Carbene complex, surface bounded

In this regard, it is noteworthy that while surface bound hydroxycarbenes are postulated species, discrete complexes containing hydroxy- and alkoxy-carbenes have been known since E. O. Fischer s studies beginning in 1964 (56, 57). These complexes are possibly analogous to proposed surface intermediates, and their chemistry may model some of the heterogeneously catalyzed transformations. Coupling of alkoxy carbenes, for example, gives dialkoxy olefins as observed in (20). 

Ionic liquids (ILs) were introduced in catalysis by Yves Chauvin in the 1990s [33a] and have received considerable attention in this field [33b,cj. Yves Chauvin introduced the imidazolium salts that are the most frequently used ILs in catalysis. ILs are valuable media for catalysis with PdNPs because the substituted imidazolium cation is bulky, favoring the electrosteric stabilization of NPs, as do the t-Bu N salts in Fig. 1.1. The size of the cation (that can eventually be tuned by the choice of the N-alkyl substituents) also has an important influence on the stabilization, size and solubUity of the NPs, these factors playing a role in catalysis. ILs are also non-innocent, however, as they readily produce Pd-N-heterocyclic carbene complexes upon deprotonation of the imidazoHum salt at sufficiently high temperature. Thus, these carbene ligands can be bound to the NP surface or give mononuclear mono- or bis-carbene complexes subsequent to leaching of Pd atoms from the PdNP surface (vide infra) [33]. 

It should be noted that, so far, these studies have been mostly confined to relatively simple organometallic molecular complexes, and none have involved nanoparticle molecules. Therefore, a fundamental question arises, when redox-active moieties are bound onto a transition-metal nanoparticle surface through conjugated chemical bonds will effective electronic communication take place between these particle-bound functional moieties This issue has been addressed in a recent study in which carbene-functionalized ruthenium nanoparticles are used as the nanoscale structural scaffold, and ferrocene moieties are exploited as the molecular probe because of well-known electrochemical and spectroscopic characteristics. 

---