Labile Low-Valent Tin Azides: Syntheses, Structural Characterization, and Thermal Properties.

The first two examples of the class of tetracoordinate low-valent, mixed-ligand tin azido complexes, Sn(N3)2(L)2, are shown to form upon reaction of SnCl2 with NaN3 and SnF2 with Me3SiN3 in either pyridine or 4-picoline (2, L = py; 3, L = pic). These adducts of Sn(N3)2 are shock- and friction-insensitive and stable at r.t. under an atmosphere of pyridine or picoline, respectively. A new, fast, and efficient method for the preparation of Sn(N3)2 (1) directly from SnF2, and by the stepwise de-coordination of py from 2 at r.t., is reported that yields 1 in microcrystalline form, permitting powder X-ray diffraction studies. Reaction of 1 with a nonbulky cationic H-bond donor forms the salt-like compound {C(NH2)3}Sn(N3)3 (4) which is comparably stable despite its high nitrogen content (55%) and the absence of bulky weakly coordinating cations that are conventionally deemed essential in related systems of homoleptic azido metallates. The spectroscopic and crystallographic characterization of the polyazides 1-4 provides insight into azide-based H-bonded networks and unravels the previously unknown structure of 1 as an important lighter binary azide homologue of Pb(N3)2. The atomic coordinates for 1 and 2-4 were derived from powder and single crystal XRD data, respectively; those for 1 are consistent with predictions made by DFT-D calculations under periodic boundary conditions.

Homoleptic Poly(nitrato) Complexes of Group 14 Stable at Ambient Conditions.

Using a novel approach in homoleptic nitrate chemistry, Sn(NO3)6(2-) (3c) as well as the previously unknown hexanitrato complexes Si(NO3)6(2-) (1c), Ge(NO3)6(2-) (2c) were synthesized from the element tetranitrates as salt-like compounds which were isolated and characterized using (1)H, (14)N, and (29)Si NMR and IR spectroscopies, elemental and thermal analyses, and single-crystal XRD. All hexanitrates are moderately air-sensitive at 298 K and possess greater thermal stability toward NO2 elimination than their charge-neutral tetranitrato congeners as solids and in solution. The complexes possess distorted octahedral coordination skeletons and adopt geometries that are highly symmetric (3c) or deformed (1c, 2c) depending on the degree of steric congestion of the ligand sphere. As opposed to the κ(2)O,O' coordination mode reported for Sn(NO3)4 previously,1 all nitrato ligands of 3c coordinate in κ(1)O mode. Six geometric isomers of E(NO3)6(2-) were identified as minima on the PES using DFT calculations at the B3LYP/6-311+G(d,p) level of which two were observed experimentally.

Taming Tin(IV) Polyazides.

The first charge-neutral Lewis base adducts of tin(IV) tetraazide, [Sn(N3)4(bpy)], [Sn(N3)4(phen)] and [Sn(N3)4(py)2], and the salt bis{bis(triphenylphosphine)iminium} hexa(azido)stannate [(PPN)2Sn(N3)6] (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; py = pyridine; PPN = N(PPh3)2) have been prepared using covalent or ionic azide-transfer reagents and ligand-exchange reactions. The azides were isolated on the 0.3 to 1 g scale and characterized by IR and NMR spectroscopies, microanalytical and thermal methods and their molecular structures determined by single-crystal XRD. All complexes have a distorted octahedral Sn[N]6 coordination geometry and possess greater thermal stability than their Si and Ge homologues. The nitrogen content of the adducts of up to 44% exceed any Sn(IV) compound known hitherto.

Dinitrogen release from arylpentazole: a picosecond time-resolved infrared, spectroelectrochemical, and DFT computational study.

p-(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 (E1/2 = +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.