CO-induced ring-slippage reactions of molybdenocene and tungstenocene carbonyl complexes. Electrochemical and elevated-pressure infrared evidence for an electron-transfer catalysis
Abstract Infrared studies at a CO pressure of 120 bar show (η 5 -C 5 H 5 ) 2 W(CO) to be completely resistant to an excess of CO in the absence of oxidants, but cyclovoltammetric measurements with this complex and with (η 3 -C 5 H 5 )(η 5 -C 5 H 5 )W(CO) 2 in THF solution at 0°C indicate that the ring-slipped dicarbonyl complex is catalytically generated by a one-electron oxidation of the tungstenocene monocarbonyl under CO at ambient pressure. Similar results are found for the reaction of (η 5 -C 5 H 5 ) 2 Mo(CO) with CO.
Reaktivität von Metall‐Metall‐Bindungen. Bildung und Zerfall einfacher Metallcarbonyl‐Zweikernkomplexe als Gleichgewichtsreaktion
Durch Kombination der 17-Elektronen-Metallcarbonyl-Bausteine Cp(CO)3Cr, Cp(CO)3Mo, Cp(CO)3 W, (CO)5Mn, Cp(CO)2Fe, (CO)4Co und Cp(CO)Ni sind die sieben bekannten homonuclearen sowie 21 heteronucleare Zweikernkomplexe mit Metall-Metall-Bindung denkbar. Alle diese heterodinuclearen Komplexe entstehen in benzolischer Losung aus Mischungen der entsprechen den homodinuclearen Verbindungen. Die acht bisher nicht beschriebenen und alle bekannten Hetero-Zweikernkomplexe sind so leichter zuganglich als mit den bisher verwendeten Verfahren. Die Reaktionen fuhren zu Gleichgewichtsgemischen, die in gleicher Weise von den zwei homodinuclearen wie von den reinen heterodinuclearen Komplexen aus erreicht werden. Bei Beteiligung der Bausteine Cp(CO)3Cr, (CO)4Co und Cp(CO)Ni liegen die Gleichgewichte mit drei Ausnahmen vollstandig auf der Seite der gemischten Verbindungen. Die aufgefundene Aquilibrierungsreaktion ist von prinzipieller Bedeutung fur die Chemie der Metall-Metall-Bindungen. 
 
 
 
Reactivity of Metal-Metal Bonds. Formation and Fragmentation of Simple Dinuclear Metal-Carbonyl Complexes as an Equilibrium Reaction 
 
 
 
By combination of the 17-electron carbonylmetal units Cp(CO)3Cr, Cp(CO)3Mo, Cp(CO)3W, (CO)5Mn, Cp(CO)2Fe, (CO)4Co, and Cp(CO)Ni the seven homonuclear as well as 21 heteronuclear dimetal complexes with metal-metal bonds can be conceived. All these heterodinuclear complexes are formed in benzene solution from mixtures of the corresponding homodinuclear compounds. The eight hitherto unreported and all known heterodinuclear complexes are thus accessible more simply than with the previously used procedures. The reactions lead to equilibrium mixtures which result equally from the two homodinuclear as well as from the heterodinuclear complexes. Upon participation of the units Cp(CO)3Cr, (CO)4Co, and Cp(CO)Ni the equilibria with three exceptions ly completely on the side of the mixed compounds. The equilibration reaction found here is of elementary importance for the chemistry of metal-metal bonds.
Mechanism of the depressor response to dopamine in the rat treated with phenoxybenzamine.
Alterations of hypotensive responses to dopamine by antagonists were characterized in alpha-blocked, anaesthetized rats. Responses were not affected by d-propranolol (0.1 mg/kg) whereas d,1-propranolol (0.1 mg/kg) or haloperidol (1.0 mg/kg) attenuated them; higher doses of inhibitors (1.0 mg/kg; 5.0 mg/kg, respectively) failed to produce a higher inhibition, but combinations of low doses abolished the depressor responses. In adrenalectomized rats, hypotensive responses decreased; haloperidol always attenuated the responses while d,1-propranolol became ineffective. Dopamine produced an enhancement of plasma adrenaline and noradrenaline levels, which was decreased by d,1-propranolol and increased by haloperidol. The data suggest that in rats the depressor component of dopamine is due to activation of both dopaminergic and beta-adrenoceptors. The beta component appears to be due to the release of adrenaline. The results also support the concept of the existence in sympathetic nerve endings and adrenal glands of stimulatory beta-adrenergic and inhibitory dopaminergic prejunctional receptors.