Cocondensation, compounds

Further reactions of gold atoms (132) with mixed OJCO matrices led to some interesting results. By cocondensing Au atoms with equimolar mixtures of Oj/CO at 10- 12K, a single compound was isolated which, by means of = C 0/> 02, and C 0/ = C 0/ HD /... 

Chromium atoms were cocondensed with benzyl sulfide at 77 K (35), the primary result being desulfurization to form bibenzyl and trans-stilbene. Coordination compounds were not characterized in this system. 

C. Synthesis of Trifluoromethyl Organometallic Compounds by Cocondensation of Trifluoromethyl Radicals and Metals... 

When Ag vapor is cocondensed with CO at 10-12 K the compound Ag(CO), is formed as separate molecules in a CO matrix. When this is warmed to 30-37 K for about 1 h dimerization takes place ... 

This reaction is diffusion controlled in solid CO. The binuclear carbonyl is unstable and even at these low T decomposes to Ag2 or higher clusters. Similarly, Au forms Au(CO)[ or 2, which does not dimerize. However, Cu cocondensed with CO and Ar forms compounds Cu (CO) (n = 1-4), which after warming to 35 K decompose to larger Cu carbonyl clusters of indeterminate composition, the IR spectra of which resemble CO chemisorbed onto bulk Cu. 

The stability of molecules depends in the first place on limiting conditions. Small, mostly triatomic silylenes and germylenes have been synthesized successfully at high temperatures and low pressures, 718). Their reactions can be studied by warming up the frozen cocondensates with an appropriate reactant, whereas their structures are determined by matrix techniques 17,18). In addition, reactions in the gas phase or electron diffraction are valuable tools for elucidating the structures and properties of these compounds. In synthetic chemistry, adequate precursors are often used to produce intermediates which spontaneously react with trapping reagents 7). The analysis of the products is then utilized to define more accurately the structure of the intermediate. 

Bis(Tj6-jV,-/V-dimethylaniline)molybdenum has been prepared in good yield by cocondensation of molybdenum atoms with a fifty-fold excess of Af,Af-dimethyl-aniline vapor on a liquid nitrogen cooled surface. This method has been extended to the synthesis of other molybdenum arene complexes and is at present the only synthetic route to such compounds. 

The reaction of aerosol droplets with gases can also be used to prepare particles of internally mixed composition, such as consisting of different metal oxides. In principle, these powders can be obtained by first cocondensing vapor of the two or more volatile metal compounds (preferably alkoxides), or by nebulizing liquids of mixed composition. In both cases the droplets are then reacted with vapors. 

Fig. 2, Apparatus for cocondensing a metal vapor and the vapor of a compound on a gram scale.

I. Methods of Reacting Atoms and Compounds CC Cocondensation of the vapor of a compound and a metal vapor formed by thermal evaporation of a metal... 

The ESR spectra of all zerovalent derivatives are consistent with the paramagnetism expected for 17-electron d5 compounds with one unpaired electron ([Nb(7/6-C6H5Me)2] (g) = 1.992, (A) = 45.9 G). Cocondensation of Nb atoms with N2 in an Ar matrix gave... 

These complexes are rare, doubtless owing to the comparatively ready oxidation of amines. However, the template preparation of Ce(N03)4L-3H20 has been described L is the eighteen-membered macrocycle formed by cocondensation of two molecules of ethylenedi-amine and two molecules of 2,6-diacetylpyridine. The structure of this compound is unknown and it is uncertain to what extent the macrocycle is bonded to the metal ion.689... 

A special technique which has yielded highly unstable and simple dinitrogen complexes trapped in low-temperature solids (N2 or Ar) is the metal atom cocondensation technique in low-temperature matrices. By the cocondensation of nickel atoms and N2 at 4.2-10 K the binary compounds Ni(N2) (n = 1-4) result, whose structure has been inferred from IR and... 

This general method either involves low-molar-mass azo compounds having additional functionality, which can be used to start a polymerization of a vinyl monomer selectively, or a ring-opening addition but also to participate in cocondensation reactions. 

In all, the cocondensation with silicon atoms is a useful tool for the generation of silylenes. Sometimes, the same species are obtained as with chemical precursors and sometimes new, otherwise not accessible compounds can be observed. So both methods nicely complement one another. 

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