Premium
1,2‐Azaborolyl‐Komplexe, XXVIII. (η 5 ‐1‐ tert 1‐Butyl‐2‐methyl‐1,2‐azaborolyl)carbonyl‐Phosphan‐und ‐Olefin‐Cobalt‐Komplexe
Author(s) -
Schmid Günter,
Kilanowski Bert,
Boese Roland,
Bläser Dieter
Publication year - 1993
Publication title -
chemische berichte
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 0009-2940
DOI - 10.1002/cber.19931260408
Subject(s) - chemistry , olefin fiber , cobalt , medicinal chemistry , stereochemistry , chirality (physics) , isomerization , catalysis , organic chemistry , chiral symmetry breaking , physics , quantum mechanics , nambu–jona lasinio model , quark
1,2‐Azaborolyl Complexes, XXVIII [1] . – (η 5 ‐1‐ tert 1‐Butyl‐2‐methyl‐1,2‐azaborolyl)carbonyl Phosphane and ‐Olefin Cobalt Complexes By using (η 5 ‐1‐ tert 1‐butyl‐2‐methyl‐1,2‐azaborolyl)dicarbonyl‐cobalt [η 5 1‐AbCo(CO) 2 ] ( 1 ) as starting material, various phos‐phane and olefin derivatives of the type AbCo(CO)L are synthesized. The phosphanes LPMe 3 , PEt 3 , P( n Pr) 3 , P( n Bu) 3 , and P(OPh) 3 give, due to the chirality of 1 , the enantiomeric compounds 2–6 , whereas the phosphanes P( t Bu)MePh, P(O s Bu)Ph 2 , and PPh 2 [OCH(CH 3 )CO 2 CH 3 ] 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 [η 5 1‐AbCo(CO)PMe 3 ] ( 2 ) has been studied by means of intermediates at low temperatures. To avoid a 20e configuration when PMe 3 is added to 1 , the allyl complex [η 3 1‐AbCo(CO) 2 PMe 3 ] ( 2a ) is formed. With an excess of PMe 3 it can even be transferred into the mono‐hapto complex [η 1 1‐Ab‐Co(CO) 2 (PMe 3 ) 2 ] ( 2b ) with a Co – C‐3 s̀ bond. 2a as well as 2b change to [η 5 1‐AbCo(CO)PMe 3 ] ( 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 [η 5 1‐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.