Monocyclopentadienyl compounds

Among titanium-based precursors, monocyclopentadienyl compounds of the type CpTiCl3 or Cp TiCl3 activated by MAO or B(C6F5)3 showed the best performance, although several substituted mono-Cp or indenyl derivative and Cp-free compounds as Ti(CH2Ph)4 and Ti(OR)4 (R = alkyl, aryl) are quite active as well. In short, practically any soluble titanium compound can be used as precatalyst.154-158... 

Monocyclopentadienyl compounds, 25 116 Monodentate chelants, 5 709 Monodentate ligands, 9 396 Monodisperse model networks, with silicone, 22 570... 

There is an extensive Co1 chemisty of monocyclopentadienyl compounds, of which CpCo(CO)2 is one example. The CO may be replaced by phosphines, alkenes, isocyanides, and so on. The dicarbonyl itself can be reduced to a radical ion that contains cobalt in the formal oxidation state 0.5, and can be isolated as its (Ph P)2N+ salt ... 

Monocyclopentadienyl compounds such as [Cp Ca(I)(THF)2] and [Cp Ca(I)(THF)(] 2)] have been prepared from the metal diiodides and potassium decamethylcyclopentadienide by Eq. An alternative... 

In a specific instance a substitution mechanism should take into account the individual geometry of the starting compound. It is convenient to discuss the experimental results on the 77-C5H5 substitution and transfer reactions under three headings (1) substitution occurring in compounds leading to increased ionic character of the metal-ligand 77-bond (2) substitution of monocyclopentadienyl compounds (3) substitution in the ferrocene-like sandwich complexes. 

Sodium cyclopentadienyl reacts with indium trichloride in ether, tetrahydrofuran, or dioxan, forming the volatile compound InCsHs, which may be obtained as pale yellow needles by sublimation (56). This substance does not melt sharply, but slowly decomposes and darkens at 110°. It is very sensitive to oxidation and is slightly soluble in benzene, in which decomposition takes place it is, however, rather less soluble in ether and petroleiun ether. Water has no action on the compound, but on addition of a little sulfuric acid it is vigorously decomposed. The crystals are slightly sensitive to light. In the preparation of InCsHs an intermediate product, InlCsHsls, can be isolated in very small yield as golden crystals. On sublimation at above 160° it decomposes to form the monocyclopentadienyl compound. 

Silicon compounds of formula (C6H6)Si(CH3)3 and (C5H5)2Si(CH3)2 are obtained by the action of cyclopentadienyl magnesium bromide on trimethylchlorosilane and dimethyldichlorosilane they are colorless liquids which boil at 43-44° (19 mm pressure) and 73° (25 mm), respectively 89). The monocyclopentadienyl compound darkens on exposure to air, and it forms an adduct of mp 105° with maleic anhydride, thus showing the retention of the conjugated system in the compound. 

Although it was originally thought that there was some special feature of the bonding that gave the parallel ring, or ferrocene-like, structure, this view had to be modified to account for the monocyclopentadienyl compounds and the subsequent observation that in several di-/j5-cyclopentadienyl compounds the rings are not parallel. 

Most of the known monocyclopentadienyl compounds of trivalent lanthanoids are dichloride complexes of CpLnCl2(THF) type. Besides these compounds, the ytterbium p-diketonates, lanthanum and cerium iodides (Me5C5)Lnl2 and the lutetium triflate complex CpLu(0S02CF3)2(THF)3 have been obtained (Table 111.14)... 

There are a few examples of monocyclopentadienyl compounds that catalyze non-conjugated dienes. The cationic titanium compound [Cp TiMe2] [172] and mono(pentamethylcyclopentadienyl)yttrium alkoxides [53] catalyzed cyclopolymerization of 1,5-hexadiene, whereas neither of them gave highly stere-oregulated polymers. 

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