Vinyl and carbene ruthenium(II) complexes from hydridoruthenium(II) precursors

The reactions of the hydrido compounds [RuHCl(CO)(L)2][L = PiPr3 (1), PCy3 (2)] with HC(triple bond)CR (R = H, Ph, tBu) afforded by insertion of the alkyne into the Ru-H bond the corresponding vinyl complexes [RuCl(CHCHR)(CO)(L)2], 3-8, which upon protonation with HBF4 gave the cationic five-coordinated ruthenium carbenes [RuCl(CHCH2R)(CO)(L)2]BF4, 9-14. Subsequent reactions of the carbene complexes with PR3(R = Me, iPr) and CH3CN led either to deprotonation and re-generation of the vinyl compounds or to cleavage of the ruthenium-carbene bond and the formation of the six-coordinated complexes [RuCl(CO)(CH3CN)2(PiPr3)2]BF4, 17, and [RuH(CO)(CH3CN)2(PiPr3)2]X, 18a,b. The acetato derivative [RuH(2-O2CCH3)(CO)(PCy3)2], 19, also reacted with acetylene and phenylacetylene by insertion to yield the related vinyl complexes [Ru(CHCHR)(kappa2-O2CCH3)(CO)(PCy3)2], 20, 21, of which that with R = H was protonated with HBF4 to yield the corresponding cationic ruthenium carbene 22. With [RuHCl(H2)(PCy3)2], 25, as the starting material, the five-coordinated chloro(hydrido)ruthenium(II) compounds [RuHCl(PCy3)(dppf)], 26(dppf = [Fe(eta5-C5H4PPh2)2]), [RuHCl[Sb(CH2Ph)3](PCy3)2], 27, and [RuHCl(CH3CN)(PCy3)2], 30, were prepared. The reactions of 27 with HCCR (R = H, Ph) gave the hydrido(vinylidene) complexes [RuHCl(CCHR)(PCy3)2], 28 and 29, whereas treatment of 30 with HC(triple bond)CPh afforded the vinyl compound [RuCl(CHCHPh)(CH3CN)(PCy3)2], 31. The molecular structures of 11(R = tBu, L = PiPr3) and 26 were determined crystallographically.     

Ruthenium-cluster-mediated activation of all bonds of a methyl group of 6,6'-dimethyl-2,2'-bipyridine and 2,9-dimethyl-1,10-phenanthroline: transformation of the latter into a 2-alkenyl-9-methyl-1,10-phenanthroline ligand

The treatment of [Ru3(CO)12] with 6,6'-dimethyl-2,2'-bipyridine (Me2bipy) or 2,9-dimethyl-1,10-phenanthroline (Me2phen) in THF at reflux temperature gives the trinuclear dihydride complexes [Ru3(mu-H)2(mu3-L1)(CO)8] (L1 = HCbipyMe 1 a, HCphenMe 1 b), which result from the activation of two C-H bonds of a methyl group. The hexa-, hepta-, and pentanuclear derivatives [Ru6(mu3-H)(mu5-L2)(mu-CO)3(CO)13] (L2 = CbipyMe 2 a, CphenMe 2 b), [Ru7(mu3-H)(mu5-L2)(mu-CO)2(CO)16] (L2 = CbipyMe 3 a, CphenMe 3 b), and [Ru5(mu-H)(mu5-C)(mu-L3)(CO)13] (L3 = bipyMe 4 a, phenMe 4 b) can also be obtained by treating 1 a and 1 b with [Ru3(CO)12]. Compounds 2 a and 2 b have a basal edge-bridged square-pyramidal metallic skeleton with a carbyne-type C atom capping the four Ru atoms of the pyramid base. The structures of 3 a and 3 b are similar to those of 2 a and 2 b, respectively, but an additional Ru atom now caps a triangular face of the square-pyramidal fragment of the metallic skeleton. The most interesting feature of 2 a, 2 b, 3 a, and 3 b is that their carbyne-type C atoms were originally bound to three hydrogen atoms in Me2bipy or Me2phen and, therefore, they arise from the unprecedented activation of all three C-H bonds of C-bound methyl groups. The pentanuclear compounds 4 a and 4 b contain a carbide ligand surrounded by five Ru atoms in a distorted trigonal-bipyramidal environment. They are the products of a series of processes that includes the activation of all bonds (three C-H and one C-C) of organic methyl groups, and are the first examples of complexes having carbide ligands that arise from C-bonded methyl groups. The alkenyl derivatives [Ru5(mu5-C)(mu-p-MeC6H4CHCHphenMe)(CO)13] (5 b), [Ru5(mu-H)(mu5-C)(mu-p-MeC6H4CHCHphenMe)(p-tolC2)(CO)12] (6 b), and [Ru5(mu-H)(mu5-C)(mu-PhCHCHphenMe)(PhC2)(CO)12] (7 b) have been obtained by treating 4 b with p-tolyl- and phenylacetylene, respectively. Their heterocyclic ligands contain an alkenyl fragment in the position that was originally occupied by a methyl group. Therefore, these complexes are the result of the formal substitution of an alkenyl group for a methyl group of 2,9-dimethyl-1,10- phenanthroline.     

"Heavy fluorous" cyclopentadienes and cyclopentadienyl complexes with three to five ponytails: facile syntheses from polybromocyclopentadienyl complexes, phase properties, and electronic effects

The reactions between [(eta5-C5H(5-x)Br(x))M(CO)3] (M = Re, Mn; x = 1, 3, 4, 5) and [IZn[(CH2)(n)R(f8)]] (n = 2, 3; R(f8) = (CF2)7CF3) in the presence of [Cl2PdL2] catalysts give the title complexes [[eta5-C5H(5-x)[(CH2)(n)R(f8)]x]M(CO)3]. In the case of x = 5, the major product is actually [[eta5-C5H[(CH2)(n)R(f8)]4]M(CO)3], in which one of the bromides has been substituted by hydride. Minor amounts of multiple hydride substitution products are formed, all of them readily separable on fluorous silica gel. Irradiation of the manganese complexes in CF3C6H5/MeOH/ether gives uncoordinated cyclopentadienes, which can be deprotonated and reattached to other metals. Partition coefficients have been measured (CF3C6F11/toluene): complexes with three or more ponytails are highly fluorophilic, with values of > 99.8: < 0.2. The IR [symbol: see text]CO bands have been used to probe the inductive effects of the ponytails at the metal centers.     

Spectral, structural, and electrochemical properties of ruthenium porphyrin diaryl and aryl(alkoxycarbonyl) carbene complexes: influence of carbene substituents, porphyrin substituents, and trans-axial ligands

A wide variety of ruthenium porphyrin carbene complexes, including [Ru(tpfpp)(CR(1)R(2))] (CR(1)R(2) = C(p-C(6)H(4)Cl)(2) 1 b, C(p-C(6)H(4)Me)(2) 1 c, C(p-C(6)H(4)OMe)(2) 1 d, C(CO(2)Me)(2) 1 e, C(p-C(6)H(4)NO(2))CO(2)Me 1 f, C(p-C(6)H(4)OMe)CO(2)Me 1 g, C(CH==CHPh)CO(2)CH(2)(CH==CH)(2)CH(3) 1 h), [Ru(por)(CPh(2))] (por=tdcpp 2 a, 4-Br-tpp 2 b, 4-Cl-tpp 2 c, 4-F-tpp 2 d, tpp 2 e, ttp 2 f, 4-MeO-tpp 2 g, tmp 2 h, 3,4,5-MeO-tpp 2 i), [Ru(por)[C(Ph)CO(2)Et]] (por=tdcpp 2 j, tmp 2 k), [Ru(tpfpp)(CPh(2))(L)] (L = MeOH 3 a, EtSH 3 b, Et(2)S 3 c, MeIm 3 d, OPPh(3) 3 e, py 3 f), and [Ru(tpfpp)[C(Ph)CO(2)R](MeOH)] (R = CH(2)CH==CH(2) 4 a, Me 4 b, Et 4 c), were prepared from the reactions of [Ru(por)(CO)] with diazo compounds N(2)CR(1)R(2) in dichloromethane and, for 3 and 4, by further treatment with reagents L. A similar reaction of [Os(tpfpp)(CO)] with N(2)CPh(2) in dichloromethane followed by treatment with MeIm gave [Os(tpfpp)(CPh(2))(MeIm)] (3 d-Os). All these complexes were characterized by (1)H NMR, (13)C NMR, and UV/Vis spectroscopy, mass spectrometry, and elemental analyses. X-ray crystal structure determinations of 1 d, 2 a,i, 3 a, b, d, e, 4 a-c, and 3 d-Os revealed Ru==C distances of 1.806(3)-1.876(3) A and an Os==C distance of 1.902(3) A. The structure of 1 d in the solid state features a unique "bridging" carbene ligand, which results in the formation of a one-dimensional coordination polymer. Cyclic voltammograms of 1 a-c, g, 2 a-d, g-k, 3 b-d, 4 a, b, and 3 d-Os show a reversible oxidation couple with E(1/2) values in the range of 0.06-0.65 V (vs Cp(2)Fe(+/0)) that is attributable to a metal-centered oxidation. The influence of carbene substituents, porphyrin substituents, and trans-ligands on the Ru==C bond was examined through comparison of the chemical shifts of the pyrrolic protons in the porphyrin macrocycles ((1)H NMR) and the M==C carbon atoms ((13)C NMR), the potentials of the metal-centered oxidation couples, and the Ru==C distances among the various ruthenium porphyrin carbene complexes. A direct comparison among iron, ruthenium, and osmium porphyrin carbene complexes is made.     

Sigma-organyl complexes of ruthenium and osmium supported by a mixed-donor ligand

A series of vinyl, aryl, acetylide and silyl complexes [Ru(R)(kappa2-MI)(CO)(PPh3)2] (R = CH=CH2, CH=CHPh, CH=CHC6H4CH3-4, CH=CH(t)Bu, CH=2OH, C(C triple bond CPh)=CHPh, C6H5, C triple bond CPh, SiMe2OEt; MI = 1-methylimidazole-2-thiolate) were prepared from either [Ru(R)Cl(CO)(PPh3)2] or [Ru(R)Cl(CO)(BTD)(PPh3)2](BTD = 2,1,3-benzothiadiazole) by reaction with the nitrogen-sulfur mixed-donor ligand, 1-methyl-2-mercaptoimidazole (HMI), in the presence of base. In the same manner, [Os(CH=CHPh)(kappa2-MI)(CO)(PPh3)2] was prepared from [Os(CH=CHPh)(CO)Cl(BTD)(PPh3)2]. The in situ hydroruthenation of 1-ethynylcyclohexan-1-ol by [RuH(CO)Cl(BTD)(PPh3)2] and subsequent addition of the HMI ligand and excess sodium methoxide yielded the dehydrated 1,3-dienyl complex [Ru(CH=CHC6H9)(kappa2-MI)(CO)(PPh3)2]. Dehydration of the complex [Ru(CH=CHCPh2OH)(kappa2-MI)(CO)(PPh3)2] with HBF4 yielded the vinyl carbene [Ru(=CHCH=CPh2)(kappa2-MI)(CO)(PPh3)2]BF4. The hydride complexes [MH(kappa2-MI)(CO)(PPh3)2](M = Ru, Os) were obtained from the reaction of HMI and KOH with [RuHCl(CO)(PPh3)3] and [OsHCl(CO)(BTD)(PPh3)2], respectively. Reaction of [Ru(CH=CHC6H4CH3-4)(kappa2-MI)(CO)(PPh3)2] with excess HC triple bond CPh leads to isolation of the acetylide complex [Ru(C triple bond CPh)(kappa2-MI)(CO)(PPh3)2], which is also accessible by direct reaction of [Ru(C triple bond CPh)Cl(CO)(BTD)(PPh3)2] with 1-methyl-2-mercaptoimidazole and NaOMe. The thiocarbonyl complex [Ru(CPh = CHPh)Cl(CS)(PPh3)2] reacted with HMI and NaOMe without migration to yield [Ru(CPh= CHPh)(kappa2-MI)(CS)(PPh3)2], while treatment of [Ru(CH=CHPh)Cl(CO)2(PPh3)2] with HMI yielded the monodentate acyl product [Ru{eta(1)-C(=O)CH=CHPh}(kappa2-MI)(CO)(PPh3)2]. The single-crystal X-ray structures of five complexes bearing vinyl, aryl, acetylide and dienyl functionality are reported.     

C-C alpha insertion: insertion of an alkyne into the C-C single bond between the carbene-carbon atom and the alpha-carbon atom of a Fischer carbene complex by an unprecedented metalla(di-pi-methane) skeletal rearrangement

The first examples of insertion of a C(triple bond)C bond of an alkyne into a C(carbene)-Calpha single bond of a carbene complex (C-Calpha insertion) are reported. (prim-Alkyl)carbene complexes [(OC)(5)M=C(OEt)CH(2)R] (1 a-f; M=Cr, W; R=nPr, C(7)H(7), Ph) undergo C-Calpha insertion of electron-deficient alkynes [PhC(triple bond)CC(XEt)NMe(2)]BF(4) (5 a,b; X=O, S) to give zwitterionic carbiminium carbonylmetalates 3 a-g, which are thermally transformed into (CO)(4)M chelate carbene complexes 4 a-g by elimination of CO. The overall reaction is highly regio- and stereoselective. It involves an unprecedented metalla(di-pi-methane) rearrangement as the key step.     

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.     

Primary and secondary phosphane complexes of metalloporphyrins: isolation, spectroscopy, and X-ray crystal structures of ruthenium and osmium porphyrins binding phenyl- or diphenylphosphane

[Ru(II)(por)(PH(n)Ph(3-n))2], [Os(II)(por)(CO)(PH(n)Ph(3-n))] (n=1, 2), and [Os(II)(F20-tpp){P(OH)Ph2}(PHPh2)] (F20-tpp=5,10,15,20-tetrakis(pentafluorophenyl)porphyrinato dianion) were prepared from the reaction of [M(II)(por)(CO)] (M=Ru, Os) or [Os(VI)(por)O2] with the respective primary/secondary phosphane and characterized by 1H NMR, 31P NMR, UV/Vis, and IR spectroscopy, mass spectrometry, and elemental analysis. The reaction of [Os(VI)(por)O2] with PHPh2 also gave minor amounts of [Os(II)(por){P(OH)Ph2}2]. [Ru(II)(F20-tpp)(PH2Ph)2] exhibits a remarkable stability toward air and shows a reversible metal-centered oxidation couple at E(1/2)=0.39 V versus [Cp2Fe](+/0) in the cyclic voltammogram. The structures of [Ru(II)(F20-tpp)(PH2Ph)2] x 2CH2Cl2, [Ru(II)(4-Cl-tpp)(PHPh2)2] x 2CH2Cl2 (4-Cl-tpp=5,10,15,20-tetrakis(p-chlorophenyl)porphyrinato dianion), [Ru(II)(F20-tpp)(PHPh2)2], and [Os(II)(F20-tpp){P(OH)Ph2}2] were determined by X-ray crystallography and feature Ru-P distances of 2.3397(11)-2.3609(9) A and an Os-P distance of 2.369(2) A.     

Syntheses, crystal structures, and magneto-structural correlations of novel Cu(II) complexes containing a planar [Cu(mu-L1)]2 (HL1 = 3-(2-pyridyl)pyrazole) unit: from dinuclear to tetranuclear and then to one-dimensional compounds

Seven new Cu(II) complexes based on a binuclear planar unit [Cu(mu-L(1))](2), [[Cu(mu-L(1))(NO(3))(H(2)O)](2) (1), [Cu(mu-L(1))(HL(1))(ClO(4))](2) (2), [Cu(4)(mu-L(1))(6)(NO(3))(2)] (3), [Cu(4)(mu-L(1))(6)(L(1))(2)] (4), [Cu(4)(mu-L(1))(6)(mu-L(2))](n) (5), [Cu(4)(mu-L(1))(6)(mu-L(3))](n) (6), [[Cu(4)(mu-L(1))(4)(mu-L(4))(2)](H(2)O)(3)](n) (7) (HL(1) = 3-(2-pyridyl)pyrazole, L(2) = 1,8-naphthalenedicarboxylate, L(3) = terephthalate, L(4) = 2,6-pyridinedicarboxylate)}, have been synthesized and characterized by elemental analysis, IR, and X-ray diffraction. In 1 and 2, the Cu(II) centers are linked by deprotonated pyrazolyl groups to form dinuclear structures. 3 and 4 have similar gridlike tetranuclear structures in which two additional deprotonated L(1) ligands bridge two [Cu(mu-L(1))](2) units perpendicularly. 5 and 6 consist of similar one-dimensional (1-D) chains in which gridlike tetranuclear copper(II) units similar to that of 3 are further linked by L(2) or L(3) ligands, respectively. And, in 7, L(4) ligands link [Cu(mu-L(1))](2) binuclear units to form a tetranuclear gridlike structure in chelating/bridging mode and simultaneously bridge the tetranuclear units to form a 1-D chain. The magnetic properties of all complexes were studied by variable-temperature magnetic susceptibility and magnetization measurements. The obtained parameters of J range from -33.1 to -211 cm(-1), indicating very strong antiferromagnetic coupling between Cu(II) ions. The main factor that affects the |J| parameter is the geometry of the Cu(N(2))(2)Cu entity. From the magnetic point of view, 1 and 2 feature "pure" dinuclear, 3 and 5 tetranuclear, and 4, 6, and 7 pseudodinuclear moieties.     

Non-innocent behaviour of ancillary and bridging ligands in homovalent and mixed-valent ruthenium complexes [A2Ru(mu-L)RuA2]n, A = 2,4-pentanedionato or 2-phenylazopyridine, L(2-) = 2,5-bis(2-oxidophenyl)pyrazine

Structurally characterised 2,5-bis(2-hydroxyphenyl)pyrazine (H2L) can be partially or fully deprotonated to form the complexes [(acac)2Ru(mu-L)Ru(acac)2], [1], acac = acetylacetonato = 2,4-pentanedionato, [(pap)2Ru(mu-L)Ru(pap)2](ClO4)2, [2](ClO4)2, pap = 2-phenylazopyridine, or [(pap)2Ru(HL)](ClO4), [3](ClO4). Several reversible oxidation and reduction processes were observed in each case and were analysed with respect to oxidation state alternatives through EPR and UV-VIS-NIR spectroelectrochemistry. In relation to previously reported compounds with 2,2'-bipyridine as ancillary ligands the complex redox system [1]n is distinguished by a preference for metal-based electron transfer whereas the systems [2]n and [3]n favour an invariant Ru(II) state. Accordingly, the paramagnetic forms of [1]n, n = -, 0, +, exhibit metal-centred spin whereas the odd-electron intermediates [2]+, [2](3+) and [3] show radical-type EPR spectra. A comparison with analogous complexes involving the 3,6-bis(2-oxidophenyl)-1,2,4,5-tetrazine reveals the diminished pi acceptor capability of the pyrazine-containing bridge.     

Rhenium ethoxy- and hydroxycarbene complexes with thiophene substituents

Reaction of mono- and dilithiated thiophene (a), bithiophene (b) and 2,5-dibromothiophene (c) with [Re(2)(CO)(10)] afforded, after subsequent alkylation with triethyloxonium tetrafluoroborate, tetra- and binuclear Fischer carbene complexes, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)X}], n = 1, X = H (1a); n = 2, X = H (1b); n = 1, X = Br (1c); n = 1, X = C(OEt)Re(2)(CO)(9), (2a); n = 2, X = C(OEt)Re(2)(CO)(9) (2b), as major products. The dirhenium acylate intermediates from this reaction not only gave the expected novel ethoxycarbene complexes with alkylation but after rhenium-rhenium bond breaking afforded a number of minor products. The (1)H NMR spectrum of the crude reaction mixture revealed the formation of four metal hydride complexes and aldehydes. Protonation with HBF(4) instead of alkylation with Et(3)OBF(4) significantly increased the yields of the hydride complexes, which enabled the positive identification of three of these complexes. In addition to the known compounds [Re(CO)(5)H] and [Re(3)(CO)(14)H] (3), a unique complex displaying a hydroxycarbene fragment connected to an acyl fragment via an O-H···O hydrogen bond and a Re···H···Re bond linking the two Re centers, [(μ-H){Re(CO)(4)C(OH){C(4)H(2)S}(n)H}{Re(CO)(4)C(O){C(4)H(2)S}(n)H}], n = 1 (4a) or n = 2 (4b), were isolated. The formation of thiophene aldehydes, H{C(O)}(m){C(4)H(2)S}(n)C(O)H (m = 0 or 1 and n = 1 or 2), were observed and the novel monocarbene complexes with terminal aldehyde groups, [Re(2)(CO)(9){C(OEt){C(4)H(2)S}(n)C(O)H}], n = 1 (5a) and n = 2 (5b) could be isolated. A higher yield of 5b was obtained after stirring crystals of 2b in wet THF. The crystal structures of 1a, 2a, 4a and 5b are reported.     

Multi-dimensional transition-metal coordination polymers of 4,4'-bipyridine-N,N'-dioxide: 1D chains and 2D sheets

Reaction of 4,4'-bipyridine -N, N' -dioxide (L) with a variety of transition-metal salts in MeOH affords a range of coordination polymer products. For the complexes [FeCl 3(mu-L)] infinity, 1, and ([Cu(L) 2(OHMe) 2(mu-L)].2PF 6. n(solv)) infinity, 2, 1D chain structures are observed, whereas ([Mn(mu-L) 3].2ClO 4) infinity, 3, and ([Cu(mu-L) 3].2BF 4) infinity, 4, both show 2D sheet architectures incorporating an unusual 3 (6)- hxl topology. The more common 4 (4)- sql topology is observed in [Cd(ONO 2) 2(mu-L) 2] infinity, 5, ([Cu(OHMe) 2(mu-L) 2].2ZrF 5) infinity, 6, ([Cu(L) 2(mu-L) 2].2EF 6) infinity ( 7 E = P; 8 E = Sb), and ([Et 4N][Cu(OHMe) 0.5(mu-L) 2(mu-FSiF 4F) 0.5].2SbF 6. n(solv)) infinity, 9. In 6, the [ZrF 5] (-) anion, formed in situ from [ZrF 6] (2-), forms 1D anionic chains ([ZrF 5] (-)) infinity of vertex-linked octahedra, and these chains thread through a pair of inclined polycatenated ([Cu(OHMe) 2(mu-L) 2] (2+)) infinity 4 (4)- sql grids to give a rare example of a triply intertwined coordination polymer. 9 also shows a 3D matrix structure with 4 (4)- sql sheets of stoichiometry ([Cu(L) 2] (2+)) infinity coordinatively linked by bridging [SiF 6] (2-) anions to give a structure of 5-c 4 (4).6 (6)- sqp topology. The mononuclear [Cu(L) 6].2BF 4 ( 10) and [Cd(L) 6].2NO 3 ( 11) and binuclear complexes [(Cu(L)(OH 2)) 2(mu-L) 2)].2SiF 6. n(solv), 12, are also reported. The majority of the coordination polymers are free of solvent and are nonporous. Thermal treatment of materials that do contain solvent results in structural disintegration of the complex structures giving no permanent porosity.     

Synthesis, characterization, and structural studies of multimetallic ferrocenyl carbene complexes of group VII transition metals

Fischer carbene complexes of the group VII transition metals (Mn and Re) containing at least two or three different transition metal substituents, all in electronic contact with the carbene carbon atom, were synthesized. The structural features and their relevance to bonding in the carbene multimetal compounds were investigated, as they represent indicators of possible reactivity sites in polymetallic carbene assemblies. For complexes of the type [ML(x){C(OR)R'}] (ML(x) = MnCp(CO)(2) or Re(2)(CO)(9)), ferrocenyl (Fc) was chosen as the R' substituent, while the OR substituent was systematically varied between an ethoxy or a titanoxy group, to yield the complexes 1a (ML(x) = MnCp(CO)(2), R = Et, R' = Fc), 2a (ML(x) = MnCp(CO)(2), R = TiCp(2)Cl, R' = Fc), 3a (ML(x) = Re(2)(CO)(9), R = Et, R' = Fc), and 4a (ML(x) = Re(2)(CO)(9), R = TiCp(2)Cl, R' = Fc). Direct lithiation of the ferrocene with n-BuLi/TMEDA at elevated temperatures, followed by the Fischer method of carbene preparation, resulted in formation of the novel biscarbene complexes with bridging ferrocen-1,1'-diyl (Fc') substituents [{π-Fe(C(5)H(4))(2)-C,C'}{C(OEt)ML(x)}(2)] (1b, ML(x) = MnCp(CO)(2); 3b, ML(x) = Re(2)(CO)(9)) or the unusual bimetallacyclic bridged biscarbene complexes [{π-TiCp(2)O(2)-O,O'}{π-Fe(C(5)H(4))(2)-C,C'}{CML(x)}(2)] (2b, ML(x) = MnCp(CO)(2); 4b, ML(x) = Re(2)(CO)(9)). The target compounds that were isolated displayed a variety of different geometric isomers and conformations. The greater reactivity of the binary dirhenium acylates in solution, compared to that of the cyclopentadienyl manganese acylate, resulted in a complex reaction mixture. Although the stabilization of hydroxycarbene or hydrido-acyl intermediates of dirhenium carbonyls could not be achieved, their existence in solution was confirmed by the isolation of [(π-H)(2)-(Re(CO)(4){C(O)Fc})(2)] (8), the unique dichloro-bridged biscarbene complex fac-[(π-Cl)(2)-(Re(CO)(3){C(OEt)Fc})(2)] (6), the known hydrido complex [Re(3)(CO)(14)H] (5), the acyl complex [Re(CO)(5){C(O)Fc}] (7), and the aldehyde-functionalized eq-[Re(2)(CO)(9){C(OTiCp(2)Cl)(Fc'CHO)}] (9).     

Remarkable reactions of cyclooctatetraene diiron-bridging carbyne complexes with amino and amido compounds: nucleophilic addition to and breaking of the cyclooctatetraene ring

The reactions of the cationic, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(8)-C(8)H(8))]BF(4) (1, Ar=C(6)H(5); 2, Ar=p-CH(3)C(6)H(4); 3, Ar=p-CF(3)C(6)H(4)) with LiN(C(6)H(5))(2) in THF at low temperature gave novel N-nucleophilic-addition products, namely, the neutral, diiron-bridging carbyne complexes [Fe(2)(mu-CAr)(CO)(4)(eta(7)-C(8)H(8)N(C(6)H(5))(2))] (4, Ar=C(6)H(5); 5, Ar=p-CH(3)C(6)H(4); 6, Ar=p-CF(3)C(6)H(4))). Cationic bridging carbyne complexes 1-3 react with (C(2)H(5))(2)NH, (iC(3)H(7))(2)NH, and (C(6)H(11))(2)NH under the same conditions with ring cleavage of the COT ligand to produce the novel diiron-bridging carbene inner salts [Fe(2)[mu-C(Ar)C(8)H(8)NR(2)](CO)(4)] (7, Ar=C(6)H(5), R=C(2)H(5); 8, Ar=p-CH(3)C(6)H(4), R=C(2)H(5); 9, Ar=p-CF(3)C(6)H(4), R=C(2)H(5); 10, Ar=C(6)H(5), R=iC(3)H(7); 11, Ar=p-CH(3)C(6)H(4), R=iC(3)H(7); 12, Ar=p-CF(3)C(6)H(4), R=iC(3)H(7); 13, Ar=C(6)H(5), R=C(6)H(11); 14, Ar=p-CH(3)C(6)H(4), R=C(6)H(11), 15, Ar=p-CF(3)C(6)H(4), R=C(6)H(11)). Piperidine reacts similarly with cationic carbyne complex 3 to afford the corresponding bridging carbene inner salt [Fe(2)[mu-C(Ar)C(8)H(8)N(CH(2))(5)](CO)(4)] (16). Compound 9 was transformed into a new diiron-bridging carbene inner salt 17, the trans isomer of 9, by heating in benzene. Unexpectedly, the reaction of C(6)H(5)NH(2) with 2 gave a novel COT iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NHC(6)H(5)](mu-CO)(CO)(3)(eta(8)-C(8)H(8))] (18). However, the analogous reactions of 2-naphthylamine with 2 and of p-CF(3)C(6)H(4)NH(2) with 3 produce novel chelated iron-carbene complexes [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(10)H(7)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (19) and [Fe(2)[=C(C(6)H(4)CF(3)-p)NC(6)H(4)CF(3)-p](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (20), respectively. Compound 18 can also be transformed into the analogous chelated iron-carbene complex [Fe(2)[=C(C(6)H(4)CH(3)-p)NC(6)H(5)](CO)(4)(eta(2):eta(3):eta(2)-C(8)H(9))] (21). The structures of complexes 6, 9, 15, 17, 18, and 21 have been established by X-ray diffraction studies.     

Multimetal Fischer carbene complexes of Group VI transition metals: synthesis, structure and substituent effect investigation

Fischer carbene complexes of tungsten with substituents containing up to two additional different transition metals, with all the metals in electronic contact with the carbene carbon atom, were synthesised and studied both in solution and in the solid state. For the complexes of the type [W(CO)(5){C(OR')R}], the substituents chosen were heteroaromatic 2-benzo[b]thienyl (2-BT), or 2-BT π-bonded to a chromium tricarbonyl fragment ([Cr(CO)(3)(2-η(6)-BT)]) or ferrocenyl (Fc) as the R-substituent, while the OR'-substituent was systematically varied between an ethoxy or a titanoxy group, to yield the complexes 1b (R' = Et, R = 2-BT), 2b (R' = Et, R = [Cr(CO)(3)(2-η(6)-BT)]), 3b (R' = TiCp(2)Cl, R = 21-BT), 4b (R' = TiCp(2)Cl, R = [Cr(CO)(3)(2-η(6)-BT)]), 5b (R' = Et, R = Fc) and 6b (R' = TiCp(2)Cl, R = Fc). The structural features and their relevance to bonding in the multimetal carbene compounds of both these tungsten and the analogous chromium complexes were investigated as they represent indicators of possible reactivity sites in multimetal carbene assemblies. The possibility of using DFT calculations to quantify the effect of metal-containing substituents on the carbene ligands was tested and correlated with experimental parameters by employing methods such as vibrational spectroscopy, molecular orbital analysis, and cyclic voltammetry.     

Reactivity of alkynes containing alpha-hydrogen atoms with a triruthenium hydrido carbonyl cluster: alkenyl versus allyl cluster derivatives

The reactions of the hydrido-triruthenium cluster complex [Ru3(mu-H)(mu3-kappa(2)-HNNMe2)(CO)9] (1; H2NNMe2 = 1,1-dimethylhydrazine) with alkynes that have alpha-hydrogen atoms give trinuclear derivatives containing edge-bridging allyl or face-capping alkenyl ligands. Under mild conditions (THF, 70 degrees C) the isolated products are as follows: [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(3)-1-syn-Me-3-anti-EtC3H3)(mu-CO)2(CO)6] (2) and [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(3)-1-syn-Me-3-syn-EtC3H3)(mu-CO)2(CO)6] (3) from 3-hexyne; [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(3)-3-anti-PhC3H4)(mu-CO)2(CO)6] (4), [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(2)-MeCCHPh)(mu-CO)2(CO)6] (5) and [Ru3(mu3-kappa(2)-HNNMe2)(mu3-kappa(2)-PhCCHMe)(mu-CO)2(CO)6] (6) from 1-phenyl-1-propyne; [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(2)-3-anti-PrC3H4)(mu-CO)2(CO)6] (7), [Ru3(mu3-kappa(2)-HNNMe2)(mu3-kappa(2)-BuCCH2)(mu-CO)2(CO)6] (8), and [Ru3(mu3-kappa(2)-HNNMe2)(mu3-kappa(2)-HCCHBu)(mu-CO)2(CO)6] (9) from 1-hexyne; [Ru3(mu3-kappa(2)-HNNMe2)(mu3-kappa(2)-HOH2CCCH2)(mu-CO)2(CO)6] (10) from propargyl alcohol; and [Ru3(mu3-kappa(2)-HNNMe2)(mu3-kappa(2)-MeOCH2CCH2)(mu-CO)2(CO)6] (11) from 3-methoxy-1-propyne. The regioselectivity of these reactions depends upon the nature of the alkyne reagent, which affects considerably the kinetic barriers of important reaction steps and the stability of the final products. It has been established that the face-capped alkenyl derivatives are not precursors to the allyl products, which are formed via edge-bridged alkenyl intermediates. At higher temperature (toluene, 110 degrees C), the complexes that have allyl ligands with an anti substituent are isomerized into allyl derivatives with that substituent in the syn position, for example, 4 into [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(3)-3-syn-PhC3H4)(mu-CO)2(CO)6] (14). The diene complex [Ru3(mu-H)(mu3-kappa(2)-HNNMe2)(mu-kappa(4)-trans-EtC4H5)(CO)7] (13) has been obtained from the thermolysis of compounds 2 and 7 at 110 degrees C (3 and [Ru3(mu3-kappa(2)-HNNMe2)(mu-kappa(2)-3-syn-PrC3H4)(mu-CO)2(CO)6] (12) are also formed in these reactions). A DFT theoretical study has allowed a comparison of the thermodynamic stabilities of isomeric compounds and has helped rationalize the experimental results. Mechanistic proposals for the synthesis of the allyl complexes and their isomerization processes are also provided.     

Heterobi‐ and ‐trinuclear Complexes with an Amino(ethynyl)carbene as Bridging Ligand

The sequential reaction of the amino(trimethylsilyl)carbene complex [(CO)₅W=C(NH₂)C≡CSiMe₃] ( 1 ) with nBuLi and [I‐Fe(CO)₂Cp] affords the C(carbene)‐N bridged heterobinuclear complex [(CO)₅W=C{NHFe(CO)₂Cp}C≡CSiMe₃] ( 2 ). Desilylation of 1 is achieved by treatment with KF in THF/MeOH. From the reaction of the resulting complex [(CO)₅W=C(NH₂)C≡CH] ( 3 ) with nBuLi and [I‐Fe(CO)₂Cp] two binuclear WFe compounds in a ratio of approximately 1:1 are obtained: the C(carbene)‐C≡C bridged complex 4 and the C(carbene)‐N bridged complex 5 . Repetition of the deprotonation/metallation sequence yields the trinuclear WFe₂ complex 6 . One Fe(CO)₂Cp fragment in 6 is bonded to the amino group and the other one to the terminal carbon atom of the ethynyl substituent. The analogous reaction of 3 with nBuLi and [Br‐Ni(PMe₂Ph)₂Mes] gives a ca. 1:1 mixture of two heterobinuclear complexes ( 7 and 8 ). Complex 7 is bridged by the C(carbene)‐C≡C and complex 8 by the C(carbene)‐N fragment. Subsequent reaction of 7 with BuLi and [Br‐Ni(PMe₂Ph)₂Mes] finally affords the trinuclear WNi₂ complex 9 related to 6 . The solid‐state structure of 2 is established by an X‐ray diffraction analysis. The spectroscopic data of the bi‐ and trinuclear complexes indicate electronic communication between the metal centers through the bridging group.     

Oxidation-promoted synthesis of ferrocenyl planar chiral rhodium(iii) complexes for C–H functionalization catalysis

The chemical oxidation of rhodium(i) complexes [Rh(L)(COD)][BF4], where L is a ferrocenyl phosphine/N-heterocyclic carbene ligand, with 2 equiv. of a triaryl-aminium salt [(4-BrC6H4)3N][BF4] in acetonitrile gave planar chiral, air-stable [Rh(L–H)(MeCN)3][BF4]2 complexes where the ferrocene (C5H4CH2ImR or C5H4CH2BImCH2Mes) ring has been C–H activated at the position 2 in good to excellent yields. An important reactivity difference between our complexes and the ubiquitous [Cp*Rh(MeCN)3]X2 complex has been observed in the Grignard-type arylation of 4-nitrobenzaldehyde.     

Subtle reactivity patterns of non-heteroatom-substituted manganese alkynyl carbene complexes in the presence of phosphorus probes

The non-heteroatom-substituted manganese alkynyl carbene complexes (eta5-MeC5H4)(CO)2Mn=C(R)C[triple bond]CR'(3; 3a: R = R'= Ph, 3b: R = Ph, R'= Tol, 3c: R = Tol, R'= Ph) have been synthesised in high yields upon treatment of the corresponding carbyne complexes [eta5-MeC5H4)(CO)2Mn[triple bond]CR][BPh4]([2][BPh4]) with the appropriate alkynyllithium reagents LiC[triple bond]CR' (R'= Ph, Tol). The use of tetraphenylborate as counter anion associated with the cationic carbyne complexes has been decisive. The X-ray structures of (eta5-MeC5H4)(CO)2Mn=C(Tol)C[triple bond]CPh (3c), and its precursor [(eta5-MeC5H4)(CO)2Mn=CTol][BPh4]([2b](BPh4]) are reported. The reactivity of complexes toward phosphines has been investigated. In the presence of PPh3, complexes act as a Michael acceptor to afford the zwitterionic sigma-allenylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R)=C=C(PPh3)R' (5) resulting from nucleophilic attack by the phosphine on the remote alkynyl carbon atom. Complexes 5 exhibit a dynamic process in solution, which has been rationalized in terms of a fast [NMR time-scale] rotation of the allene substituents around the allene axis; metrical features within the X-ray structure of (eta5-MeC5H4)(CO)2MnC(Ph)=C=C(PPh3)Tol (5b) support the proposal. In the presence of PMe3, complexes undergo a nucleophilic attack on the carbene carbon atom to give zwitterionic sigma-propargylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R)(PMe3)C[triple bond]CR' (6). Complexes 6 readily isomerise in solution to give the sigma-allenylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R')=C=C(PMe3)R (7) through a 1,3 shift of the [(eta5-MeC5H4)(CO)2Mn] fragment. The nucleophilic attack of PPh2Me on 3 is not selective and leads to a mixture of the sigma-propargylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R)(PPh(2)Me)C[triple bond]CR' (9) and the sigma-allenylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R)=C=C(PPh(2)Me)R' (10). Like complexes 6, complexes 9 readily isomerize to give the sigma-allenylphosphonium complexes (eta5-MeC5H4)(CO)2MnC(R')=C=C(PPh2Me)R'). Upon gentle heating, complexes 7, and mixtures of 10 and 10' cyclise to give the sigma-dihydrophospholium complexes (eta5-MeC5H4)(CO)2MnC=C(R')PMe2CH2CH(R)(8), and mixtures of complexes (eta5-MeC5H4)(CO)2MnC=C(Ph)PPh2CH2CH(Tol)(11) and (eta5-MeC5H4)(CO)2MnC=C(Tol)PMe2CH2CH(Ph)(11'), respectively. The reactions of complexes 3 with secondary phosphines HPR(1)(2)(R1= Ph, Cy) give a mixture of the eta2-allene complexes (eta5-MeC5H4)(CO)2Mn[eta2-{R(1)(2)PC(R)=C=C(R')H}](12), and the regioisomeric eta4-vinylketene complexes [eta5-MeC5H4)(CO)Mn[eta4-{R(1)(2)PC(R)=CHC(R')=C=O}](13) and (eta5-MeC5H4)(CO)Mn[eta4-{R(1)(2)PC(R')=CHC(R)=C=O}](13'). The solid-state structure of (eta5-MeC5H4)(CO)2Mn[eta2-{Ph2PC(Ph)=C=C(Tol)H}](12b) and (eta5-MeC5H4)(CO)Mn[eta4-{Cy2PC(Ph)=CHC(Ph)=C=O}](13d) are reported. Finally, a mechanism that may account for the formation of the species 12, 13, and 13' is proposed.     

The bridging function of an apparently nonbridging ligand: dinuclear rhodium complexes with Rh(mu-SbR3)Rh as a molecular unit

Novel dinuclear rhodium complexes of the general composition [Rh2Cl2(mu-CRR')2(mu-SbiPr3)] (4-6) were prepared by thermolysis of the mononuclear precursors trans-[RhCl(=CRR')(SbiPr3)2] in excellent yield. The X-ray crystal structure analysis of 4 (R = R' = Ph) confirms the symmetrical bridging position of the stibane ligand. Related compounds [Rh2Cl2(mu-CPh2)(mu-CRR')(mu-SbiPr3)] (7, 8) with two different carbene units were obtained either from trans-[RhCl(=CPh2)(SbiPr3)2] (1) and RR'CN2 or by a conproportionation of 4 and 5 (R = R' = p-Tol) or 4 and 6 (R= Ph, R' = p-Tol), respectively. While CO reacts with 4 to give the polymeric product [[RhCl(CPh2)(CO)]n] (9), tert-butyl isocyanide replaces the bridging stibane and yields [Rh2Cl2(mu-CPh2)2(mu-CNtBu)] (10). The reaction of 4 with tertiary phosphanes PR3 leads to complete bridge cleavage and affords the mononuclear compounds trans-[RhCl(=CPh2)(PR3)2] (11-15). In contrast, treatment of 4 with SbMe3 and SbEt3 yields the related triply bridged complexes [Rh2Cl2(mu-CPh2)2(mu-SbR3)] (16, 17) by substitution of SbiPr3 for the smaller stibanes. The displacement of the chloro ligands in 4-6 and 10 by n5-cyclopentadienyl gives the dinuclear complexes [(n5-C5H5)2Rh2(mu-CRR')2] (18-20) and [(n5-C5H5)2Rh2(mu-CPh2)2(mu-CNtBu)] (21), of which 18 (R = R' = Ph) was characterized crystallographically.