Bis ligation

Metal complexation with RlifCOI))2 +HI 4 only gives the mono-ligated catalyst (.S)-94, unlike metal complexations with MiniPhos, which affords the bis-ligated complex [Rh(MiniPhos)2]+BF4, 114... 

In addition to kinetic shifts, the threshold for a CID process can be delayed by competition with another decomposition channel. Consider the bis-ligated sodium cation, Na+(H20)(NH3), which can decompose by losing either ligand, Eq. (6) ... 

The lack of facial selectivity in BF3-OEt2-mediated reactions (entries 1, 6, 8 and 10) is not surprising as this Lewis acid is incapable of bis-ligation. Using an excess of gaseous BF.i a conformationally rigid... 

Satterlee etal extended these studies to characterize the axial lability of various imidazoles and pyridines in bis-ligated low-spin Fe complexes of synthetic porphyrins, including tetraphenyl-, octaethyl-, and tetra-n-propylporphyrins. For L = A -methylimidazole, typical rate constants k are 35-100s for TPPFeCl and T-n-PrPFeCl, and 950 s for OEPFeCl typical activation parameters determined in this study are = 17-20kcalmol = 15 —19 J mol More recently it has been shown by... 

Therefore, the structure of the reactive Pd(0) in oxidative addition (Pd (Cb) versus Pd°(Cb)2) is governed by the bulk of the carbene ligand but the reactivity is not necessarily controlled by the structure of the reactive species, since a bis-ligated Pd (Cb)2 (e.g. Cb = Cb ) may be even more reactive than a monoligated Pd (Cb ) (e.g. Cb = Cb ). Electronic factors must also be taken into consideration, C—C saturated carbenes (as Cb ) being stronger a-donors than C=C unsaturated carbenes (as Cb ) [65g]. 

Figure 8.2 Solid-state structure of nickel complexes featuring bis-ligating and monochelating TTP-type phosphonite ligands [39, 42).

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