Metal vapors, reactions with

Metal vapor chemistry showed that the lanthanides had quite an extensive chemistry with unsaturated hydrocarbons. Some of the early surveys of metal vapor reactions with unsaturated hydrocarbons included some lanthanide metals and showed that reactivity was present for these metals (14-18). Subsequent synthetic studies in which the products were isolated and characterized led to some of the most unusual organolanthanide complexes currently known (19-28). 

The simple hydrocarbon substrates included ethene, 1,2-propa-diene, propene and cyclopropane (22). Their reactivity with Sm, Yb and Er was surveyed. In contrast to the reactions discussed above, lanthanide metal vapor reactions with these smaller hydrocarbons did not provide soluble products (with the exception of the erbium propene product, Er(C H ) ). Information on reaction pathways had to be obtained primarily by analyzing the products of hydrolysis of the metal vapor reaction product. 

Lanthanide metal vapor reactions with unsaturated hydrocarbons such as CsHft (75) or CgHg (76), which are readily reduced by electropositive metals to common anionic ligands, give products arising from the reduction of the ligand and oxidation of the metal [Eqs. (24)-(26)]. The products of... 

In contrast to the above systems, lanthanide metal vapor reactions with unsaturated substrates not readily convertible to stable organic anions common as ligands generate some of the most unusual organolanthanide... 

Later, a similar metal vapor reaction with cobalt produced 122, among other products, which was stmcturally established using the X-ray technique the yields in such processes are low, typically <10% (Scheme 26) <2001JOM212>. 

Macroscale metal vapor reactions with alkanes have led to complex pseudo-organometallic composites, where surface H, alkyl, C, CH, CHj, etc. are bound to metal cluster surfaces Thus, C-H and C-C cleavage occurs on metal atoms or metal clusters in the matrix as it warms. For Ni only clusters react in this way, whereas for Zr, atoms and clusters react ... 

Analysis of possible structures and reaction pathways in reactions 1-4 led to various model structures for these complexes (9t25). Some of these involved C-H activation of the substituents attached to the unsaturated carbon atoms. To test the validity of these models, two additional types of metal vapor reactions were examined. In one case, reactions with simpler unsubstituted hydrocarbons were examined. In another case, substrates ideally set up for oxidative addition of C-H to the metal center were examined. As described in the following paragraphs, both of these approaches expanded the horizons of organolanthanide chemistry. 

A remarkable cobalt-arene complex was also isolated from the metal vapor reaction of cobalt atoms with toluene (Scheme 13) and subsequent addition of an aUcyne (acetylene, butyne, or BTSA). According to EPR spectra, compounds of the type (toluene)Co(alkyne) are 19-electron complexes of near-axial symmetry where the aUcyne acts as a four-electron ligand on the cobalt atom. The methyl derivative has been structurally characterized with Co-Caikyne distances of 1.88 and 1.90 A, and a C C distance of 1.254 A (Figure 11). 

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... 

Thin films were made by vacuum deposition of rare earth metals and reaction with Se vapor at 500 to 600°C, Miller et al. [23]. 

CpJSm (Evans et al. 1984b) was obtained by metal vapor reaction of samarium with CsMesH as a green complex, or from the red 2THF solvated species by desolvation and... 

The corrosion behavior of plutonium metal has been summarized (60,61). a-Plutonium oxidizes very slowly in dry air, typically <10 mm/yr. The rate is accelerated by water vapor. Thus, a bright metal surface tarnishes rapidly in normal environments and a powdery surface soon forms. Eventually green PUO2 [12059-95-9] covers the surface. Plutonium is similar to uranium with respect to corrosion characteristics. The stabilization of 5-Pu confers substantial corrosion resistance to Pu in the same way that stabilization of y-U yields a more corrosion-resistant metal. The reaction of Pu metal with Hquid water produces both oxides and oxide-hydrides (62). The reaction with water vapor above 100°C also produces oxides and hydride (63). 

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