Synthesis, structure, and reactivity of allene complexes of the chiral rhenium fragment [(.eta.5-C5H5)Re(NO)(PPh3)]+ Academic Article uri icon

abstract

  • Reactions of the chlorobenzene complex [(η5-C5H5)Re(NO)(PPh3)(ClC6H5)]+BF4− and excess (a) allene, (b) methylallene, and (c) 1,1-dimethylallene give the π adducts [(η5-C5H5)Re(NO)(PPh3) (PPh3) (η2-H2C=C= CRR')]+BF4− (1a-c) in 90-91% yields. The crystal structure of 1a (monodinic, P21/n, a = 10.327 (1) Å, b = 10.401 (1) Å, c = 23.919 (2) Å, β = 99.233 (2)°, Z = 4) shows the coordinated =CH2 group to be syn to the PPh3 ligand, with a 23.7° angle between the Re—P bond and the Re—C=C plane. NMR data show that the methyl groups in 1b,c occupy the less hindered positions on the free C=C linkages. Analogous reactions of chiral 1,3-dialkylallenes give mixtures of diastereomeric adducts with modest selectivities. Reaction of 1a and t-BuO−K+ in THF (−80 to +25 °C) gives the methylacetylide complex (η5-C5H5)Re-(NO)(PPh3)(C≡CCH3) (3, 92%). A similar reaction of 1a and CH3Li gives the allenyl complex (η5-C5H5)Re(NO)(PPh3)(CH=C=CH2) (4, 70%), which upon treatment with HBF4·OEt2 gives mainly the propyne complex [(η5-C5H5)Re(NO)(PPh3)(HC≡CCH3)]+BF4− (5). Reaction of Li+[(η5-C5H5)Re(NO)(PPh3)]− and HC≡CCH2OTs gives the propargyl complex (η5-C5H5)Re(NO)(PPh3)(CH2C≡CH), which isomerizes to 4 at 67-80 °C. Thus, the conversion of 1a to 3 is proposed to involve 4 and 5 as intermediates. © 1992, American Chemical Society. All rights reserved.

author list (cited authors)

  • Pu, J., Peng, T. S., Arif, A. M., & Gladysz, J. A.

citation count

  • 46

publication date

  • October 1992