The Basics of Organometallic Complexes

CHAPTER 12 ORGANOTRANSITION METAL REACTION MECHANISMS AND CATALYSIS 

---

As discussed above in the mechanism of the alkene dimerization reaction, the polymerization of simple alkenes proceeds by the basic metathesis mechanism. Since polymers that are prepared from complex monomers require homogeneous catalysts, much of the early organometallic catalyst development has had polymer synthesis as the driving force. Recently, developments in the synthesis of organometallic complexes that serve as well-defined catalysts for metathesis have opened many opportunities in the area of polymer synthesis. ... 

Considerable progress has been made on C02 fixation in photochemical reduction. The use of Re complexes as photosensitizers gave the best results the reduction product was CO or HCOOH. The catalysts developed in this field are applicable to both the electrochemical and photoelectrochemical reduction of C02. Basic concepts developed in the gas phase reduction of C02 with H2 can also be used. Furthermore, electrochemical carboxyla-tion of organic molecules such as olefins, aromatic hydrocarbons, and alkyl halides in the presence of C02 is also an attractive research subject. Photoinduced and thermal insertion of C02 using organometallic complexes has also been extensively examined in recent years. 

In previous chapters, we have presented a great deal of information about structure and bonding in coordination compounds. This chapter will be devoted to describing some of the important chemistry in the broad areas of organometallic complexes and those in which there are metal-metal bonds. The body of literature on each of these topics is enormous, so the coverage here will include basic concepts and a general survey. 

It should be clear from the earlier sections that the basic requirement in applying the principles of organometallic chemistry is counting electrons associated with a complex. The formalisms arising out of this have been combined into two powerful rules of electron bookkeeping the 18-electron rule and its corollary the 16-18-electron rule. 

These results show that not only are novel radical-anions formed by interaction of Michael acceptors with I and related organometallics, but that the epr technique is an excellent method of ascertaining the basicity of the latter, as well as shedding light on the subtle aspects of the donor-acceptor interactions involved. The chemistry in Equation (1) is exactly analogous to that which occurs in initiation of Atom Transfer Radical Polymerization (ATRP) catalysis, Equation (2), where the same basic metal complexes and others are active (X = halide). 

---