Premium
New Chiral Cyclopentadienylrhenium Lewis Acids Featuring Fluorinated Triarylphosphanes and Enhanced Acceptor Abilities − An Unusual Carbon−Fluorine Bond Activation in a Metal Coordination Sphere
Author(s) -
Mohr Wolfgang,
Stark Gene A.,
Jiao Haijun,
Gladysz J. A.
Publication year - 2001
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/1099-0682(200104)2001:4<925::aid-ejic925>3.0.co;2-n
Subject(s) - chemistry , lewis acids and bases , fluorine , acceptor , coordination sphere , metal , carbon fibers , polymer chemistry , organic chemistry , catalysis , physics , materials science , composite number , composite material , condensed matter physics
The acetonitrile complex [(η 5 ‐C 5 H 5 )Re(NO)(NCCH 3 )(CO)] + BF 4 − ( 1 ) and P(4‐C 6 H 4 CF 3 ) 3 slowly react (2 d, room temperature) to give the substitution product [(η 5 ‐C 5 H 5 )Re(NO){P(4‐C 6 H 4 CF 3 ) 3 }(CO)] + BF 4 − ( 3 , 85%). The reaction of 1 and less nucleophilic P(C 6 F 5 ) 3 must be conducted in a melt at 140 °C, but [(η 5 ‐C 5 H 5 )Re(NO){P(C 6 F 5 ) 3 }(CO)] + BF 4 − ( 11 ) is isolated in 90% yield. Reduction of 3 by NaBH 4 gives the methyl complex (η 5 ‐C 5 H 5 )Re(NO){P(4‐C 6 H 4 CF 3 ) 3 }(CH 3 ), which is treated with TfOH and H 3 CN=C(H)C 6 H 5 to give the imine complex [(η 5 ‐C 5 H 5 )Re(NO)(PPh 3 ){N(CH 3 )=C(H)C 6 H 5 }] + TfO − ( 9 ). Complex 9 was, like the non‐fluorinated analog, unreactive towards allyltin nucleophiles. Complex 11 should lead to a more reactive imine complex, but NaBH 4 gave a methyl complex that was difficult to purify. However, NaOCH 3 or NaSCH 3 /methanol gave easily purified (η 5 ‐C 5 H 5 )Re(NO){P(4‐C 6 F 4 OCH 3 ) 3 }(CO 2 CH 3 ) (85%) or (η 5 ‐C 5 H 5 )Re(NO){P(4‐C 6 F 4 SCH 3 ) 3 }(CO 2 CH 3 ) (51%), in which all para ‐fluorine atoms have undergone nucleophilic displacements, and the carbonyl ligands methoxide additions. This suggests that catalytic chemistry of the chiral Lewis acid [(η 5 ‐C 5 H 5 )Re(NO){P(C 6 F 5 ) 3 }] + ( I ‐F 15 ) will be complicated by nucleophilic degradation. Nonetheless, density functional calculations show that I ‐F 15 is a much stronger σ acceptor and weaker π donor than less fluorinated analogs.