From Sn(II) to Sn(IV): Enhancing Lewis Acidity Via Oxidation.

We demonstrate the increased Lewis acidity on going from Sn(II) to Sn(IV) by oxidizing TpMe2SnOTf (OTf = SO3CF3) to TpMe2SnF(OTf)2. Replacement of the fluoride ion in TpMe2SnF(OTf)2 by a triflate, resulting in TpMe2Sn(OTf)3 further enhances the Lewis acidity at tin. 119Sn NMR spectroscopy, modified Gutmann-Beckett test, computational analysis, and catalytic phosphine oxide deoxygenation support the claims.

Camouflaging Structural Diversity: Co-crystallization of Two Different Nanoparticles Having Different Cores But the Same Shell.

Two ligand-protected nanoscale silver moieties, [Ag46 (SPhMe2 )24 (PPh3 )8 ](NO3 )2 and [Ag40 (SPhMe2 )24 (PPh3 )8 ](NO3 )2 (abbreviated as Ag46 and Ag40 , respectively) with almost the same shell but different cores were synthesized simultaneously. As their external structures are identical, the clusters were not distinguishable and become co-crystallized. The occupancy of each cluster was 50 %. The outer shell of both is composed of Ag32 S24 P8 , which is reminiscent of fullerenes, and it encapsulates a well-studied core, Ag14 and a completely new core, Ag8 , which correspond to a face-centered cube and a simple cube, respectively, resulting in the Ag46 and Ag40 clusters. The presence of two entities (Ag40 and Ag46 clusters) in a single crystal and their molecular formulae were confirmed by detailed electrospray ionization mass spectrometry. The optical spectrum of the mixture showed unique features which were in good agreement with the results from time-dependent density functional theory (TD-DFT).

From helical supramolecular arrays to gel-forming networks: lattice restructuring and aggregation control in peptide-based sulfamides to integrate new functional attributes.

While supramolecular organisation is central to both crystallization and gelation, the latter is more complex considering its dynamic nature and multifactorial dependence. This makes the rational design of gelators an extremely difficult task. In this report, the assembly preference of a group of peptide-based sulfamides was modulated by making them part of an acid-amine two-component system to drive the tendency from crystallization to gelation. Here, the peptide core directed the assembly while the long-chain amines, introduced through salt-bridges, promoted layering and anisotropic development of primary aggregates. This proved to be very successful, leading to gelation of a number of solvents. Apart from this, it was possible to fine-tune their aggregation using an amphiphilic polymer like F-127 as an additive to get honey-comb-like 3D molecular architectures. These gels also proved to be excellent matrices for entrapping silver nanoparticles with superior emissive properties.

Synthesis, Chemistry, and Electronic Structures of Group 9 Metallaboranes.

Dimetallaoctaborane(12) of Ru, Co, and Rh have been well-characterized by a range of spectroscopic techniques and X-ray diffraction studies. Thus, reinvestigation of the Ir-system became of interest. As a result, a slight modification in the reaction conditions enabled us to isolate the missing Ir analogue of octaborane(12), [(Cp*Ir)2B6H10], 1. Compound 1 adapts a geometry similar to that of its parent octaborane(12) and Ru, Co, and Rh analogues. In [M2B6H10+x](M = Ru, x = 2; M = Co and Rh, x = 0), there exist two M-H-B protons. However, a significant difference observed in [(Cp*Ir)2B6H10] is the presence of two Ir-H instead of Ir-H-B protons that eventually controls the reactivity of this molecule. For example, unlike [M2B6H10](M = Co or Rh), the Ir-analogue does not react with metal carbonyl compounds or [Au(PPh3)Cl]. Along with 1, a closo trimetallic 8-vertex iridaborane [(Cp*Ir)3B5H4Cl], 2 was also isolated. Additionally, from another reaction, 12-vertex closo iridaboranes [(Cp*Ir)2B10Hy(OH)z], 3a and 3b (3a: y = 12, z = 0; 3b: y = 8, z = 2), have also been isolated. Further, density functional theory calculations were performed to gain useful insight into the structure and stability of these compounds.

Sensitive Skin: Assessment of the Skin Barrier Using Confocal Raman Microspectroscopy.

BACKGROUND/AIMS: Sensitive skin (SS), a frequently reported condition in the Western world, has been suggested to be underlined by an impaired skin barrier. The aim of this study was to investigate the skin barrier molecular composition in SS subjects using confocal Raman microspectroscopy (CRS), and to compare it with that of non-SS (NSS) individuals as well as atopic dermatitis (AD) and allergic rhinoconjunctivitis (AR) subjects, who frequently report SS. METHODS: Subjects with SS (n = 29), NSS (n = 30), AD (n = 11), and AR (n = 27) were included. Stratum corneum (SC) thickness, water, ceramides/fatty acids, and natural moisturizing factor (NMF) were measured by CRS along with transepidermal water loss and capacitance on the ventral forearm, thenar, and cheek. Sebum levels were additionally measured on the forearm and cheek. RESULTS: No differences between SS and NSS subjects were found regarding SC thickness, water, and NMF content, yet a trend towards lower ceramides/fatty acids was observed in the cheek. Compared to AD subjects, the SS group showed higher ceramides/fatty acid content in the forearm, whereas no differences emerged with AR. The correlation of macroscopic biophysical techniques and CRS was weak, yet CRS confirmed the well-known lower content of NMF and water, and thinner SC in subjects with filaggrin mutations. CONCLUSION: The skin barrier in SS is not impaired in terms of SC thickness, water, NMF, and ceramides/fatty acid content. The failure of biophysical techniques to follow alterations in the molecular composition of the skin barrier revealed by CRS emphasizes a strong need in sensitive and specific tools for in vivo skin barrier analysis.

η(4) -HBCC-σ,π-Borataallyl Complexes of Ruthenium Comprising an Agostic Interaction.

Thermolysis of [Cp*Ru(PPh2 (CH2 )PPh2 )BH2 (L2 )] 1 (Cp*=η(5) -C5 Me5 ; L=C7 H4 NS2 ), with terminal alkynes led to the formation of η(4) -σ,π-borataallyl complexes [Cp*Ru(µ-H)B{R-C=CH2 }(L)2 ] (2 a-c) and η(2) -vinylborane complexes [Cp*Ru(R-C=CH2 )BH(L)2 ] (3 a-c) (2 a, 3 a: R=Ph; 2 b, 3 b: R=COOCH3 ; 2 c, 3 c: R=p-CH3 -C6 H4 ; L=C7 H4 NS2 ) through hydroboration reaction. Ruthenium and the HBCC unit of the vinylborane moiety in 2 a-c are linked by a unique η(4) -interaction. Conversions of 1 into 3 a-c proceed through the formation of intermediates 2 a-c. Furthermore, in an attempt to expand the library of these novel complexes, chemistry of σ-borane complex [Cp*RuCO(µ-H)BH2 L] 4 (L=C7 H4 NS2 ) was investigated with both internal and terminal alkynes. Interestingly, under photolytic conditions, 4 reacts with methyl propiolate to generate the η(4) -σ,π-borataallyl complexes [Cp*Ru(µ-H)BH{R-C=CH2 }(L)] 5 and [Cp*Ru(µ-H)BH{HC=CH-R}(L)] 6 (R=COOCH3 ; L=C7 H4 NS2 ) by Markovnikov and anti-Markovnikov hydroboration. In an extension, photolysis of 4 in the presence of dimethyl acetylenedicarboxylate yielded η(4) -σ,π-borataallyl complex [Cp*Ru(µ-H)BH{R-C=CH-R}(L)] 7 (R=COOCH3 ; L=C7 H4 NS2 ). An agostic interaction was also found to be present in 2 a-c and 5-7, which is rare among the borataallyl complexes. All the new compounds have been characterized in solution by IR, (1) H, (11) B, (13) C NMR spectroscopy, mass spectrometry and the structural types were unequivocally established by crystallographic analysis of 2 b, 3 a-c and 5-7. DFT calculations were performed to evaluate possible bonding and electronic structures of the new compounds.

First-row transition-metal-diborane and -borylene complexes.

A combined experimental and quantum chemical study of Group 7 borane, trimetallic triply bridged borylene and boride complexes has been undertaken. Treatment of [{Cp*CoCl}2 ] (Cp*=1,2,3,4,5-pentamethylcyclopentadienyl) with LiBH4 ⋅thf at -78 °C, followed by room-temperature reaction with three equivalents of [Mn2 (CO)10 ] yielded a manganese hexahydridodiborate compound [{(OC)4 Mn}(η(6) -B2 H6 ){Mn(CO)3 }2 (µ-H)] (1) and a triply bridged borylene complex [(µ3 -BH)(Cp*Co)2 (µ-CO)(µ-H)2 MnH(CO)3 ] (2). In a similar fashion, [Re2 (CO)10 ] generated [(µ3 -BH)(Cp*Co)2 (µ-CO)(µ-H)2 ReH(CO)3 ] (3) and [(µ3 -BH)(Cp*Co)2 (µ-CO)2 (µ-H)Co(CO)3 ] (4) in modest yields. In contrast, [Ru3 (CO)12 ] under similar reaction conditions yielded a heterometallic semi-interstitial boride cluster [(Cp*Co)(µ-H)3 Ru3 (CO)9 B] (5). The solid-state X-ray structure of compound 1 shows a significantly shorter boron-boron bond length. The detailed spectroscopic data of 1 and the unusual structural and bonding features have been described. All the complexes have been characterized by using (1) H, (11) B, (13) C NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. The DFT computations were used to shed light on the bonding and electronic structures of these new compounds. The study reveals a dominant B-H-Mn, a weak B-B-Mn interaction, and an enhanced B-B bonding in 1.

Chemistry of N,S-Heterocyclic Carbene and Metallaboratrane Complexes: A New η(3)-BCC-Borataallyl Complex.

A high-yielding synthetic route for the preparation of group 9 metallaboratrane complexes [Cp*MBH(L)2], 1 and 2 (1, M=Rh, 2, M=Ir; L=C7H4NS2) has been developed using [{Cp*MCl2}2] as precursor. This method also permitted the synthesis of an Rh-N,S-heterocyclic carbene complex, [(Cp*Rh)(L2)(1-benzothiazol-2-ylidene)] (3; L=C7H4NS2) in good yield. The reaction of compound 3 with neutral borane reagents led to the isolation of a novel borataallyl complex [Cp*Rh(L)2B{CH2C(CO2Me)}] (4; L=C7H4NS2). Compound 4 features a rare η(3)-interaction between rhodium and the B-C-C unit of a vinylborane moiety. Furthermore, with the objective of generating metallaboratranes of other early and late transition metals through a transmetallation approach, reactions of rhoda- and irida-boratrane complexes with metal carbonyl compounds were carried out. Although the objective of isolating such complexes was not achieved, several interesting mixed-metal complexes [{Cp*Rh}{Re(CO)3}(C7H4NS2)3] (5), [Cp*Rh{Fe2(CO)6}(µ-CO)S] (6), and [Cp*RhBH(L)2W(CO)5] (7; L=C7H4NS2) have been isolated. All of the new compounds have been characterized in solution by mass spectrometry, IR spectroscopy, and (1)H, (11)B, and (13)C NMR spectroscopies, and the structural types of 4-7 have been unequivocally established by crystallographic analysis.

Hydroboration of Alkynes with Zwitterionic Ruthenium-Borate Complexes: Novel Vinylborane Complexes.

Building upon previous studies on the synthesis of bis(sigma)borate and agostic complexes of ruthenium, the chemistry of nido-[(Cp*Ru)2 B3 H9] (1) with other ligand systems was explored. In this regard, mild thermolysis of nido-1 with 2-mercaptobenzothiazole (2-mbzt), 2-mercaptobenzoxazole (2-mbzo) and 2-mercaptobenzimidazole (2-mbzi) ligands were performed which led to the isolation of bis(sigma)borate complexes [Cp*RuBH3 L] (2 a-c) and ß-agostic complexes [Cp*RuBH2 L2] (3 a-c; 2 a, 3 a: L=C7 H4 NS2 ; 2 b, 3 b: L=C7 H4 NSO; 2 c, 3 c: L=C7 H5 N2 S). Further, the chemistry of these novel complexes towards various diphosphine ligands was investigated. Room temperature treatment of 3 a with [PPh2 (CH2 )n PPh2 ] (n=1-3) yielded [Cp*Ru(PPh2 (CH2 )n PPh2 )-BH2 (L2)] (4 a-c; 4 a: n=1; 4 b: n=2; 4 c: n=3; L=C7 H4 NS2). Mild thermolysis of 2 a with [PPh2 (CH2)n PPh2 ] (n=1-3) led to the isolation of [Cp*Ru(PPh2 (CH2)n PPh2 )(L)] (L=C7 H4 NS2 5 a-c; 5 a: n=1; 5 b: n=2; 5 c: n=3). Treatment of 4 a with terminal alkynes causes a hydroboration reaction to generate vinylborane complexes [Cp*Ru(R-C=CH2 )BH(L2)] (6 and 7; 6: R=Ph; 7: R=COOCH3; L=C7 H4 NS2). Complexes 6 and 7 can also be viewed as η-alkene complexes of ruthenium that feature a dative bond to the ruthenium centre from the vinylinic double bond. In addition, DFT computations were performed to shed light on the bonding and electronic structures of the new compounds.

New Routes to a Series of σ-Borane/Borate Complexes of Molybdenum and Ruthenium.

A series of agostic σ-borane/borate complexes have been synthesized and structurally characterized from simple borane adducts. A room-temperature reaction of [Cp*Mo(CO)3 Me], 1 with Li[BH3 (EPh)] (Cp*=pentamethylcyclopentadienyl, E=S, Se, Te) yielded hydroborate complexes [Cp*Mo(CO)2 (µ-H)BH2 EPh] in good yields. With 2-mercapto-benzothiazole, an N,S-carbene-anchored σ-borate complex [Cp*Mo(CO)2 BH3 (1-benzothiazol-2-ylidene)] (5) was isolated. Further, a transmetalation of the B-agostic ruthenium complex [Cp*Ru(µ-H)BHL2 ] (6, L=C7 H4 NS2 ) with [Mn2 (CO)10 ] affords a new B-agostic complex, [Mn(CO)3 (µ-H)BHL2 ] (7) with the same structural motif in which the central metal is replaced by an isolobal and isoelectronic [Mn(CO)3 ] unit. Natural-bond-orbital analyses of 5-7 indicate significant delocalization of the electron density from the filled σBH orbital to the vacant metal orbital.

Homometallic Cubane Clusters: Participation of Three-Coordinated Hydrogen in 60-Valence Electron Cubane Core.

This work describes the synthesis, structural characterizations, and electronic structures of a series of novel homometallic cubane clusters [(Cp*Ru)2{Ru(CO)2}2BH(µ3-E)(µ-H)B(µ-H)3M], (2, M = Cp*Ru, E = CO; 3, M = Ru(Cp*Ru)2(µ-CO)3(µ-H)BH), E = BH), [(Cp*Ru)3(µ3-CO)(BH)3(µ3-H)3], 4, and [(Cp*Ru)2(µ3-CO){Ru(CO)3}2(BH)2(µ-H)B], 5 (Cp* = η(5)-C5Me5). These cubane clusters have been isolated from a thermally driven reaction of diruthenium analogue of pentaborane(9) [(Cp*RuH)2B3H7], 1, and [Ru3(CO)12]. Structural and spectroscopic studies revealed the existence of triply bridged hydrogen (µ3-H) atoms that participate as a vertex in the cubane core formation for compounds 2, 3, and 4. In addition, the crystal structure of these clusters clearly confirms the presence of an electron precise borane ligand (borylene fragment) which is triply bridged to the trimetallic units. Bonding of these novel complexes has been studied computationally by DFT methods, and the studies demonstrate that the cubane clusters 2 and 3 possess 60 cluster valence electrons (cves) with six metal-metal bonds. All the new compounds have been characterized in solution by mass spectrometry; IR; and (1)H, (11)B, and (13)C NMR studies, and the structural types were unequivocally established by crystallographic analysis of compounds 2-5.

Microspectroscopic Confocal Raman and Macroscopic Biophysical Measurements in the in vivo Assessment of the Skin Barrier: Perspective for Dermatology and Cosmetic Sciences.

Skin barrier function, confined to the stratum corneum, is traditionally evaluated using established, noninvasive biophysical methods like transepidermal water loss, capacitance and conductance. However, these methods neither measure skin molecular composition nor its structure, hindering the actual causes of skin barrier change or impairment. At the same time, confocal Raman microspectroscopy (CRS) can directly measure skin molecular composition and structure and has proven itself to be a powerful technique for biomolecular analysis. The aims of this literature review were to evaluate noninvasive biophysical methods in view of CRS and to outline a direction towards more specific and informative skin measurement methods. We address this by investigating, for the first time, the relation between in vivo assessment of the skin barrier using indirect biophysical methods and the actual skin composition and structure as given by CRS, and emphasize the high potential of CRS for dermatology and cosmetic sciences. CRS acceptance in these fields will require close collaboration between dermatologists, skin scientists and spectroscopy experts towards simplifying the technology and creating robust, rapid, easy-to-use and less expensive CRS applications.

A novel heterometallic µ9-boride cluster: synthesis and structural characterization of [(η(5)-C5Me5Rh)2{Co6(CO)12}(µ-H)(BH)B].

The preparation, characterization, and electronic structure of the first heterometallic µ9-boride cluster [(Cp*Rh)2{Co6(CO)12}(µ-H)(BH)B)] has been reported. The interstitial boron atom in the title cluster is within the bonding contact of eight metal and one boron atom in a unique tricapped trigonal prism geometry.

Reactivity of diruthenium and dirhodium analogues of pentaborane(9): agostic versus boratrane complexes.

A series of novel Cp*-based (Cp*=η(5)-C5Me5) agostic, bis(σ-borate), and boratrane complexes have been synthesized from diruthenium and dirhodium analogues of pentaborane(9). The synthesis and structural characterization of the first neutral ruthenadiborane(6) analogue are also reported. This new route offers a very efficient method for the isolation of bis(σ-borate) and agostic complexes from diruthenapentaborane(9).

Effects of polarization and apodization on laser induced optical breakdown threshold.

We investigated the influence of polarization and apodization on laser induced optical breakdown threshold in transparent and diffuse media using linearly and radially polarized light. We demonstrate a lower irradiance threshold for optical breakdown using radially polarized light. The dominance of radial polarization in higher-order multiphoton ionization has important medical applications where a lower irradiance threshold may allow reaching deeper layers inside the skin with less risk of collateral damage and thereby improving safety and efficacy of treatment.

Exploring the effect of bioisosteric replacement of carboxamide by a sulfonamide moiety on N-glycosidic torsions and molecular assembly: synthesis and X-ray crystallographic investigation of N-(ß-D-glycosyl)sulfonamides as N-glycoprotein linkage region analogues.

N-Glycoprotein linkage region constituents, 2-acetamido-2-deoxy-ß-D-glucopyranose (GlcNAc) and asparagine (Asn) are conserved among all the eukaryotes. To gain a better understanding for nature's choice of GlcNAcßAsn as linkage region constituents and inter- and intramolecular carbohydrate-protein interactions, a detailed systemic structural study of the linkage region conformation is essential. Earlier crystallographic studies of several N-(ß-glycopyranosyl)alkanamides showed that N-glycosidic torsion, φN , is influenced to a larger extent by structural variation in the sugar part than that of the aglycon moiety. To explore the effect of the bioisosteric replacement of a carboxamide group by a sulfonamide moiety on the N-glycosidic torsions as well as on molecular assembly, several glycosyl methanesulfonamides and glycosyl chloromethanesulfonamides were synthesized as analogues of the N-glycoprotein linkage region, and crystal structures of seven of these compounds have been solved. A comparative analysis of this series of crystal structures as well as with those of the corresponding alkanamido derivatives revealed that N-glycosidic torsion, φN, does not alter significantly. Methanesulfonamido and chloromethanesulfonamido derivatives of GlcNAc display a different aglycon conformation compared to other sulfonamido analogues. This may be due to the cumulative effect of the direct hydrogen bonding between N1 and O1' and C-H···O interactions of the aglycon chain, revealing the uniqueness of the GlcNAc as the linkage sugar.

New heteronuclear bridged borylene complexes that were derived from [{Cp*CoCl}2] and mono-metal-carbonyl fragments.

The synthesis, structural characterization, and reactivity of new bridged borylene complexes are reported. The reaction of [{Cp*CoCl}2] with LiBH4·THF at -70 °C, followed by treatment with [M(CO)3(MeCN)3] (M=W, Mo, and Cr) under mild conditions, yielded heteronuclear triply bridged borylene complexes, [(µ3-BH)(Cp*Co)2(µ-CO)M(CO)5] (1-3; 1: M=W, 2: M=Mo, 3: M=Cr). During the syntheses of complexes 1-3, capped-octahedral cluster [(Cp*Co)2(µ-H)(BH)4{Co(CO)2}] (4) was also isolated in good yield. Complexes 1-3 are isoelectronic and isostructural to [(µ3-BH)(Cp*RuCO)2(µ-CO){Fe(CO)3}] (5) and [(µ3-BH)(Cp*RuCO)2(µ-H)(µ-CO){Mn(CO)3}] (6), with a trigonal-pyramidal geometry in which the µ3-BH ligand occupies the apical vertex. To test the reactivity of these borylene complexes towards bis-phosphine ligands, the room-temperature photolysis of complexes 1-3, 5, 6, and [{(µ3-BH)(Cp*Ru)Fe(CO)3}2(µ-CO)] (7) was carried out. Most of these complexes led to decomposition, although photolysis of complex 7 with [Ph2P(CH2)(n)PPh2] (n=1-3) yielded complexes 9-11, [3,4-(Ph2P(CH2)(n)PPh2)-closo-1,2,3,4-Ru2Fe2(BH)2] (9: n=1, 10: n=2, 11: n=3). Quantum-chemical calculations by using DFT methods were carried out on compounds 1-3 and 9-11 and showed reasonable agreement with the experimentally obtained structural parameters, that is, large HOMO-LUMO gaps, in accordance with the high stabilities of these complexes, and NMR chemical shifts that accurately reflected the experimentally observed resonances. All of the new compounds were characterized in solution by using mass spectrometry, IR spectroscopy, and (1)H, (13)C, and (11)B NMR spectroscopy and their structural types were unequivocally established by crystallographic analysis of complexes 1, 2, 4, 9, and 10.

Efficacy of minimally invasive nonthermal laser-induced optical breakdown technology for skin rejuvenation.

We demonstrate the efficacy of a novel minimally invasive nonthermal skin rejuvenation technique for wrinkle and fine-line reduction based on laser-induced optical breakdown. The optical breakdown caused by tightly focused near-infrared laser pulses creates a grid of intradermal lesions without affecting the epidermis, leading to skin rejuvenation. The pilot in vivo efficacy test performed on five subjects successfully demonstrates wrinkle and fine-line reduction, and improvement of other skin features without pain or any other unpleasant sensations or any social downtime associated with the treatment. The efficacy is evaluated objectively and subjectively by assessing the improvement of wrinkles and/or fine lines or skin texture after the treatment. The treatment is safe without side effects or social downtime, and all test subjects reported that the treatment is "perceptible but not painful." Four out of the five subjects who participated in this pilot study were assessed to have "minor" to "significant" improvements of wrinkles and fine lines by the professional panels. The results of this clinical study are expected to bring a paradigm shift in the present laser- and light-based skin rejuvenation methods by introducing a safe treatment procedure without damaging the epidermis, with no or little social downtime and with an efficacy that might be comparable to ablative techniques.

Quantitative assessment of birefringent skin structures in scattered light confocal imaging using radially polarized light.

The polarization characteristics of birefringent tissues could be only partially obtained using linearly polarized light in polarization sensitive optical imaging. Here we analyze the change in polarization of backscattered light from birefringent structures versus the orientations of the incident polarizations using linearly, circularly and radially polarized light in a cross-polarized confocal microscope. A spatially variable retardation plate composed of eight sectors of λ/2 wave plates was used to transform linearly polarized light into a radially polarized light. Based on the experimental data obtained from ex-vivo measurements on human scalp hairs and in-vivo measurements on hair and skin, we exemplify that the underestimation of the birefringence content resulting from the orientation related effects associated with the use of linearly polarized light for imaging tissues containing wavy birefringent structures could be minimized by using radially polarized light.

Synthesis and structure of trans-bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride and diacetate. Suzuki-Miyaura coupling of polybromoarenes with high catalytic turnover efficiencies.

trans-Bis(1,4-dimesityl-3-methyl-1,2,3-triazol-5-ylidene)palladium(II) dichloride has been shown to be an excellent catalyst for the multiple Suzuki-Miyaura coupling reactions of polybromoarenes to the corresponding fully substituted polyarylarenes. The reactions proceeded in excellent yields and with high turnover numbers. With 1,4-dibromobenzene the catalyst was found to be active for up to 13 consecutive cycles with a turnover number of 1260. The polyarylarenes were obtained in pure form after crystallization once without recourse to chromatographic purification. The single-crystal X-ray structures of the chloro (1) as well as the corresponding acetato (2) complexes are also reported and compared with the corresponding complexes of 1,4-diphenyl-3-methyl-1,2,3-triazol-5-ylidene as the ligand.