Complexes cyclopentadienyl compounds

The 18-electron rale is not obeyed as consistently by these types of oiganome-tank compounds a by the carbonyl and nitrosyl complexes and their derivatives. For example, in addition to ferrocene. M(i 5-CsHs)2 compounds are known for most of the other elements of the first transition series (M — V, Cr, Mn.Co, Ni) and these cannot obey ihe 18-electron rule. However, only ferrocene shows exceptional thermal stability (stable to 500 C) and is not oxidized by air. Furthermore, cobaltocene, a 19-electron species, is readily oxidized to the 18-electron cobaltocenium ion. (Co(ip-CsH )3)4 , which reflects much of the thermal stability of ferrocene. Mixed cyclopentadienyl carbonyl complexes are common K -CjHjMCO) ]. [(if-CjH )-Cr(CO), . [( -CjHOMnCCOjJ, [(>r-C,H,>Fe(CO ,, . [fo -CjiyCoCoy. and (ip-CsH,)Ni(CO) 2. Of interest is the fact that among these compounds, the odd-atomic-number elements (V. Mn, and Co) form monomers and the even-atomic-number elements (Cr. Fe. and Ni) Ibrm dimers, which is in direct contrast to the behavior shown by the simple carbonyl complexes. Cyclopentadienyl derivatives are now known for every main group and transition metal of the periodic table and for most of the -block metals.89... 

Gold(I) forms simple cyclopentadienyl compounds as well as more complex species involving 3-center 2-electron (3c-2e) bonds, and these together with analogous 3c-2e arylgold(I) compounds are discussed here. 

The mass spectra of a considerable number of 77--bonded complexes of the group VIA metals have been reported, but in many cases mass spectrometry has only been used to determine the molecular weight, so that a detailed examination of the fragmentation processes involved has not been attempted, and only the molecular ion and perhaps a few other major peaks are reported. Within this section it is more convenient to discuss the compounds in terms of the attached ligands rather than in terms of the central metal atom. The classifications are (A) cyclopentadienyl compounds (B) arene compounds and (C) olefin, acetylene, and allyl compounds. 

The 7T-pyrrolyl complex C5H5FeC4H4N shows four fragmentation paths of the molecular ion, all of which are confirmed by observation of the appropriate metastable peaks. Thus M+ fragments either by loss of C2H2, HCN, C2H2N, or the entire C4H4N unit. Further fragmentations are as expected for cyclopentadienyl compounds (117). 

Cyclopentadienyl compounds have been thoroughly investigated as suitable precursors to rare earth doped semiconductors in MOCVD (metal-organic chemical vapor deposition) or MOVPE (metal-organic vapor phase epitaxy) processes [283]. The use of btsa complexes for the same purpose has appeared in the literature very recently [285]. Typical process conditions are shown in Scheme 14. It was found that the carbon contamination of the deposited metal is less in the btsa case. 

In addition to the types of compounds listed in Table 2.1, cyclopentadienyl compounds and ate complexes should be noted. ... 

The complexes are generally intensely yellow and, with the exception of Mn(T 5-CsH4Cl)(CO)3, are highly crystalline. The carbonyl stretching frequencies of the halogen-substituted cyclopentadienyl compounds are useful in their characterization and are given in Table I. The presence of an electron-withdraw-... 

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