141902-83-2Relevant academic research and scientific papers
Addition, cycloaddition, and metathesis reactions of the cationic carbyne complexes [Cp(CO)2Mn≡CCH2R]+ and neutral vinylidene complexes Cp(CO)2M=C=C(H)R (M = Mn, Re)
Terry, Michael R.,Mercando, Lisa A.,Kelley, Colleen,Geoffroy, Gregory L.,Nombel, Paul,Lugan, No?l,Mathieu, René,Ostrander, Robert L.,Owens-Waltermire, Beth E.,Rheingold, Arnold L.
, p. 843 - 865 (2008/10/08)
The cationic alkylidyne complexes [Cp(CO)2M≡CCH2R]+ (M = Re, R = H; M = Mn, R = H, Me, Ph) undergo facile deprotonation to give the corresponding neutral vinylidene complexes Cp(CO)2M=C=C(H)R. For [Cp(CO)2Re≡CCH3]+, this transformation occurs spontaneously at -78°C upon the addition of solvent (CH2Cl2 or THF) to the solid carbyne complex, but the manganese complexes [Cp(CO)2Mn≡CCH2R]+ (R = H, Me) require the addition of external base (e.g., Et3N) to induce their deprotonation. The manganese benzylcarbyne complex [Cp(CO)2Mn≡CCH2Ph]+ is intermediate in behavior. Except for Cp(CO)2Mn=C=C(H)Ph, these vinylidene complexes are thermally unstable and must be generated and studied at low temperature. They are potent dipolarophiles which undergo net [2 + 2] cycloaddition with imines to give cyclic carbene complexes of the general form Cp(CO)2M=CC(H)RC(H)PhN(R′) (M = Re, R = H, R′ = Me, Ph; M = Mn, R′ = Ph, R = H (17a), Me, Ph (17c)). Identical manganese products form upon treatment of the manganese carbyne complexes first with imine followed by addition of Et3N. Permanganate oxidation of the manganese cyclic carbene complexes gives the corresponding β-lactams in excellent yield. Also formed in the reactions of the rhenium complex Cp(CO)2Re=C=CH2 with imines are the products Cp(CO)2Re=CC(=C(H)Ph)C(H)PhN(R′) (R′ = Me, Ph (15b)), which have an exocyclic double bond formed via an aldol-type condensation between the initial cycloadduct and excess imine. The vinylidene complexes Cp(CO)2M=C=C(H)R react with HN=C(Ph)2 to give imino-carbene complexes of the general form Cp(CO)2M=C(CH2R)N=C(Ph)2, which are derived by addition of the N-H bond across the vinylidene C=C bond. Similar products form upon benzophenone imine addition to the manganese carbyne complexes, followed by addition of Et3N. Also formed in the reaction of Cp(CO)2Mn=C=C(H)Ph or [Cp(CO)2Mn≡CCH2Ph]+ with HN=C(Ph)2 is the [2 + 2] cycloadduct Cp(CO)2Mn=CC(H)Ph-C(Ph)2N(H). Nitrile complexes, Cp(CO)2MnN≡CCH2R, result from an organometallic analogue of the Beckmann rearrangement upon treatment of Cp(CO)2Mn=C=C(H)R (R = H, Ph) or [Cp(CO)2Mn≡CCH2R]+ (R = H, Me) with Ph2C=NNH2. Isocyanide complexes, Cp(CO)2ReC≡NR, are the result of reaction of the vinylidene complex Cp(CO)2Re=C=CH2 with carbodiimides (RN=C=NR; R = Pri, But), a reaction that proceeds via net metathesis of the vinylidene Re=C bond with the carbodiimide C=N bond. A similar isocyanide product forms upon reaction of [Cp(CO)2Mn=CCH3]+ with ButN= C=NBut and Et3N, and a 13C labeling experiment indicates a mechanism involving a 1,3-migration of the [Cp(CO)2Mn] fragment in the intermediate [Cp(CO)2MnC(=CH2)N(But)=C=N(But)]. Reaction of both [Cp(CO)2Mn≡CCH3]+ and Cp(CO)2Mn=C=CH2 with PriN=C=NPri gave the ansa-carbene complex {η5-C5H4C(=CH2)}(CO) 2Mn=C(N(H)Pri)(NPri) (41) by a path involving a similar 1,3-migration of the [Cp(CO)2Mn] fragment and insertion of the original vinylidene or carbyne α-carbon into the one of the C-H bonds of the cyclopentadienyl ligand. A byproduct of this reaction is the bis(amino)carbene complex {η5-C5H4-C(O)CH3(CO) 2Mn=C(NHPri)2 (45), with an acetyl substituent on the cyclopentadienyl ligand, a product that likely results from hydrolysis of the above-mentioned ansa-carbene complex. The unusual zwitterionic vinylidene complex Cp(CO)2Mn=C=C(Me)CN(But)B-Cl2N +(But) (46) is the principal product of the reaction of the propylidyne complex [Cp(CO)2Mn≡CCH2Me]+ with ButN=C=NBut and Et3N. With benzalazine, Ph(H)C=NN=C(H)Ph, the complexes Cp(CO)2Re=C=CH2 and [Cp(CO)2Mn≡CCH3]+ react to form the bimetallic bis(carbene) complexes Cp(CO)2M=CC(H)2C(H)PhNNC(H)PhC(H)2C=M(CO) 2Cp (M = Re, Mn (47)), which result from consecutive [3 + 2] cycloaddition reactions of the azine with 2 equiv of the organometallic reagents. Crystal structures are reported for 15b, 17a, 41, 45, 46, 47, and the η5-C5H4Me analogue of 17c.
