Activation of cluster-bound carbonyls

These can be activated by surfaces or by chemical procedures under homogeneous conditions. 

CO have been activated by reacting osmium carbido-carbonyl clusters with alcohols to form coordinated CO2R groups under mild conditions no evidence of surface effects was established. A comparable reaction is methoxide attack on 

Although chemical activation of coordinated carbonyls is mostly used for synthetic purposes, some examples relevant for comparison with the reactivity on surfaces should be mentioned. CO activation can be achieved in several ways the best known are the use of Me3NO,l of Na-benzophenone ketyl or of [PPN]X (PPN = bis(triphenylphosphino)iminium cation [N(PPh3)2]+ X = halogen) salts.I Metal complexes may also be effective these usually work via electron-transfer catalysis or radical mechanisms.  

The use of Me3NO to induce substitution of dppm (bis(diphenylphosphino)-methane) for CO molecules on dinuclear iron complexes led to insertion of CO into C-C bonds of alkyne-derived metallacycles. Similar behavior was observed when [PPNJCl salts were used to favor the formation of alkyne-substituted triruthenium dppm-containing clusters.I This behavior should be compared with the insertion of CO into allenylidene and phosphido-bridging ligands occurring when dppm coordinates to binuclear ruthenium complexes as shown in Fig. 3. This reaction is a nucleophilic attack of the coordinated allenylidene and phosphido groups on a coordinated CO (see Section 2.8.2.2). 

The formation of Me3NO can also be exploited in reductive carbonylation reactions for example, in the synthesis of benzotriazole photostabilizers from 

---