Tolman electronic parameters

0 frans-effect ligand (jt acceptor or strong o donor) Ligand labilized by L  

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Rates of oxidation of para-substituted arylphosphines with singlet oxygen show good correlation with the Hammett a parameter (p = —1.53) and with the Tolman electronic parameter. The only products are the corresponding phosphine oxides. However, for ortho-substituted phosphines with electron-donating substituents, there are two products, namely a phosphinate formed by intramolecular insertion and phosphine oxide. Kinetic analyses demonstrated that both products are formed from the same intermediate, a phosphadioxirane. VT NMR experiments showed that perox-idic intermediates can only be detected for highly hindered and very electron-rich arylphosphines 243... 

Fig. 1 Relationship between the Tolman electronic parameters and IR stretching frequencies for complex 2 (data compiled from [12,16])...

Figure 8 Enthalpy of phosphine exchange reaction (kcal mol ) vs Tolman electronic parameter (cm ) for fra 5-(PR3)2Cl2Ru=CH-CH=CPh2 complexes slope = 1.93 R = 0.98)...

Figure 4 Nolan and co-workers correlation of average values for [(L)lr(CO) CI] complexes with the Tolman electronic parameter (TEP)d° (m) Experimental values for phosphines ( ) experimental values for NEfCs and (a) values obtained by linear regression. (See insert for color/color representation of this figure)...

Tolman Electronic Parameter and Cone Angle The dependence of the electronic effect of various PR3 ligands on the nature of the R group has been quantified by Tolman,who compared the v(CO) frequencies of a series of complexes of the type LNi(CO)3, containing different PR3 ligands. The stronger donor phosphines increase the electron density on Ni, which passes some of this increase along to the COs by back donation. This, in turn, lowers v(CO) as shown in Fig. 4.4. 

Figure 2.10 Tolman electronic parameter (TEP) versus the average CO stretching frequency, i-a , for selected NHCs and phosphines. For the sake of readability, only the most popular NHCs are labeled.

IV-heterocycHc carbenes tend to be more donor than PR3—the Tolman electronic parameters (TEP) for typical NHCs w they are more donor than even the most donor phosphines PMes, 2064 cm 11.1, 20S4 cm 11.19,... 

Gusev DG, Peris E. The Tolman electronic parameter (TEP) and the metal-metal electronic communication in ditopic NHC complexes. Dalton Trans. 2013 42 7359-7364. 

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