Reaction of a Rhodium-MiniPHOS complex with dihydrogen: NMR and computational study

Ilya D. Gridnev; Tsuneo Imamoto

doi:10.1021/om000304u

Reaction of a Rhodium-MiniPHOS complex with dihydrogen: NMR and computational study

Ilya D. Gridnev, Tsuneo Imamoto

Research output: Contribution to journal › Article › peer-review

33 Citations (Scopus)

Abstract

The rhodium-MiniPHOS complex [Rh((R,R)-MeBu^tPCH₂ PMeBu^t)₂]⁺BF₄^- (1) is reversibly and stereoselectively hydrogenated at low temperatures to give one isomer of cis-dihydride 2a. The second possible diastereomer, 2b, is not observed experimentally. DFT calculations suggest that 2b is 3.5 kcal mol^-1 less stable than 2a. The parameters of the equilibrium between 2a, 1, and H₂ determined by NMR are ΔH = -7.7 ± 0.1 kcal mol^-1 and ΔS = -25 ± 1 cal mol^-1 K^-1. Formation of the trans-dihydride 3 is observed at around -20°C. Most probably 3 is formed by isomerization of 2a or 2b. This isomerization involves reversible dissociation of the Rh-P bond. Similar dissociation of the Rh-P bond in 2a might make possible the substrate binding when 1 is used as a catalyst for asymmetric hydrogenation.

Original language	English
Pages (from-to)	545-549
Number of pages	5
Journal	Organometallics
Volume	20
Issue number	3
DOIs	https://doi.org/10.1021/om000304u
Publication status	Published - 2001 Feb 5
Externally published	Yes

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Organic Chemistry
Inorganic Chemistry

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title = "Reaction of a Rhodium-MiniPHOS complex with dihydrogen: NMR and computational study",

abstract = "The rhodium-MiniPHOS complex [Rh((R,R)-MeButPCH2 PMeBut)2]+BF4- (1) is reversibly and stereoselectively hydrogenated at low temperatures to give one isomer of cis-dihydride 2a. The second possible diastereomer, 2b, is not observed experimentally. DFT calculations suggest that 2b is 3.5 kcal mol-1 less stable than 2a. The parameters of the equilibrium between 2a, 1, and H2 determined by NMR are ΔH = -7.7 ± 0.1 kcal mol-1 and ΔS = -25 ± 1 cal mol-1 K-1. Formation of the trans-dihydride 3 is observed at around -20°C. Most probably 3 is formed by isomerization of 2a or 2b. This isomerization involves reversible dissociation of the Rh-P bond. Similar dissociation of the Rh-P bond in 2a might make possible the substrate binding when 1 is used as a catalyst for asymmetric hydrogenation.",

author = "Gridnev, {Ilya D.} and Tsuneo Imamoto",

year = "2001",

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T1 - Reaction of a Rhodium-MiniPHOS complex with dihydrogen

T2 - NMR and computational study

AU - Gridnev, Ilya D.

AU - Imamoto, Tsuneo

PY - 2001/2/5

Y1 - 2001/2/5

N2 - The rhodium-MiniPHOS complex [Rh((R,R)-MeButPCH2 PMeBut)2]+BF4- (1) is reversibly and stereoselectively hydrogenated at low temperatures to give one isomer of cis-dihydride 2a. The second possible diastereomer, 2b, is not observed experimentally. DFT calculations suggest that 2b is 3.5 kcal mol-1 less stable than 2a. The parameters of the equilibrium between 2a, 1, and H2 determined by NMR are ΔH = -7.7 ± 0.1 kcal mol-1 and ΔS = -25 ± 1 cal mol-1 K-1. Formation of the trans-dihydride 3 is observed at around -20°C. Most probably 3 is formed by isomerization of 2a or 2b. This isomerization involves reversible dissociation of the Rh-P bond. Similar dissociation of the Rh-P bond in 2a might make possible the substrate binding when 1 is used as a catalyst for asymmetric hydrogenation.

AB - The rhodium-MiniPHOS complex [Rh((R,R)-MeButPCH2 PMeBut)2]+BF4- (1) is reversibly and stereoselectively hydrogenated at low temperatures to give one isomer of cis-dihydride 2a. The second possible diastereomer, 2b, is not observed experimentally. DFT calculations suggest that 2b is 3.5 kcal mol-1 less stable than 2a. The parameters of the equilibrium between 2a, 1, and H2 determined by NMR are ΔH = -7.7 ± 0.1 kcal mol-1 and ΔS = -25 ± 1 cal mol-1 K-1. Formation of the trans-dihydride 3 is observed at around -20°C. Most probably 3 is formed by isomerization of 2a or 2b. This isomerization involves reversible dissociation of the Rh-P bond. Similar dissociation of the Rh-P bond in 2a might make possible the substrate binding when 1 is used as a catalyst for asymmetric hydrogenation.

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Reaction of a Rhodium-MiniPHOS complex with dihydrogen: NMR and computational study

Abstract

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