of iron(II) salts. Water produces dimethylphosphinic acid, Me2POH, and protonates the anionic remainder of the tetraphosphane. The resulting iron(II) complexes and (tetrafluoroborate and perchlorate salts, respectively) contain the residual chelate ligand in which a methyl group, derived from the ligand skeleton, is in agostic interaction with the metal centre, and in which Me2POH, unavailable in the free state owing to rapid tautomerisation, is metal-coordinated and thus stabilised. Full NMR details are presented, including 31P simulations. The reactivity towards alcohols is similar (compounds), and has been studied using deuterium labels (NMR). P-C bond cleavage may be suppressed only if all protic agents are rigorously excluded, as in the reaction of with Fe(SO3CF3)2.2CH3CN in acetonitrile solution, which produces the complex [Fe(NCMe)](SO3CF3)2. In it, the ligand acts as an NP4 coordination cap but is severely distorted from square-pyramidal geometry. The reaction of with anhydrous ferrous bromide, FeBr2, in methanol again produces a dimethylphosphinic acid ester ligand, but the complex now contains ferric iron coordinated by a carbanionic residual chelate ligand, implicating H+ as the oxidising agent under these conditions. Full spectroscopic and X-ray structural details are presented for all compounds.

Übergangsmetall- und Lanthanoid-Komplexe von 1,4,7,10-Tetraallylund 1,4,7,10-Tetra-3-butenyl-1,4,7,10-tetraazacyclododecan

1,4,7,10-Tetraazacyclododecane (1) reacts with allylbromide and 3-butenylbromide giving 1,4,7,10-tetraallyl-1,4,7,10-tetraazacyclododecane (TAC) (2a) and 1,4,7,10-tetra-3-butenyl-1,4,7,10- tetraazacyclododecane (TBC) (2b), respectively. Compounds 2a and 2b react with FeCl2, CoCl2, RhCl3, NiCl2, CuBr2, and TmCl3 forming the complexes [FeCl(TAC)]Cl (3a), [FeCl(TBC)]Cl (3b), [CoCl(TAC)]Cl (4), [RhCl(TAC)]Cl2 (5), [NiCl(TAC)]Cl (6a), [NiCl(TBC)]Cl (6b), [CuBr(TAC)]Br (7), [TmCl(TAC)]Cl2 (8a), and [TmCl(TBC)]Cl2 (8b). The reaction of 6a with an excess of CuCl affords a coordination polymer in which [NiCl(TAC)]+ cations are connected by [Cu6Cl8]2− anions (9). The 1H and 13C NMR spectra of 2a, 2b, 5, and 6a, as well as the single crystal X-ray structures of 2a ・3HCl, 6a, 6b, 7, and 9 are reported and discussed. Graphical Abstract Übergangsmetall- und Lanthanoid-Komplexe von 1,4,7,10-Tetraallylund 1,4,7,10-Tetra-3-butenyl-1,4,7,10-tetraazacyclododecan

Electron Release and Proton Acceptance Reactions of (dpp-BIAN)Mg(THF) 3

(dpp-BIAN)Mg(THF)3 (1) (dpp-BIAN = 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene) and (PhCOO)2 react with splitting of the peroxide bridge and formation of the dimeric magnesium benzoate [(dpp-BIAN)MgOCOPh(THF)]2 (2). The reaction of 1 with PhCOOH yields the dimeric magnesium benzoate [(dpp-BIAN)(H)MgOCOPh(THF)]2 (3), whereas 1 and furanyl-2-carboxylic acid react with liberation of hydrogen and formation of (dpp-BIAN)Mg[OCO(2-C4H3O)]2 Mg(dpp-BIAN)(THF) (4). Compounds 2, 3, and 4 have been characterized by elemental analysis, IR spectroscopy, and X-ray structure analysis, compound 3 also by 1H NMR spectroscopy. The eightmembered metallacycles of the centrosymmetric dimers 2 and 3 are almost completely planar. The two magnesium atoms in 4 show different coordination spheres; one is surrounded by its ligands in a trigonal bipyramidal manner, the other one in a tetrahedral fashion. The Mg···Mg separations in 2, 3 and 4 are 4.236, 4.296, and 4.030 Å, respectively

Synthesis and structures of new conformationally rigid 1-aza-1,3-dienes of the acenaphthene series

The Wittig reaction of 1-tert-butyliminoacenaphthen-2-one with benzylidenetriphenylphosphoranes produces new 1-aza-1,3-dienes of the acenaphthene series, which can bind butyllithium to the C=C bond of the enimine fragment C=C-C=N.

Deca(4-methylbenzyl)ferrocen und -stannocen

Cyclopentadiene reacts with five equivalents of 4-methylbenzylalcohol (1:5,6 mole ratio) and sodium yielding penta(4-methylbenzyl)cyclopenta-2,4-diene (1), which upon treatment with butyl lithium affords the lithium salt [(4-MeC 6 H 4 CH 2 ) 5 C 5 ]Li (2). The reactions of 2 with FeCl 2 and SnCl 2 result in the formation of deca(4-methylbenzyl)ferrocene (3) and deca(4-methylbenzyl)stannocene (4), respectively. The 1 H and 1 3 C NMR, IR and mass spectra of the new compounds as well as the single crystal X-ray structure analysis of 1 are reported and discussed.