Ligand Oxidations in High-Spin Nickel Thiolate Complexes and Zinc Analogues
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- 作者：Balwant S. Chohan ; Steven C. Shoner ; Julie A. Kovacs ; and Michael J. Maroney
- 刊名：Inorganic Chemistry
- 出版年：2004
- 出版时间：November 29, 2004
- 年：2004
- 卷：43
- 期：24
- 页码：7726 - 7734
- 全文大小：181K
- 年卷期：v.43,no.24(November 29, 2004)
- ISSN：1520-510X
文摘
Oxidations of a trigonal-bipyramidal, high-spin Ni(II) dithiolate complex of a pentadentate, N3S2-donor ligand,N1,N9-bis(imino-2-mercaptopropane)-1,5,9-triazanonane) nickel(II), and the structurally analogous Zn(II) complex,lead to oxidations of the ligand. Oxidation of the Ni(II) complex with I2 produces a novel Ni(II) macrocyclic cationiccomplex containing a monodentate disulfide ligand (2). Crystals of the I3- salt of the complex form in the triclinicspace group P1 with cell dimensions a = 8.508(3) Å, b = 9.681(2) Å, c = 14.066(4) Å, angles 
chars/alpha.gif" BORDER=0> = 90.97(2)
,chars/beta2.gif" BORDER=0 ALIGN="middle"> = 91.61(3), chars/gamma.gif" BORDER=0 > = 90.83(2), and Z = 2. The structure was refined to R = 6.31% and Rw = 16.63% (I > 2chars/sigma.gif" BORDER=0 >(I)).Oxidation of the Ni(II) complex with O2 leads to the formation of a novel pentadentate bis-iminothiocarboxylatecomplex with trigonal-bipyramidal geometry (3). This neutral product crystallizes in the monoclinic space groupP21/c with cell dimensions a = 13.625(3) Å, b = 7.605(5) Å, c = 14.902(4) Å, angles chars/alpha.gif" BORDER=0> = chars/gamma.gif" BORDER=0 > = 90, chars/beta2.gif" BORDER=0 ALIGN="middle"> =102.81(2), and Z = 4. The structure was refined to R = 7.18% and Rw = 17.86% (I > 2chars/sigma.gif" BORDER=0 >(I)). Oxidation of theZn(II) dithiolate analogue with O2 leads to the formation of the Zn(II) complex of the pentadentate bis-iminothiocarboxylate ligand. The neutral complex is isomorphous with the Ni(II) complex and crystallizes in themonoclinic space group P21/c with cell dimensions a = 13.8465(4) Å, b = 7.6453(2) Å, c = 15.0165(6) Å, angleschars/alpha.gif" BORDER=0> = chars/gamma.gif" BORDER=0 > = 90, chars/beta2.gif" BORDER=0 ALIGN="middle"> = 103.2140(11), and Z = 4. The structure was refined to R = 3.96% and Rw = 9.45% (I >2chars/sigma.gif" BORDER=0 >(I)). Details of the crystal structures are reported. Kinetics of the O2 reactions show that the reactions of theNi(II) and Zn(II) dithiolates follow the rate law, Rate = k2[1][O2], with k2 = 1.81 M-1 s-1 for the Ni(II) complex andk2 = 1.93 × 10-2 M-1 s-1 for the Zn(II) complex. The O2 oxidation of the high-spin Ni(II) thiolate complex wasfound to follow a similar oxidation mechanism to those of low-spin Ni(II) complexes, which form transient persulfoxideintermediates that yield S-oxidation products. In the case of the high-spin system reported here, the transientpersulfoxide intermediate gives rise to an alternative ligand oxidation product, a bis-iminothiocarboxylate complex,because of the reactivity of the ligand, which contains a methylene with acidic H atoms chars/alpha.gif" BORDER=0> to the thiolate sulfur. Theproposed mechanism is supported by studies of the analogous Zn dithiolate complex, which gives rise to theanalogous bis-iminothiocarboxylate product (5).
chars/alpha.gif" BORDER=0> = 90.97(2),chars/beta2.gif" BORDER=0 ALIGN="middle"> = 91.61(3), chars/gamma.gif" BORDER=0 > = 90.83(2), and Z = 2. The structure was refined to R = 6.31% and Rw = 16.63% (I > 2chars/sigma.gif" BORDER=0 >(I)).Oxidation of the Ni(II) complex with O2 leads to the formation of a novel pentadentate bis-iminothiocarboxylatecomplex with trigonal-bipyramidal geometry (3). This neutral product crystallizes in the monoclinic space groupP21/c with cell dimensions a = 13.625(3) Å, b = 7.605(5) Å, c = 14.902(4) Å, angles chars/alpha.gif" BORDER=0> = chars/gamma.gif" BORDER=0 > = 90, chars/beta2.gif" BORDER=0 ALIGN="middle"> =102.81(2), and Z = 4. The structure was refined to R = 7.18% and Rw = 17.86% (I > 2chars/sigma.gif" BORDER=0 >(I)). Oxidation of theZn(II) dithiolate analogue with O2 leads to the formation of the Zn(II) complex of the pentadentate bis-iminothiocarboxylate ligand. The neutral complex is isomorphous with the Ni(II) complex and crystallizes in themonoclinic space group P21/c with cell dimensions a = 13.8465(4) Å, b = 7.6453(2) Å, c = 15.0165(6) Å, angleschars/alpha.gif" BORDER=0> = chars/gamma.gif" BORDER=0 > = 90, chars/beta2.gif" BORDER=0 ALIGN="middle"> = 103.2140(11), and Z = 4. The structure was refined to R = 3.96% and Rw = 9.45% (I >2chars/sigma.gif" BORDER=0 >(I)). Details of the crystal structures are reported. Kinetics of the O2 reactions show that the reactions of theNi(II) and Zn(II) dithiolates follow the rate law, Rate = k2[1][O2], with k2 = 1.81 M-1 s-1 for the Ni(II) complex andk2 = 1.93 × 10-2 M-1 s-1 for the Zn(II) complex. The O2 oxidation of the high-spin Ni(II) thiolate complex wasfound to follow a similar oxidation mechanism to those of low-spin Ni(II) complexes, which form transient persulfoxideintermediates that yield S-oxidation products. In the case of the high-spin system reported here, the transientpersulfoxide intermediate gives rise to an alternative ligand oxidation product, a bis-iminothiocarboxylate complex,because of the reactivity of the ligand, which contains a methylene with acidic H atoms chars/alpha.gif" BORDER=0> to the thiolate sulfur. Theproposed mechanism is supported by studies of the analogous Zn dithiolate complex, which gives rise to theanalogous bis-iminothiocarboxylate product (5).