Cyclopentadiene crystal structure

Hawkins and Loren225 reported simple chiral arylalkyldichloroborane catalysts 352 which were effectively used in the cycloadditions of acrylates lib and 350 to cyclopen-tadiene, affording adducts 351a and 351b, respectively (equation 99). A crystal structure of the molecular complex between methyl crotonate and the catalyst allowed the authors to rationalize the outcome of the reaction. One face of methyl crotonate is blocked by tt-tt donor-acceptor interactions, as becomes clear from the structure of complex 353. The cycloadduct of methyl acrylate and cyclopentadiene (5 equivalents) was obtained with 97% ee, using the same catalyst. Three years later, the authors reported that the cycloadduct was obtained with 99.5% ee in the presence of 10 equivalents of cyclopentadiene226. 

Upon treatment with an ethereal solution of methyllithium, both oligocydopropyl-substituted cyclopentadienes 14 and 6 in tetrahydrofuran were quantitatively deprotonated to the corresponding cyclopentadienides 14-Li and 6-Li, respectively, which were characterized by their 1H and 13 C NMR spectra. Treatment of the solutions of 14-Li and 6-Li with solutions of iron(II) chloride in tetrahydrofuran yielded the l,l, 2,2, 3,3, 4,4 -octacydopropylferrocene (16) (74%) and the decacyclopropylferrocene (17) (21%). After crystallization from hexane (for 16) and pentane/dichloromethane (for 17), the structures of both ferrocenes were established by X-ray crystal structure analyses (Scheme 3). The electron-donating effect of the cyclopropyl substituents on these cyclopentadiene systems is manifested in the oxidation potentials of the ferrocenes 16 and 17. While the parent ferrocene has an oxidation potential E1/2 (vs. SCE) = +0.475 V, that of decamethylferrocene is significantly lower with Ei/2 = —0.07 V, and so are those of 16 (Ey2 — —0.01 V) and 17 (f i/2 = —0.13 V) [13]. 

CpCo(CO)2 (18) is obtained on heating cobaltocene under CO or by heating Co2(CO)g with cyclopentadiene. Since the latter reaction works with substituted cyclopentadienes as well, a variety of substitution products are easily accessible. CpCo(CO)2 is a dark red, air- and light-sensitive oil (mp -22 °C) with a musty odor. The crystal structure has been determined and shows a conformation with one CO eclipsed by a Cp edge, whereas the Cp derivative has a different conformation with the C0-Co-T20 plane parallel to one side... 

A novel ring displacement reaction of (C5H4Me)3Ln(THF) (Ln = Sm, Tb, Ho, Yb) with cyclopentadiene has been reported to give the parent tris(cyclopentadienyls) Cp3Ln(THF) in high yields.484 The crystal structures of... 

In order to impose crystallinity on all the intermediates, several sulfonamides, derived in two steps from (+)- or (-)-camphor-lO-sulfonyl chloride, were examined. Their acrylates 17a and 17b are added to cyclopentadiene (19) and to 1,3-butadiene (18) in the presence of dichlorodi-isopropoxytitanium. The resulting cycloadducts can be purified to give a d.r. 99.5 0.5 by simple recrystallization21. Examination of the X-ray crystal structure of 17b22 confirmed the hypothetical conformation of the acrylate, earlier proposed and later calculated23. Analogous sulfones 21a-c are less diastereoselective (d.r. 82 18 - 84.5 15.5)24. 

A pentahaptofullerene metal complex 71 was obtained upon the reaction of the hexaadduct 72 with TlOEt demonstrating the acidity of the cyclopentadiene (Scheme 13) [74]. A single crystal investigation confirmed the cyclopentadienide character of the complexed five-membered ring. The length of the [6,6]-and [5,6]-bonds in the remaining Cjg moiety are similar to those of monofunc-tionalized Cgg derivatives which is also demonstrated with the crystal structure of 68. 

The X-ray crystal structures of [CpRu(Ti -CPD)(MeCN)] [PF6] and [Ru(ii -CPD)2] " [PF6] 2 (CPD = 2,4-cyclopentadien-l-one) have been reported S Selective H/D exchange in the coordinated tropone moiety in [CpRu(Ti -tropone)] [BF4] was observed on treatment with KOH/CD3OD and the key cycloheptadienyl intermediate [CpRu(l,2,3,4,5-Tl5-ex >-6-methoxy-7-oxo-cycloheptadienyl)] was isolated and characteri.sed239. 

An increasing volume in the literature is devoted to pseudo-cyclopentadienes and pseudo--arenes. A general paper describes complexation of the cyclo-Ps anion. The synthesis of the first diazacobaltocene has been described. Tert-butyl-substituted diazaferrocenes have been prepared from substituted pyrroles. Bis-(borole)nickel complexes have been prepared from dilithium txnelediides. Carborane stabilised iron indole and iron thiophene complexes have been made. The electrophilic stacking of borataferrocene and bis(borole)cobaltate ions with -Cr(CO)3 and Mn(00)3 has been described. The synthesis and crystal structure of... 

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