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d 6 and d 8 Metal Carbonyl Complexes of 7,7‐Dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene. Stereoselective Hydroformylation of an [Fe(CO) 4 (olefin)] Complex
Author(s) -
Loset Jacques,
Roulet Raymond
Publication year - 1985
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.19850680130
Subject(s) - chemistry , hydroformylation , double bond , olefin fiber , metal , bimetallic strip , stereoselectivity , medicinal chemistry , hydrolysis , alkene , stereochemistry , selectivity , regioselectivity , catalysis , organic chemistry , rhodium
Reaction of 7,7‐dimethoxy‐5,6‐dimethylidenebicyclo[2.2.1]hept‐2‐ene ( 2 ) with various metal carbonyls and their derivatives gave the η 2 ‐M(CO) 4 (M = Fe ( 17 ), Ru ( 18 )), η 4 ‐M(CO) 3 (M = Fe ( 19x, 19n ), Ru ( 20n )), and η 2 ‐M(CO) 5 and η 6 ‐M(CO) 3 (M = Cr, Mo, W) complexes. The trigonal bipyramidal η 2 ‐M(CO) 4 complexes present an exceptional C 3 v symmetry at the metal with the C,C‐double bond in an axial position. In all the η 2 ‐complexes, this double bond is stereospecifically coordinated by its exo ‐ vs. endo ‐η 4 ‐Fe(CO) 3 configuration was established by chemical correlation (hydrolysis, hydrogenation) with the corresponding complexes ( 24x, 24n ) of 7,7‐dimethoxy‐2,3‐dimethylidenebicyclo[2.2.1]heptane ( 5 ). The relative rates of hydrolysis (AcOH/H 2 O 2:1, 50°C) of ligands 2 and 5 and of complexes 19x, 19n, 24x , and 24n to the corresponding ketones showed an acceleration effect only when the metal is coordinated to the exo ‐face. This was attributed to an F‐strain effect on the leaving group of the substrate. Compound 17 was further metallated by [Fe 2 (CO) 9 ] giving the bimetallic isomers 21xn and 21xx . The endocyclic C,C‐double bond of the latter can be stereospecifically hydroformylated (1 atm CO, AcOH/H 2 O, 25°C) giving 29x (49%). Hydroformylation of 17 gave the corresponding uncoordinated aldehydes 30x/30n in better yields (76%) but with lower selectivity (3:1). These are the first examples of hydroformylation of an isolated [Fe(CO) 4 (olefin)] complex.