56791-54-9Relevant academic research and scientific papers
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.
Iron Catalyzed Hydroformylation of Alkenes under Mild Conditions: Evidence of an Fe(II) Catalyzed Process
Pandey, Swechchha,Raj, K. Vipin,Shinde, Dinesh R.,Vanka, Kumar,Kashyap, Varchaswal,Kurungot, Sreekumar,Vinod,Chikkali, Samir H.
supporting information, p. 4430 - 4439 (2018/04/05)
Earth abundant, first row transition metals offer a cheap and sustainable alternative to the rare and precious metals. However, utilization of first row metals in catalysis requires harsh reaction conditions, suffers from limited activity, and fails to tolerate functional groups. Reported here is a highly efficient iron catalyzed hydroformylation of alkenes under mild conditions. This protocol operates at 10-30 bar syngas pressure below 100 °C, utilizes readily available ligands, and applies to an array of olefins. Thus, the iron precursor [HFe(CO)4]-[Ph3PNPPh3]+ (1) in the presence of triphenyl phosphine catalyzes the hydroformylation of 1-hexene (S2), 1-octene (S1), 1-decene (S3), 1-dodecene (S4), 1-octadecene (S5), trimethoxy(vinyl)silane (S6), trimethyl(vinyl)silane (S7), cardanol (S8), 2,3-dihydrofuran (S9), allyl malonic acid (S10), styrene (S11), 4-methylstyrene (S12), 4-iBu-styrene (S13), 4-tBu-styrene (S14), 4-methoxy styrene (S15), 4-acetoxy styrene (S16), 4-bromo styrene (S17), 4-chloro styrene (S18), 4-vinylbenzonitrile (S19), 4-vinylbenzoic acid (S20), and allyl benzene (S21) to corresponding aldehydes in good to excellent yields. Both electron donating and electron withdrawing substituents could be tolerated and excellent conversions were obtained for S11-S20. Remarkably, the addition of 1 mol % acetic acid promotes the reaction to completion within 16-24 h. Detailed mechanistic investigations revealed in situ formation of an iron-dihydride complex [H2Fe(CO)2(PPh3)2] (A) as an active catalytic species. This finding was further supported by cyclic voltammetry investigations and intermediacy of an Fe(0)-Fe(II) species was established. Combined experimental and computational investigations support the existence of an iron-dihydride as the catalyst resting state, which then follows a Fe(II) based catalytic cycle to produce aldehyde.
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.
Solution Homolytic Bond Dissociation Energies of Organotransition-Metal Hydrides
Tilset, Mats,Parker, Vernon D.
, p. 6711 - 6717 (2007/10/02)
The homolytic bond dissociation energies (BDEs) of the mononuclear metal carbonyl hydride complexes (η5-C5H5)M(CO)3H (M = Cr, Mo, W), (η5-C5Me5)Mo(CO)3H, (η5-C5H5)W(CO)2(PMe3)H, (η5-C5H5)M(CO)2H (M = Fe, Ru), H2Fe(CO)4, Mn(CO)4PPh3H, Mn(CO)5H, Re(CO)5H, and Co(CO)3LH (L = CO, PPh3, P(OPh)3) have been estimated in acetonitrile solution by the use of a thermochemical cycle that reguires knowledge of the metal hydride pKa and the oxidation potential of its conjugate base (anion).The BDE values obtained by this method fall in the range 50-67 kcal/mol.In mostcases, these results agree well with literature data.Our data provide strong support for the common assumption that the M-H bond energies are greater for third-row and for second-row metals than for first-row metals, the difference being 5-11 kcal/mol.Effects of neither phosphine or phosphite substitution nor permethylation of the cyclopentadienyl ring on the M-H bond energies could be detected within the error limits of the method.The results are discussed in relation to previous M-H BDE estimates and metal hydride reactivity patterns.
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.
Comparitive Reactivities of Two Isoelectronic Transition-Metal Hydrides with Transition-Metal Carbonyls and Alkyls
Jones, William D.,Huggins, John M.,Bergman, Robert G.
, p. 4415 - 4423 (2007/10/02)
The two isoelectronic hydrides PPN+CpV(CO)3H- (1) and -CpMo(CO)3H (2) react with a variety of metal carbonyls and alkyls.Treatment of Fe(CO)5, Cr(CO)6, (CH3C5H4)V(CO)4, CH3Re(CO)5, and (CH3CO)Re(CO)5 with 1 produces HFe(CO)4-, HCr(CO)5-, (CH3C5H4)V(CO)3H-,(H)(CH3)Re(CO)4-, and (H)(CH3CO)Re(CO)4-, respectively, and CpV(CO)4 (3). 1 also catalyzes ligand substitution reactions in 3 and CpFe(CO)(PPh3)(COCH3).In comparison 2 reacts only with CH3Mn(CO)5 and CpMo(CO)3R (R=CH3, C2H5, CH2C6H5) producing aldehydes and the dimers 2 (4a) and 2 (5a).Reaction of 2 with ethylene produces ethane and diethyl ketone. 1 is proposed to react by an electron-transfer mechanism, whereas 2 is proposed to react by hydrogen transfer to a vacant coordination site.The relationship of the molybdenum hydride/alkyl reaction to the final step in hydroformylation (oxo process) is discussed.
