Polymerization of phenylacetylene by novel Rh (I)-, Ir (I)- and Ru (IV) 1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R = mesityl, 2-propyl): Influence of structure on activity and polymer structure

The preparation of novel Rh (I) and Ir (I) complexes, i.e. [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)]⁺[PF₆]⁻ (1), Rh(CF₃SO₃)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (2) and Ir(CF₃CO₂)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (3) (COD = 1,5-cyclooctadiene), is described. Compounds 1 and 3 were structurally characterized by X-ray diffraction. In 1, the N-heterocyclic carbene acts as a bidentate ligand with the carbene coordinating to the Rh(I) center and an arene group acting as a homoazallyl ligand. The catalytic activity of complexes 1–3 in the polymerization of phenylacetylene was studied and compared to that of RhCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (4), Rh(CF₃COO)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (5), [Rh(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD)]⁺[BF₄]⁻ (6), IrCl(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (7), IrCl(1,3-diisopropyl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) (8), IrBr(1,3-di-2-propylimidazolin-2-ylidene)(COD) (9), RuCl₂(PCy₃)(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH–C₆H₅) (10), RuCl₂(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO₂-C₆H₃) (11), Ru(CO₂CF₃)₂(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)(CH-2-(2-PrO)-5-NO₂-C₆H₃) (12). Compounds 1–6 were active in the polymerization of phenylacetylene. cis-Poly(phenylacetylene) (PPA) was obtained with the rhodium-based catalysts 1, 2, 4–6, trans-PPA was obtained with the Ir-based catalysts 3 and 8. In addition, compounds 1 and 6 were found to produce highly stereoregular PPA with a cis-content of 100% in the presence of water. Finally, the Ru-based metathesis initiator 12 allowed for the synthesis of trans-PPA, representing the first example of a ruthenium complex being active in the polymerization of a terminal alkyne.     

Copper (I) 1,3-R2-3,4,5,6-tetrahydropyrimidin-2-ylidenes (R=mesityl, 2-propyl): synthesis, X-ray structures, immobilization and catalytic activity

The synthesis of novel copper (I) N-heterocyclic carbene complexes is described. Thus, reaction of CuX with 1,3-di(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene yields CuX(1,3-di(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) (X=Cl, (1a), Br (1b)); however, reaction of CuCl with 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene yields the bis-N-heterocylcic carbene complex Cu(1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidene)₂⁺CuBr₂⁻ (2). A supported version of 1, i.e. PS-DVB-CH₂-OCO-CF₂-CF₂-CF₂-COOCu(1,3-di(2-propyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) (3) was prepared from 1 and PS-DVB-CH₂-OCO-CF₂-CF₂-CF₂-COOAg. A copper loading of 4.15 μmol/g was realized. The new compounds were used as catalysts in carbonyl hydrosilylation and cyanosilylation reactions. Excellent reactivity was observed, giving raise to turn-over numbers (TONs) of up to 100,000. Compounds 1a, 1b, and 2 have also been used as catalysts for the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA). A linear conversion of monomer with time was observed, however, no control over molecular weight of PMMA was observed.     

Novel rhodium-1,3-dialkyl-3,4,5,6-tetrahydropyrimidin-2-ylidene complexes as catalysts for arylation of aromatic aldehydes

Six new rhodium-tetrahydropyrimidin-2-ylidene complexes (2a–f) have been prepared and characterized by C, H, N analysis, ¹H NMR and ¹³C NMR. Phenylboronic acid reacts with aldehydes in the presence of a catalytic amount of the new rhodium(I)-carbene complexes, RhCl(COD)(1,3-dialkyl-3,4,5,6-tetrahydropyrimidin-2-ylidene), (2a–f), to give the corresponding secondary aryl alcohols in good yields (72–96%).     

Syntheses, structures, and electrochemical properties of platinum(II) complexes containing di-tert-butylbipyridine and crown ether annelated dithiolate ligands

A series of new platinum(II) complexes containing both 4,4'-di-tert-butyl-2,2'-bipyridine (dbbpy) and the extended tetrathiafulvalenedithiolate ligands have been prepared and characterized. These complexes include [Pt(dbbpy)(C8H4S8)] (1; C8H4S82- = 2-{(4,5-ethylenedithio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate), [Pt(dbbpy)(ptdt)] (2; ptdt = 2-{(4,5-cyclopentodithio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate), [Pt(dbbpy)(mtdt)] (3; mtdt = 2-{(4,5-methylethylenedithio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate), [Pt(dbbpy)(btdt)] (4; btdt = benzotetrathiafulvalenedithiolate), [Pt(dbbpy)(C8H6S8)] (5; C8H6S82- = 2-{4,5-bis(methylthio)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate), [Pt(dbbpy)(3O-C6S8)] (6; 3O-C6S82- = 2-{4,5-dithia-(3',6',9'-trioxaundecyl)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate), and [Pt(dbbpy)(4O-C6S8)] (7; 4O-C6S82- = 2-{4,5-dithia-(3',6',9',12'-tetraoxatetradecyl)-1,3-dithiol-2-ylidene}-1,3-dithiol-4,5-dithiolate). The crystal structures of a new ligand precursor (2-[4,5-dithia-(3',6',9',12'-tetraoxatetradecyl)-1,3-dithiol-2-ylidene]-4,5-bis(2-cyanoethylsulfanyl)-1,3-dithiole, IIIc) and complexes 5-7 have been determined by X-ray crystallography. Complexes 1-7 show intense electronic absorption bands in the UV-vis region due to the intramolecular mixed metal/ligand-to-ligand charge-transfer transition, and they display significant solvatochromic behavior. Redox properties of these compounds have been investigated by cyclic voltammetry, and complex 7 shows a significant response for Na+ ions with a large positive shift of ca. 45 mV.     

The reactivity of N-heterocyclic carbenes and their precursors with [Ru(3)(CO)(12)

The ambient temperature reaction of the N-heterocyclic carbenes (NHCs) 1,3-dimesitylimidazol-2-ylidene (IMes) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (IDipp) with the triruthenium cluster [Ru(3)(CO)(12)], in a 3 : 1 stoichiometric ratio, results in homolytic cleavage of the cluster to quantitatively afford the complexes [Ru(CO)(4)(NHC)] (; NHC = IMes, ; NHC = IDipp). Reaction of the 2-thione or hydrochloride precursors to IMes, i.e. S[double bond, length as m-dash]IMes and IMes.HCl, with the same triruthenium cluster affords the complexes [Ru(4)(mu(4)-S)(2)(CO)(9)(IMes)(2)] () and [Ru(4)(mu(4)-S)(CO)(10)(IMes)(2)] () (3 : 1 and 2 : 1 reaction), and [{Ru(mu-Cl)(CO)(2)(IMes)}(2)] () (3 : 1 reaction) respectively. By contrast, the complex [Ru(3)(mu(3)-S)(2)(CO)(7)(IMeMe)(2)] (), where IMeMe is 1,3,4,5-tetramethylimidazol-2-ylidene, is the sole product of the 2 : 1 stoichiometric reaction of S[double bond, length as m-dash]IMeMe with [Ru(3)(CO)(12)]. Compounds -, and have been structurally characterised by single crystal X-ray diffraction.     

Stoichiometric and catalytic reactivity of the N-heterocyclic carbene ruthenium hydride complexes [Ru(NHC)(L)(CO)HCl] and [Ru(NHC)(L)(CO)H(eta2-BH4)] (L=NHC, PPh3)

Thermolysis of [Ru(AsPh3)3(CO)H2] with the N-aryl heterocyclic carbenes (NHCs) IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) or the adduct SIPr.(C6F5)H (SIPr=1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), followed by addition of CH2Cl2, affords the coordinatively unsaturated ruthenium hydride chloride complexes [Ru(NHC)2(CO)HCl] (NHC=IMes , IPr , SIPr ). These react with CO at room temperature to yield the corresponding 18-electron dicarbonyl complexes . Reduction of and [Ru(IMes)(PPh3)(CO)HCl] () with NaBH4 yields the isolable borohydride complexes [Ru(NHC)(L)(CO)H(eta2-BH4)] (, L=NHC, PPh3). Both the bis-IMes complex and the IMes-PPh3 species react with CO at low temperature to give the eta1-borohydride species [Ru(IMes)(L)(CO)2H(eta1-BH4)] (L=IMes , PPh3), which can be spectroscopically characterised. Upon warming to room temperature, further reaction with CO takes place to afford initially [Ru(IMes)(L)(CO)2H2] (L=IMes, L=PPh3) and, ultimately, [Ru(IMes)(L)(CO)3] (L=IMes , L=PPh3). Both and lose BH3 on addition of PMe2Ph to give [Ru(IMes)(L)(L')(CO)H2](L=L'=PMe2Ph; L=PPh3, L'=PMe2Ph). Compounds and have been tested as catalysts for the hydrogenation of aromatic ketones in the presence of (i)PrOH and H2. For the reduction of acetophenone, catalytic activity varies with the NHC present, decreasing in the order IPr>IMes>SIMes.     

Anellated N-heterocyclic carbenes: 1,3-dineopentylnaphtho[2,3-d]imidazol-2-ylidene: synthesis, KOH addition product, transition-metal complexes, and anellation effects

Two novel anellated N-heterocyclic carbenes (NHC), 1,3-dineopentylnaphtho[2,3-d]imidazol-2-ylidene, and 1,3-dineopentyl-2-ylido-imidazolo[4,5-b]pyridine were obtained by reduction of the respective thiones with potassium, the former also by deprotonation of the corresponding naphthimidazolium hexafluorophosphate by using excess KH in THF. The use of equimolar amounts of KH provided an unexpected formal addition product of this NHC with KOH. X-ray crystal structure analysis of the adduct provided evidence for a distorted tetrameric N-heterocyclic alkoxide, stabilized by two THF molecules. In C(6)D(6) the compound undergoes disproportionation. Transition-metal complexes [(NHC)AgCl], [(NHC)Rh(cod)Cl], and (E)-[(NHC)(2)PdCl(2)] of the novel naphthimidazol-2-ylidene were synthesized. X-ray crystal structures and (1)H and (13)C NMR spectroscopic data provided detailed structural information. Comparing characteristic data with those of nonanellated and differently anellated NHCs or their complexes provides information on the influence of the extended anellation.     

Synthesis of N-heterocyclic carbene rhenium(I) carbonyl complexes

Reaction of aminophosphinimine [RHN(CH(2))(2)N[double bond, length as m-dash]PPh(3)] (R = H, Et) with Re(2)(CO)(10) provided the NH-functionalized carbene rhenium complex [Re(2)(CNHCH(2)CH(2)NR)(CO)(9)] (3a, R = H, 3b, R = Et). Treatment of 3 with Br(2) provided the mono nuclear [Re(CNHCH(2)CH(2)NR)(CO)(4)Br] (1, R = H, 2, R = Et). However, NH-functionalized carbene complexes 1-3 did not undergo N-alkylation with alkyl halides to yield the N-substituted NHC complexes. The direct ligand substitution of [Re(CO)(5)Br] with a carbene donor was employed to prepare [Re(IMes(2))(CO)(4)Br] (6a, IMes(2) = 1,3-di-mesitylimidazol-2-ylidene; 6b, IMes(2) = 1,3-dimesityl-4,5-dihydroimidazol-2-ylidene). Analyses of spectroscopic and crystal data of 6a and 6b show similar corresponding data among these complexes, suggesting the saturated and unsaturated NHCs have similar bonding with Re(I) metal centers. Reduction of 6a and 6b with LiEt(3)BH yielded the corresponding hydrido complexes 7a-b [ReH(CO)(4)(IMes(2))], but not 1 and 2. Ligand substitution of 1, 6a and 6b toward 2,2'-bipyridine (bipy) was investigated. Crystal structures of 1, 3a-b, 6a-b and 7b were determined for characterization and comparison.     

Rh(1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) tetrafluoroborate, an unsymmetrical Rh-homoazallylcarbene: synthesis, X-ray structure and reactivity in carbonyl arylation and hydrosilylation reactions

The synthesis of novel Rh(1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene)(COD) tetrafluoroborate (1, COD = η⁴-1,5-cyclooctadiene) is described. The N-heterocyclic carbene acts as a bidentate ligand with the carbene coordinating to the Rh(I) center and an arene group acting as a homoazallyl ligand. 1 was used in various carbonyl arylation and hydrosilylation reactions allowing the formation of the desired products with unprecedented selectivity and efficiency. Thus, turn-over numbers (TONs) up to 2000 were achieved.     

Novel metathesis catalysts based on ruthenium 1,3-dimesityl-3,4,5,6-tetrahydropyrimidin-2-ylidenes: synthesis, structure, immobilization, and catalytic activity

The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm).     

Synthesis and catalytic properties of N -functionalised carbene complexes of rhodium(I)

Reaction of [RhCl(COD)]₂, with 1,3-dialkylimidazolinylidene (1) or 1,3-dialkylbenzimidazolinylidene (2) resulted in the formation of rhodium(I) 1,3-dialkylimidazolin-2-ylidene (3a-c) and 1,3-dialkylbenzimidazolin-2-ylidene (4a,b) complexes. Triethylsilane reacts with acetophenone derivatives in the presence of catalytic amounts of RhCl(COD)(1,3-dialkylimidazolin-2-ylidene) or RhCl(COD)(1,3-dialkylbenzimidazolin-2-ylidene) to give the corresponding silylethers in good yield (57–98%).     

新型氮杂环卡宾银(I)配合物的合成及其晶体结构

以取代苄氯(1a~1c)为起始原料,与咪唑经氮烷基化反应制得苄基咪唑氯盐(2a~2c); 2a~2c与氧化银经原位去质子化反应合成了3种新型的氮杂环卡宾银配合物--(NHC)AgCl［NHC: 1,3-二(4-甲氧基苄基)咪唑-2-亚基(3a), 1,3-二(3-甲氧基苄基)咪唑-2-亚基(3b)］和［(NHC)AgCl]₂［NHC=1,3-二(4-氯苄基)咪唑-2-亚基(3c)］,其结构经¹H NMR, ¹³C NMR, IR,元素分析和X-射线单晶衍射表征。3a~3c单晶结构均属单斜晶系,3a为P2₁/n空间群,3b和3c为P2₁/c空间群,3a和3b为单核银配合物,3c为双核银配合物。     

Chemistry surrounding monomeric copper(I) methyl, phenyl, anilido, ethoxide, and phenoxide complexes supported by N-heterocyclic carbene ligands: reactivity consistent with both early and late transition metal systems

Monomeric copper(I) alkyl complexes that possess the N-heterocyclic carbene (NHC) ligands IPr, SIPr, and IMes [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, SIPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene, IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene] react with amines or alcohols to release alkane and form the corresponding monomeric copper(I) amido, alkoxide, or aryloxide complexes. Thermal decomposition reactions of (NHC)Cu(I) methyl complexes at temperatures between 100 and 130 degrees C produce methane, ethane, and ethylene. The reactions of (NHC)Cu(NHPh) complexes with bromoethane reveal increasing nucleophilic reactivity at the anilido ligand in the order (SIPr)Cu(NHPh) < (IPr)Cu(NHPh) < (IMes)Cu(NHPh) < (dtbpe)Cu(NHPh) [dtbpe = 1,2-bis(di-tert-butylphosphino)ethane]. DFT calculations suggest that the HOMO for the series of Cu anilido complexes is localized primarily on the amido nitrogen with some ppi(anilido)-dpi(Cu) pi-character. [(IPr)Cu(mu-H)]2 and (IPr)Cu(Ph) react with aniline to quantitatively produce (IPr)Cu(NHPh)/dihydrogen and (IPr)Cu(NHPh)/benzene, respectively. Analysis of the DFT calculations reveals that the conversion of [(IPr)Cu(mu-H)]2 and aniline to (IPr)Cu(NHPh) and dihydrogen is favorable with DeltaH approximately -7 kcal/mol and DeltaG approximately -9 kcal/mol.     

1,3-Diarylimidazolidin-2-ylidene (NHC) complexes of Pd(II): Electronic effects on cross-coupling reactions and thermal decompositions

The synthesis of 1,3-diarylimidazolidin-2-ylidene (NHC) precursor, 1,3-bis(2,4,6-trimethylphenyl)imidazolinium chloride, (3b) has been extended to the electronically and sterically modified NHC precursors 3a (X = H), 3c (X = Br) and 3e (X = Cl) in order to investigate the electronic effect of a p-substituent (X) on cross-coupling catalysts. Complexes of the type PdCl₂(NHC)₂ (5), PdCl₂(NHC)(PPh₃) (6) and [RhCl(NHC)(cod)] (7) were prepared from 3 or 4d (1,3-bis(2,4-dimethylphenyl)-2-trichloromethylimidazolidin). Initial decomposition temperatures of the complexes 5 and 6 were determined by TGA. In situ formed complexes from Pd(OAc)₂ and 3 as well as the preformed complexes 5 and 6 have been tested as catalysts in coupling of phenylboronic acid with 4-haloacetophenones. The electron donating ability of NHCs derived from 3 was assessed by measuring C-O frequencies in the respective [RhCl(NHC)(CO)₂] complex 8 which was prepared by replacement of cod ligand of 7 with CO. An interesting correlation between the electron-donating nature of the aryl substituent and catalytic activity and also initial decomposition temperature of the complexes 5 and 6 was observed.     

Synthesis, structural characterization, and ligand replacement reactions of gem-dithiolato-bridged rhodium and iridium complexes

The reaction of gem-dithiol compounds R 2C(SH) 2 (R = Bn (benzyl), (i) Pr; R 2 = -(CH 2) 4-) with dinuclear rhodium or iridium complexes containing basic ligands such as [M(mu-OH)(cod)] 2 and [M(mu-OMe)(cod)] 2, or the mononuclear [M(acac)(cod)] (M = Rh, Ir, cod = 1,5-cyclooctadiene) in the presence of a external base, afforded the dinuclear complexes [M 2(mu-S 2CR 2)(cod) 2] ( 1- 4). The monodeprotonation of 1,1-dimercaptocyclopentane gave the mononuclear complex [Rh(HS 2Cptn)(cod)] ( 5) that is a precursor for the dinuclear compound [Rh 2(mu-S 2Cptn)(cod) 2] ( 6). Carbonylation of the diolefin compounds gave the complexes [Rh 2(mu-S 2CR 2)(CO) 4] ( 7- 9), which reacted with P-donor ligands to stereoselectively produce the trans isomer of the disubstituted complexes [Rh 2(mu-S 2CR 2)(CO) 2(PR' 3) 2] (R' = Ph, Cy (cyclohexyl)) ( 10- 13) and [Rh 2(mu-S 2CBn 2)(CO) 2{P(OR') 3} 2] (R' = Me, Ph) ( 14- 15). The substitution process in [Rh 2(mu-S 2CBn 2)(CO) 4] ( 7) by P(OMe) 3 has been studied by spectroscopic means and the full series of substituted complexes [Rh 2(mu-S 2CBn 2)(CO) 4- n {P(OR) 3} n ] ( n = 1, 4) has been identified in solution. The cis complex [Rh 2(mu-S 2CBn 2)(CO) 2(mu-dppb)] ( 16) was obtained by reaction of 7 with the diphosphine dppb (1,4-bis(diphenylphosphino)butane). The molecular structures of the diolefinic dinuclear complexes [Rh 2(mu-S 2CR 2)(cod) 2] (R = Bn ( 1), (i) Pr ( 2); R 2 = -(CH 2) 4- ( 6)) and that of the cis complex 16 have been studied by X-ray diffraction.     

Novel metal-organic frameworks with specific topology from new tripodal ligands: 1,3,5-tris(1-imidazolyl)benzene and 1,3-bis(1-imidazolyl)-5-(imidazol-1-ylmethyl)benzene

Reactions of two new tripodal ligands 1,3,5-tris(1-imidazolyl)benzene (4) and 1,3-bis(1-imidazolyl)-5-(imidazol-1-ylmethyl)benzene (5) with metal [Ag(I), Cu(II), Zn(II), Ni(II)] salts lead to the formation of novel two-dimensional (2D) metal-organic frameworks [Ag(2)(4)(2)][p-C(6)H(4)(COO)(2)].H(2)O (6), [Ag(4)]ClO(4) (7), [Cu(4)(2)(H(2)O)(2)](CH(3)COO)(2).2H(2)O (8), [Zn(4)(2)(H(2)O)(2)](NO(3))(2) (9), [Ni(4)(2)(N(3))(2)].2H(2)O (10), and [Ag(5)]ClO(4) (11). All the structures were established by single-crystal X-ray diffraction analysis. Crystal data for 6: monoclinic, C2/c, a = 23.766(3) A, b = 12.0475(10) A, c = 13.5160(13) A, beta = 117.827(3) degrees, Z = 4. For compound 7: orthorhombic, P2(1)2(1)2(1), a = 7.2495(4) A, b = 12.0763(7) A, c = 19.2196(13) A, Z = 4. For compound 8: monoclinic, P2(1)/n, a = 8.2969(5) A, b = 12.2834(5) A, c = 17.4667(12) A, beta = 96.5740(10) degrees, Z = 2. For compound 9: monoclinic, P2(1)/n, a =10.5699(3) A, b = 11.5037(3) A, c = 13.5194(4) A, beta = 110.2779(10) degrees, Z = 2. For compound 10: monoclinic, P2(1)/n, a = 9.8033(3) A, b = 12.1369(5) A, c = 13.5215(5) A, beta = 107.3280(10) degrees, Z = 2. For compound 11: monoclinic C2/c, a = 18.947(2) A, b = 9.7593(10) A, c = 19.761(2) A, beta = 97.967(2) degrees, Z = 8. Both complexes 6 and 7 are noninterpenetrating frameworks based on the (6, 3) nets, and 8, 9 and 10 are based on the (4, 4) nets while complex 11 has a twofold parallel interpenetrated network with 4.8(2) topology. It is interesting that, in complexes 6,7, and 11 with three-coordinated planar silver(I) atoms, each ligand 4 or 5 connects three metal atoms, while in the case of complexes 8, 9, and 10 with six-coordinated octahedral metal atoms, each ligand 4 only links two metal atoms, and another imidazole nitrogen atom of 4 did not participate in the coordination with the metal atoms in these complexes. The results show that the nature of organic ligand and geometric needs of metal atoms have great influence on the structure of metal-organic frameworks.     

Isomerism in rhodium(I) N,S-donor heteroscorpionates: ring substituent and ancillary ligand effects

The heteroscorpionate ligands [HB(taz)(2)(pz(R))](-) (pz(R) = pz, pz(Me2), pz(Ph)) and [HB(taz)(pz)(2)](-), synthesised from the appropriate potassium hydrotris(pyrazolyl)borate salt and 4-ethyl-3-methyl-5-thioxo-1,2,4-triazole (Htaz), react with [{Rh(cod)(μ-Cl)}(2)] to give [Rh(cod)Tx] {Tx = HB(taz)(2)(pz), HB(taz)(2)(pz(Me2)), HB(taz)(2)(pz(Ph)), HB(taz)(pz)(2)}; the heteroscorpionate rhodaboratrane [Rh{B(taz)(2)(pz(Me2))}{HB(taz)(2)(pz(Me2))}] is the only isolable product from the reaction of [{Rh(nbd)(μ-Cl)}(2)] with K[HB(taz)(2)(pz(Me2))]. Carbonylation of the cod complexes gave a mixture of [Rh(CO)(2)Tx] and [(RhTx)(2)(μ-CO)(3)] which reacts with PR(3) to give [Rh(CO)(PR(3))Tx] (R = Cy, NMe(2), Ph, OPh). In the solid state the complexes are square planar with the particular structure dependent on the steric and/or electronic properties of the scorpionate and ancillary ligands. The complex [Rh(cod){HB(taz)(pz)(2)}] has the heteroscorpionate κ(2)[N(2)]-coordinated to rhodium with the B-H bond directed away from the rhodium square plane while [Rh(cod){HB(taz)(2)(pz(Me2))}] is κ(2)[SN]-coordinated, with the B-H bond directed towards the metal. The complexes [Rh(CO)(PPh(3)){HB(taz)(2)(pz)}] and [Rh(CO)(PPh(3)){HB(taz)(2)(pz(Me2))}] are also κ(2)[SN]-coordinated but with the pyrazolyl ring cis to PPh(3); in the former the B-H bond is directed towards rhodium while in the latter the ring is pseudo-parallel to the rhodium square plane, as also found for [Rh(CO)(2){HB(taz)(2)(pz(Me2))}]. The analogues [Rh(CO)(PR(3)){HB(taz)(2)(pz(Me2))}] (R = Cy, NMe(2)) have the phosphines trans to the pyrazolyl ring. Uniquely, [Rh(CO)(PPh(3)){HB(taz)(2)(pz(Ph))}] is κ(2)[S(2)]-coordinated. A qualitative mechanism is given for the rapid ring-exchange, and hence isomerisation, observed in solution.     

Silsesquioxyl rhodium(I) complexes--synthesis, structure and catalytic activity

The first bi- and mononuclear rhodium(I) complexes [{Rh(μ-OSi(8)O(12)(i-Bu)(7))(cod)}(2)] (5), [Rh(cod)(PCy(3))(OSi(8)O(12)(i-Bu)(7))] (6) with a hindered hepta(iso-butyl)silsesquioxyl ligand bonded to the rhodium(I) center through Rh-O-Si bonds have been synthesized and their structures have been solved by spectroscopic methods and X-ray analysis. Their exemplary catalytic properties in silylative coupling of vinylsilanes with styrene are also presented.     

Efficient C-F and C-C activation by a novel N-heterocyclic carbene-nickel(0) complex

The NHC-stabilized complex [Ni2(iPr2Im)4(cod)] (1) was isolated in good yield from the reaction of [Ni(cod)2] with 1,3-diisopropylimidazole-2-ylidene (iPr2Im). Compound 1 is a source of the [Ni(iPr2Im)2] complex fragment in stoichiometric and catalytic transformations. The reactions of 1 with ethylene and CO under atmospheric pressure or with equimolar amounts of diphenylacetylene lead to the compounds [Ni(iPr2Im)2(eta2-C2H4)] (2), [Ni(iPr2Im)2(eta2-C2Ph2)] (3), and [Ni(iPr2Im)2(CO)2] (4) in good yields. In all cases the [Ni(iPr2Im)2] complex fragment is readily transferred without decomposition or fragmentation. In the infrared spectrum of carbonyl complex 4, the CO stretching frequencies are observed at 1847 and 1921 cm(-1), and are significantly shifted to lower wavenumbers compared with other nickel(0) carbonyl complexes of the type [NiL2(CO)2]. Complex 1 activates the C--F bond of hexafluorobenzene very efficiently to give [Ni(iPr2Im)2(F)(C6F5)] (5). Furthermore, [Ni2(iPr2Im)4(cod)] (1) is also an excellent catalyst for the catalytic insertion of diphenylacetylene into the 2,2' bond of biphenylene. The reaction of 1 with equimolar amounts of biphenylene at low temperature leads to [Ni(iPr2Im)2(2,2'-biphenyl)] (6), which is formed by insertion into the strained 2,2' bond. The reaction of diphenylacetylene and biphenylene at 80 degrees C in the presence of 2 mol % of 1 as catalyst yields diphenylphenanthrene quantitatively and is complete within 30 minutes.     

Different transmetallation behaviour of [M(P4HR4)] salts toward rhodium(I) and copper(I) (M = Na, K; R = Ph, Mes; Mes = 2,4,6-Me3C6H2)

[K(2)(P(4)Mes(4))] (1) or [Na(2)(THF)(4)(P(4)Mes(4))] (2) (Mes = 2,4,6-Me(3)C(6)H(2)) reacts with one equivalent of HCl and subsequently with 0.5 equivalents of [{RhCl(cod)}(2)] (cod = 1,5-cyclooctadiene) to give a mixture of rhodium complexes, from which [Rh(P(4)HMes(4))(cod)] (3) and the secondary product [Rh(2)(micro-P(2)HMes(2))(mu-PHMes)(cod)(2)] (4) were isolated and characterised by X-ray diffraction studies. Alternatively, the reaction of [K(2)(P(4)Ph(4))] (5) or [Na(2)(THF)(5)(P(4)Ph(4))] (6) with one equivalent of HCl and subsequently with one equivalent of [CuCl(PCyp(3))(2)] (Cyp = cyclo-C(5)H(9)) gave the complex [Cu(4)(P(4)Ph(4))(2)(PH(2)Ph)(2)(PCyp(3))(2)] (7), presumably via disproportionation of the monoanion (P(4)HPh(4))(-).