Novel (fulvalene)dichromium alkyl and acyl complexes of the types FvCr2(CO)6−nLnRR′ and Et4N[FvCr2(CO)6−nLnR] (R, R′ = Me, CH2CN, COMe; L = CO, PMe2Ph; n = 0, 1, 2)

Abstract

The compound FvCr2(CO)6Me2 (1) is obtained, via the intermediate formation of Et4N[FvCr2(CO)6Me] (2), by stepwise addition of 2 equivalents of methyl iodide to (Et4N)2[FvCr2(CO)6]; the analogous cyanomethyl compounds FvCr2(CO)6(CH2CN)2 (3) and Et4N[FvCr2(CO)6(CH2CN)] (4) are formed similarly. Compound 1 readily undergoes CO insertion upon treatment with 2 equivalents of PMe2Ph, giving rise to trans,trans-FvCr2(CO)4(PMe2Ph)2(COMe)2 (6), also in two steps via trans-FvCr2(CO)5(PMe2Ph)(Me)(COMe) (8). The neutral methyl "half" of 2 reacts similarly with PMe2Ph to form Et4N[trans-FvCr2(CO)5(PMe2Ph)(COMe)] (7), while the anionic "half" of 2 is alkylated with ClCH2CN to give FvCr2(CO)6(CH2CN)Me (5). Treatment of 5 with PMe2Ph also results in CO insertion into the Cr—Me bond to give trans-FvCr2(CO)5(PMe2Ph)(CH2CN)(COMe) (10). Although 3 is inert to both substitution and insertion reactions with PMe2Ph, the phosphine-substituted dialkyl (fulvalene)dichromium complex trans,trans-FvCr2(CO)4(PMe2Ph)2(CH2CN)2 (9) is prepared by reaction of ClCH2CN with (Et4N)2[FvCr2(CO)4(PMe2Ph)2]. Key words: chromium, metal–metal bonds, fulvalene.