Metallocenes nomenclature

Mercury, tris(l,10-phenanthroline)-structure, 64 Mercury(II) complexes masking agent, 536 Mercury electrodes potential range aqueous solution, 480 Metal carbonyls structure, 16 Metallocenes nomenclature, 126,127 Metallochromic indicators, 554 Metallofluorescent indicators, 558 Metallothionein proteins, 142 Mettd-metal bonding, 137,169 gravimetry, 525 history, 21,23 nomenclature, 122, 123 Metal nitrosyls structure, 16 Metal-phthalein metallochromic indicator, 557 Metal template reactions, 416,433 equilibrium kinetic, 434 thermodynamic, 434 Methane, dichloro-... 

Metallocene derivatives may be named by either standard organic suffix (functional)7 or prefix nomenclature. Substituents are given the lowest numerical locants in the usual manner on the equivalent cyclopentadienyl rings of the ocene entity. The first ring is numbered 1 to 5 and the second ring is numbered V to 5. In metallocenes composed of multiple ocene groupings the cyclopentadienyl rings are further numbered 1" to 5", V" to 5", etc. The radical names -ocenyl, -ocenediyl, -ocenetriyl, etc. are used. For examples see Table 25. 

FIGURE 5.11 Absolute configuration of l,2 -disubstituted metallocenes with the nomenclature (solid line is upper ring substituent and dotted line is lower ring substituent). 

One important chemistry fallout from the creation of cylindrical names shall arise when the two anchor atoms normally do not have a coordination greater than two — such as is the situation with oxygen. In Chapter 6, after having developed properties of the boranes and the metallocenes, cylindrical nomenclature shall be applied to some supramolecular clusters. 

A modification of (1) called "sandwich" nomenclature for that class of organometallic compounds called "metallocenes" ... 

Table 1.2 provides a summary of commonly used classifications in the polyethylene industry. A brief note is warranted here to conclude the survey of polyethylene classifications and nomenclature. In the early 1990s, several types of polyethylene manufactured with metallcxiene catalysts (a type of single site catalyst, see Chapter 6) were introduced to the market. To differentiate polyethylene produced with metallocenes from polyethylene manufactured using older conventional catalysts, metallocene grades are sometimes abbreviated mVLDPE, mLLDPE, etc. 

Metallocene derivatives may be named either by the standard organic suffix (functional) nomenclature or by prefix nomenclature. The organic functional suffix system is described in Section P-33 of Ref. 3. Metallocene substituent group names have endings ocenyl , ocenediyl , ocenetriyl , etc. 

Chemical nomenclature proposals based on hydrocarbons axe of limited applicability because they cannot be used directly for chemical structures, such as boron cages and metallocenes, which contain atoms... 

In this section we present the elements of chirality relevant to the stereospecific polymerization of propene with group 4 metallocenes. First of all, coordination of a prochiral olefin, such as propene, gives rise to nonsuperimposable coordinations. To distinguish between the two propene coordinations, we prefer the nomenclature re, si—defined for specifying heterotopic half-spaces— instead of the nomenclature R,. defined for double or triple bonds jr-bonded to a metal atom—in order to avoid confusion with the symbols R and S used for other chiralities at the same catalytic site, or the nomenclature Re, Si-defined for reflection—variant units—and used by Pino and co-workers in refs 83—86. The use of the si, re nomenclature can be confusing when different monomers are considered, because the name of a fixed enantioface of an 1-olefin depends on the bulkiness of the substituent in position 1. However, since propene is the only monomer considered in this review, this problem does not exist here. We only remark that the re and si coordinations sketched in Scheme 3 correspond to the R and S coordinations, respectively. 

For achiral metallocene-based catalysts Czv and achiral Q metallocenes in Chart 2) the chain-end control is present as the only stereocontrol mechanism. It derives from the presence of an asymmetric carbon atom on the last inserted monomer. The chirality R or 5) of this atom is related to the enantiotopic face of the olefin where the insertion took place (Scheme 34). In the NMR spectrum of the polymer we lose this kind of information, as two successive insertions of the re olefin face and two successive insertions of the si face produce the same m diad (see section II.G). As a consequence, we can observe only the relative chirality between consecutive inserted monomer units (5,5 or R,R as m diads and S,R or R,S as r diads) disregarding the absolute configuration of tertiary atoms. We prefer to use the re and si nomenclature indicating the stereochemistry of the methines in the polymer chain (Scheme 35), bearing in mind that the insertion of the re propene enantioface will produce an 5 configuration on the methine. 

Application of the (RyS) system to metallocenes The most widely employed system for specification of metallocene chirality was put forward by Schlogl in consultation with Cahn and Prelog [7 ]. The bond from the central metal atom to the ring carbon atom under consideration is treated as a formal single bond. The carbon atom is then considered as a chiral centre and (7 ,5) nomenclature is applied in the usual way. 

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