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Of great si&icance in both biological and synthetic systems are two-electron processes in which a divalent atom such as oxygen is completely transferred between two reaction partners.' Until now, the endogenous three-electron atom transfer process has been limited to examples of intermetallic nitrogen atom transfer as exemplified by the reaction (TTP)Cr + N=Mn(TTP) -(TTP)CFN 4-Mn(TTP).2 In the present work we establish a three-electron redox process in which a nitrogen atom from nitrous oxide is transferred to a molybdenum(II1) coordination complex.The complex Mo(NRAr)3 (1; R = C(CD3)2CH3, Ar = 33-C6H3Me2) was prepared for this work since d3 1 could conceivably engage in three-electron redox processes. Of the various possibilities, N-atom transfer was a particularly attractive target since stable nitrido complexes of the kind N=MoX3 (X = alkyl,3 amide? or &oxide5) are known. In a typical preparation, M o C~~( T H F )~~ (4.164 "01) and Li(NRAr)(OEt2)7 (8.315 m o l ) were added to 70 mL of cold (-100 "C) ether, and the mixture was stirred for 2.5 h after warming to 28 "C. The precipitated LiCl and excess MoC13(THF)3 were removed by filtration. Analysis of the filtrate by 2H NMR spectroscopy showed only one major product, with a relatively sharp (Avll2 = 35 Hz) signal at 64.6 ppm corresponding to the 2H-labeled tert-butyl groups in paramagnetic M O ( N R A~)~.~ The filtrate was concentrated and cooled to -35 "C under an argon atmosphere to produce orange-red, crystalline Mo(NRAr)3 (mp 126-128 "C, yield 70%)? MO(NR&)3 (1) is extremely oxygen-and (1) Holm, R. H.; Donahue,

Syntheses and characterizations are reported for dimolybdenum(II) compounds supported by the diarylformamidinate (ArNC(H)NAr(-)) ligand, where Ar is XC(6)H(4)(-), with X as p-OMe (1), H (2), m-OMe (3), p-Cl (4), m-Cl (5), m-CF(3) (6), p-COMe (7), p-CF(3) (8), or Ar is 3,4-Cl(2)C(6)H(3)(-) (9) or 3,5-Cl(2)C(6)H(3)(-) (10). The (quasi)reversible oxidation potentials measured for the Mo(2)(5+)/Mo(2)(4+) couple were found to correlate with the Hammett constant (sigma(X)) of the aryl substituents according to the following equation: DeltaE(1/2) = E(1/2)(X) - E(1/2)(H) = 87(8sigma(X)) mV. Molecular structure determinations of compounds 1, 2, 5, and 10 revealed an invariant core geometry around the Mo(2) center, with statistically identical Mo-Mo quadruple bond lengths of 2.0964(5), 2.0949[8], 2.0958(6), and 2.0965(5) Å, respectively. Magnetic anisotropies for compounds 1-10 estimated on the basis of (1)H NMR data were similar and unrelated to sigma(X). Similarity in UV-vis spectra was also found within the series, which, in conjunction with the features of both molecular structures and (1)H NMR spectra, was interpreted as the existence of a constant upper valence structure across the series. Results of Fenske-Hall calculations performed for several model compounds paralleled the experimental observations.