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

The reactions of 1,8-diaminonaphthalene with paraformaldehyde and secondary phosphines (HPR2, R = Ph, Cy) directly afford N,N′-bis(phoshinomethyl)dihydroperimidines H2C(NCH2PR2)2C10H6 (R Ph (1a), Cy (1b)), the methylene group which undergoes chelate-assisted double C–H activation [RhCl(PPh3)3] to dihydroperimidine-derived N-heterocyclic pincer carbene (per-NHC) complexes [RhCl{═C(NCH2PR2)2C10H6}] (2a), (2b)). Insight into mechanism these processes is provided by reaction 1b [IrCl(CO)(PPh3)2]...

The reaction of [Et4N][Mo(CSe)(CO)2(Tp*)}] (Tp* = hydrotris(dimethylpyrazolyl)borate) with [Ir(NCMe)(CO)(PPh3)2]BF4 results not in the anticipated isoselenocarbonyl complex [(Tp*)(CO)2Mo−CSe−Ir(CO)(PPh3)2] but rather tetranuclear bis(μ-carbido) (μ-Se2)[Ir2{C≡Mo(CO)2(Tp*)}2(CO)2(PPh3)2].

The reaction of HB(NCH2PPh2)2C6H4-1,2 with [MCl2(PPh3)3] (M = Ru, Os) affords the six-coordinate σ-borane complexes [MCl2(PPh3){σ-BH-κ2-P,P′-HB(NCH2PPh2)2-C6H4}], in which B–H bond remains intact while coordinated to metal center. Replacement unique phosphine by π-acceptor ligands, e.g., CO and CNC6H2Me3, induces activation followed spontaneous dehydrochlorination formation boryl pincer [RuCl(CA)2{B(NCH2PPh2)2C6H4}] (A O, NC6H2Me3-2,4,6).

The reaction of N,N′-bis(dicyclohexylphosphinomethyl)dihydroperimidine (H2C(NCH2PCy2)2C10H6-1,8, 1a) with [RuCl2(PPh3)3] in THF affords the perimidinylidene-based N-heterocyclic carbene (per-NHC) pincer complex [RuCl2(OC4H8){═C(NCH2PCy2)2C10H6}] (2) via chelate-assisted double C–H activation. In contrast, reactions tetraphenyl analogue H2C(NCH2PPh2)2C10H6 (1b) and 1a [RuCl(R)(CO)(PPh3)2] (R = Ph, CH═CHPh) do not result activation but rather give asymmetric, PNP-coordinated complexes...

Double geminal aminal C–H activation processes of the dihydroperimidine based NHC pincer pro-ligands H₂C(NCH₂PR₂)₂C₁₀H₆ are described leading to dihydroperimidinylidene complexes including first osmium examples.

The reaction of [Et4N][Mo(CSe)(CO)2(Tp*)] (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with [Rh2(μ-Cl)2(η4-cod)2] (cod cyclo-octa-1,5-diene) results in the formation tetrametallic complex [Rh2{SeCMo(CO)2(Tp*)}2(η4-cod)2] which CSe ligand adopts a crystallographically confirmed and unprecedented μ3:σ,σ′(Se),σ″(C) coordination mode.

The reactions of<italic>N</italic>,<italic>N</italic>′-bis(phosphinomethyl)dihydroperimidine pro-ligands H₂C(NCH₂PR₂)₂C₁₀H₆-1,8 (R = Ph<bold>1a</bold>, R Cy<bold>1b</bold>) with iridium(<sc>i</sc>) substrates have been investigated and shown to readily result in chelate-assisted C–H activation processes.

From the mid-1800s to late 1950s, conservation by alum salts (aluminum potassium sulfate dodecahydrate)—with some variations—was a routine method for treating highly deteriorated waterlogged archaeological wood in many countries, especially Scandinavia. It was eventually replaced newer methods 1960s, such as that using polyethylene glycol. Accordingly, signs of deterioration collections and reasons behind them are not well known among current preservation specialists. The research Saving...

The heterogeneity and molecular weight of a chitosan low (molar mass) degree acetylation (0.1) for potential use as consolidant decayed archaeological wood were examined by sedimentation velocity equilibrium in the analytical ultracentrifuge before after depolymerisation. Sedimentation depolymerisation revealed uniform distribution coefficient with little concentration dependence. SEDFIT-MSTAR analysis average Mw (14.2 ± 1.2) kDa, polydispersity index ~ 1.2. Further using MULTISIG material...

The salt elimination reactions of [NEt4][Mo(CSe)(CO)2(Tp*)] ([NEt4][2], Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) with a range metal halide complexes (ClMLn) have been investigated as possible route to isoselenocarbonyl [Mo(CSeMLn)(CO)2(Tp*)]. Thus the [NEt4][2] [RuCl(L)2(η-C5R5)] provide molybdenum-ruthenium derivatives [Mo{CSeRu(L)2(η-C5R5)}(CO)2(Tp*)] (L PPh3, R H 4, L CO, Me 5), both which were structurally characterised. molybdenum-iron derivative...

The successive treatment of terminal alkynes, HC≡CR (R = C6H4Me-4, SiMe3), with nBuLi and gray selenium affords LiSeC≡CR, which in turn reacts [FeCl(CO)2(η-C5H5)], [NiCl(PPh3)(η-C5H5)], [MoI(CO)3(η-C5H5)] to afford the alkynylselenolato complexes [Fe(SeC≡CR)(CO)2(η-C5H5)], [Ni(SeC≡CR)(PPh3)(η-C5H5)], [Mo(SeC≡CR)(CO)3(η-C5H5)], two examples have been structurally characterized. When [MoI(CO)3{HB(pz)3}] (pz pyrazol-1-yl) was however employed as electrophile, low yields selenoketenyl complex...

Alum-treated wooden artefacts from the Oseberg collection display a great deal of morphological, structural and compositional inhomogeneity. Thus, an in-depth understanding chemical processes underlying their degradation requires consideration variety local environments. In addition to alum, sources inorganic compounds include metal parts, corrosion products which can migrate into surrounding wood. order characterise range environments, samples several locations in selection composite...

Abstract Anthony Hill joined Gordon Stone's research group as a post-doctoral assistant from 1986-8 in the halcyon days of “E317” lab at University Bristol. The supportive environment creative and imaginative synthetic design that fostered Bristol was unparalleled, quite without apology for pursuit curiosity-driven science bordered on molecular fine arts. In 1996 handed over reins Advances Organometallic Chemistry, journal series, now running to some 60 volumes, which inaugurated 1964 with...

Abstract From the mid-1800s to late 1960s, conservation by alum salts (KAl(SO 4 ) 2 ·12H O—potassium aluminium sulphate), using various recipes, was a common method prevent shrinkage and strengthen waterlogged archaeological wooden objects. This mainly used in Scandinavia. The appears have also been applied highly degraded wood other countries, for example U.S Germany. Today, many of objects treated with show extreme deterioration very low pH, which are attributed effects alum-treatment....

Samples of conserved archaeological wood different ages, origins, and conservation histories were aged in a climate chamber for seven months, while the humidity alternated between 30% RH 12 hours 80% at constant temperature 30°C. Photographs taken once every hour, which enabled creation time-lapse movie. Some samples degraded visibly, whereas others unaffected. Most robust would be able to survive well even very poor museum climate. Among sensitive samples, three types degradation...

Alum-treated wooden artefacts suffer from extreme deterioration, and the stability of these objects salts they contain to variations in climate conditions is an important issue. Responses potassium alum (KAl(SO4)2·12H2O), ammonium (NH4Al(SO4)2·12H2O), bisulfate (KHSO4) alum-treated wood changing temperature relative humidity (RH) were therefore investigated at crystalline level using powder X-ray diffraction (XRD). The XRD analysis showed changes crystal structures that suggest some degree...

Abstract Alum-treatment was extensively applied to archaeological wood from the Oseberg collection in early 1900s, and a common conservation method at time involving impregnating objects with hot concentrated solutions of potassium alum (KAl(SO 4 ) 2 ⋅12H O). This now obsolete consolidation has led dramatic long-term consequences, heavily affecting state preservation historical wooden artefacts, dedicated chemical characterisation campaigns have been undertaken better understand degradation...