Benchmarking of Halogen Bond Strength in Solution with Nickel Fluorides: Bromine versus Iodine and Perfluoroaryl versus Perfluoroalkyl Donors

TY - JOUR

T1 - Benchmarking of Halogen Bond Strength in Solution with Nickel Fluorides

T2 - Bromine versus Iodine and Perfluoroaryl versus Perfluoroalkyl Donors

AU - Perutz, Robin Noel

AU - Pike, Sarah Jane

AU - Brammer, Lee

AU - Hunter, Christopher A

N1 - © 2019 WILEY‐VCH Verlag GmbH & Co. This is an author-produced version of the published paper. Uploaded in accordance with the publisher’s self-archiving policy. Further copying may not be permitted; contact the publisher for details.

PY - 2019/7/11

Y1 - 2019/7/11

N2 - The energetics of halogen bond formation in solution have been investigated for a series of nickel fluoride halogen bond acceptors; trans-[NiF(2-C 5NF 4)(PEt 3) 2] (A1), trans-[NiF{2-C 5NF 3(4-H)}(PEt 3) 2] (A2), trans-[NiF{2-C 5NF 3(4-NMe 2)}(PEt 3) 2] (A3) and trans-[NiF{2-C 5NF 2H(4-CF 3)}(PCy 3) 2] (A4) with neutral organic halogen bond donors, iodopentafluorobenzene (D1), 1-iodononafluorobutane (D2) and bromopentafluorobenzene (D3), in order to establish the significance of changes from perfluoroaryl to perfluoroalkyl donors and from iodine to bromine donors. 19F NMR titration experiments have been employed to obtain the association constants, enthalpy, and entropy for the halogen bond formed between these donor-acceptor partners in protiotoluene. For A2–A4, association constants of the halogen bonds formed with iodoperfluoroalkane (D2) are consistently larger than those obtained for analogous complexes with the iodoperfluoroarene (D1). For complexes formed with A2–A4, the strength of the halogen bond is significantly lowered upon modification of the halogen donor atom from I (in D1) to Br (in D3) (for D1: 5≤K 285≤12 m −1, for D3: 1.0≤K 193≤1.6 m −1). The presence of the electron donating NMe 2 substituent on the pyridyl ring of acceptor A3 led to an increase in −ΔH, and the association constants of the halogen bond complexes formed with D1–D3, compared to those formed by A1, A2 and A4 with the same donors.

AB - The energetics of halogen bond formation in solution have been investigated for a series of nickel fluoride halogen bond acceptors; trans-[NiF(2-C 5NF 4)(PEt 3) 2] (A1), trans-[NiF{2-C 5NF 3(4-H)}(PEt 3) 2] (A2), trans-[NiF{2-C 5NF 3(4-NMe 2)}(PEt 3) 2] (A3) and trans-[NiF{2-C 5NF 2H(4-CF 3)}(PCy 3) 2] (A4) with neutral organic halogen bond donors, iodopentafluorobenzene (D1), 1-iodononafluorobutane (D2) and bromopentafluorobenzene (D3), in order to establish the significance of changes from perfluoroaryl to perfluoroalkyl donors and from iodine to bromine donors. 19F NMR titration experiments have been employed to obtain the association constants, enthalpy, and entropy for the halogen bond formed between these donor-acceptor partners in protiotoluene. For A2–A4, association constants of the halogen bonds formed with iodoperfluoroalkane (D2) are consistently larger than those obtained for analogous complexes with the iodoperfluoroarene (D1). For complexes formed with A2–A4, the strength of the halogen bond is significantly lowered upon modification of the halogen donor atom from I (in D1) to Br (in D3) (for D1: 5≤K 285≤12 m −1, for D3: 1.0≤K 193≤1.6 m −1). The presence of the electron donating NMe 2 substituent on the pyridyl ring of acceptor A3 led to an increase in −ΔH, and the association constants of the halogen bond complexes formed with D1–D3, compared to those formed by A1, A2 and A4 with the same donors.

KW - NMR spectroscopy

KW - halogen bonds

KW - nickel fluorides

KW - perfluoroaryl and perfluoroalkyl donors

KW - solution

UR - http://www.scopus.com/inward/record.url?scp=85067828274&partnerID=8YFLogxK

U2 - 10.1002/chem.201900924

DO - 10.1002/chem.201900924

M3 - Article

SN - 0947-6539

VL - 25

SP - 9237

EP - 9241

JO - Chemistry : A European Journal

JF - Chemistry : A European Journal

IS - 39

M1 - chem.201900924R1

ER -