Conversion of tetrahedral to octahedral structures upon solvent coordination: studies on the M[(OPPh₂)(SePPh₂)N]₂(M = Co, Ni) and [Ni{(OPPh₂)(EPPh₂)N}₂(dmf)₂] (E = S, Se) complexes

Abstract

The synthesis of the M[(OPPh(2))(SePPh(2))N](2), M = Co (1), Ni (2) complexes was accomplished by metathetical reactions between the corresponding M(II) salts and the deprotonated form of the dichalcogenated imidodiphosphinato ligand [(OPPh(2))(SePPh(2))N](-). X-Ray crystallography revealed a pseudo-tetrahedral MO(2)Se(2) coordination sphere, owing to the asymmetric (O,Se) nature of the chelating ligand. Slow diffusion of the coordinating solvent dimethylformamide into dichloromethane solutions of Ni[(OPPh(2))(SPPh(2))N](2) or 2, afforded the pseudo-octahedral trans-[Ni{(OPPh(2))(EPPh(2))N}(2)(dmf)(2)], E = S (3), Se (4) complexes, respectively. UV-vis spectra provided evidence that, in solution, complexes 3 and 4 revert to the corresponding pseudo-tetrahedral complexes, most likely due to the removal of the dmf molecules from the coordination sphere. The IR spectra of all complexes reflect the structural features observed by X-ray crystallography. The magnetic properties of the S = 3/2 complex 1, as well as the S = 1 complexes 2, 3 and 4, were extensively studied, and the magnitude of their g and zero-field splitting D parameters was estimated. The reported structures establish a structural transformation of tetrahedral to octahedral geometry of Ni(II) complexes bearing asymmetric imidodiphosphinate ligands, upon recrystallization from coordinating solvents. The structural correlations between the Ni(II) coordination spheres are aided by DFT and ab initio multi-configuration MCSCF calculations, which investigate the corresponding interconversion pathways. In addition, the calculations provide descriptions of the bonding interactions in the octahedral Ni(II) complexes, as well as predictions of their D values.

Zero-field splitting in nickel(II) complexes: A comparison of DFT and multi-configurational wavefunction calculations

“…76 In both these papers, the authors compared the ab initio and DFT calculations and arrived at conclusions similar to the present work. Ferentinos and co-workers 44 reported DFT calculations of the ZFS in a distorted octahedral nickel(II) complex and obtained the splitting of a few cm −1 , in agreement with experiments. Maurice and co-workers 41 reported ab initio calculations for three nickel(II) complexes, one of them (Ni(iPrtacn)Cl 2 ) also studied here.…”

“…Other works on nickel(II) concentrated on either ab initio methods [41][42][43] or DFT. 44 Among the DFT work, we wish to mention in particular the paper by Mareš et al 45 who presented calculations of magnetic properties, including ZFS, for aqueous nickel(II) solutions. They combined the first-principles molecular dynamics for generating hydrated ion structures 46 with DFT calculations of the ZFS, in a similar way as in earlier work from our laboratory 15 but using the state-of-the-art methods of today.…”

Nickel(II) complexes having different configurations controlled by N,N,O-donor Schiff-base ligands in presence of isothiocyanate as co-ligand: Synthesis, structures, comparative biological activity and DFT study

“…The non-adherent tumor cells were Table 1 Crystallographic data and details of structure refinement for the complexes. (1)(2)(3)(4) and also in presence of a standard free radical scavenger 10 nM N-acetyl cysteine (NAC). At the end of the culture, media along with the cells were aspirated and were aspirated and were centrifuged at 3000 rpm for 5 min.…”

“…Nickel(II) has very rich coordination chemistry owing to its inherent ability to espouse various geometries [1][2][3][4][5][6][7]. This versatile coordination chemistry of nickel has an area of considerable importance in inorganic chemistry with implications in other areas of chemistry and biology [8][9][10].…”

Synthesis of a labile sulfur-centred ligand, [S(H)C(PPh2S)2]−: structural diversity in lithium(i), zinc(ii) and nickel(ii) complexes

“…Serendipitously, at the same time we also isolated small amounts of the red, square-planar isomer 5b in which the two [S(H)C(PPh2S)2] − (3) ligands are S,S′-chelated to the Ni(II) centre leaving a pendant Ph2P=S group. Although the 5 conversion of four-coordinate to six-coordinate nickel(II) complexes upon coordination of solvent is well-known, 13 the identification of both four-and six-coordinate isomers incorporating the same ligand is, to our knowledge, unprecedented. [ The crystal structure of the homoleptic Zn(II) complex 4 is illustrated in Figure 1b.…”