TY - JOUR
T1 - Controlling P−C/C−H bond cleavage in Nickel Bis(diphosphine) Complexes
T2 - Reactivity scope, mechanism, and computations
AU - Zhang, Shaoguang
AU - Li, Haixia
AU - Appel, Aaron M.
AU - Hall, Michael B.
AU - Bullock, R. Morris
N1 - Funding Information:
The research at PNNL was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy. H.L. and M.B.H. thank the National Science Foundation (CHE-1300787 and 1664866) and the Welch Foundation (A-0648) for financial support and the Texas A&M High Performance Research Computing Center and the Laboratory for Molecular Simulation for providing computing resources.
Publisher Copyright:
© 2020 American Chemical Society
PY - 2020/9/28
Y1 - 2020/9/28
N2 - The synthesis of heteroleptic [Ni(P2N2)(diphosphine)][BF4]2 complexes and the cleavage of P−C and C−H bonds of the P2N2 ligand in those complexes are reported. The products are five-coordinate complexes in which Ni−C and P−H bonds have formed to give a cyclic moiety containing Ni−CH=NR2. The reactivity of [Ni(P2N2)(diphosphine)][BF4]2 complexes is influenced by the rigidity of the diphosphine, the steric effect of the substituents, and length of the carbon linker of the diphosphine ligands. Diphosphine ligands bearing a rigid backbone (e.g., dmpbz, 1,2-bis(dimethylphosphino)benzene) or aromatic substituents (e.g., dppe, 1,2-bis(diphenylphosphino)ethane) react with [Ni(PtBu2NBn2)(CH3CN)2][BF4]2 to give P−C/C−H bond cleavage products. Both [Ni(PtBu2NBn2)(dmpe)(MeCN)][BF4]2 and [Ni(PtBu2NBn2)(dmpm)(MeCN)][BF4]2 (dmpm = 1,2-bis-(dimethylylphosphino)methane) were prepared by the reaction of [Ni(PtBu2NBn2)(CH3CN)2][BF4]2 with the corresponding diphosphine ligands. [Ni(PtBu2NBn2)(dmpe)(MeCN)][BF4]2 readily undergoes P−C/C−H bond cleavage in nitromethane. In sharp contrast, [Ni(PtBu2NBn2)(dmpm)][BF4]2 is stabilized by dmpm, a diphosphine with small bite angle, and does not show P−C/C−H bond cleavage reactivity. Computational results show that for complexes bearing less bulky diphosphine ligands, such as dmpm, the barriers for the rate-determining transition states are in some examples higher than 30 kcal/mol with the M06 functional, higher than those for complexes bearing more rigid or more bulky ligands, consistent with experimental studies. The calculated barriers for the first transition state correlated with increased values of the dihedral angle formed by the two NiP2 planes.
AB - The synthesis of heteroleptic [Ni(P2N2)(diphosphine)][BF4]2 complexes and the cleavage of P−C and C−H bonds of the P2N2 ligand in those complexes are reported. The products are five-coordinate complexes in which Ni−C and P−H bonds have formed to give a cyclic moiety containing Ni−CH=NR2. The reactivity of [Ni(P2N2)(diphosphine)][BF4]2 complexes is influenced by the rigidity of the diphosphine, the steric effect of the substituents, and length of the carbon linker of the diphosphine ligands. Diphosphine ligands bearing a rigid backbone (e.g., dmpbz, 1,2-bis(dimethylphosphino)benzene) or aromatic substituents (e.g., dppe, 1,2-bis(diphenylphosphino)ethane) react with [Ni(PtBu2NBn2)(CH3CN)2][BF4]2 to give P−C/C−H bond cleavage products. Both [Ni(PtBu2NBn2)(dmpe)(MeCN)][BF4]2 and [Ni(PtBu2NBn2)(dmpm)(MeCN)][BF4]2 (dmpm = 1,2-bis-(dimethylylphosphino)methane) were prepared by the reaction of [Ni(PtBu2NBn2)(CH3CN)2][BF4]2 with the corresponding diphosphine ligands. [Ni(PtBu2NBn2)(dmpe)(MeCN)][BF4]2 readily undergoes P−C/C−H bond cleavage in nitromethane. In sharp contrast, [Ni(PtBu2NBn2)(dmpm)][BF4]2 is stabilized by dmpm, a diphosphine with small bite angle, and does not show P−C/C−H bond cleavage reactivity. Computational results show that for complexes bearing less bulky diphosphine ligands, such as dmpm, the barriers for the rate-determining transition states are in some examples higher than 30 kcal/mol with the M06 functional, higher than those for complexes bearing more rigid or more bulky ligands, consistent with experimental studies. The calculated barriers for the first transition state correlated with increased values of the dihedral angle formed by the two NiP2 planes.
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U2 - 10.1021/acs.organomet.0c00388
DO - 10.1021/acs.organomet.0c00388
M3 - Article
AN - SCOPUS:85091407007
VL - 39
SP - 3306
EP - 3314
JO - Organometallics
JF - Organometallics
SN - 0276-7333
IS - 18
ER -