Mononuclear Ru/Os Compounds with η1 and C5–C6 Ligands

Photocatalytic Conversion of CO2 to Formate/CO by an (η6-para-Cymene)Ru(II) Half-Metallocene Catalyst: Influence of Additives and TiO2 Immobilization on the Catalytic Mechanism and Product Selectivity

“…On the other hand, the incorporation of bulky η 5 - and η 6 -carbon donor ligands (i.e., Cp* and benzene derivatives) to a transition metal complex, which consequently forms a half-metallocene type metal complex, can be considered another potent strategy to prevent the intermolecular interaction during catalysis and enhance the related catalytic acitivity due to their intrinsic bulkiness of the aromatic carbon ligands that efficiently prevents catalyst–catalyst dimerization during catalysis and the stabilization effect of multiple redox states of the metal center by a synergetic bonding associated with metal-to-carbon back-donation and carbon-to-metal σ- and π-donation between metal and the carbon donor ligands, which adopts multiple oxidation/reduction states of the metal center [M 2+ ↔ M 0 for group 8 (Fe, Ru, and Os) and M 3+ ↔ M 1+ for group 9 (Co, Rh, and Ir)]. − In diverse catalytic applications using such half-metallocene complexes as a catalyst, a lot of papers showed that the face-bounded aromatic carbon rings can help stabilize the multivalent metal center and inhibit the intermolecular interaction during catalysis, allowing commonly the easy electrochemical detection of metal-hydride intermediates and showing the absence of dimeric catalytic route. , In this strategy, the aromatic five- or six-membered aromatic ring ligands, such as cyclopentadien (Cp) or benzene (Bz), have been extensively utilized as the primary bulky carbon donor ligands to construct a half-metallocene transition metal complex due to the convenient synthetic methods available for introducing bulky alkyl substituents (methyl or isopropyl groups) onto the Cp and Bz rings. − …”

Arene-Osmium(II) Complexes in Homogeneous Catalysis

“…Although the behavior of (η 6 -arene)-osmium(II) complexes mimics to some extent that of their ruthenium counterparts, the chemistry of the former has been comparatively much less studied [11,[36][37][38][39]. However, their catalytic potential is well documented and different works have shown that, in some instances, a comparable or even superior effectiveness can be achieved with this particular class of compounds when compared to their ruthenium analogues, or to related half-sandwich complexes of other metals more commonly employed in homogeneous catalysis, such as rhodium and iridium.…”