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Dalton Transactions

The international journal for inorganic, organometallic and bioinorganic chemistry



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Dalton Trans., 2009, 9410 - 9417, DOI: 10.1039/b910237j

(-2:2-Disulfido)dinickel(II) complexes supported by 6-methyl-TPA ligands

Masayuki Inosako, Atsushi Kunishita, Minoru Kubo, Takashi Ogura, Hideki Sugimoto and Shinobu Itoh

A series of (-2:2-disulfido)dinickel(II) complexes 2n have been synthesized by the reaction of Na2S2 and nickel(II) complexes 1n supported by tris[(pyridin-2-yl)methyl]amine (TPA; 10) [(6-methylpyridin-2-yl)methyl]bis[(pyridin-2-yl)methyl]amine (Me1TPA; 11), bis[(6-methylpyridin-2-yl)methyl][(pyridin-2-yl)methyl]amine (Me2TPA; 12) and tris[(6-methylpyridin-2-yl)methyl]amine (Me3TPA; 13), respectively, and characterised by UV-vis and resonance Raman spectroscopy. X-ray crystallographic analyses on 22 and 23 supported by Me2TPA and Me3TPA, respectively, have revealed that the Ni2S2 core is largely bent (30°) along the S–S axis, being in sharp contrast to the planar Ni2S2 core structure of the (-2:2-disulfido)dinickel(II) complexes reported so far. The UV-vis spectra of 20 and 21 supported by TPA and Me1TPA, respectively, exhibiting an intense absorption band at 360 nm together with a shoulder around 400 nm and a weak and broad absorption band around 450–600 nm, are very close to those of 22 and 23, suggesting that 20 and 21 also exhibit a similar distorted Ni2S2 core structure. Resonance Raman spectra of 2n showed a characteristic S–S stretching vibration mode at 450 cm-1 with an isotope shift (32S–34S) = 10–15 cm-1. The reaction of 2n with (p-Me-C6H4)3P gave (p-Me-C6H4)3PS quantitatively based on 2n. Hammett analysis on the sulfur atom transfer process from 2n to the phosphine derivatives [(p-X-C6H4)P; X = OMe, Me, H and Cl] has indicated that the reaction involves an electrophilic ionic mechanism. Moreover, the order of reactivity of 2n toward PPh3 has been found as 20 > 23 > 21 > 22. On the basis of these results, the ligand effects of MenTPA on the structure and reactivity of the nickel(II) complexes have been discussed.

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