Rhodium-Promoted Linear Tetramerization and Cyclization of 3,3-Dimethylbut-l-yne

With tetrahydrofuran as the solvent [Rh(thf)₂(cod)]⁺ promotes the selective coupling of tBuC₂H to form triene-yne 1 ; at high alkyne concentrations, however, an unusual C−H activation process intervenes, leading to the formation of complex 2 , which contains two linked five-membered rings. cod=1,5-cyclooctadiene.     

Synthesis and X-ray structures of new titanium(IV) aryloxides and their exploitation for the ring opening polymerization of epsilon-caprolactone

A series of titanium catecholates have been prepared and characterized by single-crystal X-ray diffraction studies. Complexes 1a-7a were synthesized by the reaction of 1 equiv of ligand with Ti(OiPr)4. All are dimers in the solid-state, in which a catechol bridges between two titanium centers. Electronic (nitro and methoxy groups) and steric (tert-butyl groups) effects of the ligand have been investigated. Complex 1b was synthesized by reaction of 2 equiv of ligand with Ti(OiPr)4. A dimer is again observed with the same bridging ligand together with a terminal catechol moiety. All complexes contain a coordinated 2-propanol ligand on each titanium center forming pseudo-octahedral metal centers. All complexes were tested for the ring-opening-polymerization of epsilon-caprolactone to afford polycaprolactone (PCL). Reasonable yields (up to 79%) were obtained at room temperature, and narrow molecular weight distributions (1.13-1.27) were observed for the PCL produced. The most active complex was found to be complex 1a, containing unsubsituted catechol ligands.     

Crystallographic characterisation of novel Zn(II) silsesquioxane complexes and their application as initiators for the production of polylactide

Herein, the solid state structures of the products from the reaction of the silsesquioxane triol (iso-C₄H₉)₇Si₇O₁₂(OH)₃ (1) with two equivalents of ZnMe₂ in both THF and toluene are reported. In both cases tetrametallic Zn(II) complexes were isolated, with toluene [(iso-C₄H₉)₇Si₇O₁₂]₂Zn₄Me₂ (2) was prepared while performing the reaction in THF the analogous complex [(iso-C₄H₉)₇Si₇O₁₂]₂Zn₄Me₂(THF)₂ (3) was formed. Both species have also been characterised via¹H, ¹³C{¹H} and ²⁹Si{¹H} NMR spectroscopy, which confirm the solid state structures are maintained in solution. Both 2 and 3 show modest activities for the polymerisation of rac-lactide and a heterogeneous catalyst has also been prepared.     

Transformation of an η-coordinated phosphaalkyne into a bridging phosphinidene ligand

The tripalladium cluster [Pd₃(μ₃-CO)(μ-dppm)₃](PF₆)₂ (1) reacts with two equivalents of ^tBuCP to give [Pd₃(μ-dppm)₃(η¹-PCBu^t)₂](PF₆)₂ (2). Prolonged storage of acetone solutions of 2 only resulted in the isolation of [Pd₃(μ-dppm)₃(η¹:μ₃-PCH₂Bu^t)(OCMe₂)](PF₆)₂ (3). Compound 3 has been characterized by X-ray crystallography.     

Fluoride-assisted synthesis of mullite (Al5.65Si0.35O9.175) nanowires

Novel silicon-deficient mullite (Al5.65Si0.35O9.175) single crystal nanowires were synthesized in large quantities on mica substrates assisted by the intermediate fluoride species. The nanowires have diameters in the range 50-100 nm and typical lengths of several microm. Aligned nanowires were observed at the substrate edge. The nanowires have strong photoluminescence (PL) emission bands at 310, 397, 452 and 468 nm.     

Structure and reactivity of new phosphine ligands containing the hemi-labile sulfone moiety

New heterofunctional phosphine ligands have been synthesised, incorporating the substitutionally labile sulfone and sulfonamide moieties as chelating groups, which display activity in the palladium-catalysed Suzuki and amination cross-coupling reactions. Single-crystal X-ray diffraction studies of the complexes formed with [Pd(mu-Cl)(dmba)] (dmba-H = N,N-dimethylbenzylamine) highlight the coordinating nature of these ligands; showing the formation of a bis chelate complex through a six-membered Pd-P-C-C-S-O ring with the sulfonamide class of ligands.     

Valuable New Cyclohexadiene Building Blocks from Cationic η5‐Iron–Carbonyl Complexes Derived from a Microbial Arene Oxidation Product

Biooxidation of benzoic acid by Ralstonia eutropha B9 provides an unusual cyclohexadiene carboxy diol that contains a quaternary stereocentre. Tricarbonyliron derivatives of this chiron, on treatment with acid, give two isomeric η⁵‐cyclohexadienyl complexes as observed by NMR spectroscopy. Both of these can be subjected to the addition of nucleophiles to provide isomeric cyclohexadiene complexes with new substituent patterns, several of which have been characterised crystallographically. De‐metallation of these provides a versatile library of cyclohexadiene building blocks, the utility of which is demonstrated by formal syntheses of oseltamivir. The mechanism of product formation and its stereochemical implications are discussed, as are the procedures undertaken to establish the enantiopurity of a representative cyclohexadiene product.     

Attenuated Organomagnesium Activation of White Phosphorus

Sequential reactions between a 2,6‐diisopropylphenyl‐substituted β‐diketiminato magnesium n‐butyl derivative and P₄ allow the highly discriminating synthesis of unusual [nBu₂P₄]^2? and [nBu₂P₈]^2? cluster dianions.