Heteroatoms in rings

•	Examine the structure of Refcode entry EBEDUK.

•

To this point, all the examples illustrated have only used hapticity to describe metal to carbon bonding; however, the use of hapticity terminology may be used to describe the bonding of any organic moiety to a metal. For example, bis(η5-2,3,4,5-tetramethylpyrrolyl)ruthenium(II). That is, two C4Me4N- ligands are bonding η5 to a ruthenium ion, as depicted in the following diagram:

 

•

In the case of (C4Me4N)2Ru, all ring carbon atoms AND the nitrogen heteroatoms are bonding to the metal, so the η5 designation is appropriate. A heteroatom in a ring need not necessarily bond to the metal, in which case it would not be included in the hapticity count. For example, the compound C13H11FeNO6 below has tetrahapto coordination to four carbon atoms; however, the nitrogen in the ring does not bond to the metal.

 

•	A good name for the this compound is 4,5,6,7-η4-(3-formyl-N-ethoxycarbonylazepine)tricarbonyl iron(0). The "4,5,6,7"preceding the "η4" is necessary to explicitly distinguish between this compound and other isomers such as the 2,3,4,5-η4 isomer. Sketch the 2,3,4,5-η4 isomer.