Lead monoxide dimer

Treatment of the olefin 49 with Zeise s dimer leads to the chloroplatination complex 50 [26], The addition adduct 50 is hydrogenated stereospecifically to the trans-disubstituted chlorocyclohexane 51. The insertion of carbon monoxide into 50, in the presence of methanol, yields the ester 52 stereoselectively. 

Considering methods of CO2 generation, we partly broached a subject of its chemical reactivity. However, some important data should be added. Disproportionation of C02 leads to carbon monoxide and a carbonate, whereas dimerization results in the formation of oxalate (see the left and right directions of the following dual equation) 02C—C02 <— 2CO2 CO + CO... 

In Sch. 1, if the 002 radical anion reacts with CO2 in solution, CO is formed via a dimeric intermediate in which a C—O bond is formed. A second electron transfer to this intermediate from either the electrode or 002 leads to the formation of carhon monoxide. The ultimate result of this pathway is the formation of the two-electron reduction product, carbon monoxide, and carbonate. In this reaction, a second CO2 molecule acts as the acceptor of the oxide ion formed in the two-electron reduction of CO2 to CO. Many of the features of these reactions are common to the catalyzed reactions discussed in the following. Because free C02 is not present in the catalyzed two-electron reductions of CO2 to CO, the reduction potentials can be considerably less negative than that required to form CO2-. 

The monoxides readily undergo the Pummerer reaction, which may lead to thiopyrylium species, or 2,2 -dimers, while the sulfone series is quite stable. The acidity of the thiopyran... 

Disproportionation of C02 leads to carbon monoxide and a carbonate, while dimerization results in oxalate formation see the left and right directions of Scheme 1-87 ... 

The thermolysis of cyclic sulfites of enediols and their benzo derivatives is characterized by elimination of sulfur monoxide. Thus 4,5-dimesityI-l,3,2-dioxathioIe 2-oxide (25) decomposes to mesitil (63JOC1075), and fragmentation of catechol sulfite (48) leads via o-benzoquinone and cyclopentadienone to the dimer (49) of the latter (67TL271). In a similar fashion, the thermolysis of 1,2,3-benzoxadithioIe 2-oxide at 670 °C resulted in cyclopen-tadienethione the intermediate formation of monothiobenzoquinone could be detected by PE spectroscopy (81AG603). 

The reaction with labeled COj gives rise to a dimer which is greatly enriched with CO. A mechanism was proposed in which a step-by-step coordination of two molecules of CO2 occurs to give [CpFe(C0) Ci04r, followed by disproportionation, which leads to COr. and CpFc(CO)/ which quickly reacts with another molecule of CpFe(CO)2 to form the dimer and carbon monoxide. 

We here report the first example of an electrochemical polymerization process which leads to formation of a modified electrode having the generic formula [Ru (bpy)(CO)2Cl]n, and which displays outstanding electrochemical activity towards reduction of carbon dioxide to either carbon monoxide or formate. A crucial stereochemical effect of the leaving groups on the feasibility of polymerization is demonstrated. Formation of the polymer occurs stepwise, through the formation of a dimeric or a tetrameric intermediate. 

As an example, the reactions of the negatively charged gold dimer and trimer cluster ions with carbon monoxide inside the rf-ion trap are presented in Fig. 1.36 [185]. While no reaction products of Au2 and Aus with carbon monoxide are detected at room temperature, cooling down leads first to the formation of mono-carbonyls and at the lowest temperatures around 100 K to a maximum adsorption of two CO molecules on Au2 and also on Au3 as can be seen from the mass spectra depicted in Fig. 1.36a. In order to deduce the reaction mechanism of the observed reactions, the reactant and product ion... 

The conditions for the synthesis must differ, as the electronic configuration of each metal changes, but the intermediate in each case probably is a complex in which acetylene and carbon monoxide are each linked to two metal atoms. Cobalt and iron compounds having both acetylene and carbonyl bridges have already been synthesized 27). The report of the preparation of a dimeric nickel hydrocarbonyl, [NiH(CO)a]2 by Behrens 28) may well lead to the isolation of a siipilar acetylene complex with nickel. 

A,ii, Cyclopentadienylirondicarbonyl (Fp) Compounds. A common organoiron reagent is cyclo-pentadienylbis(carbonyliron) (Fp, 711). " This derivative can be converted to an alkyl derivative (713, where R = alkyl) by reaction with an alkyl halide, or to the protio derivative (713, R = H) by reaction with an acid. The anionic reagent 712 is prepared by reaction of iron pentacarbonyl with the dimer of cyclopentadiene (710 - sec. 115.B) at 200°C to give the dimeric species 711. Treatment of 711 with base leads to loss of cyclopentadiene and formation of 712. A byproduct of this process is ferrocene (71 4) formed by extrusion of carbon monoxide from 711.595... 

The iodine monoxide (lO) self-reaction is relatively fast and yields mainly iodine dioxide (OlO) or I2O2 at the range of pressures in the lower atmosphere. The lO dimer formed via (8.4c) is hkely to undergo photolysis, be taken up onto existing aerosol surfaces or take part in nucleation processes leading to the formation of new particles in coastal marine environments (O Dowd and Hoffmann, 2002). 

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