(4) Seymore, S. B., Brown, S. N. Kinetic Effects on Heterometallic Dinitrogen Cleavage. Inorg. Chem. 2006, 45, 9540-9550.
(3) Seymore, S. B., Brown, S. N. Polar Effects in Nitride Coupling Reactions. Inorg. Chem. 2002, 41, 462-469. [This piece was a cover article, as seen below]
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(2) Seymore, S. B., Brown, S. N. Synthesis and Cleavage Reactions of Metal-Metal Bonded [Mo2(S2CNEt2)6](OTf)2, a Source of the Tris(dithiocarbamato)molybdenum (IV) Fragment. Inorg. Chem. 2001, 40, 6676-6683.
(1) Seymore, S. B., Brown, S. N. Charge Effects on Oxygen Atom Transfer. Inorg. Chem. 2000, 39, 325-332.
The importance of polar effects on nitrogen and oxygen atom transfer reactions is described. Phosphine oxidation is accelerated by a factor of ~1000 in the new rhenium(V) cationic oxo complex [(HCpz3)ReOCl2]+ [ORTEP of phosphine oxide adduct] as compared to the known neutral complex (HBpz3)ReOCl2 [ORTEP of phosphine oxide adduct]. This effect is much larger than the difference in ligand substitution rates, and appears to be primarily a transition state effect. This suggests that charge may be as important as the nature of ancillary ligands in tuning the reactivity of oxometal species.
The nitrido complexes MoN(S2CNEt2)3 and TpOsNCl2 couple to form dinitrogen under mild conditions. Heterobimetallic coupling is much faster than homocoupling, despite its lower driving force. Therefore, the rate acceleration is a kinetic effect, and is attributed to the electronic differences between the two nitrides. A structural analysis shows that the major reaction product, TpOsCl2(µ-N)Mo(S2CNEt2)3 [ORTEP], has a nearly linear Os-N-Mo unit with considerable π bonding to both transition metal centers, but much more to the Mo center (dMoN = 1.721(3) Å; dOsN = 1.906(3) Å).
The synthesis and characterization the new binuclear complex [Mo2(S2CNEt2)6](OTf)2 [ORTEP] is described. The dimer possesses an edge-shared pentagonal bipyramidal structure with a Mo2S2 core. The diamagnetism and optical spectra are most consistent with a Mo-Mo bond order of 2, though the Mo-Mo distance of 2.85 Å is more typical of Mo-Mo single bonds. In its ligand substitution chemistry, [Mo2(S2CNEt2)6](OTf)2 acts as a source of the [Mo(S2CNEt2)3]+ fragment [ORTEP of a phosphine adduct]. The mechanism of substitution appears to be complex and may vary with the nature of the incoming ligand.
The dinitrogen-bridged adducts [(PhMe2P)4ClRe(µ-N2)Mo(S2CNEt2)3]+ [ORTEP] and [(PhMe2P)3(Et2NCS2)Re(µ-N2)Mo(S2CNEt2)3]+ have been prepared. Structural and spectroscopic data show that weakening of the N–N bond has occurred, but cleavage is not observed. The new complex [(PhMe2P)4ReNCl]+ [ORTEP], which has been structurally characterized, is the first reported rhenium(V) nitrido complex with four equatorial monodentate phosphines. The known complex MoN(S2CNEt2)3 reacts with [(PhMe2P)4ReNCl]+ to form the unusual µ-nitrido complex mer-[Re(N)(PhMe2P)3Cl(µ-N)Mo(S2CNEt2)3]+. Interconversion between [(PhMe2P)3(Et2NCS2)Re(µ-N2)Mo(S2CNEt2)3]+ and its isomeric nitrides [(PhMe2P)4ReNCl]+ and MoN(S2CNEt2)3 is not observed from either direction, which indicates that dinitrogen cleavage and nitrido coupling are precluded by kinetic effects in this system.