Picosecond time-resolved infrared spectroscopy of rhodium and iridium azides

Picosecond time-resolved infrared spectroscopy was used to elucidate early photochemical processes in the diazido complexes M(Cp*)(N3)2(PPh3), M = Rh (1), Ir (2), using 266 nm and 400 nm excitation in THF, CH2Cl2, MeCN and toluene solutions. The time-resolved data have been interpreted with the aid of DFT calculations on vibrational spectra of the singlet ground states and triplet excited states and their rotamers. While the yields of phototransformations via N2 loss are low in both complexes, 2 cleaves a N3 ligand under 266 nm excitation. The molecular structure of 1 is also reported as determined by single crystal X-ray diffraction

Homoleptic Low-Valent Polyazides of Group 14 Elements

First examples of coordinatively unsaturated, homoleptic azido complexes of low-valent group 14 elements are reported. A simple strategy uses low-valent precursors, ionic azide transfer reagents and bulky cations to obtain salt-like compounds containing E(N3)3- of Ge(II)/Sn(II) which are fully characterised, including XRD. Remarkably, these compounds are kinetically stable at r.t. and isolable in sub-gram quantities

Time-resolved infrared (TRIR) study on the formation and reactivity of organometallic methane and ethane complexes in room temperature solution

We have used fast time-resolved infrared spectroscopy to characterize a series of organometallic methane and ethane complexes in solution at room temperature: W(CO)(5)(CH(4)) and M(η(5) [Image: see text] C(5)R(5))(CO)(2)(L) [where M = Mn or Re, R = H or CH(3) (Re only); and L = CH(4) or C(2)H(6)]. In all cases, the methane complexes are found to be short-lived and significantly more reactive than the analogous n-heptane complexes. Re(Cp)(CO)(2)(CH(4)) and Re(Cp*)(CO)(2)(L) [Cp* = η(5) [Image: see text] C(5)(CH(3))(5) and L = CH(4), C(2)H(6)] were found to be in rapid equilibrium with the alkyl hydride complexes. In the presence of CO, both alkane and alkyl hydride complexes decay at the same rate. We have used picosecond time-resolved infrared spectroscopy to directly monitor the photolysis of Re(Cp*)(CO)(3) in scCH(4) and demonstrated that the initially generated Re(Cp*)(CO)(2)(CH(4)) forms an equilibrium mixture of Re(Cp*)(CO)(2)(CH(4))/Re(Cp*)(CO)(2)(CH(3))H within the first few nanoseconds (τ = 2 ns). The ratio of alkane to alkyl hydride complexes varies in the order Re(Cp)(CO)(2)(C(2)H(6)):Re(Cp)(CO)(2)(C(2)H(5))H > Re(Cp*)(CO)(2)(C(2)H(6)):Re(Cp*)(CO)(2)(C(2)H(5))H ≈ Re(Cp)(CO)(2)(CH(4)):Re(Cp)(CO)(2)(CH(3))H > Re(Cp*)(CO)(2)(CH(4)):Re(Cp*)(CO)(2)(CH(3))H. Activation parameters for the reactions of the organometallic methane and ethane complexes with CO have been measured, and the ΔH(‡) values represent lower limits for the CH(4) binding enthalpies to the metal center of W [Image: see text] CH(4) (30 kJ·mol(−1)), Mn [Image: see text] CH(4) (39 kJ·mol(−1)), and Re [Image: see text] CH(4) (51 kJ·mol(−1)) bonds in W(CO)(5)(CH(4)), Mn(Cp)(CO)(2)(CH(4)), and Re(Cp)(CO)(2)(CH(4)), respectively

Dinitrogen Release from Arylpentazole: A Picosecond Time-Resolved Infrared, Spectroelectrochemical, and DFT Computational Study

<i>p</i>-(Dimethylamino)­phenyl pentazole, DMAP-N₅ (DMAP = Me₂N–C₆H₄), was characterized by picosecond transient infrared spectroscopy and infrared spectroelectrochemistry. Femtosecond laser excitation at 310 or 330 nm produces the DMAP-N₅ (S₁) excited state, part of which returns to the ground state (τ = 82 ± 4 ps), while DMAP-N and DMAP-N₃ (S₀) are generated as double and single N₂-loss photoproducts with η ≈ 0.14. The lifetime of DMAP-N₅ (S₁) is temperature and solvent dependent. [DMAP-N₃]⁺ is produced from DMAP-N₅ in a quasireversible, one-electron oxidation process (<i>E</i>_1/2 = +0.67 V). Control experiments with DMAP-N₃ support the findings. DFT B3LYP/6-311G** calculations were used to identify DMAP-N₅ (S₁), DMAP-N₃⁺, and DMAP-N in the infrared spectra. Both DMAP-N₅ (S₁) and [DMAP-N₅]⁺ have a weakened N₅ ring structure