A COMPLETE SERIES OF STEPWISE OXIDATION OF [CO (2-PYRIDINETHIOLATO)(EN),](2- CHARACTERIZATION OF THE 2-PYRIDINESULFENATO-N,S AND 2-PYRIDINESULFENATO-N,O, 2-PYRIDINESULFINATO-N,S AND 2-PYRIDINESULFINATO-N,O, AND 2-PYRIDINESULFONATO-N,O COMPLEXES() )

The H2O2 oxidation of [Co(pyt)(en)(2)](2+) [1, pyt = 2-pyridinethiolat e(1 -) ion, en = ethylenediamine] afforded the orange [Co(pyse-N,S)(en )(2)](2+) [2, pyse =2-pyridinesulfenate(1 -) ion] complex. Irradiation of this orange complex in the solid state yielded a green complex. Th e molecular structure of the green complex perchlorate was determined by X-ray diffraction to be [Co(pyse-N,O) (en)(2)]ClO4)(2) (4); linkage isomerization took place upon photolysis. The crystal data and final R value are: triclinic, P (1) over bar, a = 9.374(4) Angstrom, b = 11. 248(4) Angstrom, c = 9.238(8) Angstrom, alpha = 95.26(4)degrees, beta = 95.14(5)degrees, gamma = 75.75(3)degrees, V = 938(2) Angstrom(3), Z = 2 and R = 0.040 for 2757 unique reflections. The pyse-N,O complex ha s an anomalous feature in the W-vis spectrum. It has an extra band (16 400 cm(-1)) on the low-energy side of the first d-d absorption band ( 22 200 cm(-1)). This band can be rationalized as a splitting component of the first d-d band generated by the anisotropic interaction of the antibonding pi orbital of the coordinating oxygen with the t(2g) orb itals on the cobalt center. Treatment of [Co(pyt)(en)(2)](2+) with exc ess H2O2 afforded the yellow-orange sulfinato-N,S complex, [Co(pysi-N, S) (en)(2)](2+) [3, pysi = 2-pyridinesulfinate(1 -) ion]. The molecula r structure of the pysi-N,S complex was determined by X-ray diffractio n to be [Co(pysi-N,S) (en)(2)](ClO4)(2) (3), which cocrystallized with the pysi-N,O complex (5). The crystal data and final R value for the cocrystal(3/5) are: monoclinic, C2, a = 28.559(8) Angstrom, b = 6.960( 2) Angstrom, c = 10.406(3) Angstrom, beta = 99.90 (2)degrees V = 2038( 2) Angstrom(3), Z = 4 and R = 0.040 for 2391 unique reflections. The p ysi-N,S,S complex was unstable and was easily converted photochemicall y or thermally to the linkage-isomerized orange pysi-N,O complex (5). The sulfur atom becomes chiral (R and S) upon linkage isomerization, a nd two kinds of racemic salt, Lambda(R)Delta(S) and Lambda(S)Delta(R), were separated by fractional crystallization of the complex perchlora te. The molecular structure of the less soluble isomer (Lambda(S)Delta (R)-5) of the perchlorate was determined by X-ray diffraction to be La mbda(S)Delta(R)-[Co(pysi-N,O)(en)(2)](ClO4)(2). The crystal data and f inal R value are: triclinic, P (1) over bar, a = 9.384(4) Angstrom, b = 11.807(8) Angstrom, c = 8.640(5) Angstrom, alpha = 98.54(5)degrees, beta = 94.40(4)degrees, gamma = 96.65(5)degrees, V = 936(2) Angstrom(3 ) Z = 2 and R = 0.038 for 3061 unique reflection. The two diastereomer s of Lambda-[Co(pysi-N,O) (en)(2)](2+) were separated by SP-Sephadex c olumn chromatography, and one of them (A(R)-5) was structurally charac terized by X-ray crystallography. Lambda(R)-[Co(pysi-N,O) (en)(2)](ClO 4)(2), which crystallizes as orthorhombic in space group P2(1)2(1)2(1) with Z = 4, has the cell parameters a = 9.896(2) Angstrom, b = 20.758 (6) Angstrom, c = 9.494(4) Angstrom, V = 1950(2) Angstrom(3). The fina l R value was 0.041 for 1543 unique reflections. Kinetic studios of re versible isomerization (epimerization) between Lambda(R)- and Lambda(S )-[Co(pysi-N,O) (en)(2)](2+) were performed in aqueous solutions at 60 degrees C. The rate constants were kappa(Lambda(R)-->Lambda(S)) = 5.5 x 10(-6) s(-1) and kappa(Lambda(S)-->Lambda(R)) = 1-1. 7 x10(-6) s(-1 ). The orange-red [Co(pyso-N,O)(en)(2)](2+) [6, pyso = 2-pyridinesulfo nate( 1-) ion] complex was prepared by the reaction of cis-[Co{OS(O)(2 )CF3}(2)(en)(2)](+) with the 2-pyridinesulfonate ligand or by the oxid ation of [Co(pyse-N,O) (en)(2)](2+) (4) with H2O2. The molecular struc ture of the trifluoromethanePulfonate salt of complex 6 was determined by X-ray diffraction. [Co(pyso-N,O) (en)(2)](CF3SO3)(2) crystallizes as monoclinic in space group P2(1)/a with Z = 4; The cell parameters a re a = 19.079(8) Angstrom, b =16.699(6) Angstrom, c = 7.462(4) Angstro m, beta = 100.51(4)degrees, V = 2338(2) Angstrom(3). The final R value was 0.050 for 3966 unique reflections. The pyso ligand has the strong est ligand field strength among the ligands studied here. A series of sulfur oxidation from [Co(pyt)(en)(2)](2+) to [Co(pyso-N,O)(en)(2)](2) is established. (C) 1998 Elsevier Science S.A. All rights reserved.