The mechanisms of oxidative ligand dehydrogenation in high-valent ruthenium hexaamine complexes of bidentate 1,2-ethanediamine (en) and tridentate 1,1,1-tris(aminomethyl)ethane (tame) are elucidated in detail. In basic aqueous solution, [Ru(III)(tame)(2)](3+) undergoes rapid initial deprotonation (pK(III) = 10.3). This is followed by a pH-dependent disproportionation step involving either [Ru(III)(tame)(2)-H(+)](2+) + [Ru(III)(tame)(2)](3+) (k(1d) = 8300 M(-)(1) s(-)(1)) or two singly deprotonated [Ru(III)(tame)(2)-H(+)](2+) ions (k(2d) = 3900 M(-)(1) s(-)(1)). The products are [Ru(II)(tame)(2)](2+) and either the singly deprotonated species [Ru(IV)(tame)(2)-H(+)](3+) (pK(IV) = 8.2) or the doubly deprotonated [Ru(IV)(tame)(2)-2H(+)](2+). These Ru(IV) complexes undergo spontaneous dehydrogenation to give the imine [Ru(II)(imtame)(tame)](2+) (imtame = 1,1-bis(aminomethyl)-1-(iminomethyl)ethane), with first-order rate constants of k(1im) = 320 s(-)(1) and k(2im) = 1.1 s(-)(1), respectively. In the [Ru(III)(en)(3)](3+) system, the initial deprotonation (pK(III) = 10.4) is followed by the corresponding disproportionation reactions (k(1d) = 9000 M(-)(1) s(-)(1), k(2d) = 3800 M(-)(1) s(-)(1)). The complex [Ru(IV)(en)(3)-H(+)](3+) (pK(IV) = 8.9) and its deprotonated counterpart, [Ru(IV)(en)(3)-2H(+)](2+), undergo dehydrogenation to give [Ru(II)(imen)(en)(2)](2+) (imen = 2-aminoethanimine) with first-order rate constants of k(1im) = 600 s(-)(1) and k(2im) = 1.0 s(-)(1), respectively. In the light of this analysis, the disproportionation and ligand oxidation of the [Ru(III)(sar)](3+) ion are reexamined (k(1d) = 4 x 10(7) M(-)(1) s(-)(1), k(2d) >/= 2 x 10(7) M(-)(1) s(-)(1), pK(IV) = 2.0, k(1im) = 17 s(-)(1), k(2im) = 5 x 10(-)(4) s(-)(1) at 25 degrees C). While the disproportionation to Ru(II) and Ru(IV) has been recognized in such systems, the complexity of the paths has not been realized previously; the surprising variation in the rates of the intramolecular redox reaction (from days to milliseconds) is now dissected and understood. Other facets of the intramolecular redox reaction are also analyzed.

solution was dissolved in CDC13. The Cp resonance positions and peak intensities in the NMr spectrum showed that the products arising from the reaction of tungsten tricarbonyl anion and methanesulfinyl chloride are [CpW(CO)3]2 (50%), CpW(CO)3SMe (40%), CpW(CO)3Cl (7%), and CpW(C0)3S02Me (3%) (relative amounts from 'H NMR analysis in parentheses).Acknowledgment. The support of the donors to the Petroleum Research Fund, administered by the American Chemical Society, is gratefully acknowledged. Exploratory work, some of which was done by M. L. Freeman, was also supported by the Research Corp. We thank Dr. K. L. Brandenburg for samples of some CpW-(CO)3SR compounds and Dr. R. A. Vanderpool for the MeSOCl.

302ChemInform Abstract On treatment of the cage complexes (I) with H2O2 in basic solution, up to three coordinated N sites are oxidized to hydroxylamine groups. The complexes isolated using ion-exchange techniques are (IIa)-(IIe). (IId) is characterized by an X-ray structure determination (space group P212121, Z=4). The hydroxylamine groups are rather acidic and deprotonation leads to a profound change in redox potential. Reduction back to the sec. amine does not proceed fast with one-electron reagents, but is achieved using an aquo V(II) complex generating directly the aquo VO2+ compound.

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