1992
DOI: 10.1021/ic00041a004
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Spectroscopic assessment of the degree of .pi.-stabilization of unsaturation in ruthenium complex, RuH(X)CO(P-tert-Bu2Me)2

Abstract: We have argued1 that potential ir-donor ligands, X, when attached to a 15-electron fragment ML" can confer stability by forming not only an M-X tr-bond but also an X-*-M ir-bond via lone pairs on X. We have offered structural evidence of this for the d6 species Ir(H)2(ORf)(PCy3)2' and Cp*Ru(ORf)(PCy3)2 (Cp* = CsMes, Rf = CH2CF3). Both molecules nevertheless rapidly add nucleophiles under the mildest of conditions, so that any M/X ir-donation (and thus multiple bonding) still leaves them operationally unsaturat… Show more

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Cited by 117 publications
(72 citation statements)
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“…The isomeric complex with an amine at the trans position (Table , entry 4) is also predicted to react exergonically with CO 2 ; however, this insertion is over 3 kcal/mol less exergonic than that for the parent Ru hydride 1 . The weaker trans influence amine in entry 4 stabilizes the Ru–hydride bond in comparison to 1 and simultaneously destabilizes the Ru–formate bond through π-donor−π-acceptor “push–pull” effects . A further increase in π acidity at the cis position is explored with entry 5, for which a substantial decrease in the energetic favorability of CO 2 insertion is obtained, with Δ G ° 298 K = −4.6 kcal/mol.…”
Section: Results and Discussionmentioning
confidence: 99%
“…The isomeric complex with an amine at the trans position (Table , entry 4) is also predicted to react exergonically with CO 2 ; however, this insertion is over 3 kcal/mol less exergonic than that for the parent Ru hydride 1 . The weaker trans influence amine in entry 4 stabilizes the Ru–hydride bond in comparison to 1 and simultaneously destabilizes the Ru–formate bond through π-donor−π-acceptor “push–pull” effects . A further increase in π acidity at the cis position is explored with entry 5, for which a substantial decrease in the energetic favorability of CO 2 insertion is obtained, with Δ G ° 298 K = −4.6 kcal/mol.…”
Section: Results and Discussionmentioning
confidence: 99%
“…As pointed out by Doherty and Hoffman,)I this electronic substituent effect receives strong support in observed UV-vis absorption maxima and carbonyl stretching frequency shifts, since the magnitudes of both A, , , and vco in 1 increase upon descent in the halogen group.32 This ordering of the halide *-donating properties is also evident in other metal systems. 33 The extent of substituent r-donation may affect the magnitude of the activation barrier in two related ways. First, 4e/3 orbital interactions exist involving filled halide p orbitals, filled metal d orbitals, and empty CO(**) orbitals.…”
Section: H-h C-h-hmentioning
confidence: 99%
“…Alternatively, the lone pair of the oxygen atom in the POCOP framework may enhance the C→Ir‐ π ‐donation[15] and hence the filled–filled π – π interaction between the π orbital of the ipso‐ C‐atom and the filled d xy iridium orbital. The presence of the π ‐donating[17] siloxo ligands in the trans ‐position further contributes to the overall destabilization of the Ir(III) d 6 complex, thus favoring the reductive elimination with ethene to give the Ir(I) species [Ir(C 2 H 4 )(POCOP)]. It should be noted that, in the Ir(I) alkene complex, the trans arrangement of the ethene ligand, a π ‐acceptor, and of the π ‐donating ipso ‐C‐atom of the PCP ligand results in a stabilizing push–pull interaction.…”
Section: Resultsmentioning
confidence: 99%