Reaction patterns of ‘tetraferrio-azaallenium’, [(OC) 3Cp 2Fe 2(μ 4-CNC)Fe 2Cp 2(CO) 3] +, and its ‘activated cyanide’-precursor (μ-phthalimidocarbyne)tricarbonyldicyclopentadienyldiiron(1+)

Abstract

(μ-Phthalimidocarbyne)tricarbonyldicyclopentadienyldiiron(1+) ( 2) which, due to the facile cleavage with cis-[Fe 2Cp 2(CN)(μ-CO) 2CO] − ( 1) of its μ-CN bond to give ‘tetraferrio-azaallenium’ [(OC) 3Cp 2Fe 2(μ 4-CNC)Fe 2Cp 2(CO) 3] + ( 3), has been termed ‘activated cyanide’ reacts with pyrrolidine with ring opening to give the μ-acylisocyanide complex 5 carrying a further amido function in the o-position. Butyllithium gives rise to only traces of the corresponding mono deacylation product 6 while the main product is 3. Formation of complex 3 which is presumed to occur via partial bis-deacylation of 2 to give 1 and subsequent recombination with loss of phthalimide also dominates the reactions of 2 with CN − and [W(CN)(CO) 5] −. Here, however, the nucleophile also attacks the μ-carbyne carbon atom to give moderate yields of the desired μ-cyanoalkyliden complexes 7 and 10, the latter with [W]CN↔[W]NC isomerization and C–C bond formation. With [Cr(CN)(CO) 5] −, in contrast, substitution of a terminal CO ligand occurs with formation of the cyano-bridged trinuclear complex 9. The structures of complexes 7, 9 and 10 have been elucidated by X-ray analysis. Action upon ‘tetraferrio-azaallenium’ 3 of the primary amines H 2NCH 2CH 2R (R=Me, OMe, Ph) gives rise in low yields to the respective terminal isocyanides in compounds 11– 13. Here as in the reaction with NaNH 2 to give 14, a terminal carbonyl ligand is converted into an isocyanide or, respectively, cyano ligand by an exchange of oxygen for NR (N −). A second though less efficient approach to 14 is CO substitution in 3 by NaCN. Disubstitution of 3 to give 15 is observed with trimethylphosphite. In the reactions of 3 with diamines (H 2NCH 2CH 2NH 2, H 2NCH 2CH 2CH 2CH 2NH 2), on the other hand, cluster fragmentation occurs with formation of the mononuclear complexes 16 and 17 containing cyclic diaminocarbene ligands. A cyclic μ-aminocarbyne diiron complex 18 is obtained in traces from 3 and pyrrolidine.