The First Molybdenum(VI) and Tungsten(VI) Oxoazides MO2(N3)2, MO2(N3)2⋅2 CH3CN, (bipy)MO2(N3)2, and [MO2(N3)4]2− (M=Mo,W)

Molybdenum(VI) and tungsten(VI) dioxodiazide, MO₂(N₃)₂ (M=Mo, W), were prepared through fluoride–azide exchange reactions between MO₂F₂ and Me₃SiN₃ in SO₂ solution. In acetonitrile solution, the fluoride–azide exchange resulted in the isolation of the adducts MO₂(N₃)₂⋅2 CH₃CN. The subsequent reaction of MO₂(N₃)₂ with 2,2′‐bipyridine (bipy) gave the bipyridine adducts (bipy)MO₂(N₃)₂. The hydrolysis of (bipy)MoO₂(N₃)₂ resulted in the formation and isolation of [(bipy)MoO₂N₃]₂O. The tetraazido anions [MO₂(N₃)₄]²⁻ were obtained by the reaction of MO₂(N₃)₂ with two equivalents of ionic azide. Most molybdenum(VI) and tungsten(VI) dioxoazides were fully characterized by their vibrational spectra, impact, friction, and thermal sensitivity data and, in the case of (bipy)MoO₂(N₃)₂, (bipy)WO₂(N₃)₂, [PPh₄]₂[MoO₂(N₃)₄], [PPh₄]₂[WO₂(N₃)₄], and [(bipy)MoO₂N₃]₂O by their X‐ray crystal structures.     

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.     

The Molybdenum(V) and Tungsten(VI) Oxoazides [MoO(N3)3], [MoO(N3)3⋅2 CH3CN], [(bipy)MoO(N3)3], [MoO(N3)5]2−, [WO(N3)4], and [WO(N3)4⋅CH3CN]

A series of novel molybdenum(V) and tungsten(VI) oxoazides was prepared starting from [MOF₄] (M=Mo, W) and Me₃SiN₃. While [WO(N₃)₄] was formed through fluoride–azide exchange in the reaction of Me₃SiN₃ with WOF₄ in SO₂ solution, the reaction with MoOF₄ resulted in a reduction of Mo^VI to Mo^V and formation of [MoO(N₃)₃]. Carried out in acetonitrile solution, these reactions resulted in the isolation of the corresponding adducts [MoO(N₃)₃?2 CH₃CN] and [WO(N₃)₄?CH₃CN]. Subsequent reactions of [MoO(N₃)₃] with 2,2′‐bipyridine and [PPh₄][N₃] resulted in the formation and isolation of [(bipy)MoO(N₃)₃] and [PPh₄]₂[MoO(N₃)₅], respectively. Most molybdenum(V) and tungsten(VI) oxoazides were fully characterized by their vibrational spectra, impact, friction and thermal sensitivity data and, in the case of [WO(N₃)₄?CH₃CN], [(bipy)MoO(N₃)₃], and [PPh₄]₂[MoO(N₃)₅], by their X‐ray crystal structures.     

Synthesis, Thermolysis, and Mass Spectrometry of Perfluorinated Di- and Triazidopyridines

2,4-Diazido-3,5,6-trifluoropyridine and 2,4,6-triazido-3,5-difluoropyridine were obtained by the reaction of pentafluoropyridine with sodium azide in aqueous acetone. Under the action of electron impact the 2,4-diazidopyridine undergoes sequential fission of the azide groups in positions 2 and 4 of the pyridine ring and ring contraction with the formation of a characteristic [M-2N₂-F]⁺ ion. On the other hand thermolysis of the same diazide is accompanied by the selective decomposition of its -azide group with the formation of 4-amino-2-azido-3,5,6-trifluoropyridine. The effect of selective decomposition of the azide groups in 2,4-diazidopyridines on thermolysis and under electron impact is caused by the different distribution of bonding orbital density at the - and -azide groups respectively in the initial diazide and its radical cation. One of the routes of the triazide decomposition under electron impact is the form! ation of the [M-N₂2]⁺ ion due to decomposition of the -azide group.     

Preparation of the First Manganese(III) and Manganese(IV) Azides

Fluoride‐azide exchange reactions of Me₃SiN₃ with MnF₂ and MnF₃ in acetonitrile resulted in the isolation of Mn(N₃)₂ and Mn(N₃)₃?CH₃CN, respectively. While Mn(N₃)₂ forms [PPh₄]₂[Mn(N₃)₄] and (bipy)₂Mn(N₃)₂ upon reaction with PPh₄N₃ and 2,2′‐bipyridine (bipy), respectively, the manganese(III) azide undergoes disproportionation and forms mixtures of [PPh₄]₂[Mn(N₃)₄] and [PPh₄]₂[Mn(N₃)₆], as well as (bipy)₂Mn(N₃)₂ and (bipy)Mn(N₃)₄. Neat and highly sensitive Cs₂[Mn(N₃)₆] was obtained through the reaction of Cs₂MnF₆ with Me₃SiN₃ in CH₃CN.