Ring tilting

Ru(CO)(TDCPP) reacts with styrene oxide (stO) in CH Cl giving Ru(CO)(stO) (TDCPP), the X-ray crystal stmcture of which was determined. The epoxide is coordinated via its oxygen atom to the Ru (Ru-0 2.220(3) A) with the coordinated epoxide ring tilted at 49° to the porphyrin ring. Such a species could be a model for intermediates formed during aUcene epoxidations catalysed by Ru porphyrinate complexes [864],... 

Fig. 15.36 Solid-state structure of (MejCd-Ba. Metallocene units are arranged in quasipolymeric chains and a ring-Ba-ring tilt of 131 is observed. Lines connecting Bu and methyl groups indicate the shortest intermolecular contacts. [From Williams, R. A. Hanusa, T. P. Hoffman. J. C. J. Chem. Soc. Chem. Cuminim. 1988. 1045-1046. Reproduced with permission. ...

Substitution of methyl groups on the oxirane ring tilts the stability of the tautomers in favor of oxepin. Thus 1-methylbenzene oxide (154) exists as 2-methyloxepin (155), in rapid equilibrium with the benzene oxide tautomer 154.74 The AH has been calculated as 0.4 0.02 kcal/mol, i.e., 1.3 kcal/mol... 

In contrast to the unidentate and open-bridging dppf complexes, the chelates generally exhibit a greater extent of ring tilting but minimal divergence of the phosphorus atoms. Mean values of 6 of known chelates 4.1° 0.05 A, com-... 

There is also evidence that Cp ring tilting is most marked among the square-planar chelates. This tilt could provide a facile mechanism to release the strain that is brought about by a small bite. A good example is illustrated in [Ir(dppf-P, P )2][BPh4]... 

Fig. 1-10. Skeletal freedom of dppf in its bridging state (1) Cp...Fe...Cp torsional twist (2) Cp ring tilting (3) displacement of phosphorus atom from coplanarity with Cp ring (4) rotation of C(Cp)-P bond (5) skewing of ferrocenyl backbone with respect to the M-M bonding axis.

Si- and C2-bridged ferrocenophanes have same ring-tilt angle (21°)... 

The appearance of nontotally symmetric modes in the emission spectrum has important ramifications to the structure of the excited state. Because they do appear, the point group of the excited state of ruthenocene is lower than Djh. The point group in the excited state must be one in which these vibrational modes are totally symmetric. The point group which satisfies this condition is C,. In this symmetry, the 445 cm ring-metal stretch and one component of the ring tilt mode are totally symmetric. The involvement of... 

To prepare [2]metallocenophanes that are even more strained than [2]ferrocenophanes 30, species with a larger ruthenium atom in the place of iron have been synthesized (81). Such [2]ruthocenophanes would be expected to possess much greater ring-tilt angles moreover, because ruthenocene is known to possess significantly different electrical properties compared to ferrocene, modified polymer properties would be anticipated (57). 

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