Boron cyclopentadienyl derivatives

An interesting compound, cyclopentadienyl(manganese tricarbonyl) copper, was obtained from the boronic acid derivative on treatment with copper(II) acetate in aqueous 2% sodium hydroxide (209). 

As a second illustrative aspect of the boron/carbon connection, we consider the dicarbollide ion, C2B9H112-, which can be pictured as derived from Bi2Hi22- by removing one BH(t) vertex and replacing two adjacent borons of the exposed pentagonal face by carbon atoms, as shown in Fig. 3.116. This ion exhibits remarkable electronic mimicry of the cyclopentadienyl ion (C5H5-, Section 3.3.2), forming similar coordination and sandwich complexes with many metallic species.162... 

A novel approach to derivatives of a boron heterocycle isoelectronic to benzene was reported in the reaction of phenylboron dihalide with bis-(cyclopentadienyl)cobalt followed by reaction with tin tetrahromide ... 

The ring systems now known to form such stacked organometallic arrays include mono- and di- as well as tri-boronated derivatives of the cyclopentadienyl anion (BR)x(C R )5 similar derivatives of benzene (IiR)i((T ),j,ijL... 

Figure 17. The 10-vertex metallacarborane deltahedra in the (C5H5M)2C2BeH8 (M = Fe, Co) complexes discovered by Hawthorne and co-workers in the 1970s showing the contrast between the closo dicobalt derivative with 22 skeletal electrons and the isocloso diiron derivative with only 20 skeletal electrons. Hydrogen atoms on the boron and carbon atoms and cyclopentadienyl rings on the metal atoms are not shown.

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