Towards ligand simplification in manganese-catalyzed hydrogenation and hydrosilylation processes

Well-Defined Phosphine-Free Manganese(II)-Complex-Catalyzed Synthesis of Quinolines, Pyrroles, and Pyridines

“…The development of sustainable catalytic systems for alcohol dehydrogenation and related coupling reactions using earth-abundant transition metals is exciting and highly desirable. − In the past decade, significant progress has been made on 3d transition-metal (Fe, Co, Mn, Ni, etc. )-catalyzed alcohol dehydrogenation and associated reactions because of its higher abundance, lower toxicity, and lesser cost of these metals.…”

The Dichotomy of Mn–H Bond Cleavage and Kinetic Hydricity of Tricarbonyl Manganese Hydride Complexes

“…Generally, the formation of catalytically relevant transition metal hydrides from the corresponding bromide precursors proceeds in situ in the presence of various basic additives. This activation step can be nicely illustrated for Mn(I) complexes fac-[(P-NHC)Mn(CO) 3 Br] (P-NHC = κ 2 P,C-Ph 2 PCH 2 -NHC) [4] and fac-[(dppm R )Mn(CO) 3 Br] (dppm = κ 2 P,P-Ph 2 PCH(R)PPh 2 , R = H, Me, Ph) [5] in the presence of KHMDS leading to the formation of cyclometalated species capable of activating dihydrogen via unconventional metal-ligand cooperation. The resulting hydride products fac-[(L-L )Mn(CO) 3 H] interact with organic substrates to form non-covalent adducts and typically the formation of such intermediates directly precedes hydride/proton transfer steps providing in fine the hydrogenation of polar C=X bonds.…”

“…A search for inexpensive and efficient catalysts that give more sustainable alternatives to platinum group metals recently led to remarkable progress in the development of catalytic systems based on organometallic manganese complexes [1,2]. While pincer-type Mn(I) derivatives still dominate in the field of catalytic (de)hydrogenation, it was demonstrated that less elaborated bidentate systems fac-[(L-L )Mn(CO) 3 Br] may also be highly efficient [3]. Generally, the formation of catalytically relevant transition metal hydrides from the corresponding bromide precursors proceeds in situ in the presence of various basic additives.…”

“…Nevertheless, there are a few families of hydrides in which the same hydride complex possesses distinct reactivity. Dual reactivity is well documented, for example, for groups 6-8 metal complexes [CpM(CO) 3 H] (M = Mo, W), [(CO) 5 MH] (M = Mn, Re) and [CpM(CO) 2 H] (M = Fe, Ru, Os) [8,[10][11][12]. Whether the M-H bond releases a proton or hydride, obviously, depends on the partner reagent.…”

Mechanistic insight into borrowing-hydrogenN-alkylation catalyzed by an MLC catalyst with dual proton-responsive sites

“…The choice of ligand has been shifted to the phosphine-free ligand as well. [15][16][17][18] With the gradual extension of research in this area, novel strategies have been proposed, particularly the introduction of dual active sites on the ligand utilizing different MLC modes, which enables the catalyst to switch the favourable MLC mode automatically when encountering multiple catalytic stages. In 2014, Milstein et al synthesized a Ru-PNNH complex (Scheme 1a Cat.1), which possesses the N-H functionality and the aromatization/dearomatization active sites on the lutidinederived ligand.…”