Steric Effects in the Oxidative Addition of MeI to a Sulfido-Bridged ZrRh2 Early−Late Heterobimetallic Compound
Autores: Duc Hanh Nguyen, F. Javier Modrego, J. Miguel Cetina-Casas, Daniel Gómez-Bautista, M. Victoria Jiménez, Ricardo Castarlenas, Fernando J. Lahoz, Luis Oro y Jesús J. Pérez-Torrente
Ref. revista: Organometallics, 31, 6395-6407 (2012)
Reaction of the early−late heterobimetallic compound
[Cptt
2Zr(μ3-S)2{Rh(CO)}2(μ-dppm)] (1) with MeI affords the unusual
oxidative addition product [Cptt
2Zr(μ3-S)2Rh2(μ-CO)(μ-dppm)(I)-(COCH3)] (4), showing the presence of a bridging carbonyl and a terminal acetyl ligand. The optimized structure of 4 by DFT calculations is further substantiated by the spectroscopic data of the 13CO-labeled complex 4*. The same reaction carried out on the structurally related gem-dithiolate dinuclear complexes [Rh2(μ-S2CR2)(CO)2(PPh3)2] (2, 3) gives the one-center oxidative addition acetyl products [Rh2(μ-S2CR2)(COCH3)(I)(CO)(PPh3)2] (R2 = −(CH2)5−, 5; R = Bn (benzyl), 6). Reaction of 3 with molecular iodine affords the dinuclear compounds [Rh2(μ-S2CBn2)(I)2(μ-CO)(PPh3)2] (7) and [Rh2(μ-S2CBn2)(I)2(CO)2(PPh3)2] (8), the transannular oxidative addition product, in a 40:60 ratio. Compound 7 was also formed in the reaction of 3 with MeI after a prolonged reaction time. The molecular structures of compounds 5 and 7 have been determined by X-ray analyses. A natural bond orbital (NBO) analysis has shown an analogous bonding scheme in the “Rh2(μ-CO)P2” subunit of complexes 4 and 7. Although both complexes can be formally described as composed of a Rh(III)−Rh(III) unit, assuming a ketonic character of the bridging carbonyl ligand, the natural charges on the rhodium atoms and the WBI indexes for the Rh−Rh and CO bonds points to electronically unsaturated metal centers bridged by a carbonyl ligand lacking ketonic character and a significant metal−metal interaction. In addition, DFT calculations on the reaction pathway leading to the formation of 4 evidenced the key role of the bulky “Cptt 2Zr” fragment in the course of the reaction.
Reaction of the early−late heterobimetallic compound
[Cptt
2Zr(μ3-S)2{Rh(CO)}2(μ-dppm)] (1) with MeI affords the unusual
oxidative addition product [Cptt
2Zr(μ3-S)2Rh2(μ-CO)(μ-dppm)(I)-(COCH3)] (4), showing the presence of a bridging carbonyl and a terminal acetyl ligand. The optimized structure of 4 by DFT calculations is further substantiated by the spectroscopic data of the 13CO-labeled complex 4*. The same reaction carried out on the structurally related gem-dithiolate dinuclear complexes [Rh2(μ-S2CR2)(CO)2(PPh3)2] (2, 3) gives the one-center oxidative addition acetyl products [Rh2(μ-S2CR2)(COCH3)(I)(CO)(PPh3)2] (R2 = −(CH2)5−, 5; R = Bn (benzyl), 6). Reaction of 3 with molecular iodine affords the dinuclear compounds [Rh2(μ-S2CBn2)(I)2(μ-CO)(PPh3)2] (7) and [Rh2(μ-S2CBn2)(I)2(CO)2(PPh3)2] (8), the transannular oxidative addition product, in a 40:60 ratio. Compound 7 was also formed in the reaction of 3 with MeI after a prolonged reaction time. The molecular structures of compounds 5 and 7 have been determined by X-ray analyses. A natural bond orbital (NBO) analysis has shown an analogous bonding scheme in the “Rh2(μ-CO)P2” subunit of complexes 4 and 7. Although both complexes can be formally described as composed of a Rh(III)−Rh(III) unit, assuming a ketonic character of the bridging carbonyl ligand, the natural charges on the rhodium atoms and the WBI indexes for the Rh−Rh and CO bonds points to electronically unsaturated metal centers bridged by a carbonyl ligand lacking ketonic character and a significant metal−metal interaction. In addition, DFT calculations on the reaction pathway leading to the formation of 4 evidenced the key role of the bulky “Cptt 2Zr” fragment in the course of the reaction.