Dinitrogen photolysis

Vogler A, Kimkely H. Photooxidation of coordinated dinitrogen. Photolysis of the CIO2 adduct of [(NH3)50s( 1-N 0s(NH3)5] Inorg Chem Commun. 2012 18 73-74. 

In the photolysis of difiuorodiazirine (218) a singlet carbene was also observed (65JA758). Reactions of the difiuorocarbene were especially studied with partners which are too reactive to be used in the presence of conventional carbene precursors, such as molecular chlorine and iodine, dinitrogen tetroxide, nitryl chloride, carboxylic acids and sulfonic acids. Thus chlorine, trifiuoroacetic acid and trifiuoromethanesulfonic acid reacted with difiuorodiazirine under the conditions of its photolysis to form compounds (237)-(239) (64JHC233). 

The new dinitrogen complex [Ni(CO)3N2] can be generated in a pressure cell by UV photolysis of tetracarbonylnickel in liquid krypton, doped with N2 at 114K. The decomposition of this complex was followed over the temperature range 122-127 K and a value of the Ni—N2 bond dissociation energy estimated at lOkcal moN1.2474... 

Investigations into the mechanism of this reaction revealed several interesting facts (61). Compelling evidence was presented that a discreet Cu nitrenoid was involved in the catalytic cycle. Photolysis of a solution of tosyl azide and styrene in the presence of the catalyst afforded aziridine with the same enantioselectivity as obtained from the PhI=NTs reaction, Eq. 69. Since photolysis of tosyl azide is known to extrude dinitrogen and form the free nitrene, the authors argue that this is indicative of a common Cu-nitrenoid intermediate in this reaction. 

Dinitrogen, Nitrosyl, Isocyanide, and Cyanide Complexes.—Spectroscopic evidence has been presented for the formation of [Mo(CO)5N2] and [W(C0)5N2] complexes subsequent to photolysis of the hexacarbonyls in a nitrogen matrix at 20 The complexes [Mo(N2)(PPh3)2,PhMe] and... 

The first carbene ever isolated was la, which was prepared using the most classical route to transient carbenes, namely, the decomposition of diazo compounds. The [bis(diisopropylamino)phosphino](trimethylsilyl)diazomethane precursor (la) was obtained by treatment of the lithium salt of trimethylsilyldiazomethane with 1 equiv of bis(diisopropylamino)chlorophosphine. Dinitrogen elimination occurs by photolysis (300 nm) or thermolysis (250 °C under vacuum) affording carbene la as a red oily material in 80% yield (Scheme 8.1). Carbene la is stable for weeks at room temperature and can even be purified by flash distillation under vacuum (10-2 Torr) at 75-80 °C. 

In cocondensation experiments of nickel atoms in various CO/N2 matrices, mixed carbonyl-dinitrogen species Ni(CO)x(N2)4 x (jc = 1-3) were observed.243 The Ni(CO)3(N2)244 245 species was also generated by the UV photolysis of Ni(CO)4 in N2-doped liquid Kr, and the decay kinetics were studied.246 The Ni—N2 dissociation energy was estimated to be about 42kJmor1. 

M-1s-1) to form RhCl(PPh3)2 and RhCl(H2C=CH2)(PPh3)2, respectively however, reaction with H2 to form the dihydride is much slower, (1 x 10 M-- -s-- -). Also described are flash photolysis studies of the dinitrogen species IrCl(N2) (PPI13) 2 and the dihydride H2lrCl(C0)(PPh3)2- In both cases, the transient IrCl(PPh3)2 is formed. These results indicate that CO labilization from the Ir(lII) dihydride is a facile photochemical pathway and the photo-reductive elimination of H2 is a more complicated mechanism than previously inferred. 

Flash photolysis of the analogous dinitrogen complex trans-IrCl (N2)(PPh3)2 (17) demonstrates that flash photolysis leads in both cases to immediate appearance of a transient spectrum the same, within experimental uncertainty, as that attributed above to... 

The photolysis of [Os(NH3)5N2l2 and Os(NH3)4(N2)2 2 f at 229-366 nm is complex. The mono(dinitrogen) complex loses dinitrogen, aquates, and is oxidized by protons, and the resultant reaction manifold is complicated. The bis(dinitrogen) complex solely photoaquates yielding 0s(NH3)4(H20)N212+ which can also oxidize. For both com-... 

The predominant product depends on conditions, especially the F2/NH3 ratio. Dinitrogen difluoride may also be prepared by photolysis of N2F4 in the presence of Br2. 

A study of chemically induced dynamic electron polarization, CIDEP (see Section 12.3.3) on F and G pairs of radicals formed under photolysis of a common termo- and photoinitiator 2,2 -azobis(2-methylpropionitrile) (AIBN) led to a tentative conclusion that initial spatial separation of 2-cyano-2-propyl radicals does not depend upon viscosity However, it is plausible that the diamagnetic dinitrogen molecule formed under photolysis of AIBN (and is invisible by ESR) separates further from a contact RP under photolysis in solvents of lower viscosity. The problem of initial spatial separation and mutual orientation ofradicals under photolysis still waits experimental elucidation. 

Visible photolysis of Mo(CO)s trapped in matrices containing N2 results, not only in the regeneration of Mo(CO)6, but also in the formation of a dinitrogen complex Mo(CO)s (N2) (Scheme 3). This molecule has been characterized by IR and Raman spectroscopy. Studies involving isotopic substitution with N2, and COhave confirmed that the molecule... 

More direct evidence for the formation of difluorocarbene as an intermediate comes from the photolysis of difluorodiazirine in the presence of chlorine, iodine, dinitrogen tetroxide, and nitryl chloride when the corresponding difluoromethane derivatives were formed, and in the presence of isobutene, buta-l,3-diene, and cis- and frans-but-2-ene when the corresponding 1,1-difluorocyclopropane derivatives were formed. Even with considerable excesses of olefins, appreciable tetra-... 

The test matrix that will be carried out in the EUPHORE chamber is shown in Tables 1 and 2. These series of tests provide experiments that will examine the effects of aging, photolysis, HO, O3 and the NO3 radieal (in the dark) on the eomposition of diesel exhaust. The experiments are divided into dark (Table 1) and light (Table 2) exposures test matrixes. The dark experiments D-1, D-2, and D-5 provide baselines for other experiments. Experiment D-3 investigates the effeets of O3 on diesel exhaust in the dark and experiment D-4 allows the effect of the NO3 radical on diesel exhaust to be studied. Dinitrogen pentoxide is used as a source of NO3 radicals. N2O5 is prepared by reacting ozone with NO2 direetly in the chamber. 

Nitrate radicals are prepared by photolysis of dinitrogen pentoxide in the dark ... 

A number of unimolecular photoredox reactions have been studied. Kirk and Porter [130] reported a AF value of +4.8 cm3 mol"1 for the charge-transfer photolysis of Co(NH-,)5Br24 and suggested the formation of a caged radical pair, Con(Br ), from the LMCT excited state. Dissociation of this radical pair to the reaction products was suggested to account for the increase in volume as reflected by the positive volume of activation. Charge-transfer photolysis of trans -Pt(CN)4(N3)2 results in the reductive elimination of azide to produce Pt(CN) and dinitrogen [131,132], On... 

Similarly, the transient Ni(CO)3(N2) has been identified following its generation by photolysis of Ni(CO)4 in liquid krypton doped with N2 at 114 K. Ultraviolet irradiation establishes a steady-state concentration of Ni(CO)3(N2) as soon as the photolysis source is switched off, the dinitrogen complex begins to decay, reacting thermally with CO to regenerate Ni(CO)4. The kinetics of the decay reaction,... 

Some remarkable reactions of M(N2)2(dpe)2 [M = W or Mo dpe = 1,2-bis(diphenylphosphino)ethane] have been reported. Addition of an alkyl group to the dinitrogen ligand takes place during photolysis in the presence of RBr in benzene solution (reaction 67) (R = Me, Et, or Bu ).213 In THF solution compounds of type (25), in which the ligating N2 has apparently displaced the oxygen from THF, are also formed.214... 

---