Synthesis and Reactions of (π-Allyl)bromo- [hydrotris(3,5-dimethylpyrazolyl)borato]rhodium(III)

Abstract

Tp Me2 Rh(coe)(MeCN) (1) (Tp Me2 ) hydrotris(3,5-dimethylpyrazolyl)borato, coe ) cyclooctene) has been found to readily undergo oxidative addition of allyl bromide at room temperature to give Tp Me2 Rh(σ-allyl)Br(MeCN) (4). On prolonged reaction time or heating, complex 4 is converted to the π-allyl complex Tp Me2 Rh(π-allyl)Br ( 5) with liberation of MeCN. Complex 5 exhibits high reactivity toward MeMgBr and Li[BHEt 3 ], giving Tp Me2 Rh(π-allyl)Me ( 8) and Tp Me2 Rh(π-allyl)H ( 9), respectively. Deuterium-labeling experiments using Li[BDEt 3 ] indicate that complex 9 is formed mainly by nucleophilic addition of Hto the central carbon of the π-allyl ligand, followed by β-hydrogen elimination of the resultant rhodacyclobutane intermediate. Complex 9 reacts with a variety of alkyl bromides by a radical process to afford 5 and alkanes.

Reactions of Tris(oxazolinyl)phenylborato Rhodium(I) with C−X (X = Cl, Br, OTf) Bonds: Stereoselective Intermolecular Oxidative Addition

“…In contrast, Rh−C coupling was not observed in the N -methylated 6 . A similar spectral signature to that observed for 7 was reported for Tp*Rh(η 1 -C 3 H 5 )Br(NCMe) (δ RhC = 18.0; 1 J RhC = 18 Hz) . Additionally, the 13 C{ 1 H} NMR spectrum of 7 contained a single carbonyl resonance at 186.5 ppm ( 1 J RhC = 60 Hz).…”

“…A similar spectral signature to that observed for 7 was reported for Tp*Rh(η 1 -C 3 H 5 )Br(NCMe) (δ RhC = 18.0; 1 J RhC = 18 Hz). 29 Additionally, the 13 C{ 1 H} NMR spectrum of 7 contained a single carbonyl resonance at 186.5 ppm ( 1 J RhC = 60 Hz). In contrast to the C s -symmetric, N-alkylation product formed from MeOTf and 3, compound 7 is C 1 symmetric.…”

Synthesis of a Series of Rhodium Complexes, TpiPrRhIL2and TpiPrRhIII(X)(Y)(MeCN), with the Hydridotris(3,5-diisopropylpyrazolyl)borato Ligand (TpiPr) from a Versatile Precursor, (κ3-TpiPr)Rh(coe)(MeCN), and Dependence of κ2−κ3Interconversion Rate of the TpiPrLigand on the Chelate Ring Size

“…In this study we examined only the Tp iPr system, but analogous Tp R Rh(coe)(MeCN) complexes should be accessible via a similar procedure. Actually, Ozawa and co-workers prepared the 3,5-dimethylpyrazolyl derivative of 1 following our procedure and examined the synthesis of π-allyl complexes …”

The Isolation and Characterization of a Rhodacycle Intermediate Implicated in Metal‐Catalyzed Reactions of Alkylidenecyclopropanes

“…Interestingly, the π‐allyl rhodium‐alkyl intermediate iii (or iv ) would require forcing conditions to induce C(sp 2 )–C(sp 3 ) reductive elimination to provide x 9. 10 Alternatively, cycle B outlines the ene‐cycloisomerization in which rhodacycle vii leads to viii to facilitate β‐hydride elimination and reductive elimination to afford 5 . We reasoned that although metallacycle vii undergoes rapid exo ‐β‐hydride elimination, intermediate iii should be stable to endo ‐elimination owing to the poor alignment of the bridgehead proton with the rhodium atom.…”