Dataset Information

Versatile Coordination and C-C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0).

ABSTRACT: Ligands that can adapt their coordination mode to the electronic properties of a metal center are of interest to support catalysis or small molecule activation processes. In this context, the ability of imine moieties to bind in either an ?1(N)-fashion via ?-donation of the lone pair or, less commonly, in an ?2(C,N)-fashion via ?-coordination is potentially attractive for the design of new metal-ligand cooperative systems. Herein, the coordination chemistry of chelating ligands with a diphosphine imine framework (PCNP) to nickel is investigated. The imine moiety binds in an ?1(N)-fashion in a Ni(II)Cl2 complex. The uncommon ?2(C,N)-interaction is obtained in Ni(0) complexes in the presence of a PPh3 coligand. Increasing the bulk on the phosphine side-arms in the Ni(0) complexes, by substituting phenyl for o-tolyl groups, leads to a distinct binding mode in which only one of the phosphorus atoms is coordinated. In the absence of a coligand, a mixture of two different dimeric Ni(0) complexes is formed. In one of them, the imine adopts an uncommon ?1(N)?2(C,N) bridging mode of the ligand to nickel, while the second one may involve reactivity on the ligand by the formation of a new C-C bond by oxidative coupling. The latter is supported by the isolation and structural characterization of a crystalline bis-CO derivative featuring a C-C bond formed by oxidative coupling of two imine moieties.

SUBMITTER: Verhoeven DGA

PROVIDER: S-EPMC6150681 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Publications

Versatile Coordination and C-C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0).

Verhoeven Dide G A DGA Negenman Hidde A HA Orsino Alessio F AF Lutz Martin M Moret Marc-Etienne ME

Inorganic chemistry 20180816 17

Ligands that can adapt their coordination mode to the electronic properties of a metal center are of interest to support catalysis or small molecule activation processes. In this context, the ability of imine moieties to bind in either an η<sup>1</sup>(N)-fashion via σ-donation of the lone pair or, less commonly, in an η<sup>2</sup>(C,N)-fashion via π-coordination is potentially attractive for the design of new metal-ligand cooperative systems. Herein, the coordination chemistry of chelating lig ...[more]

PMID: 30113165

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Project description:Accurate experimental XAFS (X-ray absorption fine-structure) data including uncertainties are required during analysis for valid comparison of results and conclusions of hypothesis testing on structural determinations. Here an approach is developed to investigate data without standard interpolation of experimental data and with minimal loss of information content in the raw data. Nickel coordination complexes bis(i-n-propylsalicylaldiminato)nickel(II) (i-pr) and bis(N-n-propylsalicylaldiminato)nickel(II) (n-pr) are investigated. The additional physical insight afforded by the correct propagation of experimental uncertainty is used to determine newly refined structures for the innermost co-ordination shell. Two sets of data are investigated for each complex; one optimized for high point accuracy and one optimized for high point density. Clearly both are important and in this investigation the quality of the physical insight from each is directly provided by measured and propagated uncertainties to fairly represent the relevant accuracies. The results provide evidence for an approximate tetrahedral geometry for the i-pr Ni complex that is more symmetric than previously concluded, with our high point accuracy data yielding ligand lengths of 2.017 ± 0.006 Å and 2.022 ∓ 0.006 Å for Ni-N and Ni-O bonds, respectively, and an even more skewed square-planar (i.e. rhombohedral) arrangement for the n-pr complex with corresponding bond lengths of 2.133 ± 0.004 Å and 1.960 ∓ 0.003 Å. The ability to distinguish using hypothesis testing between the subtle differences in XAFS spectra arising from the approximate local tetrahedral and square-planar geometries of the complexes is also highlighted. The effect of standard interpolation on experimental XAFS spectra prior to fitting with theoretical model structures is investigated. While often performed as a necessary step for Fourier transformation into position space, this will nonetheless skew the fit away from actual data taken, and fails to preserve the information content within the data uncertainty. The artificial effects that interpolation imposes on χr2 are demonstrated. Finally, a method for interpolation is introduced which locally preserves the χr2 and thus information content, when a regular grid is required, e.g for further analysis in r-space.

Dataset Information

Versatile Coordination and C-C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0).

Publications

Versatile Coordination and C-C Coupling of Diphosphine-Tethered Imine Ligands with Ni(II) and Ni(0).

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