Structural Diversity and Dynamics of Nickel Complexes with Ambidentate Phosphorus Heterocycles

Abstract

The reaction of [Ni(C 2 H 4 )(dtbpe)] with 1-alkyl-1,2-diphospholes afforded [Ni(1-alkyl-1,2-diphosphole)(dtbpe)] complexes. Both DNMR experimental and DFT calculation results have shown that in solution these complexes are in an equilibrium of two P−P side-on η 2 -coordinated 1-alkyl-1,2-diphosphole isomers. In one form, unusual η 2 bonding occurred at a P 2 −P 1 side, presumably at the expense of a vicinal P 2 −C 1 π bond, and it could be characterized as a phosphametallacycle with the formal oxidation state of Ni(II). In the second isomer with the Ni(0) state, Ni bonds to the ligand through two σ interactions with phosphorus lone pairs. The P 2 chemical shift, being heavily dependent on structure, can be used to monitor these isomer populations.

Synthesis of P,P-bidentate caged phosphines via tungsten pentacarbonyl-promoted cycloaddition reactions of 1-alkyl-1,2-diphospholes

“…Both phosphorus atoms in 1-alkyl-1,2-diphospholes have a similar reactivity, as evidenced by the formation of complexes [Ni(1-alkyl-1,2-diphosphole)-(dtbpe)] (dtbpe = 1,2-bis(di-tert-butylphosphino)ethane, alkyl = Et, i-Pr) in which the 1-alkyl-1,2-diphosphole serves as a chelating ligand. 37,38 The decisive factor for a bidentate or monodentate bonding mode of this ligand is the coordination capability at the metal center. In the case of pentacarbonyl tungsten(0), it is obvious that 1-alkyl-1,2-diphosphole acts as a monodentate ligand, affording k 1 -P-complexes.…”

DFT Approach for Predicting 13C NMR Shifts of Atoms Directly Coordinated to Pd

“…In this regard, modern NMR correlation methods are very effectivespin–spin couplings allow us to almost directly determine the chemical structure in many cases as these arise from the connectivity between nuclei in the molecule. However, it is often difficult or impossible to establish reliably fine details such as a 3D structure or a type of coordination from the NMR experiment alone …”

“…However, it is often difficult or impossible to establish reliably fine details such as a 3D structure or a type of coordination from the NMR experiment alone. 11 In this regard, the NMR shifts of nuclei directly bound to the metal are very sensitive to the electronic structure and can serve as a source of information both on the type of coordination and on the electronic structure near the coordination sphere of metal. 12,13 However, this requires nonempirical calculation methods that would allow one to unambiguously and reliably correlate the structure and NMR parameters.…”

The synthesis of 1,2-azaphospholes, 1,2-azaphosphorines and 1,2-azaphosphepines

“…23,24 Much attention has been directed to the synthesis of phosphorus heterocycles due to their wideranging utilities as synthetic intermediates in organic syntheses. [25][26][27][28][29][30][31] Among these phosphorus heterocycles, 1,2-azaphospholes, 1,2-azaphosphorines and 1,2-azaphosphepines are of interest in several laboratories due to their potent pharmacological activities such as antitumor, 32 complexing agents, 33,34 and inhibitor of mammalian dihydroorotase. 35 The present review is focused on the most methodologies for the construction of 1,2-azaphospholes, 1,2-azaphosphorines and 1,2-azaphosphepines up to the end of 2019 and to supplement the information available in literature.…”