James D. E. T. Wilton-Ely

Multimetallic Assemblies Using Piperazine-Based Dithiocarbamate Building Blocks

Treatment of cis-[RuCl2(dppm)2] (dppm = bis(diphenylphosphino)methane) with dithiocarbamates, NaS2CNR2 (R = Me, Et) and [H2NC5H10][S2CNC5H10], yields cations [Ru(S2CNR2)2(dppm)2](+) and [Ru(S2CNC5H10)2(dppm)2](+), respectively. The zwitterions S2CNC4H8NHR (R = Me, Et) react with the same metal complex in the presence of base to yield [Ru(S2CNC4H8NR)(dppm)2](+). Piperazine or 2,6-dimethylpiperazine reacts with carbon disulfide to give the zwitterionic dithiocarbamate salts H2NC4H6(R2-3,5)NCS2 (R = H; R = Me), which form the complexes [Ru(S2CNC4H6(R2-3,5)NH2)(dppm)2](2+) on reaction with cis-[RuCl2(dppm)2]. Sequential treatment of [Ru(S2CNC4H8NH2)(dppm)2](2+) with triethylamine and carbon disulfide forms the versatile metalla-dithiocarbamate complex [Ru(S2CNC4H8NCS2)(dppm)2] which reacts readily with cis-[RuCl2(dppm)2] to yield [{Ru(dppm)2}2(S2CNC4H8NCS2)]. Reaction of [Ru(S2CNC4H8NCS2)(dppm)2] with [Os(CH=CHC6H4Me-4)Cl(CO)(BTD)(PPh3)2] (BTD = 2,1,3-benzothiadiazole), [Pd(C6H4CH2NMe2)Cl]2, [PtCl2(PEt3)2], and [NiCl2(dppp)] (dppp = 1,3-bis(diphenylphosphino)propane) results in the heterobimetallic complexes [(dppm)2Ru(S2CNC4H8NCS2)ML(n))](m+) (ML(n) = Os(CH=CHC6H4Me-4)(CO)(PPh3)2](+), m = 1; ML(n) = Pd(C,N-C6H4CH2NMe2), m = 1; ML(n) = Pt(PEt3)2, m = 2; ML(n) = Ni(dppp), m = 2). Reaction of [NiCl2(dppp)] with H2NC4H8NCS2 yields the structurally characterized compound, [Ni(S2CNC4H8NH2)(dppp)](2+), which reacts with base, CS2, and cis-[RuCl2(dppm)2] to provide an alternative route to [(dppm)2Ru(S2CNC4H8NCS2)Ni(dppp)](+). A further metalla-dithiocarbamate based on cobalt, [CpCo(S2CNC4H8NH2)(PPh3)](2+), is formed by treatment of CpCoI2(CO) with S2CNC4H8NH2 followed by PPh3. Further reaction with NEt3, CS2, and cis-[RuCl2(dppm)2] yields [(Ph3P)CpCo(S2CNC4H8NCS2)Ru(dppm)2](2+). Heterotrimetallic species of the form [{(dppm)2Ru(S2CNC4H8NCS2)}2M](2+) result from the reaction of [Ru(S2CNC4H8NCS2)(dppm)2] and M(OAc)2 (where M = Ni, Cu, Zn). Reaction of [Ru(S2CNC4H8NCS2)(dppm)2] with Co(acac)3 and LaCl3 results in the formation of the compounds [{(dppm)2Ru(S2CNC4H8NCS2)}3Co](3+) and [{(dppm)2Ru(S2CNC4H8NCS2)}3La](3+), respectively. The electrochemical behavior of selected examples is also reported.

The Use of Imidazolium-2-dithiocarboxylates in the Formation of Gold(I) Complexes and Gold Nanoparticles††Dedicated to Prof. Dr. Hubert Schmidbaur on the occasion of his 75th birthday.

The imidazolium-2-dithiocarboxylate ligands IPr.CS(2), IMes.CS(2), and IDip.CS(2) react with [AuCl(PPh(3))] to yield [(Ph(3)P)Au(S(2)C.IPr)](+), [(Ph(3)P)Au(S(2)C.IMes)](+), and [(Ph(3)P)Au(S(2)C.IDip)](+), respectively. The compounds [(L)Au(S(2)C.IMes)](+) are prepared from the reaction of IMes.CS(2) with [AuCl(L)] (L = PMe(3), PCy(3), CN(t)Bu). The carbene-containing precursor [(IDip)AuCl] reacts with IPr.CS(2) and IMes.CS(2) to afford the complexes [(IDip)Au(S(2)C.IPr)](+) and [(IDip)Au(S(2)C.IMes)](+) with two carbene units, one bound to the metal center and the other to the dithiocarboxylate unit. Treatment of the diphosphine-gold complex [(dppm)(AuCl)(2)] with 1 equiv of IMes.CS(2) yields [(dppm)Au(2)(S(2)C.IMes)](2+), while the reaction of [L(2)(AuCl)(2)] (L(2) = dppb, dppf) with 2 equiv of IMes.CS(2) results in [(L(2)){Au(S(2)C.IMes)}(2)](2+). The homoleptic complexes [Au(S(2)C.IPr)(2)](2+), [Au(S(2)C.IMes)(2)](2+), and [Au(S(2)C.IDip)(2)](2+) are obtained from the reaction of [AuCl(tht)] with 2 equiv of the appropriate imidazolium-2-dithiocarboxylate ligand. The compounds [(Ph(3)P)Au(S(2)C.NHC)](+) (NHC = IMes, IDip) and [(IDip)Au(S(2)C.NHC)](+) (NHC = IPr, IMes) are characterized crystallographically. The IMes.CS(2) ligand is also used to prepare functionalized gold nanoparticles with diameters of 11.5 (+/-1.2) and 2.6 (+/-0.3) nm.

Reusable and highly active supported copper(I)-NHC catalysts for Click chemistry.

Immobilised [Cu(NHC)] catalysts are reported for the preparation of 1,2,3-triazoles. In addition to showing outstanding catalytic activity, the catalyst systems are easy to prepare and can be recycled many times.

Multimetallic Arrays: Bi-, Tri-, Tetra-, and Hexametallic Complexes Based on Gold(I) and Gold(III) and the Surface Functionalization of Gold Nanoparticles with Transition Metals

Reaction of [AuCl(PPh(3))] with the zwitterion S(2)CNC(4)H(8)NH(2) yields [(Ph(3)P)Au(S(2)CNC(4)H(8)NH(2))]BF(4). Treatment of this species with NEt(3) and CS(2) followed by [AuCl(PPh(3))] leads to [{(Ph(3)P)Au}(2)(S(2)CNC(4)H(8)NCS(2))], which can also be obtained directly from [AuCl(PPh(3))] and KS(2)CNC(4)H(8)NCS(2)K. A heterobimetallic variant, [(dppm)(2)Ru(S(2)CNC(4)H(8)NCS(2))Au(PPh(3))](+), can be prepared by the sequential reaction of [(dppm)(2)Ru(S(2)CNC(4)H(8)NH(2))](2+) with NEt(3) and CS(2) followed by [AuCl(PPh(3))]. Reaction of the same ruthenium precursor with [(dppm)(AuCl)(2)] under similar conditions yields the trimetallic complex [(dppm)(2)Ru(S(2)CNC(4)H(8)NCS(2))Au(2)(dppm)](2+). Attempts to prepare the compound [(dppm)Au(2)(S(2)CNC(4)H(8)NH(2))](2+) from [(dppm)(AuCl)(2)] led to isolation of the known complex [{(dppm)Au(2)}(2)(S(2)CNC(4)H(8)NCS(2))](2+) via a symmetrization pathway. [{(dppf)Au(2)}(2)(S(2)CNC(4)H(8)NCS(2))](2+) was successfully prepared from [(dppf)(AuCl)(2)] and crystallographically characterized. In addition, a gold(III) trimetallic compound, [{(dppm)(2)Ru(S(2)CNC(4)H(8)NCS(2))}(2)Au](3+), and a tetrametallic gold(I) species, [{(dppm)(2)Ru(S(2)CNC(4)H(8)NCS(2))Au}(2)](2+), were also synthesized. This methodology was further exploited to attach the zwitterionic (dppm)(2)Ru(S(2)CNC(4)H(8)NCS(2)) unit to the surface of gold nanoparticles, which were generated in situ and found to be 3.4 (+/-0.3) and 14.4 (+/-2.5) nm in diameter depending on the method employed. Nanoparticles with a mixed surface topography were also explored.

A chromo-fluorogenic synthetic "canary" for CO detection based on a pyrenylvinyl ruthenium(II) complex.

The chromo-fluorogenic detection of carbon monoxide in air has been achieved using a simple, inexpensive system based on ruthenium(II). This probe shows exceptional sensitivity and selectivity in its sensing behavior in the solid state. A color response visible to the naked eye is observed at 5 ppb of CO, and a remarkably clear color change occurs from orange to yellow at the onset of toxic CO concentrations (100 ppm) in air. Even greater sensitivity (1 ppb) can be achieved through a substantial increase in turn-on emission fluorescence in the presence of carbon monoxide, both in air and in solution. No response is observed with other gases including water vapor. Immobilization of the probe on a cellulose strip allows the system to be applied in its current form in a simple optoelectronic device to give a numerical reading and/or alarm.

Coordinatively unsaturated ruthenium allenylidene complexes: highly effective, well defined catalysts for the ring-closure metathesis of α,ω-dienes and dienynes

The well defined, conveniently accessible and coordinatively unsaturated allenylidene complexes [RuCl2(CC CPh2)(PCy3)2] and [Ru2Cl4(CCCPh2)(PCy3)(η-MeC6-H4Pri-4)] are highly effective catalysts for the ambient temperature ring-closure metathesis of α,ω-dienes and dienynes, illustrated by the facile and high yielding formation of variously functionalised 5, 6, 7, 8, 15, 16 and 18 membered mono- and bi-cyclic ring systems.

On the Importance of Purity for the Formation of Self-Assembled Monolayers from Thiocyanates

Assembly of dodecyl thiocyanate (C12SCN) from ethanol solution onto Au(111)/mica substrates was investigated by scanning tunneling microscopy (STM), near edge X-ray absorption fine structure spectroscopy (NEXAFS), X-ray photoelectron spectroscopy (XPS), and infrared reflection-absorption spectroscopy (IRRAS). Contrary to previous reports, thiolate monolayers formed by cleavage of the S-CN bond can be obtained whose quality is at least as good as that of self-assembled monolayers (SAMs) formed directly from the thiol analogue of C12SCN, dodecanethiol (C12SH). However, the achievable quality is strikingly dependent on the purity of the thiocyanate with even low levels of contamination impeding the formation of structurally well-defined monolayers.

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).

Non-innocent Behaviour of Dithiocarboxylate Ligands Based on N-Heterocyclic Carbenes

While metal complexes of dithiocarbamate or xanthate ligands are well known in the literature, only a few dithiocarboxylate compounds (LnMS2CR, in which R is a carbonbased substituent) have been described to date. This situation may be explained at least in part by the relative difficulty associated with the synthesis of dithiocarboxylate ligands compared with analogous dithiocarbamate or xanthate species. The lack of exploration in the field of dithiocarboxylate coordination chemistry may be contrasted with the explosion of interest in the use of N-heterocyclic carbenes (NHCs) as ligands over the past two decades. Often seen as an excellent alternative to phosphines, these divalent carbon species have been embraced by those involved in catalysis. Indeed, their tuneable, electron-rich nature, and steric bulk coupled with their lack of lability represent excellent attributes for the development of catalytic systems based on a wide range of transition metals, including ruthenium, palladium, gold and copper among many others. Although stable free carbenes were first isolated and characterised in the late 1980s, the chemistry of their formal enetetramine dimers has been under investigation since the 1960s. It was soon recognised that these electron-rich alkenes could be easily cleaved by various electrophiles to yield stable zwitterionic adducts. This approach has been successfully extended to the reaction of free carbenes with CS2 to afford the corresponding betaines in high yields and purities. Despite this ease of preparation, the coordination chemistry of NHC·CS2 adducts is still largely uncharted territory. Early exploratory work by Borer et al. showed that 1,3-dimethylimidazolium-2-dithiocarboxylate formed stable complexes with a number of transition-metal halides or nitrates, although the intimate structure of these compounds remained elusive. The organometallic chemistry of zwitterionic ligands derived from (benz)imidazolium salts such as the carbodicarbenes (or bent allenes) is also a rather unexploited field thus far. Our investigations of zwitterionic piperazine-based dithiocarbamates in the formation of multimetallic arrays led to our interest in the very recent report of the compounds [RuCl ACHTUNGTRENNUNG(p-cymene)ACHTUNGTRENNUNG(NHC·CS2)] ACHTUNGTRENNUNG[PF6] (p-cymene=1-isopropyl4-methylbenzene). This prompted us to further investigate the reaction of NHC·CS2 betaines with transition-metal complexes. An additional stimulus for this research is the low suitability of NHCs for high-valent metal centres. In contrast, NHC·CS2 ligands would be able to combine a much greater stabilisation of both high and low oxidation states, as seen for other 1,1’-dithio ligands, but with an adjustable steric profile. Herein, we report the synthesis and characterisation of ruthenium–alkenyl complexes with NHC·CS2 ligands and provide evidence of a remarkable rearrangement caused by their steric effect. The most convenient triphenylphosphine-stabilised complexes to use as entry points for Group 8 alkenyl chemistry are those of the form [Ru ACHTUNGTRENNUNG(CR1=CHR2)Cl(CO) ACHTUNGTRENNUNG(PPh3)2][13] or [Ru ACHTUNGTRENNUNG(CR1=CHR2)Cl(CO) ACHTUNGTRENNUNG(btd)ACHTUNGTRENNUNG(PPh3)2],[14] in which BTD is the labile 2,1,3-benzothiadiazole ligand. A bright red solution of [Ru(CH=CHC6H4Me-4)Cl(CO) ACHTUNGTRENNUNG(btd) ACHTUNGTRENNUNG(PPh3)2] (1) in dichloromethane was treated with a slight excess of 1,3-dicyclohexylimidazolium-2-dithiocarboxylate (ICy·CS2) [8f] in the presence of NH4PF6 for an hour at room temperature (Scheme 1). The retention of the 4-tolylvinyl ligand in the [a] S. Naeem, Dr. J. D. E. T. Wilton-Ely Department of Chemistry, Imperial College London South Kensington Campus, London SW7 2AZ (UK) Fax: (+44) 207-594-5804 E-mail : j.wilton-ely@imperial.ac.uk [b] Dr. A. L. Thompson Chemical Crystallography, Inorganic Chemistry Laboratory Department of Chemistry, South Parks Road, Oxford, Oxford OX1 3QR (UK) [c] Dr. L. Delaude Center for Education and Research on Macromolecules (CERM) Institut de Chimie (B6a), Universit de Li ge Sart-Tilman par 4000 Li ge (Belgium) Supporting information (detailed experimental procedures for the synthesis of complexes 2, 3, 5 and 6, and crystallographic data for the structures of 2 and 6) for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201001235.

The functionalisation of ruthenium(II) and osmium(II) alkenyl complexes with amine- and alkoxy-terminated dithiocarbamates.

The complex cis-[RuCl(2)(dppm)(2)] reacts with the amine-terminated dithiocarbamates KS(2)CN(CH(2)CH(2)NEt(2))(2) and KS(2)CN(CH(2)CH(2)CH(2)NMe(2))(2) to form the compounds [Ru{S(2)CN(CH(2)CH(2)NEt(2))(2)}(dppm)(2)](+) and [Ru{S(2)CN(CH(2)CH(2)CH(2)NMe(2))(2)}(dppm)(2)](+), respectively. The methoxy-terminated dithiocarbamate compound [Ru{S(2)CN(CH(2)CH(2)OMe)(2)}(dppm)(2)](+) was also prepared from the same precursor using KS(2)CN(CH(2)CH(2)OMe)(2). The alkenyl complexes [RuRCl(CO)(BTD)(PPh(3))(2)] (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, CH=CHCPh(2)OH), [Ru(C(C[triple bond]CBu(t))=CHBu(t))Cl(CO)(PPh(3))(2)] and [Os(CH=CHC(6)H(4)Me-4)Cl(CO)(BTD)(PPh(3))(2)] also react cleanly with KS(2)CN(CH(2)CH(2)CH(2)NMe(2))(2) and KS(2)CN(CH(2)CH(2)NEt(2))(2) to yield [MR{S(2)CN(CH(2)CH(2)CH(2)NMe(2))(2)}(CO)(PPh(3))(2)] and [MR{S(2)CN(CH(2)CH(2)NEt(2))(2)}(CO)(PPh(3))(2)], respectively. In a similar fashion, the compounds [RuR{S(2)CN(CH(2)CH(2)OMe(2))(2)}(CO)(PPh(3))(2)] (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C[triple bond]CBu(t))=CHBu(t)) were also prepared. Treatment of [Ru(CH=CHBu(t)){S(2)CN(CH(2)CH(2)CH(2)NMe(2))(2)}(CO)(PPh(3))(2)] and [Ru{S(2)CN(CH(2)CH(2)NEt(2))(2)}(dppm)(2)](+) with trifluoroacetic acid affords the ammonium complexes [Ru(CH=CHBu(t)){S(2)CN(CH(2)CH(2)CH(2)NHMe(2))(2)}(CO)(PPh(3))(2)](2+) and [Ru{S(2)CN(CH(2)CH(2)NHEt(2))(2)}(dppm)(2)](2+), while the same reagent generates the tricationic vinylcarbene complex [Ru(=CHCH=CPh(2)){S(2)CN(CH(2)CH(2)CH(2)NHMe(2))(2)}(CO)(PPh(3))(2)](3+) through loss of water from [Ru(CH=CHCPh(2)OH){S(2)CN(CH(2)CH(2)CH(2)NMe(2))(2)}(CO)(PPh(3))(2)]. The structures of [Ru{S(2)CN(CH(2)CH(2)OMe)(2)}(dppm)(2)]PF(6) and [Ru(CH=CHC(6)H(4)Me-4){S(2)CN(CH(2)CH(2)OMe)(2)}(CO)(PPh(3))(2)] were determined crystallographically.