Further examples of binuclear phosphido-bridged complexes of rhodium(I). Evidence for bridge-cleavage reactions

Burkhardt, Eric W.; Mercer, William C.; Geoffrey, Gregory L.

doi:10.1021/ic00180a027

Cited by 19 publications

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“…For a Pd compound, two isomeric crystals of different color were isolated, but no structural characterization was reported . Evidence for the existence of more than one isomer in solution has been proposed in several cases, − based on the NMR spectra. An extra structural variability may appear when the two terminal ligands at the same metal atom are different, since the equivalent ligands attached to different metal atoms can appear either in a transoid or in a cisoid conformation. , …”

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confidence: 99%

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study

2000

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The binuclear complexes of d8 transition metal ions of the type [M2(mu-XR2)2L4] (where M = RhI, IrI, NiII, PdII, PtII, or AuIII; X = S, N, P, or As) appear in a variety of molecular conformations in which the coordination planes around the two metal atoms are sometimes coplanar, sometimes bent. For the bent compounds with asymmetric bridges, XR1R2, the substituents adopt different orientations relative to the metal framework and to each other. Ab initio theoretical studies on the different conformers of 30 representative complexes, complemented with a structural database analysis, have allowed the establishment of structural correlations in this family of compounds. The conformational choice results from a delicate balance of different interactions which are qualitatively analyzed, such as the changes in bond angles around the bridging atoms, the existence of weak metal...metal bonding in the bent structures, and steric interactions involving the terminal ligands and the substituents at the bridging atoms.

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confidence: 99%

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study

2000

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“…Complex 4 is stable in the solid state but gradually decomposes in solutions at room temperature (half-life approximately 4 days) to give Cp 2 Nb(NBu t )Cl and the known complex [Rh 2 (μ-Cl)(μ-PPh 2 )(COD) 2 ], identified by the 31 P NMR . After a few days, the latter product partially rearranges to [Rh(μ-PPh 2 )(COD)] 2 …”

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confidence: 99%

Niobium/Rhodium Bimetallic Complexes: Synthesis, Structure, and Catalytic Hydrosilylation of Acetophenone and Benzaldehyde

et al. 2009

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Reactions of a new imido phosphido complex, Cp 2 Nb(dNBu t )(PPh 2 ) (1), with olefin complexes of rhodium afford two types of compounds. With [(μ-Cl)Rh(C 2 H 4 ) 2 ] 2 , an imido/phosphido-bridged complex, Cp(Cl)Nb(μ-NBu t )(μ-PPh 2 )RhCp (2), characterized by NMR and X-ray diffraction, was prepared. Formation of 2 represents a rare example of a Cp/Cl exchange reaction in organometallic chemistry. When 1 reacts with [(μ-Cl)Rh(COD)] 2 , the target phosphido-bridged bimetallic complex Cp 2 Nb(dNBu t )(μ-PPh 2 )Rh(Cl)(COD) ( 4) is formed. The structure of this product was established by NMR and an X-ray diffraction study. Both 2 and 4 are catalyst precursors for hydrosilylation of benzaldehyde and acetophenone. The activity of the neutral complex 4 exceeds that of the cation [Cp 2 Nb(NBu t )(PPh 2 )Rh(COD)] þ derived from 4 by chloride anion abstraction.

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Rhodium Complexes in P−H Bond Activation Reactions

Varela‐Izquierdo

Geer

Bruin

et al. 2019

Chemistry A European J

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The feasibility of oxidative addition of the P−H bond of PHPh2 to a series of rhodium complexes to give mononuclear hydrido‐phosphanido complexes has been analyzed. Three main scenarios have been found depending on the nature of the L ligand added to [Rh(Tp)(C2H4)(PHPh2)] (Tp= hydridotris(pyrazolyl)borate): i) clean and quantitative reactions to terminal hydrido‐phosphanido complexes [RhTp(H)(PPh2)(L)] (L=PMe3, PMe2Ph and PHPh2), ii) equilibria between RhI and RhIII species: [RhTp(H)(PPh2)(L)]⇄[RhTp(PHPh2)(L)] (L=PMePh2, PPh3) and iii) a simple ethylene replacement to give the rhodium(I) complexes [Rh(κ2‐Tp)(L)(PHPh2)] (L=NHCs‐type ligands). The position of the P−H oxidative addition–reductive elimination equilibrium is mainly determined by sterics influencing the entropy contribution of the reaction. When ethylene was used as a ligand, the unique rhodaphosphacyclobutane complex [Rh(Tp)(η1‐Et)(κC,P‐CH2CH2PPh2)] was obtained. DFT calculations revealed that the reaction proceeds through the rate limiting oxidative addition of the P−H bond, followed by a low‐barrier sequence of reaction steps involving ethylene insertion into the Rh−H and Rh−P bonds. In addition, oxidative addition of the P−H bond in OPHPh2 to [Rh(Tp)(C2H4)(PHPh2)] gave the related hydride complex [RhTp(H)(PHPh2)(POPh2)], but ethyl complexes resulted from hydride insertion into the Rh−ethylene bond in the reaction with [Rh(Tp)(C2H4)2].

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Further examples of binuclear phosphido-bridged complexes of rhodium(I). Evidence for bridge-cleavage reactions

Cited by 19 publications

References 0 publications

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study

Niobium/Rhodium Bimetallic Complexes: Synthesis, Structure, and Catalytic Hydrosilylation of Acetophenone and Benzaldehyde

Rhodium Complexes in P−H Bond Activation Reactions

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Further examples of binuclear phosphido-bridged complexes of rhodium(I). Evidence for bridge-cleavage reactions

Cited by 19 publications

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Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d8 Complexes with XR2 Bridges. A Theoretical Study

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d8 Complexes with XR2 Bridges. A Theoretical Study

Niobium/Rhodium Bimetallic Complexes: Synthesis, Structure, and Catalytic Hydrosilylation of Acetophenone and Benzaldehyde

Rhodium Complexes in P−H Bond Activation Reactions

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Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study

Structural Correlations and Conformational Preference in Edge-Sharing Binuclear d⁸ Complexes with XR₂ Bridges. A Theoretical Study