Reaction of Carbon Dioxide and Heterocumulenes with an Unsymmetrical Metal-Metal Bond. Direct Addition of Carbon Dioxide across a Zirconium-Iridium Bond and Stoichiometric Reduction of Carbon Dioxide to Formate

Synthesis and Reactions of Polynuclear Polyhydrido Rare Earth Metal Complexes Containing “(C5Me4SiMe3)LnH2” Units: A New Frontier in Rare Earth Metal Hydride Chemistry

“…Although a large number of studies on the hydrogenation of CO 2 with both homogeneous and heterogeneous systems have been reported, the observation of formation of a methylene diolate species remains rare. [18] The present formation of the methylene diolate species is in sharp contrast with what was observed previously in the case of other transition metal polyhydride complexes such as [{(C 5 H 5 )Ti(µ-H)} 2 (C 10 H 8 )], [19] [(C 5 H 5 ) 2 Zr(H)(µ-H)(µ-NtBu)Ir(C 5 Me 5 )], [20] [H 2 Ru(dmpe) 2 ], [21] and [H 4 Mo(dmpe) 2 ], [22] [dmpe = 1,2-bis(dimethylphosphanyl)ethane] which yield either bis(formate), [18,21] mixed hydride/formate, [19,20] or mixed hydride/carbonate complexes [21] upon reaction with CO 2 . Further insertion of CO 2 into the metal-diolate bonds in 23 could also take place to give the mono-and dicarbonate complexes 24 and 25 in a stepwise manner, with possible release of formaldehyde (HCHO; Scheme 11).…”

Aerobic Oxidation of Carbon Monoxide in a Tetrametallic Complex

“…The structural data of the CO 2 moiety indicate a partial π bond delocalization in the CO bonds, with angles around the carbon (C35) close to 120° and quite different CO bond lengths for the free (C35–O7≅1.24 Å) and coordinated (C35–O8≅1.35 Å) oxygen atoms. Moreover, these data, along with the chemical shift for the carbon ( δ =173.4 ppm), suggest a description of this group as a dianionic formate ligand 12b. Accordingly, the $\tilde \nu $ (CO 2 ) band for 4 at 1610 cm −1 , identified by the 13 C isotopically induced band shift (to 1574 cm −1 ), lies in the frequency range of carboxylate groups.…”

CO2 Activation and Catalysis Driven by Iridium Complexes

“…The only crystal structure of a CO 2 molecule coordinated to an iridium center reported so far is that published by Bergman in 1995 7a. That imido complex was synthesized by direct insertion of a CO 2 molecule into the IrZr bond of ELHB complex 3 to afford resulting Ir‐(μ 2 ‐η 2 C,O )‐CO 2 ‐Zr bridged complex 4 (Scheme ).…”