Heterobimetallic, cubane-like Mo(3)S(4)M' cluster cores containing the noble metals M' = Ru, Os, Rh, Ir. Unprecedented tri(mu-carbonyl) bridge between ruthenium atoms in [(eta(5)-Cp')(3)Mo(3)S(4)Ru)2(mu-CO)3]2+

Reaction of the methylcyclopentadienyl (Cp') cluster compound [(eta(5)-Cp')(3)Mo(3)S(4)][pts] (pts = p-toluenesulfonate) with noble metal alkene complexes resulted in the formation of four new heterobimetallic cubane-like Mo(3)S(4)M' cluster cores (M' = Ru, Os, Rh, Ir). Thus, reaction with [(1,5-cod)Ru(CO)(3)] or [(1,3-cod)Os(CO)(3)] (cod = cyclooctadiene) afforded [(eta(5)-Cp')(3)Mo(3)S(4)M'(CO)(2)][pts] (M' = Ru: [1][pts]; M' = Os: [2][pts]). When [1][pts] was kept in CH(2)Cl(2)/pentane solution, partial loss of carbonyl ligands occurred and the carbonyl-bridged dicubane cluster [((eta(5)-Cp')(3)Mo(3)S(4)Ru)(2)(mu-CO)(3)][pts](2) was isolated. An X-ray crystal structure revealed the presence of the hitherto unobserved Ru(mu-CO)(3)Ru structural element. The formation of cluster compounds containing Mo(3)S(4)Rh and Mo(3)S(4)Ir cores was achieved in boiling methanol by reacting [(eta(5)-Cp')(3)Mo(3)S(4)][pts] with [M'Cl(cyclooctene)(2)](2) (M' = Rh, Ir) in the presence of PPh(3). In this way [(eta(5)-Cp')(3)Mo(3)S(4)M'Cl(PPh(3))][pts] (M' = Rh, Ir) could be isolated. An alternative route to the Mo(3)S(4)Rh cluster core was found in the reaction of [(eta(5)-Cp')(3)Mo(3)S(4)][pts] with [RhCl(1,5-cod)](2), which yielded [(eta(5)-Cp')(3)Mo(3)S(4)Rh(cod)][pts](2) ([7][pts](2)). Substitution of the cod ligand in [7][pts](2) by 1,3-bis(diphenylphosphanyl)propane (dppp) gave [(eta(5)-Cp')(3)Mo(3)S(4)Rh(dppp)][pts](2).     

Tetranuclear [Rh4(mu-PyS2)2(diolefin)4] complexes as building blocks for new inorganic architectures: synthesis of coordination polymers and heteropolynuclear complexes with electrophilic d8 and d10 metal fragments

The reaction of [Rh4(mu-PyS2)2(cod)4] (PyS2 = 2,6-pyridinedithiolate, cod = 1,5-cyclooctadiene) with CF3SO3Me gave the cationic complex [Rh(4)(mu-PyS(2)Me)(2)(cod)4][CF3SO3]2 (1) with two 6-(thiomethyl)pyridine-2-thiolate bridging ligands from the attack of Me+ at the terminal sulfur atoms of the starting material. Under identical conditions [Rh4(mu-PyS2)2(tfbb)4] (tfbb = tetrafluorobenzobarrelene) reacted with CF3SO3Me to give the mixed-ligand complex [Rh(4)(mu-PyS2)(mu-PyS2Me)(tfbb)4][CF3SO3] 2. The nucleophilicity of the bridging ligands in the complexes [Rh4(mu-PyS2)2(diolefin)4] was exploited to prepare heteropolynuclear species. Reactions with [Au(PPh3)(Me2CO)][ClO4] gave the hexanuclear complexes [(PPh3)2Au2Rh4(mu-PyS2)2(diolefin)4][ClO4]2 (diolefin = cod (3), tfbb (4)). The structure of 4, solved by X-ray diffraction methods, showed the coordination of the [Au(PPh3)]+ fragments to the peripheral sulfur atoms in [Rh4(mu-PyS2)2(diolefin)4] along with their interaction with the neighbor rhodium atoms. Neutral coordination polymers of formula [ClMRh4(mu-PyS2)2(diolefin)4]n (M = Cu (5, 6), Au (7)) result from the self-assembly of alternating [Rh4(mu-PyS2)2(diolefin)4] ([Rh4]) blocks and MCl linkers. The formation of the infinite polymetallic chains was found to be chiroselective for M = Cu; one particular chain contains exclusively homochiral [Rh4] complexes. Cationic heterometallic coordination polymers of formula [MRh4(mu-PyS2)2(diolefin)4]n[BF4]n (M = Ag (8, 9), Cu (10, 11)) and [Rh5(mu-PyS2)2(diolefin)5]n[BF4]n (12, 13) result from the reactions of [Rh4] with [Cu(CH2CN)4]BF4, AgBF4, and [Rh(diolefin)(Me2CO)2]BF4, respectively. The heterometallic coordination polymers exhibit a weak electric conductivity in the solid state in the range (1.2-2.8) x 10(-7) S cm(-1).     

Triazenide-bridged rhodium-palladium complexes: [I2Rh(mu-p-MeC6H4NNNC6H4Me-p)2Pd(eta(3)-C3H5)]-, a stable paramagnetic [RhPd]4+ species with a localised Rh(II) centre

Deprotonation of mixtures of the triazene complexes [RhCl(CO)2(p-MeC6H4NNNHC6H4Me-p)] and [PdCl(eta(3)-C3H5)(p-MeC6H4NNNHC6H4Me-p)] or [PdCl2(PPh3)(p-MeC6H4NNNHC6H4Me-p)] with NEt3 gives the structurally characterised heterobinuclear triazenide-bridged species [(OC)2Rh(mu-p-MeC6H4NNNC6H4Me-p)2PdLL'] {LL' = eta(3)-C3H5 1 or Cl(PPh3) 2} which, in the presence of Me3NO, react with [NBu(n)4]I, [NBu(n)4]Br, [PPN]Cl or [NBu(n)4]NCS to give [(OC)XRh(mu-p-MeC6H4NNNC6H4Me-p)2PdCl(PPh3)]- (X = I 3-, Br 4-, Cl 5- or NCS 6-) and [NBu(n)4][(OC)XRh(mu-p-MeC6H4NNNC6H4Me-p)2Pd(eta(3)-C3H5)], (X = I 7- or Br 8-). The allyl complexes 7- and 8- undergo one-electron oxidation to the corresponding unstable neutral complexes 7 and 8 but, in the presence of the appropriate halide, oxidative substitution results in the stable paramagnetic complexes [NBu(n)4][X2Rh(mu-p-MeC6H4NNNC6H4Me-p)2Pd(eta(3)-C3H5)], (X = I 9- or Br 10-). X-Ray structural (9-), DFT and EPR spectroscopic studies are consistent with the unpaired electron of 9- and 10- localised primarily on the Rh(II) centre of the [RhPd]4+ core, which is susceptible to oxygen coordination at low temperature to give Rh(III)-bound superoxide.     

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.     

Synthesis and properties of Rh(I) and Ir(I) distibine complexes with organometallic co-ligands

The first series of Rh(I) distibine complexes with organometallic co-ligands is described, including the five-coordinate [Rh(cod)(distibine)Cl], the 16-electron planar cations [Rh(cod)(distibine)]BF4 and [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 and the five-coordinate [Rh(CO)(distibine)2][Rh(CO)2Cl2] (distibine=R2Sb(CH2)3SbR2, R=Ph or Me, and o-C6H4(CH2SbMe2)2). The corresponding Ir(I) species [Ir(cod)(distibine)]BF4 and [Ir{Ph2Sb(CH2)3SbPh2}2]BF4 have also been prepared. The complexes have been characterised by 1H and 13C{1H} NMR and IR spectroscopy, electrospray mass spectrometry and microanalysis. The crystal structure of the anion exchanged [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF(6).3/4CH2Cl2 is also described. The methyl-substituted distibine complexes are less stable than the complexes of Ph2Sb(CH2)3SbPh2, with C-Sb fission occurring in some of the complexes of the former. The salts [Rh(CO){Ph2Sb(CH2)3SbPh2}2]PF6 and [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 undergo oxidative addition with Br2 to give the known [RhBr2{Ph2Sb(CH2)3SbPh2}2]+, while using HCl gives the same hydride complex from both precursors, which is tentatively assigned as [RhHCl2{Ph2Sb(CH2)3SbPh2}]. An unexpected further Rh(III) product from this reaction, trans-[RhCl2{Ph2Sb(CH2)3SbPh2}{PhClSb(CH2)3SbClPh}]Cl, was identified by a crystal structure analysis and represents the first structurally characterised example of a chlorostibine coordinated to a metal. [Rh{Ph2Sb(CH2)3SbPh2}2]BF4 reacts with CO to give [Rh(CO){Ph2Sb(CH2)3SbPh2}2]BF4 initially, and upon further exposure this species undergoes further reversible carbonylation to give a cis-dicarbonyl species thought to be [Rh(CO)2{Ph2Sb(CH2)3SbPh2}{kappa1Sb-Ph2Sb(CH2)3SbPh2}]BF4 which converts back to the monocarbonyl complex when the CO atmosphere is replaced with N2.     

Cyanide-bridged linkage isomers with catecholateruthenium(II) centres bound to Mn(I) or M(alkyne) units

Two series of stable cyanide-bridged linkage isomers, namely [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)] (XY = CN or NC, L = CNBu(t) or CNXyl) and [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC-CPh)Tp'] {M = Mo or W, L = PPh3 or P(OPh)3, Tp' = hydrotris(3,5-dimethylpyrazolyl)borate} have been synthesised; pairs of isomers are distinguishable by IR spectroscopy and cyclic voltammetry. The molecular structure of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-NC)Mo(CO)(PhC-CPh)Tp'] has the catecholate-bound ruthenium atom cyanide-bridged to a Mo(CO)(PhC[triple band]CPh)Tp' unit in which the alkyne acts as a four-electron donor; the alignment of the alkyne relative to the Mo-CO vector suggests the fragment (CN)Ru(CO)2(PPh3)(o-O2C6Cl4) acts as a pi-acceptor ligand. The complexes [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)Mn(NO)L(eta-C5Me5)] undergo three sequential one-electron oxidation processes with the first and third assigned to oxidation of the ruthenium-bound o-O2C6Cl4 ligand; the second corresponds to oxidation of Mn(I) to Mn(n). The complexes [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp'] are also first oxidised at the catecholate ligand; the second oxidation, and one-electron reduction, are based on the M(CO)(PhC[triple band]CPh)Tp' fragment. Chemical oxidation of [(o-O,C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)] with [Fe(eta-C5H4COMe)(eta-C5H5)][BF4], or of [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp'] with AgBF4, gave the paramagnetic monocations [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)]+ and [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp']+, the ESR spectra of which are consistent with ruthenium-bound semiquinone ligands. Linkage isomers are distinguishable by the magnitude of the 31P hyperfine coupling constant; complexes with N-bound Ru(o-O2C6Cl4) units also show small hyperfine coupling to the nitrogen atom of the cyanide bridge.     

Key factors determining the course of methyl iodide oxidative addition to diamidonaphthalene-bridged diiridium(I) and dirhodium(I) complexes

The course of methyl iodide oxidative addition to various nucleophilic complexes, [Ir2(mu-1,8-(NH)2naphth)(CO)2(PiPr3)2] (1), [IrRh(mu-1,8-(NH)2naphth)(CO)2(PiPr3)2] (2), and [Rh2(mu-1,8-(NH)2naphth)(CO)2(PR3)2] (R = iPr, 3; Ph, 4; p-tolyl, 5; Me, 6), has been investigated. The CH3I addition to complex 1 readily affords the diiridium(II) complex [Ir2(mu-1,8-(NH)2naphth)I(CH3)(CO)2(PiPr3)2] (7), which undergoes slow rearrangement to give a thermodynamically stable stereoisomer, 8. The reaction of the Ir-Rh complex 2 gives the ionic compound [IrRh(mu-1,8-(NH)2naphth)(CH3)(CO)2(PiPr3)2]I (10). The dirhodium compounds, 3-5, undergo one-center additions to yield acyl complexes of the formula (Rh2(mu-1,8-(NH)2naphth)I(COCH3)(CO)(PR3)2] (R = iPr, 12; Ph, 13; p-tolyl, 14). The structure of 12 has been determined by X-ray diffraction. Further reactions of these Rh(III)-Rh(I) acyl derivatives with CH3I are productive only for the p-tolylphosphine derivative, which affords the bis-acyl complex [Rh2(mu-1,8-(NH)2naphth)(CH3CO)2I2(P(p-tolyl)3)2] (15). The reaction of the PMe3 derivative, 6, allows the isolation of the bis-methyl complex [Rh2(mu-1,8-(NH)2naphth)(mu-I)(CH3)2(CO)2(PMe3)2]I (16a), which emanates from a double one-center addition. Upon reaction with methyl triflate, the starting materials, 1, 2, 3, and 6, give the isostructural cationic methyl complexes 9, 11, 17, and 18, respectively. The behavior of these cationic methyl compounds toward CH3I, CH3OSO2CF3, and tetrabutylamonium iodide is consistent with the role of these species as intermediates in the SN2 addition of CH3I. Compounds 18 and 17 react with an excess of methyl triflate to give [Rh2(mu-1,8-(NH)2naphth)(mu-OSO2CF3)(CH3)2(CO)2(PMe3)2][CF3SO3] (19) and [Rh2(mu-1,8-(NH)2naphth)(OSO2CF3)(COCH3)(CH3)(CO)(PiPr3)2][CF3SO3] (20), respectively. Upon treatment with acetonitrile, complexes 17 and 18 give the isostructural cationic acyl complexes [Rh2(mu-1,8-(NH)2naphth)(COCH3)(NCCH3)(CO)(PR3)2][CF3SO3] (R = iPr, 21; Me, 22). A kinetic study of the reaction leading to 21 shows that formation of these complexes involves a slow insertion step followed by the fast coordination of the acetonitrile. The variety of reactions found in this system can be rationalized in terms of three alternative reaction pathways, which are determined by the effectiveness of the interactions between the two metal centers of the dinuclear complex and by the steric constraints due to the phosphine ligands.     

Metal-metal charge transfer and solvatochromism in cyanomanganese carbonyl complexes of ruthenium and osmium

The complexes [(H3N)5Ru(II)(mu-NC)Mn(I)Lx]2+, prepared from [Ru(OH2)(NH3)5]2+ and [Mn(CN)L(x)] {L(x) = trans-(CO)2{P(OPh)3}(dppm); cis-(CO)2(PR3)(dppm), R = OEt or OPh; (PR3)(NO)(eta-C5H4Me), R = Ph or OPh}, undergo two sequential one-electron oxidations, the first at the ruthenium centre to give [(H3N)5Ru(III)(mu-NC)Mn(I)Lx]3+; the osmium(III) analogues [(H3N)5Os(III)(mu-NC)Mn(I)Lx]3+ were prepared directly from [Os(NH3)5(O3SCF3)]2+ and [Mn(CN)Lx]. Cyclic voltammetry and electronic spectroscopy show that the strong solvatochromism of the trications depends on the hydrogen-bond accepting properties of the solvent. Extensive hydrogen bonding is also observed in the crystal structures of [(H3N)5Ru(III)(mu-NC)Mn(I)(PPh3)(NO)(eta-C5H4Me)][PF6]3.2Me2CO.1.5Et2O, [(H3N)5Ru(III)(mu-NC)Mn(I)(CO)(dppm)2-trans][PF6]3.5Me2CO and [(H3N)5Ru(III)(mu-NC)Mn(I)(CO)2{P(OEt)3}(dppm)-trans][PF6]3.4Me2CO, between the amine groups (the H-bond donors) at the Ru(III) site and the oxygen atoms of solvent molecules or the fluorine atoms of the [PF6]- counterions (the H-bond acceptors).     

Intermolecular alkene and alkyne hydroacylation with beta-S-substituted aldehydes: mechanistic insight into the role of a hemilabile P-O-P ligand

A straightforward to assemble catalytic system for the intermolecular hydroacylation reaction of beta-S-substituted aldehydes with activated and unactivated alkenes and alkynes is reported. These catalysts promote the hydroacylation reaction between beta-S-substituted aldehydes and challenging substrates, such as internal alkynes and 1-octene. The catalysts are based upon [Rh(cod)(DPEphos)][ClO(4)] (DPEphos=bis(2-diphenylphosphinophenyl)ether, cod=cyclooctadiene) and were designed to make use of the hemilabile capabilities of the DPEphos ligand to stabilise key acyl-hydrido intermediates against reductive decarbonylation, which results in catalyst death. Studies on the stoichiometric addition of aldehyde (either ortho-HCOCH(2)CH(2)SMe or ortho-HCOC(6)H(4)SMe) and methylacrylate to precursor acetone complexes [Rh(acetone)(2)(DPEphos)][X] [X=closo-CB(11)H(6)Cl(6) or [BAr(F) (4)] (Ar(F)=3,5-(CF(3))(2)C(6)H(3))] reveal the role of the hemilabile DPEphos ligand. The crystal structure of [Rh(acetone)(2)(DPEphos)][X] shows a cis-coordinated diphosphine ligand with the oxygen atom of the DPEphos distal from the rhodium. Addition of aldehyde forms the acyl hydride complexes [Rh(DPEphos)(COCH(2)CH(2)SMe)H][X] or [Rh(DPEphos)(COC(6)H(4)SMe)H][X], which have a trans-spanning DPEphos ligand and a coordinated ether group. Compared to analogous complexes prepared with dppe (dppe=1,2-bis(diphenylphosphino)ethane), these DPEphos complexes show significantly increased resistance towards reductive decarbonylation. The crystal structure of the reductive decarbonylation product [Rh(CO)(DPEphos)(EtSMe)][closo-CB(11)H(6)I(6)] is reported. Addition of alkene (methylacrylate) to the acyl-hydrido complexes forms the final complexes [Rh(DPEphos)(eta(1)-MeSC(2)H(4)-eta(1)-COC(2)H(4)CO(2)Me)][X] and [Rh(DPEphos)(eta(1)-MeSC(6)H(4)-eta(1)-COC(2)H(4)CO(2)Me)][X], which have been identified spectroscopically and by ESIMS/MS. Intermediate species in this transformation have been observed and tentatively characterised as the alkyl-acyl complexes [Rh(CH(2)CH(2)CO(2)Me)(COC(2)H(4)SMe)(DPEphos)][X] and [Rh(CH(2)CH(2)CO(2)Me)(COC(6)H(4)SMe)(DPEphos)][X]. In these complexes, the DPEphos ligand is now cis chelating. A model for the (unobserved) transient alkene complex that would result from addition of alkene to the acyl-hydrido complexes comes from formation of the MeCN adducts [Rh(DPEphos)(MeSC(2)H(4)CO)H(MeCN)][X] and [Rh(DPEphos)(MeSC(6)H(4)CO)H(MeCN)][X]. Changing the ligand from DPEphos to one with a CH(2) linkage, [Ph(2)P(C(6)H(4))](2)CH(2), gave only decomposition on addition of aldehyde to the acetone precursor, which demonstrated the importance of the hemiabile ether group in DPEphos. With [Ph(2)P(C(6)H(4))](2)S, the sulfur atom has the opposite effect and binds too strongly to the metal centre to allow access to productive acetone intermediates.     

A new route to coordination complexes of nitroxyl (HN=O) via insertion reactions of nitrosonium triflate with transition-metal hydrides

Nitrosonium triflate reacts with cold methylene chloride solutions of mer,trans-ReH(CO)3(PPh3)2 (1) with 1,1-insertion of NO+ into the Re-H bond to give the orange nitroxyl complex [mer,trans-Re(NH=O)(CO)3(PPh3)2][SO3CF3] (3) in 86% isolated yield. Use of [NO][PF6] or [NO][BF4] gives analogous insertion products at low temperature, which decompose on warning to ambient temperature to the fluoride complex mer,trans-ReF(CO)3(PPh3)2 (4). A related 1,1-insertion is observed in the reaction of 1 with [PhN2][PF6] in acetone that affords the yellow-orange phenyldiazene salt [mer,trans-Re(NH=NPh)(CO)3(PPh3)2][PF6] (2), which has been characterized by X-ray crystallographic methods. The methyl derivative mer,trans-Re(CH3)(CO)3(PPh3)2 (5) also undergoes a 1,1-insertion reaction with [NO][SO3CF3] to give the nitrosomethane adduct [mer,trans-Re{N(CH3)=O}(CO)3(PPh3)2][SO3CF3] (6) as red crystals in 75% yield. The nitroxyl complex [cis,trans-OsBr(NH=O)(CO)2(PPh3)2][SO3CF3] (8) can be similarly prepared as orange crystals in 52% yield by reaction of cis,trans-OsHBr(CO)2(PPh3)2 (7) with [NO][SO3CF3] in cold methylene chloride solution.     

Dimethylsulfoxide as a ligand for RhI and IrI complexes--isolation, structure, and reactivity towards X-H bonds (X=H, OH, OCH3)

Novel neutral and cationic Rh(I) and Ir(I) complexes that contain only DMSO molecules as dative ligands with S-, O-, and bridging S,O-binding modes were isolated and characterized. The neutral derivatives [RhCl(DMSO)(3)] (1) and [IrCl(DMSO)(3)] (2) were synthesized from the dimeric precursors [M(2)Cl(2)(coe)(4)] (M=Rh, Ir; COE=cyclooctene). The dimeric Ir(I) compound [Ir(2)Cl(2)(DMSO)(4)] (3) was obtained from 2. The first example of a square-planar complex with a bidentate S,O-bridging DMSO ligand, [(coe)(DMSO)Rh(micro-Cl)(micro-DMSO)RhCl(DMSO)] (4), was obtained by treating [Rh(2)Cl(2)(coe)(4)] with three equivalents of DMSO. The mixed DMSO-olefin complex [IrCl(cod)(DMSO)] (5, COD=cyclooctadiene) was generated from [Ir(2)Cl(2)(cod)(2)]. Substitution reactions of these neutral systems afforded the complexes [RhCl(py)(DMSO)(2)] (6), [IrCl(py)(DMSO)(2)] (7), [IrCl(iPr(3)P)(DMSO)(2)] (8), [RhCl(dmbpy)(DMSO)] (9, dmbpy=4,4'-dimethyl-2,2'-bipyridine), and [IrCl(dmbpy)(DMSO)] (10). The cationic O-bound complex [Rh(cod)(DMSO)(2)]BF(4) (11) was synthesized from [Rh(cod)(2)]BF(4). Treatment of the cationic complexes [M(coe)(2)(O=CMe(2))(2)]PF(6) (M=Rh, Ir) with DMSO gave the mixed S- and O-bound DMSO complexes [M(DMSO)(2)(DMSO)(2)]PF(6) (Rh=12; Ir=in situ characterization). Substitution of the O-bound DMSO ligands with dmbpy or pyridine resulted in the isolation of [Rh(dmbpy)(DMSO)(2)]PF(6) (13) and [Ir(py)(2)(DMSO)(2)]PF(6) (14). Oxidative addition of hydrogen to [IrCl(DMSO)(3)] (2) gave the kinetic product fac-[Ir(H)(2)Cl(DMSO)(3)] (15) which was then easily converted to the more thermodynamically stable product mer-[Ir(H)(2)Cl(DMSO)(3)] (16). Oxidative addition of water to both neutral and cationic Ir(I) DMSO complexes gave the corresponding hydrido-hydroxo addition products syn-[(DMSO)(2)HIr(micro-OH)(2)(micro-Cl)IrH(DMSO)(2)][IrCl(2)(DMSO)(2)] (17) and anti-[(DMSO)(2)(DMSO)HIr(micro-OH)(2)IrH(DMSO)(2)(DMSO)][PF(6)](2) (18). The cationic [Ir(DMSO)(2)(DMSO)(2)]PF(6) complex (formed in situ from [Ir(coe)(2)(O=CMe(2))(2)]PF(6)) also reacts with methanol to give the hydrido-alkoxo complex syn-[(DMSO)(2)HIr(micro-OCH(3))(3)IrH(DMSO)(2)]PF(6) (19). Complexes 1, 2, 4, 5, 11, 12, 14, 17, 18, and 19 were characterized by crystallography.     

Pyridine-based SNS-iridium and -rhodium sulfide complexes, including d8-d8 metal-metal interactions in the solid state

The cationic, pincer-type complexes [(SNS)Ir(COE)][BF4] (1) and [(SNS)Rh(COE)][BF4] (2) (SNS = 2,6-bis(t-butylthiomethy1)pyridine; COE = cyclooctene) complexes were prepared, and their structure and reactivity were studied. They are fluxional at room temperature as a result of "arm" hemilability, which can be frozen at low temperatures. Reaction of complex 1 with H2 resulted in a dimeric dihydride complex [(SNS)Ir(H2)]2[BF4]2 (3) in which the sulfur atoms bridge between two metal centers. The Rh complex 2 did not react with H2. Both the carbonyl complexes [(SNS)Ir(CO)][BF4] (5) and [(SNS)Rh(CO)][BF4] (6) show differences in the IR stretching frequencies in solution vs. solid states, which are a result of uncommon metal-metal interactions between square planar d8 systems in the solid state. Complexes 1, 3, 5 and 6 were structurally characterized by X-ray crystallography. A network of hydrogen bonds involving the BF4(-) counter anion and hydrogen atoms of complex 5 was observed.     

Reactivity of novel N,N'-diphosphino-silanediamine-based rhodium(I) derivatives

The coordination abilities of the novel N,N'-diphosphino-silanediamine ligand of formula SiMe(2)(NtolPPh(2))(2) (SiNP, 1) have been investigated toward rhodium, and the derivatives [RhCl(SiNP)](2) (2), [Rh(SiNP)(COD)][BF(4)] (3), and Rh(acac)(SiNP) (4) have been synthesized. The stability of the dinuclear frame of [RhCl(SiNP)](2) (2) toward incoming nucleophiles has been shown to be dependent on their π-acceptor ability. Indeed, the mononuclear complexes RhCl(SiNP)(L) (L = CO, 5; CN(t)Bu, 6) have been isolated purely and quantitatively upon reaction of 2 with CO and CN(t)Bu, respectively. Otherwise, PPh(3) and RhCl(SiNP) equilibrate with Rh(Cl)(SiNP)(PPh(3)) (7). Carbon electrophiles such as MeI and 3-chloro-1-proprene afforded the oxidation of rhodium(I) to rhodium(III) and the formation of RhCl(2)(η(3)-C(3)H(5))(SiNP) (8) and Rh(Me)(I)(SiNP)(acac) (10), respectively. The methyl derivative 10 is thermally stable and does not react either with CO or with CN(t)Bu even in excess. Otherwise, RhCl(2)(η(3)-C(3)H(5))(SiNP) (8) is thermally stable but reacts with CO, affording 3-chloro-1-proprene and RhCl(SiNP)(CO) (5). Finally, upon reaction of Rh(acac)(SiNP) (4) and 3-chloro-1-proprene, RhCl(acac)(η(1)-C(3)H(5))(SiNP) (9a) and [Rh(acac)(η(3)-C(3)H(5))(SiNP)]Cl (9b) could be detected at 233 K. At higher temperatures, 9a and 9b smoothly decompose, affording the dinuclear derivative [RhCl(SiNP)](2) (2) and the CC coupling product 3-allylpentane-2,4-dione.     

Iodination of triazenide-bridged rhodium and iridium complexes: oxidative addition vs. one-electron oxidation

The triazenide-bridged tetracarbonyls [(OC)(2)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)] (M = Rh or Ir) undergo oxidative addition of iodine across the dimetal centre, giving the [RhM](4+) complexes [I(OC)(2)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)I], structurally characterised for M = Ir. The anionic tricarbonyl iodide [I(OC)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)Rh(CO)(2)](-) forms [I(2)(OC)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)Rh(CO)I](-) by initial one-electron transfer whereas the analogous tricarbonyl phosphine complexes [(OC)(Ph(3)P)Rh(mu-p-MeC(6)H(4)NNNC(6)H(4)Me-p)(2)M(CO)(2)] (M = Rh or Ir) undergo bridge cleavage, giving mononuclear [Rh(p-MeC(6)H(4)NNNC(6)H(4)Me-p)I(2)(CO)(PPh(3))] and dimeric [I(OC){RNNN(R)C(O)}M(mu-I)(2)M{C(O)N(R)NNR}(CO)I] (M = Rh or Ir, R = C(6)H(4)Me-p) in which CO has been inserted into a metal-nitrogen bond.     

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.     

Synthesis,characterization, and solution redox properties of (trimpsi)M(CO)(2)(NO) complexes [M = V,Nb, Ta; trimpsi = (t)BuSi(CH(2)PMe(2))(3)

Treatment of [Et(4)N][M(CO)(6)] (M = Nb, Ta) with I(2) in DME at -78 degrees C produces solutions of the bimetallic anions [M(2micro-I)(3)(CO)(8)](-). Addition of the tripodal phosphine (t)BuSi(CH(2)PMe(2))(3) (trimpsi) followed by refluxing affords (trimpsi)M(CO)(3)I [M = Nb (1), Ta (2)], which are isolable in good yields as air-stable, orange-red microcrystalline solids. Reduction of these complexes with 2 equiv of Na/Hg, followed by treatment with Diazald in THF, results in the formation of (trimpsi)M(CO)(2)(NO) [M = Nb (3), Ta (4)] in high isolated yields. The congeneric vanadium complex, (trimpsi)V(CO)(2)(NO) (5), can be prepared by reacting [Et(4)N][V(CO)(6)] with [NO][BF(4)] in CH(2)Cl(2) to form V(CO)(5)(NO). These solutions are treated with 1 equiv of trimpsi to obtain (eta(2)-trimpsi)V(CO)(3)(NO). Refluxing orange THF solutions of this material affords 5 in moderate yields. Reaction of (trimpsi)VCl(3)(THF) (6) with 4 equiv of sodium naphthalenide in THF in the presence of excess CO provides [Et(4)N][(trimpsi)V(CO)(3)] (7), (trimpsi)V(CO)(3)H, and [(trimpsi)V(micro-Cl)(3)V(trimpsi)][(eta(2)-trimpsi)V(CO)(4)].3THF ([8][9].3THF). All new complexes have been characterized by conventional spectroscopic methods, and the solid-state molecular structures of 2.(1)/(2)THF, 3-5, and [8][9].3THF have been established by X-ray diffraction analyses. The solution redox properties of 3-5 have also been investigated by cyclic voltammetry. Cyclic voltammograms of 3 and 4 both exhibit an irreversible oxidation feature in CH(2)Cl(2) (E(p,a) = -0.71 V at 0.5 V/s for 3, while E(p,a) = -0.55 V at 0.5 V/s for 4), while cyclic voltammograms of 5 in CH(2)Cl(2) show a reversible oxidation feature (E(1/2) = -0.74 V) followed by an irreversible feature (0.61 V at 0.5 V/s). The reversible feature corresponds to the formation of the 17e cation [(trimpsi)V(CO)(2)(NO)](+) ([5](+)()), and the irreversible feature likely involves the oxidation of [5](+)() to an unstable 16e dication. Treatment of 5 with [Cp(2)Fe][BF(4)] in CH(2)Cl(2) generates [5][BF(4)], which slowly decomposes once formed. Nevertheless, [5][BF(4)] has been characterized by IR and ESR spectroscopies.     

Competitive C-I versus C-CN reductive elimination from a Rh(III) complex. Selectivity is controlled by the solvent

The RhIII complex [(PNP)Rh(CN)(CH3)][I] 5, obtained by oxidative addition of methyl iodide to [(PNP)Rh(CN)] 2, reacts selectively in two pathways: In aprotic solvents C-I reductive elimination of methyl iodide followed by its electrophilic attack on the cyano ligand takes place, giving the methyl isonitrile RhI complex [(PNP)Rh(CNCH3)][I] 3, while in protic solvents C-C reductive elimination of acetonitrile takes place forming an iodo RhI complex [(PNP)RhI] 9. Reaction of 2 with ethyl iodide in aprotic solvents gave the corresponding isonitrile complex, while in protic solvents no reactivity was observed. The selectivity of this reaction is likely due to a hydrogen bond between the cyano ligand and the protic solvent, as observed by X-ray diffraction, which retards electrophilic attack on this ligand.     

A series of dinuclear homo- and heterometallic complexes with two or three bridging sulfido ligands derived from the tungsten tris(sulfido) complex [Et(4)N][(Me(2)Tp)WS(3)] (Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate)

The generation of heterobimetallic complexes with two or three bridging sulfido ligands from mononuclear tris(sulfido) complex of tungsten [Et(4)N][(Me(2)Tp)WS(3)] (1; Me(2)Tp = hydridotris(3,5-dimethylpyrazol-1-yl)borate) and organometallic precursors is reported. Treatment of 1 with stoichiometric amounts of metal complexes such as [M(PPh(3))(4)] (M = Pt, Pd), [(PtMe(3))(4)(micro(3)-I)(4)], [M(cod)(PPh(3))(2)][PF(6)] (M = Ir, Rh; cod = 1,5-cyclooctadiene), [Rh(cod)(dppe)][PF(6)] (dppe = Ph(2)PCH(2)CH(2)PPh(2)), [CpIr(MeCN)(3)][PF(6)](2) (Cp = eta(5)-C(5)Me(5)), [CpRu(MeCN)(3)][PF(6)], and [M(CO)(3)(MeCN)(3)] (M = Mo, W) in MeCN or MeCN-THF at room temperature afforded either the doubly bridged complexes [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)M(PPh(3))] (M = Pt (3), Pd (4)), [(Me(2)Tp)W(=S)(micro-S)(2)M(cod)] (M = Ir, Rh (7)), [(Me(2)Tp)W(=S)(micro-S)(2)Rh(dppe)], [(Me(2)Tp)W(=S)(micro-S)(2)RuCp] (10), and [Et(4)N][(Me(2)Tp)W(=S)(micro-S)(2)W(CO)(3)] (12) or the triply bridged complexes including [(Me(2)Tp)W(micro-S)(3)PtMe(3)] (5), [(Me(2)Tp)W(micro-S)(3)IrCp][PF(6)] (9), and [Et(4)N][(Me(2)Tp)W(micro-S)(3)Mo(CO)(3)] (11), depending on the nature of the incorporated metal fragment. The X-ray analyses have been undertaken to clarify the detailed structures of 3-5, 7, and 9-12.     

One-electron versus two-electron mechanisms in the oxidative addition reactions of chloroalkanes to amido-bridged rhodium complexes

The compound syn-[{Rh(mu-NH{p-tolyl})(CNtBu)(2)}(2)] (1) oxidatively adds C--Cl bonds of alkyl chlorides (RCl) and dichloromethane to each metal centre to give the cationic complexes syn-[{Rh(mu-NH{p-tolyl})(eta(1)-R)(CNtBu)(2)}(2)(mu-Cl)]Cl and anti-[{Rh(mu-NH{p-tolyl})Cl(CNtBu)(2)}(2)(mu-CH(2))]. Reaction of 1 with the chiral alkyl chloride (-)-(S)-ClCH(Me)CO(2)Me (R*Cl) gave [{Rh(mu-NH{p-tolyl})(eta(1)-R*)(CNtBu)(2)}(2)(mu-Cl)]Cl ([3]Cl) as an equimolecular mixture of the meso form (R,S)-[3]Cl-C(s) and one enantiomer of the chiral form [3]Cl-C(2). This reaction, which takes place in two steps, was modeled step-by-step by reacting the mixed-ligand complex syn-[(cod)Rh(mu-NH{p-tolyl})(2)Rh(CNtBu)(2)] (4) with R*Cl, as a replica of the first step, to give [(cod)Rh(mu-NH{p-tolyl})(2)RhCl(eta(1)-R*)(CNtBu)(2)] (5) with racemization of the chiral carbon. Further treatment of 5 with CNtBu to give the intermediate [(CNtBu)(2)Rh(mu-NH{p-tolyl})(2)RhCl(eta(1)-R*)(CNtBu)(2)], followed by reaction with R*Cl reproduced the regioselectivity of the second step to give (R,S)-[3]Cl-C(s) and [3]Cl-C(2) in a 1:1 molar ratio. Support for an S(N)2 type of reaction with inversion of the configuration in the second step was obtained from a similar sequence of reactions of 4 with ClCH(2)CO(2)Me first, then with CNtBu, and finally with R*Cl to give [(CNtBu)(2)(eta(1)-CH(2)R)Rh(mu-NH{p-tolyl})(2)(mu-Cl)Rh(eta(1)-R*)(CNtBu)(2)]Cl (R = CO(2)Me, [7]Cl) as a single enantiomer with the R configuration at the chiral carbon. The reactions of 1 with (+)-(S)-XCH(2)CH(CH(3))CH(2)CH(3) (X = Br, I) gave the related complexes [{Rh(mu-NH{p-tolyl})(eta(1)-CH(2)CH(CH(3))CH(2)CH(3))(CNtBu)(2)}(2)(mu-X)]X, probably by following an S(N)2 profile in both steps.     

Topological variations of the PDP ligand and its prospects in molybdenum(0) dearomatization agents

The compounds fac-(κ(3)-PDP)Mo(CO)(3) {1; PDP = 2-[[2-(1-(pyridin-2-ylmethyl)pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine}, [(cis-β-PDP)Mo(NO)(CO)]PF(6) ([cis-β-3]PF(6)), [(cis-α-PDP)Mo(NO)(CO)]PF(6) ([cis-α-3]PF(6)), [(cis-α-PDP)Mo(NO)Br]PF(6) ([4]PF(6)), [(trans-PDP)Cu](BF(4))(2)·CH(3)CN ([5](BF(4))(2)·CH(3)CN), and [(trans-PDP)Cu](OSO(2)CF(3))(2) ([5](OSO(2)CF(3))(2)) have been synthesized and structurally characterized by single-crystal X-ray diffraction. These are the first reported complexes of PDP on metal centers other than iron(II). The observed configurations indicate a broader range of accessible PDP topologies than has been reported. The {(cis-α-PDP)Mo(NO)}(+) fragment is found to be less π-basic than the dearomatizing {Tp(MeIm)Mo(NO)} fragment [Tp = hydridotris(1-pyrazolyl)borato; MeIm = 1-methylimidazole].