H-agostic interaction

The first step is coordination of the ethylene through its n orbital. The ethylene is trans to Cl with the C=C bond in the Cl-Ru-H plane. Facile migratory insertion (AE = 7.6 kcal.mol 1) of the coordinated ethylene in the Ru-H bond leads to an alkyl intermediate 6.2 kcal.mol 1 less stable than the n ethylene complex. The alkyl intermediate has a strong P C-H agostic interaction as illustrated by the unusually long agostic C-H bond (1.221 A) which helps to stabilize the unsaturation in the formally 14-electron alkyl intermediate. 

The single-site product of the reaction of the perhydrocarbyl Re(VII) complex [Re(-CH2- Bu)2(=CH- Bu)(=C- Bu)] with siUca Si02 7oo, [(=SiO)Re(=CH- Bu)(=C- Bu)], is very closely modeled by the reaction with the monosilanol silsesquioxane la [149] and by the reaction with triphenylsilanol [150], where, similarly to the surface data, the syn and anti isomers can be idenhfied, with the former giving rise to an H-agostic interaction [151]. An intereshng difference exists while the... 

Figure 10 Neutron structure of Zr(9-BBN)4 [9-BBN = (/r-H)2BC8 H14]. The three Zr... H agostic interactions are indicated hy hollow bonds. (Reprinted with permission from Ding, Du, Meyers, Shore, Yousufiiddin, Bau and McIntyre. 2005 American Chemical Society)...

A series of complexes of the general structure 102 has been studied. For the cyclobutyl, cyclopentyl, and cyclohexyl derivatives, crystallographic and NMR data showed a-agostic interactions. In sharp contrast, the cyclopropyl complex showed no sign of C-H agostic interactions. Instead, an unusual a-agostic C-C interaction was detected. ... 

The last member of the family [NbCl(Tp )(c-CnH2n-i)] (n = 3-6) has been also recently reported [NbCl(c-C4H7)(Tp )(MeC=CMe)] is similar to cyclopentyl and cyclohexyl analogues, and very different from the cyclopropyl derivatives. The cyclobutyl complex exhibits an a-C-H agostic interaction in the dominant isomer, with no evidence for the a-C-C agostic character found for the smaller ring that seems to be unique for the cyclopropyl complex.41... 

C-H agostic interaction from a pendant alkyl (dRuC = 2.588 A) and a weaker interaction from a phosphine methyl group (dRuC = 3.049 A).57... 

The C-H Agostic Interaction, from Early Studies to Recent Interpretations. 5... 

The High Sensitivity of the C-H Agostic interaction to the Nature of the Moiecuie... 

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