Structural organization of nickel(II) and copper(II) O,O'-dialkyl phosphorodithioate complexes as probed by X-ray diffraction, EPR, and CP/MAS 13C and 31P NMR

• The nickel(II) and copper(II) complexes [M{S2P(OR)(2)}(2)] (M = Ni, Cu-63, Cu-65; R = C2H5, C3H7, i-C3H7, C4H9, i-C4H9, s-C4H9, i-C5H11, c-C6H11) with eight symmetric O,O'-dialkyl phosphorodithioates were synthesized, and their structures and spectral properties were studied by EPR and CP/MAS C-13 and P-31 NMR. As determined by EPR, the [CuS4] chromophores in the lattice of nickel(II) complexes have predominantly a square-planar structure. The chromophores in complexes with phosphorodithioate ligands incorporating bulky alkyl substituents have somewhat distorted geometries. NMR shows that the Dtph groups in most nickel(II) complexes are structurally equivalent. An exception is [Ni{S2P(OC3H7)(2)}(2)], which gives rise to two (1 : 1) P-31 NMR signals. For [Ni(S2P(O-i-C4H9)(2))(2)], the alpha and beta modifications were obtained. In the alpha modification, the phosphorodithioate groups are nonequivalent, whereas the P modification has structurally equivalent ligands. The broadening of the P-31 NMR signal of the [Ni{S2P(O-s-C4H9)(2)}(2)] complex is rationalized by the existence of six optical isomers (due to two chiral centers in each of the ligands). For the Dtph groups acting as bidentate terminal ligands in the nickel(II) complexes, the P-31 chemical shift anisotropy delta(aniso) and asymmetry parameter eta were calculated from experimental NMR spectra. Single-crystal X-ray diffraction shows that bis(O,O'-dipropyl phosphorodithioato)nickel(II) exists in the form of two centrosymmetric molecules. In the structure of alpha-bis(O,O'-dipropyl phosphorodithioato)nickel(II), the Dtph ligands in the molecule are nonequivalent. The experimental P-31 NMR signals in the spectra of [Ni{S2P(OC3H7)(2)}(2)] and alpha-[Ni{S2P(O-i-C4H9)(2)}(2)] are assigned to the structural positions of phosphorus atoms in the corresponding molecular structures determined by X-ray diffraction.

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NATURVETENSKAP  -- Kemi -- Fysikalisk kemi (hsv//swe)

NATURAL SCIENCES  -- Chemical Sciences -- Physical Chemistry (hsv//eng)

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Chemistry of Interfaces

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