Nachweis der Zwischenstufen bei der sequenziellen Elektronen- und Wasserstoffabgabe aus einem Dicarbonylcobalthydrid-Komplex

Synthesis and Reactivity of Organometallic Intermediates Relevant to Cobalt-Catalyzed Hydroformylation

Intermediates relevant to cobalt-catalyzed alkene hydroformylation have been isolated and evaluated in fundamental organometallic transformations relevant to aldehyde formation. The 18-electron (R,R)-(^iPr DuPhos)Co(CO)₂ H has been structurally characterized, and it promotes exclusive hydrogenation of styrene in the presence of 50 bar of H₂ /CO gas (1:1) at 100 °C. Deuterium-labeling studies established reversible 2,1-insertion of styrene into the Co-D bond of (R,R)-(^iPr DuPhos)Co(CO)₂ D. Whereas rapid β-hydrogen elimination from cobalt alkyls occurred under an N₂ atmosphere, alkylation of (R,R)-(^iPr DuPhos)Co(CO)₂ Cl in the presence of CO enabled the interception of (R,R)-(^iPr DuPhos)Co(CO)₂ C(O)CH₂ CH₂ Ph, which upon hydrogenolysis under 4 atm H₂ produced the corresponding aldehyde and cobalt hydride, demonstrating the feasibility of elementary steps in hydroformylation. Both the hydride and chloride derivatives, (X=H^- , Cl^- ), underwent exchange with free ¹³ CO. Under reduced pressure, (R,R)-(^iPr DuPhos)Co(CO)₂ Cl underwent CO dissociation to form (R,R)-(^iPr DuPhos)Co(CO)Cl.

Beyond Common Metal-Metal Bonds, κ3 -Bis(donor)ferrocenyl→Transition-Metal Interactions

Ligands with 1,1'-bis(donor)ferrocene motif are capable of a wide range of binding modes, including the trans chelation mode in which there is a Fe-M interaction (κ³ -D,Fe,D), in the form of a dative Fe→TM bond (TM=transition metal). This Minireview will explore the nature of this Fe-TM interaction thorough select examples as well as how to characterize a Fe→TM dative bond using physical, computational, and spectroscopic techniques.