No abstract

The Oseberg collection includes the most complete ensemble of wooden remains from the Viking Age. However, since many of the wooden objects were treated with alum in the early 1900s, they now suffer from dramatic conservation issues. A multi-analytical approach was adopted to investigate both the organic and the inorganic components of some selected wood fragments, with the aim of fully characterising the materials and their decomposition products. A particular focus was taken on the differences between the surface and the core of the fragments analysed, and on the correlations between the results obtained by the different techniques, in order to disclose possible interactions between the materials during degradation. In addition to differences in alum concentration and wood alteration between the surface and the core, some decomposition/transformation products of alum, such as mercallite (KHSO4), were identified by FTIR and XRD. Contextual interpretation of the results obtained by ICP-OES elemental analysis of inorganic components and Py(HMDS)-GC/MS characterisation of degraded lignocellulosic materials supported some previous observations about potential relationships between specific metals (Al, Fe, Ca) and wood degradation and enabled new correlations to be highlighted. Although similar degradation patterns were revealed in the investigated objects–depletion of holocellulose, oxidation of lignin and some transformation of alum - a notable variability at the molecular level was highlighted. This is an important factor to be taken into account for the planning of re-treatment strategies of these extremely precious artefacts

The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR 2 , R = Ph, Cy) directly afford N,N′-bis(phoshinomethyl)dihydroperimidines H 2 C(NCH 2 PR 2 ) 2 C 10 H 6 (R = Ph (1a), Cy (1b)), the methylene group of which undergoes chelate-assisted double C−H activation with [RhCl-(PPh 3 ) 3 ] to afford dihydroperimidine-derived N-heterocyclic pincer carbene (per-NHC) complexes [RhCl{C(NCH 2 PR 2 ) 2 C 10 H 6 }] (R = Ph (2a), Cy (2b)). Insight into the mechanism of these C−H activation processes is provided by the reaction of 1b with [IrCl(CO)(PPh 3 ) 2 ] to provide the dihydroperimidinyl-hydrido complex [IrHCl(CO){CH(NCH 2 PR 2 ) 2 C 10 H 6 }] (3b), which in turn reacts with silver salts Ag[Y] to afford, via hydride abstraction and subsequent C−H activation, the per-NHC ligated salts [IrHCl(CO){C(NCH 2 PR 2 ) 2 C 10 H 6 }] ([4b]Y, Y = PF 6 , SbF 6 , PO 2 F 2 ).

Selective formylation and methylation of amines using low pressure CO2 as a carbon source; mechanistic studies, time course and reaction scope.