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Several rhenium(V) oxo complexes with tetradentate N(2)O(2) Schiff base ligands were synthesized and characterized. The general synthetic procedure involved reaction of [NBu(4)][ReOCl(4)] with a tetradentate Schiff base ligand (L(1) = N,N'-ethylenebis(acetylacetoneimine), (acac(2)en) or L(2) = N,N'-propylenebis(acetylacetoneimine) (acac(2)pn)) in ethanol solution to generate complexes of the form trans-ReOX(L) where X = Cl(-), MeO(-), ReO(4)(-), or H(2)O. The product isolated from the reaction was found to be dependent on the reaction conditions, in particular the presence or absence of water and/or base. The mu-oxo-Re(2)O(3)(L)(2) dimers were synthesized and characterized for chemical and structural comparison to the related monomers. Conversion of the monomer to its dimer analogue was followed qualitatively by spectrophotometry. The complexes were characterized by (1)H and (13)C NMR, UV-vis, and IR spectroscopy, elemental analysis, and single crystal X-ray diffraction. The crystallographic data reported for the structures are as follows: trans-[ReO(OH(2))(acac(2)en)]Cl (H(20)C(12)ClN(2)O(4)Re) 1, triclinic (Ponemacr;), a = 7.2888(6) A, b = 9.8299(8) A, c = 10.8195(9) A, alpha = 81.7670(10) degrees, beta = 77.1510(10) degrees, gamma = 87.6200(10) degrees, V = 747.96(11) A(3), Z = 2; trans-[ReO(OReO(3))(acac(2)en)] (H(18)C(12)N(2)O(7)Re(2)) 2, monoclinic (P2(1)/c), a = 7.5547(4) A, b = 8.7409(5) A, c= 25.7794(13) A, beta = 92.7780(10) degrees, V = 1700.34(16) A(3), Z = 4; trans-[ReOCl(acac(2)pn)] (H(20)C(13)N(2)O(3)ClRe) 3, monoclinic (P2(1)/c), a = 8.1628(5) A, b = 13.0699(8) A, c = 28.3902(17) A, beta = 97.5630(10) degrees, V = 3002.5(3) A(3), Z = 8; trans-[ReO(OMe)(acac(2)pn)] (H(23)C(14)N(2)O(4)Re) 4, monoclinic (P2(1)/c), a = 6.7104(8) A, b = 27.844(3) A, c = 8.2292(9) A, beta = 92.197(2) degrees, V = 1536.4(3) A(3), Z = 4; trans-[mu-oxo-Re(2)O(3)(acac(2)en)(2)] (H(36)C(24)N(4)O(7)Re(2)) 5, monoclinic (P2(1)/n), a = 9.0064(5) A, b = 12.2612(7) A, c = 12.3695(7) A, beta = 90.2853(10) degrees, V = 1365.94(13) A(3), Z = 2; and trans-[mu-oxo Re(2)O(3)(acac(2)pn)(2)] (H(40)C(26)N(4)O(7)Re(2)) 6, monoclinic (P2(1)/n), a = 9.1190(5) A, b = 12.2452(7) A, c = 12.8863(8) A, beta = 92.0510(10) degrees, V = 1438.01(14) A(3), Z = 2.

Several bis(ethylenediamine)cobalt(III) complexes containing chelated, S-bonded sulfenic acid ligands have been synthesized and characterized. [(en)2Co(S(0)CH2CH2NH2)]2+ and [(en)2Co(S(0)CH2COO)]+ are prototypes of this class of complexes. The general preparative route to sulfenato complexes involves stoichiometric oxidation of the corresponding thiolato complex with a 2-equiv oxidant, e.g., H202, in aqueous solution. Subsequent oxidation converts the sulfenato complex to the corresponding sulfinato complex. The ligand field strength and the electronegativity of the ligating sulfur atom increase monotonically along the thiolato-sulfenato-sulfinato series. The S-bonded sulfenato ligand exhibits a characteristic S-0 stretch in the region 950-1000 cm"1 and a characteristic charge-transfer absorption at ca. 360 nm. Reversible protonation of the sulfenato ligand occurs in aqueous HC104 solutions; the protonation constant of [(en)2Co(S(0)CH2CH2NH2)]2+ at 25 °C, µ = 4.0 M, is 1.4 ± 0.2 M"1. Sulfenato-cobalt(III) complexes slowly decompose in aqueous acidic media to yield a variety of products including cobalt(II). The single-crystal X-ray structure analysis of (2-sulfenatoethylamine-A,S)bis(ethylenediamine)cobalt(III) thiocyanate, refined to a conventional R factor of 0.030, is reported. The cobalt(III) center is approximately octahedrally coordinated (five N atoms and one S atom) while the sulfenato sulfur atom is three-coordinate (Co, C, and O). The Co-N bond trans to the sulfenato sulfur atom is significantly longer than the average of the cis Co-N bonds, = 0.072 (8) Á. The rates of H202 oxidation of [(en)2CoS(0)CH2CH2NH2)]2+ in aqueous perchloric acid media are reported as a function of [H202], [H+], and temperature. The mechanism of this reaction is discussed in terms of nucleophilic attack by the coordinated sulfur on the 0-0 bond of H202, the coordinated sulfur atom having about the same nucleophilicity as the sulfur atom of SCN". The observed acid catalysis presumably reflects the greater reactivity of H302+ as a nucleophilic substrate. This acid catalysis is significantly less effective in this system than in analogous H202 oxidations, implying that within the acid-catalyzed transition state there is an interaction between the proton and the sulfenato moiety which decreases the overall efficacy of

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The 7-coordinate technetium(III) and rhenium(III) monocapped tris(dioxime) complexes [MX(dioxime) 3 BR] have been prepared in which the seventh ligand, X, is thiocyanate or hydroxide (M ) Tc, Re; R ) Me, Et). Both the N-and S-bound thiocyanate linkage isomers are produced during the syntheses, however, the S-bound complex isomerizes to the N-bound analogue. The synthetic routes employed allowed isolation of sufficient quantities of the technetium and rhenium S-bound isomers to be identified; however, full characterization was not possible. The linkage isomerization reaction of TcSCN(CDOH) 2 (CDO)BMe to TcNCS(CDOH) 2 (CDO)BMe was monitored in dichloromethane by UV-visible spectrophotometry, with four isosbestic points observed, consistent with the formation of a single product. The N-bound isomers for both Tc and Re, and the S-bound isomer of Re were characterized by single-crystal X-ray diffraction analysis. The two N-bound complexes were found to be isostructural. TcNCS(CDOH) 2 (CDO)BMe crystallized in the orthorhombic space group P2 1 2 1 2 1 with a ) 15.814-(2) Å, b ) 17.855(3) Å, c ) 17.997(5) Å, Z ) 8, R ) 0.054, and R W ) 0.057. ReNCS(CDOH) 2 (CDO)BMe crystallized in the orthorhombic space group P2 1 2 1 2 1 with a ) 15.795(1) Å, b ) 17.843(2) Å, c ) 18.014(3) Å, Z ) 8, R ) 0.054, and R W ) 0.073. In both cases two independent molecules per unit cell were observed. ReSCN(CDOH) 2 (CDO)BMe crystallized in the monoclinic space group P2 1 /c with a ) 10.0866(6) Å, b ) 26.301-(2) Å, c ) 12.4592(7) Å, β ) 100.5(1) deg, Z ) 4, R ) 0.100, and R W ) 0.141.