Isocyanide, metal cations

The reactions of nucleophilic reagents with cationic and uncharged metal carbonyl complexes have received much attention in the past, and it is not surprising that these studies have now been extended to isocyanide metal complexes. Different products in these reactions can arise by three general routes these include ligand substitution, reactions involving attack at a ligand, and reduction of the metal complex. All have been observed in reactions with metal isocyanide complexes. 

To further complicate the picture, the related isocyanide-substituted cation, [Os(=Cp-tolyl)(CNp-tolyl)(CO)(PPh3)2], undergoes a fast thermal reaction with HCl as depicted in Scheme 3. The cationic carbene complex produced is converted by treatment with LiEt3BH to the neutral substituted-benzyl complex labelled B in Scheme 3. The overall two-step transformation of A into B is a good example of the conversion of a metal-carbon triple bond to a metal-carbon single bond by sequential addition of "H+ followed by "H-" [11]. 

The susceptibility of a metal complex to nucleophilic attack is enhanced by a positive charge on the complex. This fact, and the fact that most metal isocyanide complexes are cationic, probably explains why no nucleophilic reactions of uncharged isocyanide complexes have yet been reported. It is... 

The isocyanide analogues of the above carbonyls, frans-[Mo(CNR)2(dppe)2] (R = alkyl or aryl) undergo a reversible one-electron oxidation in solution4,5 and oxidation with I2 or Ag1 salts allows isolation of the paramagnetic cation [Mo(CNC6H4Me)2(dppe)2]+ = 2.01 BM). With other isocyanides, substitution at the metal centre occurs on further oxidation.48... 

Cationic 1,2-silyl migration was proposed to be involved during the reactions of carbon monooxide and isocyanides with transition metal-carbon bonds (ligand distribution) (equation 18)55-65. Typically, the reaction of l-sila-3-zirconacyclobutane 29 with carbon monooxide afforded a dioxasilazirconacyclohexane derivative 30. The reaction was considered to proceed via a CO insertion into a Zr—C bond followed by a 1,2-silyl migration as shown in equation 1960. This type of reactions are well-documented in a review of Durfee and Roth well66. 

Addition of an electrophile (see Electrophile) to metal-bound cyanides will often form an isocyanide ligand (see Electrophile), -CsN-R. For example, the compound [Fe P(OMe)3 (NO)2(j7 -C3H4R)], which is a source of the allyl cation ( -C3H4R)+, reacts with trans-[Mn(CN)(CO)(dppm)2] to alkylate the cyanide, giving an allyl isocyanide ligand (equation 8). The tungsten alkyne... 

---