Talk:Metallocene

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[edit] Proposal to rename "metallocene" as "sandwich" - also half sandwich

"In chemistry, and in particular, in organometallic chemistry, a metallocene is a compound with the general formula (C5R5)2M consisting of two cyclopentadienyl anions (Cp) bound to a metal center in the oxidation state II." HappyCamper pointed out that Uranocene would appear to be a metallocene based on its name alone. Not M(II) and not Cp₂M. How about this suggestion: we rename this article "sandwich compound" and describe Cp₂M's, uranocene, and other compounds where a metal is sandwiched between two planar hydrocarbons. Thus Cr(C₆H₆)₂ would be included. But also CpTi(η⁷-C₇H₇). When the hydrocarbon is not flat, these would be excluded but mentioned, thus [Ru(η⁶-C₆Me₆)₂]²⁺ would be included, but [Ru(η⁶-C₆Me₆)(η⁴-C₆Me₆)] would not, but we could mention this gray area? Now that we are on the subject, we should probably have a Half sandwich article. This label is preferable to piano stool where we will be confronted with the number of legs on such a piano stool: CpV(CO)₄? CpCo(CO)₂?--Smokefoot 03:58, 24 July 2006 (UTC)

I counter the renaming proposal: The IUPAC article mentioned in the sources of the article states: "Consequently, the name-ending -ocene should be con®ned to molecules of the form bis(h5-cyclopentadienyl)metal, where the metal is in the d-block [i.e. the terminology does not apply to compounds of the s or p-block elements such as Ba(C5H5)2 or Sn(C5H5)2], and where the rings are essentially coplanar to each other." Thus uranocene is strictly speaking not a metallocene. Instead of changing the name of the article I would include uranocene in the section, where it is pointed out, that in contrast to the stricter IUPAC nomenclature the term metallocene have been applied to non-transition metals (Cp2Ba), non-sandwich compounds (Cp2TiCl2). We can add here "also to non-planar metal complexes with more than two Cp rings, such as Cp3U".