oxidation reactions, typical condensation reactions such as aldol condensation or
Michael addition may be carried out with alcohols as starting material by in situ
oxidation to carbonyl moieties, employing finely tuned manganese complexes. In
this book chapter, we describe the development of the emerging field of manganesecatalyzed hydrogenation/dehydrogenation reactions in conjunction with metalligand cooperation processes.
Keywords Bidentate ligands · Dehydrogenation reactions · Homogeneous
catalysis · Hydrogenation reactions · Manganese complexes · Pincer ligands
1 Introduction
The development of sustainable synthesis is one of the major goals in modern
chemistry. Within this context, the use of catalysts in order to substitute procedures
employing reagents is highly favorable. This leads to more cost-efficient and environmentally benign processes. In the last decades, a broad variety of different
catalytic systems were implemented in modern organic synthesis. Most of these
catalysts are based on precious metals such as palladium, platinum, ruthenium, or
rhodium. These systems often show high reactivity and stability. However, the
amount of precious metals is limited, since the production from natural resources
is limited. Although recycling systems were developed over the last decades, a
supply risk may occur in the future. Therefore, the substitution of precious metals
by inexpensive and earth-abundant elements seems to be highly favorable [1]. Interestingly, the use of manganese(I) [1–3] complexes for organic synthesis was
neglected until 2016. Manganese is the third most abundant metal in the earth’s
crust. Apart from that, a broad variety of well-defined manganese(I) complexes can
be easily synthesized from the air- and moisture-stable, commercially available
manganese(I) pentacarbonyl halide [Mn(CO) 5 X] (X ¼ Cl, Br) precursors. Due to
the presence of carbonyl ligands, most of the synthesized complexes are diamagnetic
d
6 -low-spin systems, which allow characterization not only via infrared analysis but
also via NMR spectroscopy. Apart from that, the strongly bonded carbonyl ligands
stabilize the complex in this oxidation state and typically lead to air- and moisturestable complexes [4–11].
Very shortly after the first seminal reports in (de)hydrogenation reactions, a
growing number of organic and organometallic chemists used a broad variety of
well-defined manganese(I) systems for sustainable oxidation and reduction reactions
[12, 13]. Many of these catalytic reactions involve metal-ligand cooperation (MLC).
Within this book chapter, we describe the role of well-defined manganese complexes
in catalytic hydrogenation and dehydrogenation reactions. Since most of the systems
strongly rely on the possibility of metal-ligand cooperativity, we will focus on the
228
S. Weber and K. Kirchner
Michael addition may be carried out with alcohols as starting material by in situ
oxidation to carbonyl moieties, employing finely tuned manganese complexes. In
this book chapter, we describe the development of the emerging field of manganesecatalyzed hydrogenation/dehydrogenation reactions in conjunction with metalligand cooperation processes.
Keywords Bidentate ligands · Dehydrogenation reactions · Homogeneous
catalysis · Hydrogenation reactions · Manganese complexes · Pincer ligands
1 Introduction
The development of sustainable synthesis is one of the major goals in modern
chemistry. Within this context, the use of catalysts in order to substitute procedures
employing reagents is highly favorable. This leads to more cost-efficient and environmentally benign processes. In the last decades, a broad variety of different
catalytic systems were implemented in modern organic synthesis. Most of these
catalysts are based on precious metals such as palladium, platinum, ruthenium, or
rhodium. These systems often show high reactivity and stability. However, the
amount of precious metals is limited, since the production from natural resources
is limited. Although recycling systems were developed over the last decades, a
supply risk may occur in the future. Therefore, the substitution of precious metals
by inexpensive and earth-abundant elements seems to be highly favorable [1]. Interestingly, the use of manganese(I) [1–3] complexes for organic synthesis was
neglected until 2016. Manganese is the third most abundant metal in the earth’s
crust. Apart from that, a broad variety of well-defined manganese(I) complexes can
be easily synthesized from the air- and moisture-stable, commercially available
manganese(I) pentacarbonyl halide [Mn(CO) 5 X] (X ¼ Cl, Br) precursors. Due to
the presence of carbonyl ligands, most of the synthesized complexes are diamagnetic
d
6 -low-spin systems, which allow characterization not only via infrared analysis but
also via NMR spectroscopy. Apart from that, the strongly bonded carbonyl ligands
stabilize the complex in this oxidation state and typically lead to air- and moisturestable complexes [4–11].
Very shortly after the first seminal reports in (de)hydrogenation reactions, a
growing number of organic and organometallic chemists used a broad variety of
well-defined manganese(I) systems for sustainable oxidation and reduction reactions
[12, 13]. Many of these catalytic reactions involve metal-ligand cooperation (MLC).
Within this book chapter, we describe the role of well-defined manganese complexes
in catalytic hydrogenation and dehydrogenation reactions. Since most of the systems
strongly rely on the possibility of metal-ligand cooperativity, we will focus on the
228
S. Weber and K. Kirchner