Iridium-imine and -amine complexes relevant to the (S)-metolachlor process: structures, exchange kinetics, and C-H activation by Iri causing racemization

Iridium complexes of DMA-imine [2,6-dimethylphenyl-1'-methyl-2'-methoxyethylimine, 1 a) and (R)-DMA-amine [(1'R)-2,6-dimethylphenyl-1'-methyl-2'-methoxyethylamine, 2 a] that are relevant to the catalytic imine hydrogenation step of the Syngenta (S)-Metolachlor process were synthesized: metathetical exchange of [Ir2Cl2(cod)2] (cod=1,5-cyclooctadiene) with [Ag(1 a)2]BF4 and [Ag((R)-2 a)2]BF4 afforded [Ir(cod)(kappa2- -1 a)]BF4 (11) and [Ir(cod)(kappa2-(R)-2 a)]BF4 ((R)-19)), respectively. These complexes were then used in stopped-flow experiments to study the displacement of amine 2 a from complex 19 by imine 1 a to form the imine complex 11, thus modeling the product/substrate exchange step in the catalytic cycle. The data suggest a two-step associative mechanism characterized by k1=(2.6+/-0.3) x 10(2) M(-1) s(-1) and k2=(4.3+/-0.6) x 10(-2) s(-1) with the respective activation energies EA1=(7.5+/-0.6) kJ mol(-1) and EA2=(37+/-3) kJ mol(-1). Furthermore, complex 11 reacted with H2O to afford the hydrolysis product [Ir(cod)(eta(6-)-2,6-dimethylaniline)]BF4 (12), and with I2 to liberate quantitatively the DMA-iminium salt 14. On the other hand, the chiral amine complex (R)-19 formed the optically inactive eta6-bound compound [Ir(cod)(eta6-rac-2 a)]BF4 (rac-18) upon dissolution in THF at room temperature, presumably via intramolecular C-H activation. This racemization was found to be a two-step event with k'1=9.0 x 10(-4) s(-1) and k2=2.89 x 10(-5) s(-1), featuring an optically active intermediate prior to sp3 C-H activation. Compounds 11, 12, rac-18, and (R)-19 were structurally characterized by single-crystal X-ray analyses.     

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.     

Metallosupramolecular chemistry with bis(benzene-o-dithiolato) ligands

The bis(benzene-o-dithiol) ligands H(4)-1, H(4)-2, and H(4)-3 react with [Ti(OC(2)H(5))(4)] to give dinuclear triple-stranded helicates [Ti(2)L(3)](4)(-) (L = 1(4)(-), 2(4)(-), 3(4)(-)). NMR spectroscopic investigations revealed that the complex anions possess C(3) symmetry in solution. A crystal structure analysis for (PNP)(4)[Ti(2)(2)(3)] ((PNP)(4)[14]) confirmed the C(3) symmetry for the complex anion in the solid state. The complex anion in Li(PNP)(3)[Ti(2)(1)(3)] (Li(PNP)(3)[13]) does not exhibit C(3) symmetry in the solid state due to the formation of polymeric chains of lithium bridged complex anions. Complexes [13](4)(-) and [14](4)(-) were obtained as racemic mixtures of the Delta,Delta and Lambda,Lambda isomers. In contrast to that, complex (PNP)(4)[Ti(2)(3)(3)] ((PNP)(4)[15]) with the enantiomerically pure chiral ligand 3(4)(-) shows a strong Cotton effect in the CD spectrum, indicating that the chirality of the ligands leads to the formation of chiral metal centers. The o-phenylene diamine bridged bis(benzene-o-dithiol) ligand H(4)-4 reacts with Ti(4+) to give the dinuclear double-stranded complex Li(2)[Ti(2)(4)(2)(mu-OCH(3))(2)] containing two bridging methoxy ligands between the metal centers. The crystal structure analysis and the (1)H NMR spectrum of (Ph(4)As)(2)[Ti(2)(4)(2)(mu-OCH(3))(2)] ((Ph(4)As)(2)[(16]) reveal C(2) symmetry for the anion [Ti(2)(4)(2)(mu-OCH(3))(2)](2)(-). For a comparative study the dicatechol ligand H(4)-5, containing the same o-phenylene diamine bridging group as the bis(benzene-o-dithiol) ligands H(4)-4, was prepared and reacted with [TiO(acac)(2)] to give the dinuclear complex anion [Ti(2)(5)(2)(mu-OCH(3))(2)](2)(-). The molecular structure of (PNP)(2)[Ti(2)(5)(2)(mu-OCH(3))(2)] ((PNP)(2)[17]) contains a complex anion which is similar to [16](2)(-), with the exception that strong N-H...O hydrogen bonds are formed in complex anion [17](2)(-), while N-H...S hydrogen bonds are absent in complex anion [16](2)(-).     

Stepwise Construction of Polynuclear Complexes of Rhodium and Iridium Assisted by Benzimidazole-2-thiol. NMR and X-ray Diffraction Studies

Reactions of [M(2)(&mgr;-Cl)(2)(cod)(2)] (cod = 1,5-cyclooctadiene, M = Rh, Ir) with benzimidazole-2-thiol (H(2)Bzimt) afford the mononuclear complexes [MCl(H(2)Bzimt)(cod)] (M = Rh (1), Ir (2)) for which a S-coordination of the ligand is proposed based on their spectroscopic data. The dinuclear complexes [M(2)(&mgr;-HBzimt)(2)(cod)(2)] (M = Rh (3), Ir (4)) are isolated from the reaction of [M(acac)(cod)] and benzimidazole-2-thiol. They contain the monodeprotonated ligand (HBzimt(-)) bridging the two metals in a &mgr;(2)-(1kappaN,2kappaS) coordination mode and in a relative cis,cis-HT arrangement. Complexes 3 and 4 react with the appropriate species [M(cod)(Me(2)CO)(2)](+) to afford the trinuclear cationic aggregates [M(3)(&mgr;-HBzimt)(2)(cod)(3)](+) (M = Rh (5), Ir (6)) and with the [M'(2)(&mgr;-OMe)(2)(cod)(2)] compounds to give the homo- and heterotetranuclear complexes [MM'(&mgr;-Bzimt)(cod)(2)](2) (M = M' = Rh (7), Ir (8); M = Ir, M' = Rh (9)) containing the dideprotonated ligand (Bzimt(2)(-)). The trinuclear neutral complexes [M(3)(&mgr;-Bzimt)(&mgr;-HBzimt)(cod)(3)] are intermediates detected in the synthesis of the tetranuclear complexes. Protonation of 9 with HBF(4) gives the unsymmetrical complex [Ir(2)Rh(&mgr;-HBzimt)(2)(cod)(3)]BF(4) (10). This reaction involves the protonation of the bridging ligands followed by the removal of one "Rh(cod)" moiety to give a single isomer. The molecular structure of [Rh(2)(&mgr;-Bzimt)(cod)(2)](2) (7) has been determined by X-ray diffraction methods. Crystals are monoclinic, space group P2(1)/n, a = 20.173(5) ?, b = 42.076(8) ?, c = 10.983(3) ?, beta = 93.32(2) degrees, Z = 8, 7145 reflections, R = 0.0622, and R(w) = 0.0779. The complete assignment of the resonances of the (1)H NMR spectra of the complexes 3, 4, and 7-9 was carried out by selective decoupling, NOE, and H,H-COSY experiments. The differences in the chemical shifts of the olefinic protons are discussed on the basis of steric and magnetic anisotropy effects.     

Preparation of mononuclear and dinuclear Rh hydrotris(pyrazolyl)borato complexes containing arenethiolato ligands and conversion of the mononuclear complexes into dinuclear Rh-Rh and Rh-Ir complexes with bridging arenethiolato ligands

Reactions of [Tp*Rh(coe)(MeCN)](; Tp*= HB(3,5-dimethylpyrazol-1-yl)(3); coe = cyclooctene) with one equiv. of the organic disulfides, PhSSPh, TolSSTol (Tol = 4-MeC(6)H(4)), PySSPy (Py = 2-pyridyl), and tetraethylthiuram disulfide in THF at room temperature afforded the mononuclear Rh(III) complexes [Tp*Rh(SPh)(2)(MeCN)](3a), [Tp*Rh(STol)(2)(MeCN)](3b), [Tp*Rh(eta(2)-SPy)(eta(1)-SPy)](6), and [Tp*Rh(eta(2)-S(2)CNEt(2))(eta(1)-S(2)CNEt(2))](7), respectively, via the oxidative addition of the organic disulfides to the Rh(I) center in 1. For the Tp analogue [TpRh(coe)(MeCN)](2, Tp = HB(pyrazol-1-yl)(3)), the reaction with TolSSTol proceeded similarly to give the bis(thiolato) complex [TpRh(STol)(2)(MeCN)](4) as a major product but the dinuclear complex [[TpRh(STol)](2)(micro-STol)(2)](5) was also obtained in low yield. Complex 3 was treated further with the Rh(III) or Ir(III) complexes [(Cp*MCl)(2)(micro-Cl)(2)](Cp*=eta(5)-C(5)Me(5)) in THF at room temperature, yielding the thiolato-bridged dinuclear complexes [Tp*RhCl(micro-SPh)(2)MCp*Cl](8a: M = Rh, 8b: M = Ir). Dirhodium complex [TpRhCl(micro-STol)(2)RhCp*Cl](9) was obtained similarly from 4 and [(Cp*RhCl)(2)(micro-Cl)(2)]. Anion metathesis of 8a proceeds only at the Rh atom with the Cp* ligand to yield [Tp*RhCl(micro-SPh)(2)RhCp*(MeCN)][PF(6)](10), when treated with excess KPF(6) in CH(2)Cl(2)-MeCN. The X-ray analyses have been undertaken to determine the detailed structures of 3b, 4, 5, 6, 7, 8a, 9, and 10.     

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.     

Synthesis and characterization of heterometallic clusters (Ir2Rh, Ir2W, Rh3) Containing 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate chelate ligands, [(B10H10)C2S2]2-

The 16-electron half-sandwich complex [Cp*Ir[S2C2(B10H10)]] (Cp* = eta5-C5Me5) (1a) reacts with [[Rh(cod)(mu-Cl)]2] (cod = cycloocta-1,5-diene, C8H12) in different molar ratios to give three products, [[Cp*Ir[S2C2(B10H9)]]Rh(cod)] (2), trans-[[Cp*Ir[S2C2(B10H9)]]Rh[[S2C2(B10H10)]IrCp*]] (3), and [Rh2(cod)2[(mu-SH)(mu-SC)(CH)(B10H10)]] (4). Complex 3 contains an Ir2Rh backbone with two different Ir-Rh bonds (3.003(3) and 2.685(3) angstroms). The dinuclear complex 2 reacts with the mononuclear 16-electron complex 1a to give 3 in refluxing toluene. Reaction of 1a with [W(CO)3(py)3] (py = C5H5N) in the presence of BF3.EtO2 leads to the trinuclear cluster [[Cp*Ir[S2C2(B10H10)]]2W(CO)2] (5) together with [[Cp*Ir(CO)[S2C2(B10H10)]]W(CO)5] (6), and [Cp*Ir(CO)[S2C2(B10H10)]] (7). Analogous reactions of [Cp*Rh[S2C2(B10H10)]] (1 b) with [[Rh(cod)(mu-Cl)]2] were investigated and two complexes cis-[[Cp*Rh[S2C2(B10H10)]]2Rh] (8) and trans-[[Cp*Rh[S2C2(B10H10)]]2Rh] (9) were obtained. In refluxing THF solution, the cisoid 8 is converted in more than 95 % yield to the transoid 9. All new complexes 2-9 were characterized by NMR spectroscopy (1H, 11B NMR) and X-ray diffraction structural analyses are reported for complexes 2-5, 8, and 9.     

Direct addition of alcohols to organonitriles activated by ligation to a platinum(IV) center

Treatment of trans-[PtCl(4)(RCN)(2)] (R = Me, Et) with R'OH (R' = Me, Et, n-Pr, i-Pr, n-Bu) at 45 degrees C in all cases allowed the isolation of the trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] imino ester complexes, while the reaction between cis-[PtCl(4)(RCN)(2)] and the least sterically hindered alcohols (methanol and ethanol) results in the formation of cis-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R/R' = Me/Me) or trans-[PtCl(4)[(E)-NH=C(Et)OR'](2)] (R' = Me, Et), the latter being formed via thermal isomerization (ROH, reflux, 3 h) of the initially formed corresponding cis isomers. The reaction between alcohols R'OH and cis-[PtCl(4)(RCN)(2)] (R = Me, R' = Et, n-Pr, i-Pr, n-Bu; R = Et; R' = n-Pr, i-Pr, n-Bu), exhibiting greater R/R' steric congestion, allowed the isolation of cis-[PtCl(4)[(E)-NH=C(R)OR'][(Z)-NH=C(R)OR']] as the major products. The alcoholysis reactions of poorly soluble [PtCl(4)(RCN)(2)] (R = CH(2)Ph, Ph) performed under heterogeneous conditions, directly in the appropriate alcohol and for a prolonged time and, for R = Ph, with heating led to trans-[PtCl(4)[(E)-NH=C(R)OR'](2)] (R = CH(2)Ph, R' = Me, Et, n-Pr, i-Pr; R = Ph, R' = Me) isolated in moderate yields. In all of the cases, in contrast to platinum(II) systems, addition of R'OH to the organonitrile platinum(IV) complexes occurs under mild conditions and does not require a base as a catalyst. The formed isomerically pure (imino ester)Pt(IV) complexes can be reduced selectively, by Ph(3)P=CHCO(2)Me, to the corresponding isomers of (imino ester)Pt(II) species, exhibiting antitumor activity, without change in configuration of the imino ester ligands. Furthemore, the imino esters NH=C(R)OR' can be liberated from both platinum(IV) and platinum(II) complexes [PtCl(n)[H=C(R)OR'](2)] (n = 2, 4) by reaction with 1,2-bis(diphenylphosphino)ethane and pyridine, respectively. All of the prepared compounds were characterized by elemental analyses (C, H, N), FAB mass spectrometry, IR, and (1)H, (13)C[(1)H], and (195)Pt (metal complexes) NMR spectroscopies; the E and Z configurations of the imino ester ligands in solution were determined by observation of the nuclear Overhauser effect. X-ray structure determinations were performed for trans-[PtCl(4)[(E)-NH=C(Me)OEt](2)] (2), trans-[PtCl(4)[(E)-NH=C(Et)OEt](2)] (10), trans-[PtCl(4)[(E)-NH=C(Et)OPr-i](2)] (11), trans-[PtCl(4)[(E)-NH=C(Et)OPr-n](2)] (12), and cis-[PtCl(4)[(E)-NH=C(Et)OMe](2)] (14). Ab initio calculations have shown that the EE isomers are the most stable ones for both platinum(II) and platinum(IV) complexes, whereas the most stable configurations for the ZZ isomers are less stable than the respective EZ isomers, indicating an increase of the stability on moving from the ZZ to the EE configurations which is more pronounced for the Pt(IV) complexes than for the Pt(II) species.     

Asymmetric hydrogenation of prochiral olefins catalysed by furanoside thioether-phosphinite Rh(I) and Ir(I) complexes

Thioether-phosphinite ligands (P-SR, R = Ph, Pr(I) and Me) bearing substituents with different steric demands on the sulfur centre were tested in the rhodium- and iridium-catalysed asymmetric hydrogenation of prochiral olefins. High enantiomeric excesses (up to 96%) and good activities (TOF up to 860 mol product x (mol catalyst precursor x h)(-1)) were obtained for alpha-acylaminoacrylates derivatives. Our results show that enantiomeric excesses depended strongly on the steric properties of the substituent in the thioether moiety, the metal source and the substrate structure. A bulky group in the thioether moiety along with the metal Rh had a positive effect on enantioselectivity. Reaction of these chiral ligands with [M(cod)2]BF4(M = Ir, Rh; cod = 1,5-cyclooctadiene) yielded complexes [M(cod)(P-SR)]BF4, which were present in only one diastereomeric form having the sulfur substituent in a pseudoaxial disposition. The addition of H2 to iridium complexes gave the cis-dihydridoiridium(iii) complexes [IrH2(cod)(P-SR)]BF4. For complexes [IrH2(cod)(P-SPh)]BF4 and [IrH2(cod)(P-SMe)] only one isomer was present in solution. However, for the complex [IrH2(cod)(P-Si-Pr)]BF4, which contained the more hindered substituent on sulfur, two isomers were detected. In all cases there was a pseudoaxial disposition of the sulfur substituents.     

Synthesis and reactivity of Ir(I) and Ir(III) complexes with MeNH2, Me2C=NR (R = H, Me), C,N-C6H4{C(Me)=N(Me)}-2, and N,N'-RN=C(Me)CH2C(Me2)NHR (R = H, Me) ligands

Complexes [Ir(Cp*)Cl(n)(NH2Me)(3-n)]X(m) (n = 2, m = 0 (1), n = 1, m = 1, X = Cl (2a), n = 0, m = 2, X = OTf (3)) are obtained by reacting [Ir(Cp*)Cl(mu-Cl)]2 with MeNH2 (1:2 or 1:8) or with [Ag(NH2Me)2]OTf (1:4), respectively. Complex 2b (n = 1, m = 1, X = ClO 4) is obtained from 2a and NaClO4 x H2O. The reaction of 3 with MeC(O)Ph at 80 degrees C gives [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(NH2Me)]OTf (4), which in turn reacts with RNC to give [Ir(Cp*){C,N-C6H4{C(Me)=N(Me)}-2}(CNR)]OTf (R = (t)Bu (5), Xy (6)). [Ir(mu-Cl)(COD)]2 reacts with [Ag{N(R)=CMe2}2]X (1:2) to give [Ir{N(R)=CMe2}2(COD)]X (R = H, X = ClO4 (7); R = Me, X = OTf (8)). Complexes [Ir(CO)2(NH=CMe2)2]ClO4 (9) and [IrCl{N(R)=CMe2}(COD)] (R = H (10), Me (11)) are obtained from the appropriate [Ir{N(R)=CMe2}2(COD)]X and CO or Me4NCl, respectively. [Ir(Cp*)Cl(mu-Cl)]2 reacts with [Au(NH=CMe2)(PPh3)]ClO4 (1:2) to give [Ir(Cp*)(mu-Cl)(NH=CMe2)]2(ClO4)2 (12) which in turn reacts with PPh 3 or Me4NCl (1:2) to give [Ir(Cp*)Cl(NH=CMe2)(PPh3)]ClO4 (13) or [Ir(Cp*)Cl2(NH=CMe2)] (14), respectively. Complex 14 hydrolyzes in a CH2Cl2/Et2O solution to give [Ir(Cp*)Cl2(NH3)] (15). The reaction of [Ir(Cp*)Cl(mu-Cl)]2 with [Ag(NH=CMe2)2]ClO4 (1:4) gives [Ir(Cp*)(NH=CMe2)3](ClO4)2 (16a), which reacts with PPNCl (PPN = Ph3=P=N=PPh3) under different reaction conditions to give [Ir(Cp*)(NH=CMe2)3]XY (X = Cl, Y = ClO4 (16b); X = Y = Cl (16c)). Equimolar amounts of 14 and 16a react to give [Ir(Cp*)Cl(NH=CMe2)2]ClO4 (17), which in turn reacts with PPNCl to give [Ir(Cp*)Cl(H-imam)]Cl (R-imam = N,N'-N(R)=C(Me)CH2C(Me)2NHR (18a)]. Complexes [Ir(Cp*)Cl(R-imam)]ClO4 (R = H (18b), Me (19)) are obtained from 18a and AgClO4 or by refluxing 2b in acetone for 7 h, respectively. They react with AgClO4 and the appropriate neutral ligand or with [Ag(NH=CMe2)2]ClO4 to give [Ir(Cp*)(R-imam)L](ClO4)2 (R = H, L = (t)BuNC (20), XyNC (21); R = Me, L = MeCN (22)) or [Ir(Cp*)(H-imam)(NH=CMe2)](ClO4)2 (23a), respectively. The later reacts with PPNCl to give [Ir(Cp*)(H-imam)(NH=CMe2)]Cl(ClO4) (23b). The reaction of 22 with XyNC gives [Ir(Cp*)(Me-imam)(CNXy)](ClO4)2 (24). The structures of complexes 15, 16c and 18b have been solved by X-ray diffraction methods.     

Chiral bisphosphinite metalloligands derived from a P-chiral secondary phosphine oxide

Interaction of PdCl(2)(MeCN)(2) with 2 equiv of (S(P))-(t)BuPhP(O)H (1H) followed by treatment with Et(3)N gave [Pd((1)(2)H)](2)(micro-Cl)(2) (2). Reaction of 2 with Na[S(2)CNEt(2)] or K[N(PPh(2)S)(2)] afforded Pd[(1)(2)H](S(2)CNEt(2)) (3) or Pd[(1)(2)H)[N(PPh(2)S)(2)] (4), respectively. Treatment of 3 with V(O)(acac)(2) (acac = acetylacetonate) and CuSO(4) in the presence of Et(3)N afforded bimetallic complexes V(O)[Pd(1)(2)(S(2)CNEt(2))](2) (5) or Cu[Pd(1)(2)(S(2)CNEt(2))](2) (6), respectively. X-ray crystallography established the S(P) configuration for the phosphinous acid ligands in 3 and 6, indicating that 1H binds to Pd(II) with retention of configuration at phosphorus. The geometry around Cu in 6 is approximately square planar with the average Cu-O distance of 1.915(3) A. Treatment of 2 with HBF(4) gave the BF(2)-capped compound [Pd((1)(2)BF(2))](2)(micro-Cl)(2) (7). The solid-state structure of 7 containing a PdP(2)O(2)B metallacycle has been determined. Chloride abstraction of 7 with AgBF(4) in acetone/water afforded the aqua compound [Pd((1)(2)BF(2))(H(2)O)(2)][BF(4)] (8) that reacted with [NH(4)](2)[WS(4)] to give [Pd((1)(2)BF(2))(2)](2)[micro-WS(4)] (9). The average Pd-S and W-S distances in 9 are 2.385(3) and 2.189(3) A, respectively. Treatment of [(eta(6)-p-cymene)RuCl(2)](2) with 1H afforded the phosphinous acid adduct (eta(6)-p-cymene)RuCl(2)(1H) (10). Reduction of [CpRuCl(2)](x)() (Cp = eta(5)-C(5)Me(5)) with Zn followed by treatment with 1H resulted in the formation of the Zn(II) phosphinate complex [(CpRu(eta(6)-C(6)H(5)))(t)BuPO(2))](2)(ZnCl(2))(2) (11) that contains a Zn(2)O(4)P(2) eight-membered ring.     

Synthesis, structure, and catalytic oxidation chemistry from the first oxo-imido Schiff base metal complexes

The molybdenum oxo-imido complex, [Mo(O)(NtBu)Cl2(dme)] (1), was obtained from the reaction between [MoO2Cl2(dme)] and [Mo(NtBu)2Cl2(dme)]. Reactions between [Mo(O)(NR)Cl2(dme)] (where R = tBu or 2,6-iPr2C6H3) and the disodium Schiff base compounds Na(2)(3,5-tBu2)2salen, Na(2)(3,5-tBu2)2salpen, and Na(2)(7-Me)2salen afforded the first oxo-imido transition metal Schiff base complexes: [Mo(O)(NtBu)[(3,5-tBu2)2salen]] (2), [Mo(O)(NtBu)[(3,5-tBu2)2salpen]] (3), and [Mo(O)(N-2,6-iPr2C6H3)[(7-Me)2salen]] (4), respectively. The compounds [Mo(NtBu)2[(3,5-tBu2)2salpen]] (5) from [Mo(NtBu)2(NHtBu)2] and [Mo(N-2,6-iPr2C6H3)(2)[(7-Me)2salen]](6) from [Mo(N-2,6-iPr2C6H3)(2)(NHtBu)2] (7) are also reported. Compounds 1-7 were characterized by NMR, IR, and FAB mass spectroscopy while compounds 3, 4, and 5 were additionally characterized by X-ray crystallography. In conjunction with tBuOOH as oxidant, compound 3 is a catalyst for the oxidation of benzyl alcohol to benzaldehyde and cis-cyclooctene and 1-octene to the corresponding epoxides.     

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 preparation and characterisation of bimetallic iridium(II) complexes containing derivatised bridging naphthalene-1,8-disulfur or 4,5-dithiolato acephenanthrylene ligands

Oxidative addition of the disulfide compounds naphtho[1,8-cd][1,2]dithiole, 2-tert-butylnaptho[1,8-cd][1,2]dithiole, 2,7-di-tert-butylnaphtho[1,8-cd][1,2]dithiole, 4,5-dithiaacephenanthrylene and the thio/sulfinyl and thio/sulfonyl compounds naphtho[1,8-cd][1,2]dithiole 1-oxide, and naphtho[1,8-cd][1,2]dithiole 1,1-dioxide respectively to [[Ir(mu-Cl)(cod)](2)] give dinuclear Ir-Ir bonded Ir(II) compounds [[IrCl(cod)](2)(mu(2)-1,8-S(2)-nap)] 1, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2-(t)Bu-nap)] 2, [[IrCl(cod)](2)(mu(2)-1,8-S(2)-2,7-di-(t)Bu-nap)]] 3, [[IrCl(cod)](2)(mu(2)-4,5-S(2)-phenan)] 4, [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)]-nap)] 5 and [[IrCl(cod)](2)(mu(2)-1-S,8-[S(O)(2)]-nap)] 6 where the di-sulfur ligands act as bridges between the two Ir(II) metal centres. The compounds were obtained in moderate to good yields as orange or deep red powders or crystalline solids. Five of the new complexes have been structurally characterised and were found to have Ir-Ir bond lengths in the range 2.7630(8) to 2.8113(11) A.     

Dinuclear rhodium and iridium complexes with mixed amido/methoxo and amido/hydroxo bridges

The reactions of [[M(mu-OMe)(cod)](2)] (M = Rh, Ir; cod = 1,5- cyclooctadiene) with p-tolylamine, alpha-naphthylamine, and p-nitroaniline gave complexes with mixed-bridging ligands, [[M(cod)](2)(mu-NHAr)(mu-OMe)]. Similarly, the related complexes [[Rh(cod)](2)(mu-NHAr)(mu-OH)] were prepared from the reactions of [[Rh(mu-OH)(cod)](2)] with p-tolylamine, alpha-naphthylamine, and p-nitroaniline. The reactions of [[Rh(mu-OR)(cod)](2)] (R = H, Me) with o-nitroaniline gave the mononuclear complex [Rh(o-NO(2)C(6)H(4)NH)(cod)]. The syntheses of the amido complexes involve a proton exchange reaction from the amines to the methoxo or hydroxo ligands and the coordination of the amide ligand. These reactions were found to be reversible for the dinuclear complexes. The structure of [[Rh(cod)](2)(mu-NH[p-NO(2)C(6)H(4)])(mu-OMe)] shows two edge-shared square-planar rhodium centers folded at the edge with an anti configuration of the bridging ligands. The complex [[Rh(cod)](2)(mu-NH[alpha-naphthyl])(mu-OH)] cocrystallizes with [[Rh(mu-OH)(cod)](2)] and THF, forming a supramolecular aggregate supported by five hydrogen bridges in the solid state. In the mononuclear [Rh(o-NO(2)C(6)H(4)NH)(cod)] complex the o-nitroamido ligand chelates the rhodium center through the amido nitrogen and an oxygen of the nitro group.     

New ligand systems incorporating two and three 4,4'-bipyridine units. Characterization of bi- and trimetallic rhodium and iridium complexes

The synthesis of new ligand systems based on the bipyridine unit for bi- and trimetallic complexes, including a rare example of a chiral bimetallic complex, is presented. Ligands BBPX (bis-bipyridine-xylene, 3) and TBPBX (tris-bipyridine-bis-xylene, 4) were prepared in one step by reacting alpha,alpha'-dibromo-o-xylene (2) with 2 equiv of the monolithiated derivative of 4,4'-dimethyl-2,2'-bipyridine. Dilithium (S)-binaphtholate (5) reacted with 2 equiv of 4-bromomethyl-4'-methyl-2,2'-bipyridine (6), affording ligand (S)-BBPBINAP (bis-bipyridine-binaphtholate, 7). These ligands reacted cleanly with 1, 1.5, and 1 equiv of the rhodium dimer [Rh(2)Cl(2)(HD)(2)] (HD = 1,5-hexadiene), respectively. Chloride abstraction led to the isolation of the cationic complexes BBPX[Rh(HD)BF(4)](2) (8), TBPBX[Rh(HD)BF(4)](3) (10), and (S)-BBPBINAP[Rh(HD)BF(4)](2) (12). When BBPX (3), TBPBX (4), and (S)-BBPBINAP (7) were added to 2, 3, and 2 equiv of [Rh(NBD)(2)]BF(4) or [Rh(NBD)(CH(3)CN)(2)]BF(4) (NBD = norbornadiene), respectively, clean formation of BBPX[Rh(NBD)BF(4)](2) (9), TBPBX[Rh(NBD)BF(4)](3) (11), and (S)-BBPBINAP[Rh(NBD)BF(4)](2) (13) was observed. The neutral iridium complex (S)-BBPBINAP[IrCl(COD)](2) (14) was obtained by reaction of (S)-BBPBINAP (7) with 1 equiv of [Ir(2)Cl(2)(COD)(2)] (COD = cyclooctadiene). The complexes were fully characterized including X-ray structural studies of 8, 9, and 13, and preliminary studies on their catalytic activity were performed.     

Hydrolytic metal-mediated coupling of dialkylcyanamides at a Pt(IV) center giving a new family of diimino ligands

Addition of excess R(2)NCN to an aqueous solution of K(2)[PtCl(4)] led to the precipitation of [PtCl(2)(NCNR(2))(2)] (R(2) = Me(2) 1; Et(2) 2; C(5)H(10) 3; C(4)H(8)O, 4) in a cis/trans isomeric ratio which depends on temperature. Pure isomers cis-1-3 and trans-1-3 were separated by column chromatography on SiO(2), while trans-4 was obtained by recrystallization. Complexes cis-1-3 isomerize to trans-1-3 on heating in the solid phase at 110 degrees C; trans-1 has been characterized by X-ray crystallography. Chlorination of the platinum(II) complexes cis-1-3 and trans-1-4 gives the appropriate platinum(IV) complexes [PtCl(4)(NCNR(2))(2)] (cis-5-7 and trans-5-8). The compound cis-6 was also obtained by treatment of [PtCl(4)(NCMe)(2)] with neat Et(2)NCN. The platinum(IV) complex trans-[PtCl(4)(NCNMe(2))(2)] (trans-5) in a mixture of undried Et(2)O and CH(2)Cl(2) undergoes facile hydrolysis to give trans-[PtCl(4)[(H)=C(NMe(2))OH](2)] (9; X-ray structure has been determined). The hydrolysis went to another direction with the cis-[PtCl(4)(NCNR(2))(2)] (cis-5-7) which were converted to the metallacycles [PtCl(4)[NH=C(NR(2))OC(NR(2))=NH]] (11-13) due to the unprecedented hydrolytic coupling of the two adjacent dialkylcyanamide ligands giving a novel (for both coordination and organic chemistry) diimino linkage. Compounds 11-13 and also 14 (R(2) = C(4)H(8)O) were alternatively obtained by the reaction between cis-[PtCl(4)(MeCN)(2)] and neat undried NCNR(2). The structures of complexes 11, 13, and 14 were determined by X-ray single-crystal diffraction. All the platinum compounds were additionally characterized by elemental analyses, FAB mass-spectrometry, and IR and (1)H and (13)C[(1)H] NMR spectroscopies.     

Charging and deforming the pybox ligand: enantiomerically pure double helices and their interconversion

Reaction of pyrrole-2,5-biscarbonitrile (1) with an excess of (S)- or (R)-valinol in boiling chlorobenzene selectively yielded the two enantiomeric bis(oxazolinyl)pyrroles (S,S)-bis[2-(4,4'-diisopropyl-4,5-dihydrooxazolyl)]pyrrole ("S,S-iproxpH", 2 a) and (R,R)-bis[2-(4,4'-diisopropyl-4,5-dihydrooxazolyl)]pyrrole ("R,R-iproxpH", 2 b), respectively. Lithiation of 2 a and 2 b at -78 degrees C and reaction with an equimolar amount of [PdCl(2)(cod)] (cod=1,5-cyclooctadiene) gave the helical dinuclear palladium complexes (M)-[PdCl(S,S-iproxp)](2) (3 a) and (P)-[PdCl(S,S-iproxp)](2) (3 b) as well as (P)-[PdCl(R,R-iproxp)](2) (4 a) and (M)-[PdCl(R,R-iproxp)](2) (4 b). Reaction of a 1:1 mixture of lithiated 2 a and 2 b with an equimolar amount of [PdCl(2)(cod)] gave a mixture of the homochiral complexes 3 a,b and 4 a,b along with the racemic mixture of the heterochiral complex [Pd(2)Cl(2)(S,S-iproxp)(R,R-iproxp)] (5). The double helical structure as well as the absolute configuration of these neutral dinuclear palladium complexes was confirmed by X-ray diffraction studies of all five complexes. One of the oxazolyl units and the anionic pyrrolide occupy two coordination sites in an approximately square-planar ligand arrangement at the Pd centers whereas the second oxazolyl ring is twisted out of this plane and binds to the second metal center. The heterochiral complex 5 does not possess any element of molecular symmetry. The P-helical complexes 3 b and 4 a display a positive CD at 310 nm and a weaker negative CD at 350 nm, while the compounds possessing M-helicity have the corresponding mirror image CD spectra. Complexes 3 a and 4 a have an additional weak long wavelength CD feature between 380 and 420 nm which is absent in the spectra of 3 b and 4 b. Upon heating a solution of 3 b, interconversion to the diastereomer of opposite helicity 3 a sets in, for which a first-order rate law with respect to the concentration of the complex was established; activation parameters: DeltaH( not equal )=68 kJ mol(-1), DeltaS( not equal )=-99 J mol(-1) K(-1). A cross-over experiment monitored by (1)H NMR spectroscopy also gave the racemate of the mixed-ligand complex 5: (P)-[Pd(2)Cl(2)(S,S-iproxp)(R,R-iproxp)] and (M)-[Pd(2)Cl(2)(S,S-iproxp)(R,R-iproxp)] indicating an intermolecular exchange involving mononuclear [PdCl(iproxp)] complex fragments.     

Discrete triangle, square and hexametallic alkynyl cyano-bridged compounds based on [cis-Pt(Ctbond;CR)2(CN)2]2- building blocks

Novel mixed bis(alkynyl)bis(cyano)platinate(II) species [cis-Pt(Ctbond;CR)(2)(CN)(2)](2-) (1 a: R = tBu, 1 b: R = Ph) have been prepared and their potential as building blocks in the generation of self-organized systems with a variable molecular architecture has been studied. The reaction of 1 with the ditopic acceptor species [[cis-Pt(C(6)F(5))(2)S](2)(dppa)] (dppa=diphenylphosphinoacetylene) gave the dianionic cyanide/dppa bridged molecular platinotriangles (NBu(4))(2)[(C(6)F(5))(2)Pt(micro-dppa)[(micro-CN)(2)Pt(Ctbond;CR)(2)]Pt(C(6)F(5))(2)] (2). X-ray analysis of 2 a confirmed that the "Pt(2)(C(6)F(5))(4)(micro-dppa)" binuclear moiety is connected to the dianionic "Pt(Ctbond;CR)(2)(CN)(2)" unit by two bridging cyanide ligands. Moreover, treatment of 1 with the solvent cationic species [M(cod)(acetone)(2)](+) afforded heterometallic molecular squares Pt(2)M(2) (M=Rh, Ir) containing cyanide bridges and terminal alkynyl ligands, (NBu(4))(2)[cyclo[[cis-Pt(Ctbond;CR)(2)(micro-CN)(2)][M(cod)]](2)] (3: M=Rh, 4: M = Ir). The solid-state structures of phenyl derivatives have been determined by X-ray crystallography. The terminal alkynyl ligands in these cyanide-bridged molecular squares 3 and 4 have been used in the assembly of higher multimetallic complexes. Thus, very unusual bis(double-alkynide)-cyanide-bridged hexametallic compounds (NBu(4))(2)[[(C(6)F(5))(2)Pt(micro-Ctbond;CPh)(2)(micro-CN)(2)](2)[M(cod)](2)] (5 b: M=Rh, 6 b: M = Ir) were easily formed by simple reactions of 3 b and 4 b with two equivalents of [cis-Pt(C(6)F(5))(2)(thf)(2)]. An X-ray diffraction study on complex 5 b indicated that the derivative was formed by a simultaneous migration of one sigma-alkynyl group from each "Pt(Ctbond;CPh)(2)(micro-CN)(2)" corner of the square to both "Pt(C(6)F(5))(2)" units, resulting in bent sigma,pi-double-alkynyl bridging systems. Finally, the novel supramolecular anionic assemblies (NBu(4))(4)[cyclo[[cis-Pt(Ctbond;CR)(2)(micro-CN)(2)][SnPh(3)]](4)] 7 have been obtained by self-assembly of 1 and [SnPh(3)(acetone)(2)](+).     

Intervalent Bis(μ‐aziridinato)MII?MI Complexes (M=Rh,Ir): Delocalized Metallo‐Radicals or Delocalized Aminyl Radicals?

Reactions of the methoxo complexes [{M(mu-OMe)(cod)}(2)] (cod=1,5-cyclooctadiene, M=Rh, Ir) with 2,2-dimethylaziridine (Haz) give the mixed-bridged complexes [{M(2)(mu-az)(mu-OMe)(cod)(2)}] [(M=Rh, 1; M=Ir, 2). These compounds are isolated intermediates in the stereospecific synthesis of the amido-bridged complexes [{M(mu-az)(cod)}(2)] (M=Rh, 3; M=Ir, 4). The electrochemical behavior of 3 and 4 in CH(2)Cl(2) and CH(3)CN is greatly influenced by the solvent. On a preparative scale, the chemical oxidation of 3 and 4 with [FeCp(2)](+) gives the paramagnetic cationic species [{M(mu-az)(cod)}(2)](+) (M=Rh, [3](+); M=Ir, [4](+)). The Rh complex [3](+) is stable in dichloromethane, whereas the Ir complex [4](+) transforms slowly, but quantitatively, into a 1:1 mixture of the allyl compound [(eta(3),eta(2)-C(8)H(11))Ir(mu-az)(2)Ir(cod)] ([5](+)) and the hydride compound [(cod)(H)Ir(mu-az)(2)Ir(cod)] ([6](+)). Addition of small amounts of acetonitrile to dichloromethane solutions of [3](+) and [4](+) triggers a fast disproportionation reaction in both cases to produce equimolecular amounts of the starting materials 3 and 4 and metal--metal bonded M(II)--M(II) species. These new compounds are isolated by oxidation of 3 and 4 with [FeCp(2)](+) in acetonitrile as the mixed-ligand complexes [(MeCN)(3)M(mu-az)(2)M(NCMe)(cod)](PF(6))(2) (M=Rh, [8](2+); M=Ir, [9](2+)). The electronic structures of [3](+) and [4](+) have been elucidated through EPR measurements and DFT calculations showing that their unpaired electron is primarily delocalized over the two metal centers, with minor spin densities at the two bridging amido nitrogen groups. The HOMO of 3 and 4 and the SOMO of [3](+) and [4](+) are essentially M--M d-d sigma*-antibonding orbitals, explaining the formation of a net bonding interaction between the metals upon oxidation of 3 and 4. Mechanisms for the observed allylic H-atom abstraction reactions from the paramagnetic (radical) complexes are proposed.