Matrix co-condensation reaction

Moskovits and Ozin determined the structures of a large number of metal carbonyls produced via matrix co-condensation reactions. They proposed an unusual isocarbonyl structure, OsC—Au—0=C for Au(CO)2, and the... 

As stated in Sec. 1-22, a number of stable and unstable complexes of the ML type have been synthesized via matrix co-condensation reactions of metal vapor(M) with gaseous ligands(L). Table 111-53 lists typical results obtained... 

The alkali metals are easily vaporized at temperatures of 300—500"C, and most studies of this group have been reviewed in Sections 2 and 3. The reactivity of alkali metals in co-condensation reactions is high, but little different from that in diffusion flame studies. However, the alkali metals have been used in a number of low-temperature reactions, largely to produce radicals or intermediates of spectroscopic interest. For example, the trichloromethyl radical has been produced in a solid argon matrix by reaction of lithium atoms with carbon tetrachloride [294]. A similar technique has been used to produce the CBr2H radical from bromoform [295], the CCljH radical from chloroform [296], and the methyl radical from methyl iodide and methyl bromide [297]. In all these cases the corresponding lithium halide is produced. 

Co-condensation of pyrrole 1020 + atomic carbon + CO2 at 77 K followed by addition of methanolic HCI generates ion 1023 and A -methylpyridinium 3-carboxylic acid 1027 in a 1.2 1 ratio (Scheme 200) <1997JA5091>. The observation of acid 1027 provides strong chemical evidence for the ylide 1021 rather than cumulene 1022 (Scheme 198) which would not be expected to react with CO2. However, acid 1027 is not generated when CO2 is added to 77 K matrix formed upon reaction of atomic carbon with pyrrole 1020. 

In view of the very close agreement between the matrix isolation visible absorption spectra of the HAIOH molecule and the chemiluminescence features observed in the gas-phase oxidation of aluminum in the upper atmosphere (14) and in the laboratory ( ), this study further substantiates the plausibility that the continuum emitter is the divalent oxidative insertion product of a 1 1 alumlmmi hydration reaction, HAIOH. The Insertion reaction is probably facile however, it is possible that radiation from the furnaces may have photolyzed the AI...OH2 adduct to the insertion product during co-condensation. Preliminary theoretical studies indicate there is no potential energy barrier in going directly to the Insertion product from A1 + H2O ( ). 

The co-condensation technique is by far the most commonly used, although in some cases the atomic species may be condensed in an inert matrix, the second compound then condenses on the matrix, and reaction occurs when the matrix is allowed to warm up. Using this method, the reactive atoms may recombine before the second compound has diffused... 

The reaction of Fc2 dimers with methane in a matrix at 77 K gives rise to the formation of species H-FeFe-CHs or FeFe-CHj [26a], Analogously, the C-H bond in alkanes is cleaved by nickel clusters [26b], Methane activation has also been detected during the co-condensation of methane with aluminum atoms at 10 K [26c]. It is noteworthy that under the same conditions, atoms of Mg, Ti, Cr, Fe, Ga, Pd and some other metals do not react with methane. 

Following a related approach, Castelvetro et al. reported the formation and properties of hybrid latex films resulting from the coalescence of low 7 poly(BA-co-MMA-co-MPTMS) terpolymer latex particles coated by a silica shell [78], The latex was synthesized at neutral pH by semi-continuous emulsion polymerization under starved-feed conditions in order to protect the MPTMS monomer from premature hydrolysis and condensation reactions. A substantial amount of free silanols were therefore available for further reaction with the silica precursor. In order to avoid the formation of a densely crosslinked silica network around the latex core, which may significantly alter film formation, the pH was kept at around 2 (at this pH, hydrolysis is promoted and condensation is significantly retarded). TEM and AFM studies of the nanocomposite film indicated that the silica shell formed a continuous percolating network throughout the polymer matrix. A porous film of interconnected hollow silica spheres was next elaborated by thermo-oxidative decomposition of the organic phase. 

---