Metathesis with Anionic Chelating Ligands

A very successful strategy of anchoring charge neutral donor moieties is the substitution of anionic monodentate substituents by anionic chelators. In the same way, additional anionic donor moieties can be introduced in the Si coordination sphere, which are less likely to bind to Si if of monodentate nature. Various routes 

---

An extension of the research on silver complexes with Lewis base-functionalized mono(A-heterocyclic carbene) ligands has been made toward the better-studied and stronger coordinating phosphine systems. The reaction of a diphenylphosphine-functionalized imidazolium salt with silver oxide in dichloromethane affords a trinuclear silver carbene complex 50, as confirmed by electrospray-ionization mass spectrometry.96,97 Metathesis reaction of 50 in methanol using silver nitrate gives 51 in 33% yield. The crystal structures of 51 were found to be different when different solvents were used during crystallization (Scheme 12).97 One NO3- anion was found to be chelated to... 

Typical alkene metathesis precatalysts take the form displayed in Figure 2.3, consisting of a ruthenium(II) center, a carbene with substituent R, two anionic ligands X (typically chloride), a nondissociating l and L (typically a trialkylphosphine or NHC), and a dissociating ligand, which is most often either a phosphine or a chelating alkoxyarene. While the nature of X, L,, and R all influence the initiation rate and mechanism, it is the nature of L and X that detemiine the catalytic activity of the active species itself complexes G2, M2, and GH2 all produce the same active species, albeit via different mechanisms and at different rates. 

---