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BCl3 cyclizes diazadiene (2,6-Pr(i)2C6H3NCH)2 1 through a dichloroborated intermediate [(2,6-Pr(i)2C6H3NCHCl)2BCl] to give, in polar aprotic solvents, a spontaneously dehyrochlorinated C-chloro diazaborole 4. In contrast, reaction of AlCl3 with 1 forms only acyclic mono- or di-adducts 5a/b and 6. Alkali metal reductions of gave mixtures of 4 and diazaborole [(2,6-Pr(i)2C6H3NCH)2BCl] 7. Pd(0) reduction cleanly gave diazaborole 7. Reduction of 6 gave a low yield of the closed shell C-C coupled dimer 8 of the putative diazadiene radical anion 1.AlCl2 complex monomer. An alternative synthesis for diazadiene (2,6-Pr(i)2C6H4NCPh)2, 2, is reported. Reduction of 2/BCl3, in which additional phenyl groups on the diazadiene C-2 and C-3 atoms hinder the radical coupling observed in , gave predominantly diazaborole .BCl, (9a) contaminated with .BCl2, (9b) the first such stable radical diazadiene complex of boron. All compounds 2-9 were characterized by X-ray diffraction and NMR spectroscopy. Stable radical was additionally characterized by EPR spectroscopy and density functional computation.

The 40 ka caldera-forming eruption of Campi Flegrei (Italy) is the largest known eruption in Europe during the last 200 kyr, but little is known about other large eruptions at the volcano prior to a more recent caldera-forming event at 15 ka. At 29 ka a widespread volcanic ash layer, termed the Y-3 tephra, covered >150,000 km 2 of the Mediterranean. The glass compositions of the layer are consistent with Campi Flegrei being the source but no prominent proximal equivalent in the appropriate chrono-stratigraphic position had been previously identified. Here we report new glass chemistry data and 40 Ar/ 39 Ar ages (29.3 ± 0.7 ka [2σ]) that reveal the near-source Y-3 eruption deposit in a sequence at Ponti Rossi and a nearby borehole (S-19) in Naples. The dispersal and thickness of the deposits associated with this eruption, herein named the Masseria del Monte Tuff, were simulated using a tephra sedimentation model. The model indicates that ~16 km 3 DRE (dense rock equivalent) of the magma erupted was deposited as fall. This volume and the areal distribution suggest the Masseria del Monte Tuff was a magnitude 6.6 eruption (corresponding to VEI 6), similar to the 15 ka caldera-forming Neapolitan Yellow Tuff (M6.8) eruption at Campi Flegrei. However, the lack of coarse, thick, traceable, near-vent deposit suggests peculiar eruption dynamics. Our reconstruction and modelling of the eruption show the fundamental role that distal tephrostratigraphy can play in constraining the scale and tempo of past activity, especially at highly productive volcanoes.

The results of SCF molecular orbital calculations on the ammonia dimer have been used in part to parameterize a set of atom-atom potentials. When combined with a charge distribution which reproduces the experimental dipole and quadrupole moments of the monomer, and with independent estimates of the dispersion energy, the resulting intermolecular potential yields a fair description of certain properties of the condensed phases of ammonia. Liquid ammonia is predicted to have a weakly associated character.

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