Binuclear alkyne manganese carbonyls of the type (RC≡CR')Mn2(CO)
Rh(I)-catalyzed cycloisomerizations of bicyclo[1.1.0]butanes provide a fruitful approach to cyclopropane-fused heterocycles. Products and stereochemical outcome are highly dependent on catalyst. The triphenylphosphine (PPh3) ligand provides pyrrolidines, placing substituents
- NSF-PAR ID:
- 10382038
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract n (R and R'=methyl or dimethylamino;n =8, 7, 6) and their isomers related to the experimentally known (MeC2NEt2)Mn2(CO)n (n =8, 7) structures have been investigated by density functional theory. The alkyne ligand remains intact in the only low energy (Me2N)2C2Mn2(CO)8isomer, which has a central Mn2C2tetrahedrane unit and is otherwise analogous to the well‐known (alkyne)Co2(CO)6derivatives except for one more CO group per metal atom. The low‐energy structures of the unsaturated (Me2N)2C2Mn2(CO)n (n =7, 6) systems include isomers in which the nitrogen atom of one of the dimethylamino groups as well as the C≡C triple bond of the alkyne is coordinated to the central Mn2unit. In other low‐energy (Me2N)2C2Mn2(CO)n (n =7, 6) isomers the alkyne C≡C triple bond has broken completely to form two separate bridging dimethylaminocarbyne Me2NC ligands analogous to the experimentally known iron carbonyl complex (Et2NC)2Fe2(CO)6. The (alkyne)Mn2(CO)n (n =8, 7, 6) systems of the alkynes MeC≡CMe and Me2NC≡CMe with methyl substituents have significantly more complicated potential surfaces. In these systems the lowest energy isomers have bridging ligands derived from the alkyne in which one or two hydrogen atoms have migrated from a methyl group to one or both of the alkyne carbon atoms. These bridging ligands include allene, manganallyl, and vinylcarbene ligands, the first two of which have been realized experimentally in research by Adams and coworkers. Theoretical studies suggest that the mechanism for the conversion of the simple alkyne octacarbonyl (MeC2NMe2)Mn2(CO)8to the dimethylaminomanganaallyl complex Mn2(CO)7[μ‐η4‐C3H3Me2] involves decarbonylation to the heptacarbonyl and the hexacarbonyl complexes. Subsequent hydrogen migrations then occur through intermediates with C−H−Mn agostic interactions to give the final product. Eight transition states for this mechanistic sequence have been identified with activation energies of ∼20 kcal/mol for the first hydrogen migration and ∼14 kcal/mol for the second hydrogen migration. -
more » « less
Abstract Decarbonylation along with P‐atom transfer from the phosphaethynolate anion, PCO−, to the NbIVcomplex [(PNP)NbCl2(N
t BuAr)] (1 ) (PNP=N[2‐Pi Pr2‐4‐methylphenyl]2−; Ar=3,5‐Me2C6H3) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(Nt BuAr)] (2 ). Reduction of2 with CoCp*2cleaves the P−P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(Nt BuAr)] (3 ). Theoretical studies have been used to understand both the coupling of the P‐atom and the reductive cleavage of the P−P bond. Reaction of3 with a two‐electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P−P coupled ligand, namely [(PNPP)Nb=S(Nt BuAr)] (4 ). -
more » « less
Abstract Decarbonylation along with P‐atom transfer from the phosphaethynolate anion, PCO−, to the NbIVcomplex [(PNP)NbCl2(N
t BuAr)] (1 ) (PNP=N[2‐Pi Pr2‐4‐methylphenyl]2−; Ar=3,5‐Me2C6H3) results in its coupling with one of the phosphine arms of the pincer ligand to produce a phosphanylidene phosphorane complex [(PNPP)NbCl(Nt BuAr)] (2 ). Reduction of2 with CoCp*2cleaves the P−P bond to form the first neutral and terminal phosphido complex of a group 5 transition metal, namely, [(PNP)Nb≡P(Nt BuAr)] (3 ). Theoretical studies have been used to understand both the coupling of the P‐atom and the reductive cleavage of the P−P bond. Reaction of3 with a two‐electron oxidant such as ethylene sulfide results in a diamagnetic sulfido complex having a P−P coupled ligand, namely [(PNPP)Nb=S(Nt BuAr)] (4 ). -
more » « less
Abstract One route to address climate change is converting carbon dioxide to synthetic carbon‐neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo‐ and heterogeneous catalysis, deoxygenative coupling of CO to products with C−C bonds—as in liquid fuels—remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2
L (2 ), whereL 2−is a bis(β‐diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L ] (3 ), which undergoes silylation to Fe2(CO)(COSiMe3)L (4 ). Subsequent C‐OSiMe3bond cleavage and C=C bond formation occurs upon reduction of4 , yielding Fe2(μ‐CCO)L . CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallestJ value, with changes to local metal ion spin states and coupling schemes (ferro‐ vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of5 with KEt3BH or methanol releases the C2O2−ligand with retention of the diiron core -
more » « less
Abstract One route to address climate change is converting carbon dioxide to synthetic carbon‐neutral fuels. Whereas carbon dioxide to CO conversion has precedent in homo‐ and heterogeneous catalysis, deoxygenative coupling of CO to products with C−C bonds—as in liquid fuels—remains challenging. Here, we report coupling of two CO molecules by a diiron complex. Reduction of Fe2(CO)2
L (2 ), whereL 2−is a bis(β‐diketiminate) cyclophane, gives [K(THF)5][Fe2(CO)2L ] (3 ), which undergoes silylation to Fe2(CO)(COSiMe3)L (4 ). Subsequent C‐OSiMe3bond cleavage and C=C bond formation occurs upon reduction of4 , yielding Fe2(μ‐CCO)L . CO derived ligands in this series mediate weak exchange interactions with the ketenylidene affording the smallestJ value, with changes to local metal ion spin states and coupling schemes (ferro‐ vs. antiferromagnetism) based on DFT calculations, Mössbauer and EPR spectroscopy. Finally, reaction of5 with KEt3BH or methanol releases the C2O2−ligand with retention of the diiron core
