Low temperature reactions of 1,4-dichloro-2,5-dimethoxybenzene with two equivalents of lithium diisopropylamide (LDA) followed by quenches with chlorophosphines ClPR2 (R = Ph or iPr) yielded 1,4-bis(diphenylphosphino)-2,5-dichloro-3,6-dimethoxy-benzene (1a) and 1,4-bis(diisopropylphosphino)-2,5-dichloro-3,6-dimethoxy-benzene (1b). Reactions of 1a-b with 30% hydrogen peroxide yielded 1,4-bis(diphenylphosphinyl)-2,5-dichloro-3,6-dimethoxybenzene (2a) and 1,4-bis(diisopropylphosphinyl)-2,5-dichloro-3,6-dimethoxybenzene (2b). Subjecting compounds 2a-b to BBr3/CH3OH resulted in 2,5-bis(diphenylphosphinyl)-3,6-dichlorohydroquinone 3a and 2,5-bis(diisopropylphosphinyl)-3,6-dichlorohydroquinone 3b. Reactions of 3a-b with K2S2O8 under basic conditions followed by acidification allowed for isolation of 2,5-bis(diphenylphosphinyl)-3,6-dihydroxy-quinone (4a) and 2,5-bis(diisopropylphosphinyl)-3,6-dihydroxy-quinone (4b). Compounds 1a-b – 4a-b were fully characterized by spectroscopic methods (nuclear magnetic resonance [FT-NMR] spectroscopy, infrared [FT-IR] spectroscopy, and high resolution mass spectrometry [HRMS]); 3a-b and 4a-b were also investigated by cyclic voltammetry. Compounds 1a-b , 2a , and 4a-b were also characterized by single-crystal X-ray diffraction methods.

Ionic complexes [(κ4−PP3)P(OCH2PPh2)3NiX]BF4 (2 (X=Cl) and 3 (X=Br)) were formed when P(OCH2PPh2)3 ligand (1) was reacted with mixtures of salts NiX2/Ni(BF4)2 (X=Cl or Br). Single crystal X‐ray characterizations performed on complexes 2 and 3 established that metal centers are in pseudo‐trigonal bipyramidal ligand geometries formed by the phosphorus centers from coordinated 1 and the halide ligand. Reactions of 1 with other nickel(II) salts (acetate, nitrate or tetrafluoroborate) proceeded in 2 : 1 (ligand‐salt) ratio yielding complex 4, [(κ3−PP2)((−O−P)(OCH2PPh2)2)(κ2−PP)(−O−P)(OCH2PPh2)(OCH2P(=O)Ph2)Ni]. The formation of this complex required hydrolysis of one of the P−O ester bonds in ligand P(OCH2PPh2)3 thus forming O‐anionic phosphite/diphosphine fragment [−O−P(OCH2PPh2)2]. One of such fragments is coordinated to the metal center as a tridentate (κ3−PP2) ligand, whereas the other is in bidentate (κ2−PP) coordination via phosphorus centers of the −O‐P‐OCH2PPh2 chelating pocket; the remaining ‐OCH2P(=O)Ph2 arm is P‐oxidized and uncoordinated. Nickel center in 4 is in distorted trigonal‐bipyramidal geometry, with O‐anionic‐phosphite groups coordinated at the axial positions, and the three ‐PPh2 groups located in the equatorial plane. Compounds 2–4 were characterized by multinuclear NMR spectroscopy, elemental analyses, electron absorption spectroscopy, cyclic voltammetry, and single crystal X‐ray crystallography. Their electronic structures were also investigated by DFT methods.