A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium

Andrés G. Algarra; Laura J. Sewell; Heather C. Johnson; Stuart A. Macgregor; Andrew S. Weller

doi:10.1039/c3dt52771a

A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium

Andrés G. Algarra, Laura J. Sewell, Heather C. Johnson, Stuart A. Macgregor^*, Andrew S. Weller

^*Corresponding author for this work

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

26 Citations (Scopus)

Abstract

A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR₃)₂(H)₂(η²-H ₃B·NMe₃)][BAr^F ₄] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; Ar^F = 3,5-(CF₃)₂C₆H₃) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D₂ leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D₂/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy₃)₂(H)₂(η ²-H₃B·NMe₃)][BAr^F ₄]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H₂ exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. This journal is

Original language	English
Pages (from-to)	11118-11128
Number of pages	11
Journal	Dalton Transactions
Volume	43
Issue number	29
Early online date	2 Dec 2013
DOIs	https://doi.org/10.1039/c3dt52771a
Publication status	Published - 7 Aug 2014

ASJC Scopus subject areas

Inorganic Chemistry

Access to Document

10.1039/c3dt52771a

Cite this

@article{109c60e88d4c4913bcaeb1d138a6fe00,

title = "A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium",

abstract = "A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η2-H 3B·NMe3)][BArF 4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; ArF = 3,5-(CF3)2C6H3) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D2 leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D2/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy3)2(H)2(η 2-H3B·NMe3)][BArF 4]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H2 exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. This journal is",

author = "Algarra, \{Andr{\'e}s G.\} and Sewell, \{Laura J.\} and Johnson, \{Heather C.\} and Macgregor, \{Stuart A.\} and Weller, \{Andrew S.\}",

year = "2014",

month = aug,

day = "7",

doi = "10.1039/c3dt52771a",

language = "English",

volume = "43",

pages = "11118--11128",

journal = "Dalton Transactions",

issn = "1477-9226",

publisher = "Royal Society of Chemistry",

number = "29",

}

TY - JOUR

T1 - A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium

AU - Algarra, Andrés G.

AU - Sewell, Laura J.

AU - Johnson, Heather C.

AU - Macgregor, Stuart A.

AU - Weller, Andrew S.

PY - 2014/8/7

Y1 - 2014/8/7

N2 - A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η2-H 3B·NMe3)][BArF 4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; ArF = 3,5-(CF3)2C6H3) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D2 leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D2/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy3)2(H)2(η 2-H3B·NMe3)][BArF 4]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H2 exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. This journal is

AB - A combined experimental and computational study on the fluxional processes involving the M-H and B-H positions in the sigma amine-borane complexes [M(PR3)2(H)2(η2-H 3B·NMe3)][BArF 4] (M = Rh, Ir; R = Cy for experiment; R = Me, Cy for computation; ArF = 3,5-(CF3)2C6H3) is reported. The processes studied are: B-H bridging/terminal exchange; reaction with exogenous D2 leading to exchange at M-H; and intramolecular M-H/B-H exchange. Experimentally it was found that B-H bridging/terminal exchange is most accessible and slightly favoured for Rh; D2/M-H exchange occurs at qualitatively similar rates for both M = Rh and Ir, while M-H/B-H exchange is the slowest overall, with the Ir congener having a lower barrier than Rh. Evidence for the isotopic perturbation of equilibrium is also reported for the BH/BD isotopologues of [Ir(PCy3)2(H)2(η 2-H3B·NMe3)][BArF 4]. DFT calculations using model complexes (R = Me) qualitatively reproduce the relative rates of the various exchange processes for both M = Rh and Ir, i.e. barriers for B-H bridging/terminal exchange are less than those for M-H/H2 exchange, which in turn are less than those for M-H/B-H exchange. Which metal promotes these processes more effectively depends upon the nature of the rate-limiting transition state, which can change between Rh and Ir. Computational analysis of the full experimental system (R = Cy) reveals similar overall trends in terms of the relative ease of the various exchange processes. However, there are differences in the details, and these are discussed. This journal is

U2 - 10.1039/c3dt52771a

DO - 10.1039/c3dt52771a

M3 - Article

C2 - 24296549

AN - SCOPUS:84903294245

SN - 1477-9226

VL - 43

SP - 11118

EP - 11128

JO - Dalton Transactions

JF - Dalton Transactions

IS - 29

ER -

A combined experimental and computational study of fluxional processes in sigma amine-borane complexes of rhodium and iridium

Abstract

ASJC Scopus subject areas

Access to Document

Fingerprint

Cite this