Dalton Transactions

doi: 10.1039/b706231cpmid: N/A

doi: 10.1039/b706232jpmid: N/A

doi: 10.1039/b706233hpmid: N/A

Mathey, François

doi: 10.1039/b702063ppmid: 17702162

Electrophilic terminal phosphinidene complexes can be seen as singlet phosphinidenes stabilized by complexation with electron withdrawing metallic centers. They allow the development of an original P() chemistry whose latest results are summarized. These include the description of the first stable electrophilic terminal phosphinidene complexes, new precursors for the widely used transient [RP–M(CO)] complexes (M = Cr, Mo, W), new substituents at phosphorus, new reactions and new decomplexation techniques. Finally, a different approach is proposed for stabilizing singlet phosphinidenes by formation of adducts with nitrogen bases such as -methylimidazole. The resulting zwitterions are potentially equivalent to singlet nucleophilic phosphinidenes. Their synthetic potential remains to be explored.

Ghosh, Sushobhan; Turner, David R.; Batten, Stuart R.; Mukherjee, Partha Sarathi

doi: 10.1039/b702353gpmid: 17702163

Self-assembly and self-selection of a single linkage isomer of a mixed-metal molecular triangle with ferrocene functionality have been achieved using an ambidentate ligand, and the product was characterized by multinuclear NMR spectroscopy and X-ray single crystal structure determination.

Sathiyendiran, Malaichamy; Chang, Che-Hao; Chuang, Chuan-Hung; Luo, Tzuoo-Tsair; Wen, Yuh-Sheng; Lu, Kuang-Lieh

doi: 10.1039/b702810epmid: 17702164

A rigidity-modulated strategy for the conformational control of a flexible motif in the self-assembly of metallacycles is described; the span of the rigid ligand directs the conformation of the flexible motif by fixing the M⋯M separation, thereby dictating the structure of the metallacycles.

Li, Xuehui; Zhao, Jinggan; Li, Qianhe; Wang, Lefu; Tsang, Shik Chi

doi: 10.1039/b618384kpmid: 17702165

A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl, Br, BF and PF counter-anions at a concentration of 2.5 mM can be degraded at 50 °C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C–N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.

Chang, Chau-Jiun; Yang, Cheng-Han; Chen, Kellen; Chi, Yun; Shu, Ching-Fong; Ho, Mei-Lin; Yeh, Yu-Shan; Chou, Pi-Tai

doi: 10.1039/b700998dpmid: 17702166

We report the preparation of a series of new heteroleptic Ir() metal complexes chelated by two cyclometalated 1-(2,4-difluorophenyl)pyrazole ligands (dfpz)H and a third ancillary bidentate ligand (L^X). Such an intricate design lies in a core concept that the cyclometalated dfpz ligands always warrant a greater ππ* gap in these series of iridium complexes. Accordingly, the lowest one-electron excitation would accommodate the π* orbital of the ancillary L^X ligands, the functionalization of which is then exploited to fine-tune the phosphorescent emission wavelengths. Amongst the L^X ligands designed, three classes (series –) can be categorized, and remarkable bathochromic shifts of phosphorescence were observed by (i) replacing the 2-benzoxazol-2-yl substituent () with the 2-benzothiazol-2-yl group () in the phenolate complexes, (ii) converting the pyridyl group () to the pyrazolyl group () and even to the isoquinolyl group () in the pyrazolate complexes and (iii) extending the π-conjugation of the benzimidazolate ligand from to . Single-crystal X-ray diffraction study on complex [(dfpz)Ir(bzpz)] () was conducted to confirm their general molecular architectures. Complex was also used as a representative example for fabrication of multilayered, green-emitting phosphorescent OLEDs using the direct thermal evaporation technique.

Burck, Sebastian; Gudat, Dietrich; Nieger, Martin; Tirreé, Jürgen

doi: 10.1039/b702720fpmid: 17702167

-Cyclopentadienyl-substituted 1,3,2-diazaphospholenes were prepared by salt metathesis from NaCp or LiCp* and 2-chloro-1,3,2-diazaphospholenes. Comprehensive spectroscopic and X-ray diffraction studies revealed a significant lengthening of the phosphorus–carbon bonds as compared with typical P–C bond distances, and the presence of fluxional molecular structures in solution and solid state as a consequence of circumambulatory migration of the diazaphospholene moiety around the Cp-ring. The P–C bond lengthening is accompanied by the capability to react with transition metal complexes under P–C bond activation and cyclopentadienyl transfer. At the same time, 2-Cp-diazaphospholenes react with strong bases under deprotonation to afford a phosphinyl–cyclopentadienide anion that reacts further with FeCl to a 1,1′-bisphosphinyl–ferrocene. The ambivalent behaviour of the diazaphospholenes offers interesting prospects to develop new synthetic methods for functional cyclopentadienyl complexes.

Lerouge, Frédéric; Viñas, Clara; Teixidor, Francesc; Núñez, Rosario; Abreu, Arturo; Xochitiotzi, Elba; Santillan, Rosa; Farfán, Norberto

doi: 10.1039/b618771dpmid: 17702168

The reaction of α,α′-bis(3,5-bis(bromomethyl)phenoxy--xylene () with 4 equiv of the monolithium salt of 1-Ph-1,2-CBH or 1-Me-1,2-CBH gave the corresponding neutral carboranyl-functionalized aryl ether derivatives - and -, respectively. These compounds contain four clusters that were degraded using basic conditions with KOH in EtOH, affording the corresponding - and - as potassium salts. species were also isolated with tetramethylammonium as cation giving compounds - and - in good yield. The potassium salts showed good solubility in water and polar solvents. All these compounds were characterized by H, B and C NMR spectroscopy and UV-vis. The electronic data in different solvents indicated a solvatochromic shift for all compounds and a red shift of the absorption maxima for the species with respect to the derivatives. These neutral and anionic carboranyl-functionalized aryl ether derivatives represent a new family of high boron content luminescent compounds that show strong fluorescence emission in different solvents at room temperature. This phenomenon is very interesting considering the fact that none of the precursors have such a property. The fluorescence emission depends on the cluster substituent (Ph or Me) and the solvent polarity. Additionally, the fluorescence emission intensity was clearly dependent on the solvent polarity; the species showed strongest fluorescence intensities in the non-polar solvents, while anionic species were highly emissive in polar solvents.