ISSN:
0009-2940
Keywords:
1,2-Azaborole ligand
;
Cobalt complexes
;
Chemistry
;
Inorganic Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
1,2-Azaborolyl Complexes, XXVIII[1]. - (η5-1-tert1-Butyl-2-methyl-1,2-azaborolyl)carbonyl Phosphane and -Olefin Cobalt ComplexesBy using (η5-1-tert1-butyl-2-methyl-1,2-azaborolyl)dicarbonyl-cobalt [η51-AbCo(CO)2] (1) as starting material, various phos-phane and olefin derivatives of the type AbCo(CO)L are synthesized. The phosphanes L=PMe3, PEt3, P(nPr)3, P(nBu)3, and P(OPh)3 give, due to the chirality of 1, the enantiomeric compounds 2-6, whereas the phosphanes P(tBu)MePh, P(OsBu)Ph2, and PPh2 [OCH(CH3)CO2CH3] form the diaster-eoisomers 7-9. The orange-red, oily and volatile compounds are isolated with yields between 30 and 60%. The mechanism of formation of [η51-AbCo(CO)PMe3] (2) has been studied by means of intermediates at low temperatures. To avoid a 20e configuration when PMe3 is added to 1, the allyl complex [η31-AbCo(CO)2PMe3] (2a) is formed. With an excess of PMe3 it can even be transferred into the mono-hapto complex [η11-Ab-Co(CO)2(PMe3)2] (2b) with a Co - C-3 s̰ bond. 2a as well as 2b change to [η51-AbCo(CO)PMe3] (2) when warmed up to room temperature. In contrast to substitution reactions of [Cp-Co(CO)2] where intermediates have never been observed, here an addition-elimination process is proved. With dimethyl ma-leate, maleic anhydride, and methylmaleic anhydride three olefin complexes 10, 11, and 12 are obtained. However, 10 contains the fumaric ester, due to a cis-trans isomerisation during the complexation. X-ray structure analyses prove the molecular structures of 11 and 12. The original goal of this project, namely to prepare pure enantiomeric [η51-AbCo-(CO)olefin] half-sandwich complexes in order to study the ster-eoselective influence of the Ab ring on addition reactions to the olefin ligands could not yet be reached.
Additional Material:
2 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/cber.19931260408
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