2, 4‐Dimethylpenta‐1, 3‐dien‐ und 2, 4‐Dimethylpentadienyl‐Komplexe des Rhodiums und Iridiums

2, 4‐Dimethylpenta‐1, 3‐diene and 2, 4‐Dimethylpentadienyl Complexes of Rhodium and Iridium The complexes [(η⁴‐C₇H₁₂)RhCl]₂ ( 1 ) (C₇H₁₂ = 2, 4‐dimethylpenta‐1, 3‐diene) and [(η⁴‐C₇H₁₂)₂IrCl] ( 2 ) were obtained by interaction of C₇H₁₂ with [(η²‐C₂H₄)₂RhCl]₂ and [(η²‐cyclooctene)₂IrCl]₂, respectively. The reaction of 1 or 2 with CpTl (Cp = η⁵‐C₅H₅) yields the compounds [CpM(η⁴‐C₇H₁₂)] ( 3a : M = Rh; 3b : M = Ir). The hydride abstraction at the pentadiene ligand of 3a , b with Ph₃CBF₄ proceeds differently depending on the solvent. In acetone or THF the “half‐open” metallocenium complexes [CpM(η⁵‐C₇H₁₁)]BF₄ ( 4a : M = Rh; 4b : M = Ir) are obtained exclusively. In dichloromethane mixtures are produced which additionally contain the species [(η⁵‐C₇H₁₁)M(η⁵‐C₅H₄CPh₃)]BF₄ ( 5a : M = Rh; 5b : M = Ir) formed by electrophilic substitution at the Cp ring, as well as the η³‐2, 4‐dimethylpentenyl compound [(η³‐C₇H₁₃)Rh{η⁵‐C₅H₃(CPh₃)₂}]BF₄ ( 6 ). By interaction of 2, 4‐dimethylpentadienyl potassium with 1 or 2 the complexes [(η⁴‐C₇H₁₂)M(η⁵‐C₇H₁₁)] ( 7a : M = Rh; 7b : M = Ir) are generated which show dynamic behaviour in solution; however, attempts to synthesize the “open” metallocenium cations [(η⁵‐C₇H₁₁)₂M]⁺ by hydride abstraction from 7a , b failed. The new compounds were characterized by elemental analysis and spectroscopically, 4b and 5a also by X‐ray structure analysis.     

Natriumkomplexe mit Salicylideniminen: Synthesen,Strukturen, CO2‐Aufnahme und Carboxylierung von 2‐Fluorpropiophenon bzw. Estronmethylether

Chiral salicylidenphenethylamines (R)‐HA or (S)‐HA , 2‐salicylidenfurfuryl‐imines HB , and 2‐salicylidenaminoethanol HC react with sodium hydride or sodium hexamethyldisilylamide to form the sodium complexes [Na(R)‐A] ₄ · 0,5 Et ₂ , [Na(S)‐A] ₄ · 0,5 Et ₂ O (1) , [NaB] ₄ · 0,5 Ph‐Me (2) and [(dme)NaC] ₄ (3) . In the presence of 18‐crown‐6 the complex [Na(18‐crown‐6)(thf) ₂ ] ₂ [Na ₂ (C)] ₄ · THF (4) can also be isolated. The crystal structure analyses of both 1 and 2 show that heterocubane structures with a Na₄O₄ frame work are formed. Additionally, the imine nitrogen atom is bonded at the Na atom which has the coordination number 4 in 1 . Additional coordination of the furfuryl oxygen atom results in the coordination number five for the sodium atom in 2 . In 3 which is also a tetramer, two Na₂O₂ units are connected via two imino‐ethanol bridges Na(1)‐N(=CH‐phenolat)‐CH₂CH₂‐OH‐Na(2A). The crystal structure analysis displays that 4 is an ionic compound consisting of two [(thf)₂Na(18‐crown‐6)]⁺ cations and the dinuclear dianion [Na ₂ (C) ₄ ] ^2? . Both 1 and 2 are carboxylation reagents which transfer CO₂ to 2‐fluoropropiophenone. 1 is more active than 2 , but 3 and 4 are inactive.     

Zur Reaktivität von dinuklearen Platina‐β‐diketonen gegenüber Phosphanen: Diacetylplatin(II)‐Komplexe und mononukleare Platina‐β‐diketone

The Reactivity of Dinuclear Platina‐β‐diketones with Phosphines: Diacetylplatinum(II) Complexes and Mononuclear Platina‐β‐diketones Addition of mono‐ and bidentate phosphines or of AsPh₃ to the platina‐β‐diketone [Pt₂{(COMe)₂H}₂(μ‐Cl)₂] ( 1 ) followed by the addition of NaOMe at ?70 °C resulted in the formation of diacetyl platinum(II) complexes cis‐[Pt(COMe)₂L₂] (L = PPh₃, 2a ; P(4‐FC₆H₄)₃, 2b ; PPh₂(4‐py), 2c ; PMePh₂, 2d ; AsPh₃, 2d ) and [Pt(COMe)₂(L??L)] (L??L = dppe, 3b ; dppp, 3c ), respectively. The analogous reaction with dppm afforded the dinuclear complex cis‐[{Pt(COMe)₂}₂(μ‐dppm)₂] ( 4 ) that reacted in boiling acetone yielding [Pt(COMe)₂(dppm)] ( 3a ). The reactions 1 → 2 / 3 were found to proceed via thermally highly unstable cationic mononuclear platina‐β‐diketone intermediates [Pt{(COMe)₂H}L₂]⁺ and [Pt{(COMe)₂H}(L??L)]⁺, respectively, that could be isolated as chlorides for L??L = dppe ( 5a ) and dppp ( 5b ). The reversibility of the deprotonation of type 5 complexes with NaOMe yielding type 3 complexes was shown by the protonation of the diacetyl complex 3b with HBF₄ yielding the platina‐β‐diketone [Pt{(COMe)₂H}(dppe)](BF₄) ( 5c ). All compounds were fully characterized by means of NMR and IR spectroscopies, and microanalyses. X‐ray diffraction analysis was performed for the complex cis‐[Pt(COMe)₂(PPh₃)₂]·H₂O·CHCl₃ ( 2a ·H₂O·CHCl₃).     

CO2‐Speicherung. Chancen und Risiken

Anthropogenic emissions of carbon dioxide (CO₂) into the atmosphere have had a significant impact on the Earth's carbon cycle. As part of the global effort to reduce climate change, the geological storage of CO₂ has been accepted as a method that may provide up to 25 % of the total reduction of emissions, although this figure is still subject to change. In Germany and worldwide, geological storage capacities are expected to be sufficient for several decades. Carbon dioxide can be captured from sources such as large‐scale industrial (energy, steel, cement or chemical) facilities and transported to long‐term storage sites in deep saltwater‐bearing aquifers. Above the porous sandstone reservoirs in which the CO₂ is to be stored, an impermeable cap rock is required to provide a barrier for the upward‐migrating gas. In time, a significant quantity of the CO₂ can be retained within the reservoir pore space by capillary forces, dissolved in water to form carbonic acid, or deposited as carbonate minerals. The storage site must be free of potential leakage pathways. To this end, extensive monitoring programs need to be carried out. The Ketzin pilot site, an example of such a program, has shown CO₂ storage on a research scale to be safe and reliable.     

Synthesis of β‐Haloketones by β‐Addition Reactions of α,β‐Unsaturated Ketones with BX3 (X = Br,Cl) as Halide Source

A series of β‐bromoketones and β‐chloroketones were synthesized by the addition reactions of α,β‐unsaturated ketones under BX₃ (X = Br, Cl) and ethylene glycol reaction system. The α,β‐unsaturated ester also was successfully converted to its corresponding β‐bromoester under the reaction condition.     

Eisen- und Mangankomplexe mit sauerstoff-, schwefel- und methylen-verbrückten Distibanen und mit Chlorodiphenylstiban als Liganden

Complexes of Iron and Manganese with Oxygen-, Sulfur-, and Methylene-bridged Distibines and with Chlorodiphenylstibine as Ligands The photochemical reaction of CO₃Fe[P(OPh)₃]₂ and of MeCpMn(CO)₃ with the stibines Ph₂SbCl and (Ph₂Sb)₂X (X = O, S and CH₂) yields mononuclear complexes (CO)₂[P(OPh)₃]₂FeL and °Cp(CO)₂MnL (L = Ph₂SbCl, (Ph₂Sb)₂X) and the stibine bridged binuclear complexes °CO)₂[P(OPh)₃]₂Fe{(Ph₂Sb)₂X}Fe(CO)₂[P(OPh)₃]₂ and °Cp(CO)₂Mn{(Ph₂Sb)₂X}Mn(CO)₂MeCp.     

Photochemische Reaktionen von Cyclopentadienylbis(ethen)rhodium mit Phenanthren,Acenaphthylen und Triphenylen,sowie ungewöhnlicher H-Austausch zwischen η2-koordinierten Phenanthren- bzw. Acenaphthylen- und η5-Cyclopentadienyl-Liganden

Photochemical Reactions of Cyclopentadienylbis(ethene)rhodium with Phenanthrene, Acenaphthylene, and Triphenylene, and Unusual H Exchange between η²-Coordinated Phenanthrene or Acenaphthylene and η⁵-Cyclopentadienyl Ligands During UV irradiation of [CpRh(C₂H₄)₂] (Cp = η⁵-C₅H₅) in hexane/ether in the presence of phenanthrene one ethene ligand is displaced by coordination of the 9,10 double bond of phenanthrene, and (η⁵-cyclopentadienyl) (η²-ethene)(η²-9,10-phenanthrene)rhodium ( 1 ) is formed. The analogous reaction in hexane in the presence of acenaphthylene occurs with formation of the complexes (η²-1,2-acenaphthylene)(η⁵-cyclopentadienyl)(²-ethene)rhodium 2 and bis(η²-1,2-acenaphthylene)(η⁵-cyclopentadienyl)rhodium 3 in which one and two ethene molecules of [CpRh(C₂H₄)₂], respectively, are substituted by η²-1,2-acenaphthylene. The irradiation of [CpRh(C₂H₄)₂] with triphenylene in hexane yields the compounds [CpRh(η⁴-1,2,3,4-triphenylene)] ( 4 ), [(CpRh)₂(μ-η³: η³-triphenylene)] ( 5 ), and [(CpRh)₃(μ₃-η²: η²: η²-triphenylene)] ( 6 ). Despite the partially very low yields the new complexes could be unequivocally characterized spectroscopically and in the case of 1 and 3 by X-ray structural analysis. The compounds 1 and 2 in solution reveal a novel dynamic behaviour; via an intramolecular C? H activation, exchange occurs between the protons of the η²-coordinated arene and the Cp ligand. The complex 4 in solution is fluxional, too.