Chemical methods organometalic compounds

The only respect in which the hot atom chemistry of organometallic compounds has so far been applied to other fields of study is in the area of isotope enrichment. Much of this has been done for isolation of radioactive nuclides from other radioactive species for the purpose of nuclear chemical study, or for the preparation of high specific activity radioactive tracers. Some examples of these applications have been given in Table II. The most serious difficulty with preparation of carrier-free tracers by this method is that of radiolysis of the target compound, which can be severe under conditions suited to commercial isotope production, so that the radiolysis products dilute the enriched isotopes. A balance can be struck in some cases, however, between high yield and high specific activity (19, 7J),... 

Formation of metal-organic compound co-condensates presents a peculiar problem, which is difficult to study. Most experimental methods are inapplicable to the study of the processes that take place at the instant of cocondensation. This brings to the fore theoretical approaches. The state of the art of computational quantum-chemical methods makes it possible to adequately describe the structure of organometallic compounds and estimate their stability and, sometimes, reactivity. 

Chemical methods are generally based on the reaction of surface hydroxyl groups with a selectively reacting compound to form a covalently bonded surface species of well known composition. As reactive compounds, diborane,4,5 boron trichloride,6,7 diazomethane,8 organosilanes,3,6,9,10,11,12,13,14 and organometallic compounds15 have been employed. a0H is then derived from the amount of the chemisorbed species as well as the amount of volatile reaction products. 

The availability of inductively coupled plasma mass spectrometry (ICPMS) has provided a method of detection of many impurities at very low concentrations directly in the organometallic compound itself. ICP mass spectrometry is a relatively recently developed chemical analysis technique that is useful in the detection of trace element concentrations in a liquid or solid matrix. ICPMS can measure the presence of almost all elements simultaneously, thus giving a detailed, semiquantitative picture of the impurity distribution in the sample. This technique has sensitivities for many elements in the parts-per-billion to parts-per-trillion range. It has the advantage that it is extremely sensitive and can analyze small samples (10 ml or less) of organometallics directly. The ICPMS technique employs a plasma to dissociate the material to be characterized into... 

M. Dub, in Organometallic Compounds, Methods of Synthesis, Physical Constants and Chemical Reactions, 2nd Edn. (Ed. W. Weise), Vol. 2, Springer-Verlag, Berlin, 1967, pp. 1-157. 

Another deposition method is that involving the creation of a strong bond, for example, a covalent bond, between the support and the active element [7,8], This process is typically called grafting or anchoring. This procedure is carried out by a chemical reaction between functional hydroxyl groups on the surface of the support and a properly chosen inorganic or organometallic compound of the active element. 

---