Gerald Linti

Iron coordination chemistry with tetra-, penta- and hexadentate bispidine-type ligands

Described is the synthesis of tetra-, penta- and hexadentate bispidine ligands with two tertiary amine and two, three or four additional donors (pyridine, phenolate or alcoholate; bispidine/3,7-diazabicyclo[3.3.1]nonanone, coordinating substituents at positions 2,4; 2,4,7; 2,3,4; 2,3,4,7) and of their hexa-coordinate iron(II) complexes. Crystal structural analyses reveal that all complexes are six-coordinate, with one or two co-ligands, and all structures with the tetradentate bispidine ligand are asymmetrical with respect to the two tertiary amine donors, with short Fe� /N 1 and long Fe� /N 2 bonds (N 1 : position 3, N 2 : position 7). This is the same structural type as found for the Jahn/Teller labile copper(II) compounds, the manganese(II) and chromium(III) complexes but different from copper(I), zinc(II) and some cobalt(II) complexes with M � /N 1 ]/M � /N 2 . Additional donors at N 2 modify the structures, but do not lead to a change to the other structural type; additional donors at N 1 lead to structures with M� /N 1 � /M� /N 2 . Solution studies (NMR, UV/Vis, electrochemistry, magnetism) indicate that the co-ligands may be substituted by solvent, with the donors trans to N 2 being more labile than those trans to N 1 , but the over-all structural properties in solution are similar to those in the solid state. The complexes are stable towards oxidation, all except one have high spin electronic configuration. The oxidation potentials strongly depend on the two co-ligands. # 2002 Elsevier Science B.V. All rights reserved.

Zur chemie des galliums, 61: Tris(trimethylsilyl) silylgallium(I) —eine experimentelle und theoretische studie☆☆☆

Abstract The gallium(I)tris(trimethylsilyl)silyl compound {GaSi(SiMe 3 ) 3 } 4 (1) is obtained by reaction of Ga 2 Cl 4 -2dioxane with LiSi(SiMe 3 ) 3 -3THF. The crystal structure of 1 reveals a tetramer with a nearly regular tetrahedral framework of gallium atoms. The gallium-gallium distances average 258.4 pm. Ab initio calculations on various substituted gallium tetrahedrons showed a greater stability of silyl-substituted cages compared with organyl substituted ones. Crystal data, with Mo K α radiation are as follows: {GaSi(SiMe 3 ) 3 } 4 · Si(SiMe 3 ) 4 ( 1 ), a , b = 1923.3(3) pm, c = 2671.2(4) pm, V = 9.881(3) nm 3 ; tetragonal space group P 4/ ncc ; Z = 4; 1513 ( I > 2 σ ( I )) data; RI = 0.068.

Oxidative Addition Reactions of Element–Hydrogen Bonds with Different Polarities to a Gallium(I) Compound

The gallium(I) derivative [Ga({N(dipp)CMe}(2)CH)] (1; dipp = 2,6-diisopropylphenyl) undergoes facile oxidative addition reactions with various element-hydrogen bonds including N-H, P-H, O-H, Sn-H, and H-H bonds. This was demonstrated by its reaction with triphenyltin hydride, ethanol, water, diethylamine, diphenylphosphane, and dihydrogen. All products were characterized by means of single-crystal X-ray structure determination, NMR spectroscopy, IR spectroscopy, and mass spectrometry.

On the chemistry of gallium ☆: Part 19. Synthesis and crystal structure analysis of novel complexes containing Ga–FeCp(CO)2-fragments

Abstract The gallium subhalides Ga2Cl4·2dioxane and sonochemically prepared GaI were reacted with the carbonyl ferrate K[Cp(CO)2Fe] and the iron carbonyl dimer [Cp(CO)2Fe]2, respectively. In all the reactions performed, the gallium(I) and gallium(II) compounds disproportionated into elemental gallium and gallium(III) compounds. Several novel complexes containing Ga–FeCp(CO)2 fragments were isolated and characterized spectroscopically and by X-ray crystal structure analysis. These are compounds of the types Cp(CO)2FeGaX2(B) [B=THF, dioxane, I−[FeCp(C7H8)]+; X=Cl, I] and [Cp(CO)2Fe]2GaCl(B) [B=THF, 0.5 KCl]. In addition, the cage compounds [Cp(CO)2FeGa]6(μ3-O)4(μ-OH)2I2 and [Cp(CO)2FeGa]4FeK2(OEt2)4(μ3-O)2(μ-Br)4(μ3-Br)4 were isolated. In all these complexes the gallium atoms are surrounded tetrahedrally by substituents. GaFe bond lengths are in the range of 231–239 pm.

Tri(supersilyl)dialanyl (tBu3Si)3Al2• and Tetra(supersilyl)cyclotrialanyl (tBu3Si)4Al3• − New Stable Radicals of a Group 13 Element from Thermolysis of (tBu3Si)4Al2

The thermolysis of tetra(supersilyl)dialane R*2Al−AlR*2 (R* = SitBu3 = Supersilyl) in heptane or cyclohexane at 50 °C leads under Al−Al dissociation reversibly to monoalanyl radicals [R*2Al]•, which could be trapped by hydrogen or iodine (formation of R*2AlH, R*2AlI). Simultaneously, SiAl dissociation and elimination of supersilyl radicals tBu3Si• leads irreversibly and slowly to radicals [R*2Al−AlR*]•, the existence of which could be established by ESR spectroscopy. The structure was clarified by ab initio calculations (nearly planar Si2Al−AlSi and linear Al−Al−Si skeleton; short Al−Al distance). By thermolyzing R*2Al−AlR*2 at 100 °C, the radical [R*4Al3]• (ESR spectroscopically detected) and the tetrahedro-tetraalane R*4Al4 (NMR spectroscopically seen) are formed via radicals [R*3Al2]•; the supersilyl radicals tBu3Si•, formed at the same time, are stabilized by dimerization to superdisilane R*−R* and by taking up hydrogen, giving supersilane R*−H. According to X-ray structure analysis, the Al atoms in [R*4Al3]• are located at the corners of a triangle; one Al atom is connected with two groups R*, the remaining two Al atoms each bind one substituent R* in different ways.

Strukturen zweifach metallierter Derivate von 3, 3-Dimethyl-1, 5-bis(trimethylsilyl)-1, 5-diaza-pentan mit Lithium und Aluminium sowie zweier Donor-substituierter Digallane

Durch Metallierung des Diaminopropan-Derivats Me2C[CH2N(H)SiMe3]2 mit n-Butyllithium bzw. Lithiumtetrahydridoaluminat bilden sich Me2C[CH2N(Li)SiMe3]2 und Me2C[CH2N(Li)SiMe3][CH2N(AlH2)SiMe3]. Beide Verbindungen liegen dimer mit zentralem achtgliedrigen Li4N4- bzw. Li2Al2N4-Ring vor. Me2C[CH2N(Li)SiMe3]2 reagiert mit Ga2Cl4 · 2Dioxan u.a. zum entsprechenden Tetra(amino)digallan. Dieses liegt im Unterschied zum dimeren tetraalkoxysubstituierten Digallan, Ga4OtBu8, monomer vor. Alle Verbindungen wurden mittels Einkristall-Rontgenstrukturanalyse untersucht. Structural Characterization of Bis(metallated) Derivatives of 3, 3-Dimethyl-1, 5-bis(trimethylsilyl)-1, 5-diaza-pentane with Lithium and Aluminum and of two Donor-substituted Digallanes The diaminopropane derivative Me2C[CH2N(H)SiMe3]2 is metallated with n-butyllithium and lithium tetrahydridoaluminate to obtain Me2C[CH2N(Li)SiMe3]2 and Me2C[CH2N(Li)SiMe3][CH2N(AlH2)SiMe3], respectively. Both compounds exhibit a central eight-membered ring, Li4N4 or Li2Al2N4. Me2C[CH2N(Li)SiMe3]2 reacts with Ga2Cl4 · 2dioxane under formation of the corresponding tetra(amino)digallane. This is monomeric, in contrast to a dimeric tetraalkoxy-substituted digallane, Ga4OtBu8. All compounds were characterized by single crystal X-ray crystallography.

A Silatetragallane—Classical Heterobicyclopentane or closo‐Polyhedron?

Classical and nonclassical can be used to describe the bonding in the polyhedral Ga4 Si framework of the silagallanate ion [Me3 SiSi{GaSi(SiMe3 )3 }3 GaSiMe3 ]- (the GaSi framework is depicted in the picture). This is the result of density functional calculations that were carried out on model compounds. The cluster was obtained by ultrasonication of gallium and iodine and subsequent reaction with (Me3 Si)3 Li(thf)3 .

Oxidation of Diiron and Triiron Sulfurdithiolato Complexes: Mimics for the Active Site of (FeFe)-Hydrogenase

The oxidation of the hexacarbonyl(1,3‐dithiolato‐S,S′)diiron complexes 4a–4c with varying amounts of dimethyldioxirane (DMD) was systematically studied. The chemoselectivity of the oxidation products depended upon the substituent R (R=H, Me, 1/2 (CH2)5). For R=H, four oxidation products, 6a–6d, have been obtained. In the case of R=Me, three products, 7a–7c, were formed, and for R=1/2 (CH2)5, only complex 8 was observed. These observations are due to steric and electronic effects caused by the substituent R. Additionally, oxidation of the triiron complex 5 with DMD was performed to yield the products 9a and 9b. X‐Ray diffraction analyses were performed for 6a–6d, 7a, and 7c, as well as for 9a and 9b. The electronic properties were determined by density‐functional theory (DFT) calculations.

THE X-RAY STRUCTURE OF FE(FULVENE)2: THE MISSING LINK IN THE DIRECT SYNTHESIS OF ANSA- AND CPI-METALLOCENES (CPI = C5H4CHME2)

Abstract The compound (ethene) 2 (toluene)iron ( 1 ) is prepared by cocondensation of iron and toluene and subsequent treatment with ethene. Reaction of ( 1 ) with 6,6-dimethylfulvene leads to the known products ansa-ferrocens and 1,1′-bis(isopropyl)ferrocene. Reaction of ( 1 ) with 6,6-diphenylfulvene ( 2 ) gives 1,1′-bis(benzhydryl)ferrocene ( 3 ). The intermediate in the formation of ( 3 ), bis(diphenylfulvene)iron ( 4 ) was isolated. ( 4 ) was characterized by MS and a X-ray structure determination and its structure compared with the structure of the free ligand ( 2 ). The structure of ( 4 ) was also determined by DFT-ab-initio calculations.

Oxidative N-dealkylation in cobalt–bispidine–H2O2 systems

The reaction of the Co(II) complex with the rigid bispidine ligand L1 with two tertiary amine and two pyridine donors, [Co(II)(L1)(OH2)2]2+, with H2O2 and O2 produces [Co(II)(L2)(OH2)2]3+, where L2 is demethylated at one of the amine donors, and CH2O.