56791-54-9Relevant articles and documents
Lewis acid assisted reactions of N-acylimidazoles with transition-metal nucleophiles. A route to formyl transition-metal complexes
Kongshaug, Phillip A.,Miller, Roy G.
, p. 372 - 378 (1987)
Lewis acid assisted acylations of Na2M(CO)4 complexes (M = Fe, Ru, Os) by N-acylimidazoles have been investigated, and N-formyl- (1), N-acetyl- (6), N-pivaloyl- (7), and N-benzoylimidazole (8) have been examined as acyl transfer agents. The yields of NaFe(CO)4CHO on treatment of Na2Fe(CO)4 with 1 were found to be dependent upon the types of solvent and Lewis acid employed. Optimum yields were obtained in HMPA by using 2 equiv of (MeO)3B/equiv of 1. THF and N-methylpyrrolidinone could also be employed as solvents. These reaction conditions enabled the in situ synthesis of the new anionic formylmetal complexes Na-Ru(CO)4CHO and NaOs(CO)4CHO. The NaM(CO)4CHO complexes and NaFe(CO)4COPh were characterized in solution by NMR and infrared spectroscopy. [PPN]Fe(CO)4COCH3 and [PPN]Fe(CO)4CO-t-Bu have been isolated by treatment of the NaFe(CO)4COR product mixtures with PPNCl. Acylations of Na2M(CO)4 complexes by 1 and 6 occurred only in the presence of a Lewis acid. In the absence of a Lewis acid, 1 was decarbonylated to afford NaM(CO)4H and sodium imidazolate and 6 underwent a Claisen-type condensation. Sodium imidazolate also caused the decarbonylation of 1 and the self-condensation of 6. 7 and 8 acylated Na2Fe(CO)4 in both the presence and the absence of R3B Lewis acids. The results of the study show that the Lewis acid scavenges the sodium imidazolate byproduct, prohibiting its promotion of the decarbonylation of 1 and the enolization of 6. The Lewis acid also appears to increase the susceptibility of the N-acylimidazole to nucleophilic attack at the acyl carbon.
Ligand substitution processes on carbonylmetal derivatives. 2. Reaction of tetracarbonylhydridoferrates with phosphites
Brunet,Commenges,Kindela,Neibecker
, p. 3023 - 3030 (2008/10/08)
Ligand substitution processes on KHFe(CO)4 (1) have been evidenced by reaction with various phosphites. The nature of the reaction products strongly depends on (i) the nature of the solvent, (ii) the Tolman cone angle of the phosphite, and (iii) the reaction conditions. In protic media (H2O-THF), phosphites with small cone angles, such as P(OMe)3, P(OEt)3, and P(OPh)3, react (2 equiv) with 1 at room temperature to give the corresponding complexes H2Fe(CO)2[P(OR)3]2 in >90% yield, whereas a phosphite with a larger cone angle (P[O-o-C6H4Ph]3) reacts only at a higher temperature to afford the disubstituted Fe(CO)3[P{O-o-C6H4Ph}3]2 derivative in 94% yield. When the reaction with phosphites having small cone angles is conducted with a 3-fold excess of phosphite at 65°C, the trisubtituted derivatives Fe(CO)2[P(OR)3]3 are formed in 75-96% yield. In aprotic medium (THF), 1 reacts with phosphites (2 equiv) at room temperature to yield the monosubstituted anionic hydrides K+[HFe(CO)3{P(OR)3}]-, which can be isolated in >90% yield. In refluxing THF the reaction of 1 with P(OMe)3 (3 equiv) demonstrates the first synthesis of the hydridoferrate K+[HFe(CO)2{P(OMe)3}2]-. Protonation of K+[HFe(CO)3{P(OR)3}]- with trifluoroacetic acid in THF at -10°C provides an excellent route for the high-yield synthesis of the monosubstituted dihydrides H2Fe(CO)3[P(OR)3]. In situ reaction of the latter with another phosphane PZ3 (Z = Ph, OPh) leads to the mixed dihydrides H2Fe(CO)2[P(OR)3][PZ3] (R = Me, Et; Z = Ph, OPh), which are reported for the first time. Finally, reaction of H2Fe(CO)2[P(OEt)3]2 with KH under sonication allows the generation of the highly reduced derivative K2[Fe(CO)2{P(OEt)3}2], the first disubstituted analogue of the Collman reagent.
A Facile, high-yield synthesis of trans-Fe(CO)3(PR3)2 from Fe(CO)5, Fe(CO)4CHO-, HFe(CO)4-, or HFe(CO)3PR3-
Keiter, Richard L.,Keiter, Ellen A.,Hecker, Karl H.,Boecker, Carol A.
, p. 2466 - 2469 (2008/10/08)
The reaction of Fe(CO)5 with PR3 and NaBH4 in refluxing n-butyl alcohol affords high yields of trans-Fe(CO)3(PR3)2. It has been shown that Fe(CO)4PR3, which does not appear in the collected product, is also not a significant intermediate in the reaction. The reaction proceeds by initial formation of H2 gas and Fe(CO)4CHO-. The formyl complex decomposes to HFe(CO)4- which reacts with PR3 to give the disubstituted product. The principal intermediate for this substitution is believed to be HFe(CO)3PR3-, although polynuclear species may also be important. The substitution of HFe(CO)4- by PR3 is favorable when the counterion is Na+ but not when it is PPN+. The overall reaction is very sensitive to choice of solvent; substitution of ethanol for n-butyl alcohol leads to greatly reduced yields.
