Cyclopentadiene ring

The product (IV) has the Fe atom in the sandwich bonded to a Au, which itself is bonded both to a cyclopentadiene ring and to a second Au. 

Hydrogen atoms on the cyclopentadiene ring are very slightly acidic. Therefore, metallic sodium reacts with a solution of cyclopentadiene dissolved in tetrahydrofuran (THF) to liberate hydrogen, leaving... 

Ligands u/ith Phosphine Substituents Bound to both Cyclopentadiene Rings... 

Ligands with Phosphine Substituents Bound to a Cyclopentadiene Ring and to a Side Chain 839 25.4... 

Comparison of C=C barriers in Table 10 with those in Tables 3 and 4 shows that the cyclopentadiene ring has a moderate capacity for stabilizing a dipolar transition state, being slightly less efficient than two COzR groups or one CN and one C02R group. 

The dipole moment calculated for 111 is somewhat higher than for 96, as expected. The total it charge in the cyclopentadiene ring is calculated to be 0.54 electrons. A somewhat smaller polarization, 0.40 tt electrons, is calculated for 7,8-diphenylcalicene (124), and 0.34 tt electrons for hexaphenylcalicene 115, (122) by the PPP (Pariser-Parr-Pople) method. Thus it seems as if the tt polarization roughly follows the same trend as the bond lengths and the C=C torsional barriers. 

If the carbon atom of the P=C bond is an integral part of the cyclopentadiene ring, the unpaired electron distribution proceeds in the way of spin-charge scattering (Al Badri et al. 1997). Scheme 1.7 illustrates this special case. 

When ring B in 57 is exchanged for a cyclopentadiene ring as in 61 the distance between the terminal rings will increase, what will result in a decrease of the Van der Waals interaction and less shielding. The experimental data follow the expected trend, even after correction for the influence of the five-membered ring structure U3). 

The bonding between the metal and the cyclopentadiene rings involves the it electrons of the two rings, all carbons being equally bonded to the central ferrous ion. The latter, in accepting a share of 12 tt electrons from two cyclo-pentadienyl anions, achieves the 18 outer-shell electron configuration1 of the inert gas, krypton. Analysis of the structure of crystalline ferrocene shows... 

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