Redox induced reactions of transition metal π- and σ,π-complexes

Electrochemical and Spectroscopic Studies on σ-Phenyl Ruthenium Complexes Ru(CO)Cl(C6H4R-4)(PiPr3)2

“…This difference is probably rooted in a higher spin density/higher positive charge at the most reactive para -position of the phenyl complex as compared to its more delocalized styryl congener. Oxidatively induced dehydrodimerizations of complexes with carbon-rich ligands have been described on several occasions. , Examples are the couplings of vinylidene complexes Cp­(CO) 2 Mn­(CCHPh) to the ethenyl-bridged bis­(carbyne) complex Cp­(CO) 2 MnC–C­(Ph)C­(Ph)–CMn­(CO) 2 Cp or of the related Cp*Mn­(CO) 2 (CCHPh), Cp­(CO)­(PPh 3 )­Mn­(CCHPh), and Cp­(dppe)­Fe­(CCHMe) complexes to bis­(vinylidene) complexes {Mn}CC­(Ph)–C­(Ph)C{Mn} or [{Fe}CCMe-CMeC{Fe}] 2+ , respectively (Cp = η 5 -C 5 H 5 ; Cp* = η 5 -C 5 Me 5 ; dppe = 1,2-bis­(diphenylphosphanyl)­ethane). , Related dehydrodimerizations of complexes {M}–CCH to butadiynediyl-bridged dimetal complexes {M}–CC–CC–{M} on the dual action of an oxidant and a base have also been reported ({M} = Cp­(dppe)­Fe, or trans- Mn­(dmpe) 2 (CCSiMe 3 ), dmpe = 1,2-bis­(dimethylphosphanyl)­ethane) . Even closer analogies, however, exist to triarylamines with at least one unsubstituted phenyl ring, which couple oxidatively to tetraarylbenzidines with concomitant proton or H atom loss. − This adds another facet to the previously noted resemblance of {Ru} and NAr 2 entities. ,, …”

“…Oxidatively induced dehydrodimerizations of complexes with carbon-rich ligands have been described on several occasions. 54,55 Examples are the couplings of vinylidene complexes Cp(CO) 2 Mn(CCHPh) to the ethenyl-bridged bis(carbyne) complex Cp(CO) 2 MnC−C-(Ph)C(Ph)−CMn(CO) 2 Cp 56 or of the related Cp*Mn-(CO) 2 (CCHPh), Cp(CO)(PPh 3 )Mn(CCHPh), and Cp(dppe)Fe(CCHMe) complexes to bis(vinylidene) complexes {Mn}CC(Ph)−C(Ph)C{Mn} or [{Fe}CCMe-CMeC{Fe}] 2+ , respectively (Cp = η 5 -C 5 H 5 ; Cp* = η 5 -C 5 Me 5 ; dppe = 1,2-bis(diphenylphosphanyl)ethane). 57,58 Related dehydrodimerizations of complexes {M}−CCH to butadiynediyl-bridged dimetal complexes {M}−CC−CC−{M} on the dual action of an oxidant and a base have also been reported ({M} = Cp(dppe)Fe, 59 or trans-Mn(dmpe) 2 (CCSiMe 3 ), dmpe = 1,2-bis-(dimethylphosphanyl)ethane).…”

Ligand Redox Non‐Innocence in Transition‐Metal σ‐Alkynyl and Related Complexes

“…However, examples of orbital reorganisation following oxidation are known for σ-alkynyl complexes, and therefore it is prudent to explicitly consider the electronic structure of both partners in a redox pair before describing a redox reaction in terms of metal-or ligandcentred processes. [24] Previous reviews have addressed various aspects of the redox chemistry of organometallic complexes, [25] including the electronic structures and chemical reactions of 17-electron metal-centred radicals, [26] the ligand-centred reactions of organometallic radicals, [27][28][29] including the reduction chemistry of unsaturated ligands such as carbenes, [30] and the redox chemistry of complexes bearing vinylidene and higher cumulene ligands. [31] We have been drawn to the chemistry of σ-alkynyl complexes because the π-donor character of the σ-alkynyl ligand, coupled with moderate π-accepting behaviour, [32,33] provides scope for the involvement of the ligand in higher-lying molecular orbitals.…”

Redox Noninnocence of Carbene Ligands: Carbene Radicals in (Catalytic) C−C Bond Formation

“…In the field of synthetic organometallic chemistry, the playground of catalytic synthetic organic transformations, controlling the radical-type reactivity of open-shell organometallic compounds offers vast opportunities to develop a wide variety of new, fast, and selective catalytic transformations. , Organometallic complexes present many ways to form ligand radicals , which can play a dominating role in directing the open-shell reactivity of these compounds, thus providing an attractive possibility of achieving selectivity and of uncovering new reactivity in the emerging field of open-shell organometallic chemistry. − Many new discoveries can be expected from future research in this area, especially in the realm of catalysis. − …”