Synthesis and properties of chiral rhenium pentatetraenylidene complexes of the formula [(eta(5)-C5Me5)Re(NO)(PPh3)(= C = C = C = C = CAr2)]+BF4- (CAr2=9-fluorenylidene)
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abstract
The sequential reaction of (5-C5Me5)Re(NO)(PPh3)(CCCCH) with n-BuLi (one equivalent), 9-fluorenone (O=CAr2; 1.5 equivalents), and Me3O+BF4- (3.0 equivalents) gives thermally labile (5-C5Me5)Re(NO)(PPh 3)(CCCCC(OMe)Ar2) (2a) as an orange-red powder in 69% yield. Analogous reactions with 2,7-dichloro- and 2,7-dibromofluorenone give the corresponding complexes 2b,c (68-71%). Treatment of 2a-c with BF3OEt2 (one equivalent) gave the title complexes (3a-c) as labile dark blue powders (79-83%) that exhibited diagnostic cumulenic IR bands CCC (1993-1987, 1902-1894 cm-1) and Re=C 13C-NMR signals (256.9 ppm, JCP=10.8 Hz), and richly featured UV-vis spectra. Attempts to prepare stabile derivatives of 3a-c (additions of phosphines, amines, TCNE; anion metatheses) invariably gave a multitude of products. 2000 Elsevier Science S.A.
