Carbonyls, metal migratory insertion involving

The preparation of metal carbamoyl [M-C(0)NR2] and silaacyl [M-C(0)SiR3] derivatives by the migratory insertion of CO in the appropriate metal amide (M-NR2) or silyl (M-SiR3) complexes is also precedented. " Although CO reacts with metal-acyl bonds to give a-ketoacyl compounds, this and related reactions that appear to be double carbonylations but do not actually involve two consecutive CO migratory insertions have also been teported. ... 

The third route involves abstraction of CO from an organic compound. This can happen for aldehydes, alcohols, and even CO2. In the example shown in Eq. 4.7, the reaction requires three steps the second step is the reverse of migratory insertion. The success of the reaction in any given instance relies on the thermodynamic stability of the final metal carbonyl product, which is greater for a low-valent metal. Note that the first step in the case of an aldehyde is oxidative addition of the aldehyde C—H bond. It is much more difficult for the metal to break into a C—C bond. This means that ketones, R2CO, are usually resistant to this reaction. 

The insertion of CO into metal-carbon a bonds has been reviewed.585-590 Carbonylation of alkyl platinum(II) complexes usually requires elevated temperatures, although at higher temperatures the reaction is reversible (equation 211).591 With PtMe2(dppe) insertion occurs into only one of the Pt—Me bonds. For complexes PtX(Ar)L2, carbonylation follows pseudo first-order kinetics. Rates are decreased by addition of L to a maximum value where the carbonylation rate is independent of L. The pathway involves formation of a five-coordinate intermediate PtX(Ar)(CO)L2, followed by dissociation to form PtX(Ar)(CO)L. The migratory step to yield PtX(COAr)L is unaffected by added L. This pathway is outlined in Scheme 6.502... 

---