Insertion products, metal-water

The above discussion has focused on the structures of the insertion products. The remainder of this section will briefly discuss the equally Important problem of the dynamics of metal atom-water interactions. Of special Interest is the possible role of the adducts in the route to the insertion products. The matrix isolation experiments of Hauge and co-workers ( 1- ) suggest that for most metal atoms the first step of the reaction Involves formation of the adduct. Upon irradiation the adduct can Interconvert to the insertion product, which, in turn, can give rise to still other products. Two exceptions to this are Sc and A1 which in the matrix isolation experiments react spontaneously to give the hydroxyhydrides. Upon irradiation these decompose to yield metal oxides and hydroxides. 

In analogy to hydroformylation, alkenes react with SO2 and H2 to give a so-called hydrosulftnation product, sulfinic acids [116]. Cationic Pd(II) and Pt(II) complexes bearing bidentate phosphine ligands are effective catalyst precursors. A plausible mechanism for the hydrosulfination involves formation of alkyl intermediates by olefin insertion into metal hydrides, subsequent insertion of SO2, and reformation of the hydrides with the release of sulfinic acids (Scheme 7.19). However, ahphatic sulfinic acids readily undergo disproportionation to give thiosulfinic acid esters, sulfonic acids, and water at the reaction temperature. The unstable sulfinic acids can be conveniently converted into y-oxo sulfones by addition of a,-unsaturated carbonyl compounds as Michael acceptors to the reaction mixtine (Eq. 7.23) [117]. 

A metal hydride intermediate was suggested. The authors note that [Mn(CO)6] reacts with water to yield the hydride [HMn(CO)s] and carbon dioxide [208]. In a very recent communication [208a], it has been reported that both rhenium and manganese carbonyls having the formula [LM(CO)s] are attacked by nucleophiles to give insertion products, and that facile isotopic exchange occurs between H2 0 and the 0 of coordinated CO groups. 

Two main obstacles were well-known (a) diazo compounds can react directly with carbonyl compounds generating homologated products (Amdt-Eistert reaction, Scheme 7.59a), (b) diazo compounds can dimerize in the presence of metal salts and form alkenes (Scheme 7.59b) [204]. Other reactions involve carbene insertions or acid/water addition. 

Gas-fired water heaters use the same general method of construction, except that the elements are replaced with a burner beneath the tank. The combustion products from the burner are vented through a flue made out of the same thickness steel as the tank, that goes up through the center of the tank. To increase heat transfer from the hot flue gases to the inner wall of the flue, a baffle is inserted down the flue. This baffle is a twisted strip of sheet metal with folds and tabs on it. The folds and tabs are designed to... 

A nucleophilic attack by 4.7 on CH3I produces 4.8 and I. Conversion of 4.8 to 4.9 is an example of a carbonyl insertion into a metal alkyl bond. Another CO group adds onto the 16-electron species 4.9 to give 4.10, which in turn reacts with I to eliminate acetyl iodide. Formation of acetic acid and recycling of water occur by reactions already discussed for the rhodium cycle. Apart from these basic reactions there are a few other reactions that lead to product and by-product formations. As shown in Fig. 4.4, both 4.9 and 4.10 react with water to give acetic acid. The hydrido cobalt carbonyl 4.11 produced in these reactions catalyzes Fischer-Tropsch-type reactions and the formation of byproducts. Reactions 4.6 and 4.7 ensure that there is equilibrium between 4.7 and 4.11. 

This suggests that the metal center in HSi0H(H20), inserts into the coordinated water molecule on photolysis. The adduct band frequency is listed in Table I. The product band frequencies for HSIOH, HS10H(H20), SiO,and H2Si(OH)2 are listed in Table II. 

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