Sulfur Dioxide Insertion. General Considerations and Background

SULFUR DIOXIDE INSERTION. GENERAL CONSIDERATIONS AND BACKGROUND 

Sulfur dioxide insertion reactions may be represented by the equation 

Products isolated from the insertion of SO2 into transition metal-carbon bonds have been shown to adopt structures (I), (III), and possibly, (IV). The first mode of bonding, expected of class b (la) or soft metals (105), is by far the most common one encountered. In fact, oxygen-bonded insertion products have been isolated only for titanium and zirconium (131, 132). However, recent spectroscopic studies have demonstrated that (III) is the kinetic product of the insertion with a number of metal carbonyl alkyls and aryls it then isomerizes to (I) (72, 73)  

This aspect of the SO2 insertion will be considered in detail in Section III, B. 

Sulfur dioxide insertions can be either intermolecular or intramolecular. For example, in the reaction (3) (73) precoordination of the inserting 

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II. Sulfur Dioxide Insertion. General Considerations and Background... 

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