Migratory insertion bonded compounds

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high labihty, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds... 

The higher catalytic activity of the cluster compound [Pd4(dppm)4(H2)](BPh4)2 [21] (20 in Scheme 4.12) in DMF with respect to less coordinating solvents (e.g., THF, acetone, acetonitrile), combined with a kinetic analysis, led to the mechanism depicted in Scheme 4.12. Initially, 20 dissociates into the less sterically demanding d9-d9 solvento-dimer 21, which is the active catalyst An alkyne molecule then inserts into the Pd-Pd bond to yield 22 and, after migratory insertion into the Pd-H bond, the d9-d9 intermediate 23 forms. Now, H2 can oxidatively add to 23 giving rise to 24 which, upon reductive elimination, results in the formation of the alkene and regenerates 21. 

In contrast to theoretical results reported by Morokuma [29] and Ziegler [30], as well as previous studies with Pd"-phen model compounds [26], the lowest experimental energy barrier was found for the migratory insertion of the acyl (ethene) complex (Eq. (10)). The relative rates of alkyl to CO and alkyl to ethene migratory insertion reactions allowed one to estimate that sequential ethene insertions occur once for every ca. 10 insertions of CO into the Pd-alkyl bond [18]. 

Organometallic Compounds. Mononuclear carbon monoxide complexes of palladium are relatively uncommon because of palladium s high lability, tendency to be reduced, and competing migratory insertion reactions in the presence of a Pd—C bond (201). A variety of multinuclear compounds are known (202), including [Pd2Cl4(CO)2] [75991-68-3], [Pd3(P(C6H5)3)3(CO)3] [36642-60-1], and [Pd7(P(CH3)3)7(p3-CO)3(p2-CO)4] [83632-51-3]. 

In view of the dual bonding modes of NO, migratory insertion (107) is not the only transformation of this type that can be envisioned. In (108), the nitrosyl is coordinated as NO", and the migration of the R group to form a coordinated nitroso or oxime compound can be viewed, at least heuristically, as a 1,2-shift of R+. 

Cp3MR (M = U, Th, Np) CO Cp M X R Migratory insertion reaction. The r 2-bonding of the CO insertion products is characteristic of such actinide compounds 281, 421... 

Fig. 8.3 Warren R. Roper (born in 1938) studied chemistry at the University of Canterbury in Christchurch, New Zealand, and completed his Ph.D. in 1963 under the supervision of Cuthbert J. Wilkins. He then undertook postdoctoral research with James P. Collman at the University of North Carolina at Chapel Hill in the US, and returned to New Zealand as Lecturer in Chemistry at the University of Auckland in 1966. In 1984, he was appointed Professor of Chemistry at the University of Auckland and became Research Professor of Chemistry at the same institution in 1999. His research interests are widespread with the emphasis on synthetic and structural inorganic and organometallic chemistry. Special topics have been low oxidation state platinum group metal complexes, oxidative addition reactions, migratory insertion reactions, metal-carbon multiple bonds, metallabenzenoids and more recently compounds with bonds between platinum group metals and the main group elements boron, silicon, and tin. His achievements were recognized by the Royal Society of Chemistry through the Organometallic Chemistry Award and the Centenary Lectureship. He was elected a Fellow of the Royal Society of New Zealand and of the Royal Society London, and was awarded the degree Doctor of Science (honoris causa) by the University of Canterbury in 1999 (photo by courtesy from W. R. R.)...

Danoponlos et al. reported the crystal structure of a palladium pincer carbene complex that is the product of intramolecular 1,2-methyl migration from palladium to the carbene carbon atom, a process also referred to as a migratory insertion of the carbene into the Pd-methyl bond [434] (see Figure 3.150). The importance of this compound stems from the fact that it was the first unambiguous experimental evidence for this process actually to take place after it had been suspected for several years with the suspicion being backed by several theoretical calculations [447-449]. 

Alkyl iridium compounds are also accessible via insertion (see Migratory Insertion) of alkenes into Ir H bonds. Analogously, alkenyl iridium compounds may be formed via insertion of alkynes into Ir-H bonds. These types of reactions have been studied to shed tight on the mechanism of alkene and alkyne hydrogenation processes. For example, HIr(CO)(PPh3)2 (65) will react with ethylene and higher olefins to produce the alkyl iridium compounds (equation 17). 

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