Synthesis, Structure, and Fluxional Behavior of Bis(cyclooctatetraene)ruthenium(0) and Its Derivatives

Abstract

The complex Ru((1−6η)-C8H8)((1−4-η)-C8H8) (2), which is made in two steps from Ru(acac)3, shows three fluxional processes: (1) equilibration of the protons and carbon atoms of the (1−4-η)-C8H8 ring, which appear as a singlet even at −100 °C; (2) role reversal (exchange of hapticity) of the two rings; (3) a 1,5-shift within the (1−6-η)-C8H8 ring. Processes 2 and 3 cause the 1H and 13C resonances of C8H8 to appear as a broad singlet at room temperature, though the (1−6-η)-ring is static at ca. −60 °C. The free energies of activation ΔG ⧧ 235 for processes 2 and 3 have been estimated from magnetization transfer experiments to be 12.8 ± 0.2 and 13.5 ± 0.2 kcal mol-1, respectively. Complex 2 reacts with ligands L to give adducts Ru(L)((1−4-η)-C8H8)((1,2,5,6-η)-C8H8) (L = CO (4), CN-t-Bu (5), P(OMe)3 (6), PMe3 (7), and PEt3 (8)). The (1,2,5,6-η)-rings in these compounds are static at room temperature and do not exchange with the fluxional (1−4-η)-C8H8 rings. The (1−4-η)-C8H8 ring in 4 undergoes the usual 1,2-shift, the free energy of activation ΔG ⧧ 259 of 13.7 ± 0.1 kcal mol-1 being considerably higher than that of 2 or of Ru(CO)3((1−4-η)-C8H8). The X-ray structures of 2, 4, 5, and 7 are reported.

Bis(1,2,3,4-η4-anthracene)cobaltate(1−)

“…Deep green 4 is noteworthy in that it represents only the third well‐characterized anionic homoleptic cot transition metal complex,24 which is surprising in view of the good acceptor ability of this ligand. To our knowledge, the only other structurally authenticated homoleptic cot complexes of the later (Groups 7–11) transition metals are [Fe(cot) 2 ],25 [Ru(cot) 2 ],26 and [Ag(cot)] + 27. Although attempts to prepare neutral homoleptic cot complexes of cobalt (by metal vapor syntheses) were unsuccessful,28 two nickel species are well characterized, [{Ni(cot)} 2 ] and [Ni(cot) 2 ] 29a.…”

Acetato and acetylacetonato ruthenium(II) complexes containing SbPri3, PPri3 and PCy3 as ligands ‡

“…A similar observation was made by Singleton and co-workers 8 who prepared the complexes [{Ru(η 1 -O 2 CR)-(η 4 -C 8 H 12 )} 2 (µ-O 2 CR) 2 (µ-OH 2 )] (R = CF 3 , CCl 3 or CH 2 Cl), which are structurally related to 2, by a similar route. As far as the NMR data of 2 are concerned, other characteristic features are the two sets of signals for the protons and the carbon atoms of the CO 2 Me groups in the 1 H and 13 C NMR spectra and the four resonances (again both in the 1 H and 13 C NMR spectra) for the CHCH 3 and the CHCH 3 nuclei. The latter observation indicates that the two stibine ligands on each metal centre are not equivalent.…”

The fragment bis(acetylacetonato)ruthenium: a meeting-point of coordination and organometallic chemistry

“…Either zinc amalgam or freshly activated zinc powder are suitable reducing agents. In this way, the cyclooctatetraene complex [Ru(acac) 2 (g 2 , g 2 -1,3,5,7-C 8 H 8 )] has been obtained in good yield [28]. Cyclooctene gives the labile complex cis-[Ru(acac) 2 (g 2 - 1 Ligand abbreviations used in this paper: acac = acetylacetonate,2,4-pentanedionato, C 5 H 7 O 2 ; 1,5-COD = 1,5-cyclooctadiene; NBD = norbornadiene, [2,2,1]bicyclohepta-2,5-diene; phen = 1,10-phenanthroline; dppe = 1,2 bis(diphenylphosphino)ethane; dppp = 1,3-bis(diphenylphosphino)propane; S-BINAP = S-2,2 0 -bis(diphenylphosphino)-1,1 0 -binaphthyl; OEP = dianion of 2, 3,7,8,12,13,17, 18- (2), which is stable in solution only in the presence of an excess of cyclooctene [26], whereas the more stable ethene complex, cis-[Ru(acac) 2 (g 2 -C 2 H 4 ) 2 ] (3), can be isolated as a yellow-orange solid in ca.…”