Novel hydridoirida-beta-diketones containing small molecules, CO, or ethylene: their behavior in coordinating solvents such as dimethylsulfoxide or acetonitrile

New hydridoirida-beta-diketones [IrH[(PPh2(o-C6H4CO))2H](CO)]ClO4 2 and [IrH[(PPh2(o-C6H4CO))2H](olefin)]BF4 (olefin = C2H4, 5; 1-hexene, 10) have been prepared. These complexes may afford new diacylhydridoiridium(III) derivatives. In chloroform solution, complex 2 is in equilibrium with the deprotonated diacylhydride trans-[IrH(PPh2(o-C6H4CO))2(CO)] complex 3. In DMSO, deprotonation of 2 occurs to yield the kinetically favored product 3, which isomerizes to the thermodynamically favored complex cis-[IrH(PPh2(o-C6H4CO))2(CO)] 4. Reprotonation of 4 with HBF4 in chlorinated solvents gives the cation in 2. In coordinating solvents such as dimethyl sulfoxide or acetonitrile, complex 5 undergoes displacement of ethylene to afford [IrH{(PPh2(o-C6H4CO))2H](L)]BF4 (L = DMSO, 7; CH3CN, 9). Complexes 5 and 7 undergo deprotonation by NEt3 to give the corresponding diacylhydrides. The ethylene complex gives only trans-[IrH(PPh2(o-C6H4CO))2(C2H4)] 6, while the dimethyl sulfoxide derivative affords a mixture of trans- and cis-[IrH(PPh2(o-C6H4CO))2(DMSO)] 8. Complex 10 shows inhibited alkene rotation around the Ir-olefin axis. All of the complexes were fully characterized spectroscopically. Single-crystal X-ray diffraction analysis was performed on complexes 3, 4, and 9. The 13C NMR and X-ray data point to a carbenoid character in the carbon atoms bonded to iridium in the irida--diketone fragment, so that it can be considered as an acyl(hydroxycarbene) moiety.     

Carbene- and carbyne-like behavior of the Mo-P multiple bond in a dimolybdenum complex inducing trigonal-pyramidal coordination of a phosphinidene ligand

The phosphinidene complex [Mo2Cp(micro-kappa1:kappa1,eta5-PC5H4)(CO)2(eta6-R*H)] (2; Cp = eta5-C5H5; R* = 2,4,6-C6H2tBu3) has substantially different Mo-P bonds and displays a high reactivity located at the short Mo-P bond. Sideways cycloaddition or addition processes are observed toward RCCR, HCl, and [Fe2(CO)9], to give respectively metallacyclobutene and arylphosphide-bridged and heterometallic phosphinidene-bridged derivatives, a behavior reminiscent of the nucleophilic mononuclear phosphinidene complexes (carbene-like behavior), which is in good agreement with the ground-state electronic structure of 2 derived from density functional theory calculations. However, the reaction of 2 with [Co2(CO)8] implies the addition of two cobalt fragments to its short Mo-P bond and thus reveals a carbyne-like behavior of compound 2. In most of the new products, the P atom displays an unprecedented trigonal-pyramidal-like environment, instead of the expected tetrahedral distribution of bonds.     

Reaction of [M(eta3-allyl)(eta2-amidinato)(CO)2(pyridine)] complexes (M = Mo, W) with bidentate ligands: nitrogen donor vs. phosphorus donor

The reactivity of amidinato complexes of molybdenum and tungsten bearing pyridine as a labile ligand, [M(eta(3)-allyl)(eta(2)-amidinato)(CO)(2)(pyridine)](M = Mo; 1-Mo, M = W; 1-W), toward bidentate ligands such as 1,10-phenanthroline (phen) and 1,2-bis(diphenylphosphino)ethane (dppe) was investigated. The reaction of 1 with phen at ambient temperature resulted in the formation of monodentate amidinato complexes, [M(eta(3)-allyl)(eta(1)-amidinato)(CO)(2)(eta(2)-phen)](M = Mo; 2-Mo, M = W; 2-W), which has pseudo-octahedral geometry with the amidinato ligand coordinated to the metal in an eta(1)-fashion. The phen ligand was located coplanar with two CO ligands and the eta(1)-amidinato ligand was positioned trans to the eta(3)-allyl ligand. In solution, both complexes 2-Mo and 2-W showed fluxionality, and complex 2-Mo afforded allylamidine (3) on heating in solution. In the reaction of 1 with dppe at ambient temperature, the simple substitution reaction took place to give dppe-bridged binuclear complexes [{M(eta(3)-allyl)(eta(2)-amidinato)(CO)(2)}(2)(mu-dppe)](M = Mo; 5-Mo, M = W; 5-W), whereas mononuclear monocarbonyl complexes [M(eta(3)-allyl)(eta(2)-amidinato)(CO)(eta(2)-dppe)](M = Mo; 6-Mo, M = W; 6-W) were obtained under acetonitrile- or toluene-refluxing conditions. Mononuclear complex 6 was also obtained by the reaction of binuclear complex 5 with 0.5 equivalents of dppe under refluxing in acetonitrile or in toluene. The X-ray analyses and variable-temperature (31)P NMR spectroscopy of complex 6 indicated the existence of the rotational isomers of the eta(3)-allyl ligand, i.e., endo and exo forms, with respect to the carbonyl ligand. The different reactivity of complex 1 toward phen and dppe seems to have come from the difference in the pi-acceptability of each bidentate ligand.     

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.     

M-P versus M=M bonds as protonation sites in the organophosphide-bridged complexes [M2Cp2(mu-PR2)(mu-PR'2)(CO)2], (M = Mo, W; R, R' = Ph, Et, Cy)

The unsaturated complexes [W2Cp2(mu-PR2)(mu-PR'2)(CO)2] (Cp = eta5-C5H5; R = R' = Ph, Et; R = Et, R' = Ph) react with HBF4.OEt2 at 243 K in dichloromethane solution to give the corresponding complexes [W2Cp2(H)(mu-PR2)(mu-PR'2)(CO)2]BF4, which contain a terminal hydride ligand. The latter rearrange at room temperature to give [W2Cp2(mu-H)(mu-PR2)(mu-PR'2)(CO)2]BF4, which display a bridging hydride and carbonyl ligands arranged parallel to each other (W-W = 2.7589(8) A when R = R' = Ph). This explains why the removal of a proton from the latter gives first the unstable isomer cis-[W2Cp2(mu-PPh2)2(CO)2]. The molybdenum complex [Mo2Cp2(mu-PPh2)2(CO)2] behaves similarly, and thus the thermally unstable new complexes [Mo2Cp2(H)(mu-PPh2)2(CO)2]BF4 and cis-[Mo2Cp2(mu-PPh2)2(CO)2] could be characterized. In contrast, related dimolybdenum complexes having electron-rich phosphide ligands behave differently. Thus, the complexes [Mo2Cp2(mu-PR2)2(CO)2] (R = Cy, Et) react with HBF4.OEt2 to give first the agostic type phosphine-bridged complexes [Mo2Cp2(mu-PR2)(mu-kappa2-HPR2)(CO)2]BF4 (Mo-Mo = 2.748(4) A for R = Cy). These complexes experience intramolecular exchange of the agostic H atom between the two inequivalent P positions and at room-temperature reach a proton-catalyzed equilibrium with their hydride-bridged tautomers [ratio agostic/hydride = 10 (R = Cy), 30 (R = Et)]. The mixed-phosphide complex [Mo2Cp2(mu-PCy2)(mu-PPh2)(CO)2] behaves similarly, except that protonation now occurs specifically at the dicyclohexylphosphide ligand [ratio agostic/hydride = 0.5]. The reaction of the agostic complex [Mo2Cp2(mu-PCy2)(mu-kappa2-HPCy2)(CO)2]BF4 with CN(t)Bu gave mono- or disubstituted hydride derivatives [Mo2Cp2(mu-H)(mu-PCy2)2(CO)2-x(CNtBu)x]BF4 (Mo-Mo = 2.7901(7) A for x = 1). The photochemical removal of a CO ligand from the agostic complex also gives a hydride derivative, the triply bonded complex [Mo2Cp2(H)(mu-PCy2)2(CO)]BF4 (Mo-Mo = 2.537(2) A). Protonation of [Mo2Cp2(mu-PCy2)2(mu-CO)] gives the hydroxycarbyne derivative [Mo2Cp2(mu-COH)(mu-PCy2)2]BF4, which does not transform into its hydride isomer.     

Dimolybdenum cyclopentadienyl complexes with bridging chalcogenophosphinidene ligands

The reactions of the phosphinidene-bridged complex [Mo(2)Cp(2)(μ-PH)(η(6)-HMes*)(CO)(2)] (1), the arylphosphinidene complexes [Mo(2)Cp(2)(μ-κ(1):κ(1),η(6)-PMes*)(CO)(2)] (2), [Mo(2)Cp(2)(μ-κ(1):κ(1),η(4)-PMes*)(CO)(3)] (3), [Mo(2)Cp(2)(μ-κ(1):κ(1),η(4)-PMes*)(CO)(2)(CN(t)Bu)] (4), and the cyclopentadienylidene-phosphinidene complex [Mo(2)Cp(μ-κ(1):κ(1),η(5)-PC(5)H(4))(η(6)-HMes*)(CO)(2)] (5) toward different sources of chalcogen atoms were investigated (Mes* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5)). The bare elements were appropriate sources in all cases except for oxygen, in which case dimethyldioxirane gave the best results. Complex 1 reacted with the mentioned chalcogen sources at low temperature, to give the corresponding chalcogenophosphinidene derivatives [Mo(2)Cp(2){μ-κ(2)(P,Z):κ(1)(P)-ZPH}(η(6)-HMes*)(CO)(2)] (Z = O, S, Se, Te; P-Se = 2.199(2) ?). The arylphosphinidene complex 2 was the least reactive substrate and gave only chalcogenophosphinidene derivatives [Mo(2)Cp(2)(μ-κ(2)(P,Z):κ(1)(P),η(6)-ZPMes*)(CO)(2)] for Z = O and S (P-O = 1.565(2) ?), along with small amounts of the dithiophosphorane complex [Mo(2)Cp(2)(μ-κ(2)(P,S):κ(1)(S'),η(6)-S(2)PMes*)(CO)(2)], in the reaction with sulfur. The η(4)-complexes 3 and 4 reacted with sulfur and gray selenium to give the corresponding derivatives [Mo(2)Cp(2)(μ-κ(2)(P,Z):κ(1)(P),η(4)-ZPMes*)(CO)(2)L] (L = CO, CN(t)Bu), obtained respectively as syn (Z = Se; P-Se = 2.190(1) ? for L = CO) or a mixture of syn and anti isomers (Z = S; P-S = 2.034(1)-2.043(1) ?), with these diastereoisomers differing in the relative positioning of the chalcogen atom and the terminal ligand at the metallocene fragment, relative to the Mo(2)P plane. The cyclopentadienylidene compound 5 reacted with all chalcogens, and gave with good yields the chalcogenophosphinidene derivatives [Mo(2)Cp(μ-κ(2)(P,Z):κ(1)(P),η(5)-ZPC(5)H(4))(η(6)-HMes*)(CO)(2)] (Z = S, Se, Te), these displaying in solution equilibrium mixtures of the corresponding cis and trans isomers differing in the relative positioning of the cyclopentadienylic rings with respect to the MoPZ plane in each case. The sulfur derivative reacted with excess sulfur to give the dithiophosphorane complex [Mo(2)Cp(μ-κ(2)(P,S):κ(1)(S'),η(5)-S(2)PC(5)H(4))(η(6)-HMes*)(CO)(2)] (P-S = 2.023(4) and 2.027(4) ?). The structural and spectroscopic data for all chalcogenophosphinidene complexes suggested the presence of a significant π(P-Z) bonding interaction within the corresponding MoPZ rings, also supported by Density Functional Theory calculations on the thiophosphinidene complex syn-[Mo(2)Cp(2)(μ-κ(2)(P,S):κ(1)(P),η(4)-SPMes*)(CO)(3)].     

Oxidative decarbonylation of m-terphenyl isocyanide complexes of molybdenum and tungsten: precursors to low-coordinate isocyanide complexes

Synthetic studies are presented addressing the oxidative decarbonylation of molybdenum and tungsten complexes supported by the encumbering m-terphenyl isocyanide ligand CNAr(Dipp2) (Ar(Dipp2) = 2,6-(2,6-(i-Pr)(2)C(6)H(3))(2)C(6)H(3)). These studies represent an effort to access halide or pseudohalide M/CNAr(Dipp2) species (M = Mo, W) for use as precursors to low-coordinate, low-valent group 6 isocyanide complexes. The synthesis and structural chemistry of the tetra- and tricarbonyl tungsten complexes trans-W(CO)(4)(CNAr(Dipp2))(2) and trans-W(NCMe)(CO)(3)(CNAr(Dipp2))(2) are reported. The acetonitrile adducts trans-M(NCMe)(CO)(3)(CNAr(Dipp2))(2) (M = Mo, W) react with I(2) to form divalent, diiodide complexes in which the extent of decarbonylation differs between Mo and W. In the molybdenum example, the diiodide, dicarbonyl complex MoI(2)(CO)(2)(CNAr(Dipp2))(2) is generated, which has an S = 1 ground state in solution. Paramagnetic group 6 MX(2)L(4) complexes are rare, and the structure of MoI(2)(CO)(2)(CNAr(Dipp2))(2) is discussed in relation to other diamagnetic and C(2v)-distorted MX(2)L(4) complexes. Diiodide MoI(2)(CO)(2)(CNAr(Dipp2))(2) reacts further with I(2) to effect complete decarbonylation, producing the paramagnetic tetraiodide complex trans-MoI(4)(CNAr(Dipp2))(2). The reactivity of the trans-M(NCMe)(CO)(3)(CNAr(Dipp2))(2) (M = Mo, W) complexes toward benzoyl peroxide is also surveyed, and it is shown that dicarboxylate complexes can be obtained by oxidative or salt-elimination routes. The reduction behavior of the tetraiodide complex trans-MoI(4)(CNAr(Dipp2))(2) toward Mg metal and sodium amalgam is studied. In benzene solution under N(2), trans-MoI(4)(CNAr(Dipp2))(2) is reduced by Na/Hg to the η(6)-arene-dinitrogen complex, (η(6)-C(6)H(6))Mo(N(2))(CNAr(Dipp2))(2). The diiodide-η(6)-benzene complex (η(6)-C(6)H(6))MoI(2)(CNAr(Dipp2))(2) is an isolable intermediate in this reduction reaction, and its formation and structure are discussed in context of putative low-coordinate, low-valent molybdenum isocyanide complexes.     

Cooperative reactivity of early-late heterodinuclear transition metal complexes with polar organic substrates

A comprehensive investigation into the cooperative reactivity of two chemically complementary metal-complex fragments in early-late heterodinuclear complexes has been carried out. Reaction of the partially fluorinated tripodal amidozirconium complexes [HC-(SiMe2NR)3Zr(mu-Cl)2Li(OEt2)2] (R = 2-FC6H4: 2a, 2,3,4-F3C6H4: 2b) with K[CpM(CO)2] (M=Fe, Ru) afforded the stable metal-metal bonded heterodinuclear complexes [HC[SiMe2NR]3-Zr-MCp(CO)2] (3-6). Reaction of the dinuclear complexes with methyl isonitrile as well as the heteroallenes CO2, CS2, RNCO and RNCS led to insertion into the polar metal-metal bond. Two of these complexes, [HC[SiMe2N(2-FC6-H4)]3Zr(S2C)Fe(CO)2Cp] (9a) and [HC-[SiMe2N(2-FC2H4)]3Zr-(SCNPh)Fe(CO)2-Cp] (12), have been structurally characterized by a single crystal X-ray structure analysis, proving the structural situation of the inserted substrate as a bridging ligand between the early and late transition metal centre. The reactivity towards organic carbonyl derivatives proved to be varied. Reaction of the heterobimetallic complexes with benzyl and ethylbenzoate led to the cleavage of the ester generating the respective alkoxozirconium complexes [HC[SiMe2N(2-FC6H4)]3ZrOR] (R = Ph-CH2: 13a, Et: 13b) along with [CpFe-[C(O)Ph](CO)2], whereas the analogous reaction with ethyl formate gave 13b along with [CpFeH(CO)2]; this latter complex results from the instability of the formyliron species initially formed. Aryl aldehydes were found to react with the Zr-M complexes according to a Cannizzaro disproportionation pattern yielding the aroyliron and ruthenium complexes along with the respective benzoxyzirconium species. The transfer of the aldehyde hydrogen atom in the course of the reaction was established in a deuteriation experiment. [HC[SiMe2-N(2-FC6H4)]3Zr-M(CO)2Cp] reacted with lactones to give the ring-opened species containing an alkoxozirconium and an acyliron or acylruthenium fragment; the latter binds to the early transition metal centre through the acyl oxygen atom, as evidenced from the unusuallly low-field shifted 13C NMR resonances of the RC(O)M units. Ketones containing a-CH units react with the Zr-Fe complexes cooperatively to yield the aldol coupling products coordinated to the zirconium complex fragment along with the hydridoiron compound [CpFeH(CO)2], whereas 1,2-diphenylcyclopropenone underwent an oxygen transfer from the keto group to a CO ligand to give a linking CO2 unit and a cyclopropenylidene ligand coordinated to the iron fragment in [HC-[Si(CH3)2N(2,3,4-F3C6H2)]3Zr(mu-O2C)-Fe(CO)[C3Ph2)Cp] (19). The atom transfer was established by 17O and 13C labelling studies. Similar oxygen-transfer processes were observed in the reactions with pyridine N-oxide, dimethylsulfoxide and methylphenylsulfoxide.     

Thermal reactions of an overcrowded germacyclopropabenzene with group 6 metal hexacarbonyl complexes [M(CO)6](M = Cr, Mo, and W): a novel mode of CO insertion leading to the formation of cyclic germoxycarbene metal complexes

Thermal reactions of an overcrowded germacyclopropabenzene with hexacarbonyl complexes of group 6 metals resulted in the formation of the corresponding cyclic germoxycarbene complexes, i.e., 1,2-oxagermolan-5-ylidene pentacarbonyl metal complexes, via a novel mode of CO insertion reaction toward cyclopropabenzene derivatives.     

Nitrosyl derivatives of diiron(I) dithiolates mimic the structure and Lewis acidity of the [FeFe]-hydrogenase active site

This study probes the impact of electronic asymmetry of diiron(I) dithiolato carbonyls. Treatment of Fe2(S2C(n)H(2n))(CO)(6-x)(PMe3)x compounds (n = 2, 3; x = 1, 2, 3) with NOBF4 gave the derivatives [Fe2(S2C(n)H(2n))(CO)(5-x)(PMe3)x(NO)]BF4, which are electronically unsymmetrical because of the presence of a single NO(+) ligand. Whereas the monophosphine derivative is largely undistorted, the bis(PMe3) derivatives are distorted such that the CO ligand on the Fe(CO)(PMe3)(NO)(+) subunit is semibridging. Two isomers of [Fe2(S2C3H6)(CO)3(PMe3)2(NO)]BF4 were characterized spectroscopically and crystallographically. Each isomer features electron-rich Fe(CO)2PMe3 and electrophilic Fe(CO)(PMe3)(NO)(+) subunits. These species are in equilibrium with an unobserved isomer that reversibly binds CO (DeltaH = -35 kJ/mol, DeltaS = -139 J mol(-1) K(-1)) to give the symmetrical adduct [Fe2(S2C3H6)(mu-NO)(CO)4(PMe3)2]BF4. In contrast to Fe2(S2C3H6)(CO)4(PMe3)2, the bis(PMe3) nitrosyl complexes readily undergo CO substitution to give the (PMe3)3 derivatives. The nitrosyl complexes reduce at potentials that are approximately 1 V milder than their carbonyl counterparts. Results of density functional theory calculations, specifically natural bond orbital analysis, reinforce the electronic resemblance of the nitrosyl complexes to the corresponding mixed-valence diiron complexes. Unlike other diiron dithiolato carbonyls, these species undergo reversible reductions at mild potentials. The results show that the novel structural and chemical features associated with mixed-valence diiron dithiolates (the so-called H(ox) models) can be replicated in the absence of mixed-valency by the introduction of electronic asymmetry.     

Re(2)(CO)(10)-promoted S-binding, C-S bond cleavage, and hydrogenation of benzothiophenes: organometallic models for the hydrodesulfurization of thiophenes

In hydrodesulfurization model reactions of dinuclear metal complexes with thiophenes, we observe that ultraviolet photolysis of Re(2)(CO)(10) and benzothiophenes (BT) in hexanes solution produces the ring-opened BT complexes Re(2)(CO)(7)(mu-BT) (1a-d) (BT = benzothiophene (BT) 1a, 2-methylbenzothiophene (2-MeBT) 1b, 3-methylbenzothiophene (3-MeBT) 1c, and 3,5-dimethylbenzothiophene (3,5-Me(2)BT) 1d). The eta(1)(S)-bound BT complexes Re(2)(CO)(9)(eta(1)(S)-BT) (2a-d), prepared from Re(2)(CO)(9)(THF) and BT, are readily converted into 1a-d in good yields (40-60%) during UV photolysis in hexanes solution, which suggests that the eta(1)(S)-bound complexes 2a-d are precursors to 1a-d in the reactions of Re(2)(CO)(10) with BT. Irradiation of Re(2)(CO)(10) and 3,5-Me(2)BT with UV light in decane solution under an atmosphere of H(2) produces complex 1d and the partially hydrogenated BT complex Re(2)(CO)(7)(mu-3,5-Me(2)BT-H)(eta-H) (3d). Reactions of 1a with phosphines yield further ring-opened BT-Re complexes of the types Re(2)(CO)(7)(PMe(3))(3)(mu-BT) (4) and Re(2)(CO)(7)(PR(3))(2)(mu-BT) (R = Me (5), (i)Pr (6), Cy (7), and bis(diethylphosphino)ethane (8)). Structures of 1d, 2c, 3d, and 6, which demonstrate various bonding modes of benzothiophene and its C-S cleaved derivatives to two metal centers, were determined by X-ray crystallographic studies.     

Direct C-H Carboxylation with Carbon Dioxide Using 1,2,3-Triazol-5-ylidene Copper(I) Complexes

1,2,3-Triazol-5-ylidene copper(I) complexes (tzNHC-Cu) efficiently catalyzed the direct C-H carboxylation of benzoxazole and benzothiazole derivatives with CO(2) to give the corresponding esters in excellent yields after treatment with alkyl iodide. The tzNHC copper(I) complex, i.e., [(TPr)CuCl], worked somewhat more effectively than the corresponding imidazol-2-ylidene copper(I) complex [(IPr)CuCl] to give the carboxylation product in higher yields.     

Halogen derivatives of triphenylphosphine,triphenylarsine and triphenylstibine substituted molybdenum carbonyls

Summary Halogen oxidation of several LMo(CO)s andcis-L₂Mo(CO)₄ (L = Ph₃P₁Ph₃As and Ph₃Sb) derivatives has been studied. The LMo(CO)₅ complexes react with halogens to give hexacoordinate LMo(CO)₃ X₂ (X = Cl, Br or I) derivatives which are of very rare occurrence. Similar reactions withcis-L₂Mo(CO)₄ give heptacoordinate L₂Mo(CO)₃X₂ derivatives. The complexes have been characterised by elemental analysis, i.r. and conductivity measurements.     

N-phosphino-p-tolylsulfinamide ligands: synthesis, stability, and application to the intermolecular Pauson-Khand reaction

Here we synthesized a family of racemic and optically pure N-phosphino-p-tolylsulfinamide (PNSO) ligands. Their stability and coordination behavior toward dicobalt-alkyne complexes was evaluated. Selectivities of up to 3:1 were achieved in the ligand exchange process with (mu-TMSC2H)Co2(CO)6. The resulting optically pure major complexes were tested in the asymmetric intermolecular Pauson-Khand reaction and yielded up to 94% ee. X-ray studies of the major complex 18a indicated that the presence of an aryl group on the sulfinamide reduces the hemilabile character of the PNSO ligands.     

Synthesis, characterisation and biological activity of gold(III) catecholate and related complexes

The reactions of the cyclometallated gold(III) complexes [LAuCl₂] [L=2-(dimethylaminomethyl)phenyl, 2-benzylpyridyl or 2-anilinopyridyl] with catechol, tetrachlorocatechol, or the cyclic α,β-diketone SCH(CO2Et)C(O)C(O)CH(CO2Et) give stable complexes containing five-membered Au-O-C-C-O rings. These represent the first examples of well-characterised gold(III) catecholate complexes. Similarly, reactions with 2-acetamidophenol [HOC₆H₄NHC(O)CH₃] give complexes with the related AuNCCO ring. The complexes were characterised by NMR spectroscopy, electrospray ionisation mass spectrometry, elemental microanalysis, and in the case of the complex [(2-benzylpyridyl)Au{OC₆H₄NC(O)CH₃}] by an X-ray crystal structure determination. Several complexes show high activity towards P388 murine leukemia cells.     

Metal carbonyl derivatives of sulfur-containing quinones and hydroquinones: synthesis, structures, and electrochemical properties

The reaction of CpMoMn(mu-S(2))(CO)(5), 1, with 1,4-benzoquinone in the presence of irradiation with visible light yielded the quinonedithiolato complex CpMoMn(CO)(5)(mu-S(2)C(6)H(2)O(2)), 2. The new complex CpMoMn(CO)(5)(mu-S(2)C(6)Cl(2)O(2)) (4) was synthesized similarly from 1 and 2,3-dichloro-1,4-benzoquinone. Compounds 2 and 4 were reduced with hydrogen to yield the hydroquinone complexes CpMoMn(CO)(5)[mu-S(2)C(6)H(2)(OH)(2)], 3, and CpMoMn(CO)(5)[mu-S(2)C(6)Cl(2)(OH)(2)], 5. UV-vis irradiation of solutions of Fe(2)(CO)(6)(mu-S(2)) and 1,4-benzoquinone yielded the hydroquinone complex Fe(2)(CO)(6)[mu-S(2)C(6)H(2)(OH)(2)], 6. Compound 6 was oxidized to the quinone complex Fe(2)(CO)(6)(mu-S(2)C(6)H(2)O(2)), 7, by using 2,3-dichloro-5,6-dicyano-1,4-benzoquinone. Substitution of the CO ligands on 6 by PPh(3) yielded the derivatives Fe(2)(CO)(5)(PPh(3))[mu-S(2)C(6)H(2)(OH)(2)], 8, and Fe(2)(CO)(4)(PPh(3))(2)[mu-S(2)C(6)H(2)(OH)(2)], 9. The electrochemical properties of 3, 5, 6, 8, and 9 were measured by cyclic voltammetry. The molecular structure of each of the new compounds 2-9 was established by single-crystal X-ray diffraction analyses.     

Oxidative cyclisation of a tricarbonylcyclohexadieneiron complex using ferric chloride on silica gel

Treatment of the diene-Fe(CO)₃ complex (2) with dehydrated ferric chloride on silica gel support results in oxidative cyclisation of the alcohol function onto the diene ligand to give (3). This contrasts with the normal behaviour of both diene-Fe(CO)₃ complexes and alcohols toward ferric chloride.     

Chemistry of the oxophosphinidene ligand. 2. Reactivity of the anionic complexes [MCp{P(O)R*}(CO)(2)](-) (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3)) toward electrophiles based on elements different from carbon

The anionic oxophosphinidene complexes (H-DBU)[MCp{P(O)R*}(CO)(2)] (M = Mo, W; R* = 2,4,6-C(6)H(2)(t)Bu(3); Cp = η(5)-C(5)H(5), DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene) displayed multisite reactivity when faced with different electrophilic reagents. The reactions with the group 14 organochloride compounds ER(4-x)Cl(x) (E = Si, Ge, Sn, Pb) led to either phosphide-like, oxophosphinidene-bridged derivatives [MCp{P(OE')R*}(CO)(2)] (E' = SiMe(3), SiPh(3), GePh(3), GeMe(2)Cl) or to terminal oxophosphinidene complexes [MCp{P(O)R*}(CO)(2)(E')] (E' = SnPh(3), SnPh(2)Cl, PbPh(3); Mo-Pb = 2.8845(4) ? for the MoPb compound). A particular situation was found in the reaction with SnMe(3)Cl, this giving a product existing in both tautomeric forms, with the phosphide-like complex [MCp{P(OSnMe(3))R*}(CO)(2)] prevailing at room temperature and the tautomer [MCp{P(O)R*}(CO)(2)(SnMe(3))] being the unique species present below 203 K in dichloromethane solution. The title anions also showed a multisite behavior when reacting with transition-metal based electrophiles. Thus, the reactions with the complexes [M'Cp(2)Cl(2)] (M' = Ti, Zr) gave phosphide-like derivatives [MCp{P(OM')R*}(CO)(2)] (M = Mo, M' = TiCp(2)Cl, ZrCp(2)Cl; M = W, M' = ZrCp(2)Cl), displaying a bridging κ(1),κ(1)-P,O- oxophosphinidene ligand connecting MCp(CO)(2) and M'Cp(2)Cl metal fragments (W-P = 2.233(1) ?, O-Zr = 2.016(4) ? for the WZr compound]. In contrast, the reactions with the complex [AuCl{P(p-tol)(3)}] gave the metal-metal bonded derivatives trans-[MCp{P(O)R*}(CO)(2){AuP(p-tol)(3)}] (M = Mo, W; Mo-Au = 2.7071(7) ?). From all the above results it was concluded that the terminal oxophosphinidene complexes are preferentially formed under conditions of orbital control, while charge-controlled reactions tend to give derivatives with the electrophilic fragment bound to the oxygen atom of the oxophosphinidene ligand (phosphide-like, oxophosphinidene-bridged derivatives).     

Imide and anhydride bridged organoiron dinuclear homo and hetero dichalcogeno carboxylate complexes [CpFe(CO)2ECO(C6H4)CO]2NH and [CpFe(CO)2ECO(C6H4)CO]2O; E = S,Se

Organoiron thio- and seleno-terephthaloyl chloride complexes CpFe(CO)₂ECO(C₆H₄)COCl (E = S and Se) react with NaOH and NaNH₂ to give quantitative yields of the acid Cp(CO)₂ECO(C₆H₄)CO₂H and the amide CpFe(CO)₂ECO(C₆H₄)CONH₂ respectively. These amide and acid derivatives react with the terephthaloyl chloride complexes to give a new series of imide-bridged [CpFe(CO)₂ECO(C₆H₄)CO]₂NH and anhydride-bridged [CpFe(CO)₂ECO(C₆H₄)CO]₂O organoiron dinuclear homo and hetero dichalcogeno terephthalate complexes. The complexes were characterized by elemental analysis, i.r. and ¹H-n.m.r. spectra. This revised version was published online in June 2006 with corrections to the Cover Date.     

From coordinated oxophosphinidene to O,O,P-bound arylhypophosphite(2-) to build a singular Mo2Sn2O4P2 metallocycle

P-bound derivatives of the hypophosphorous acids can be prepared from complexed phosphinidene oxides. The anion [MoCp(CO) 2{P(O)R*}] (-)[(H-DBU) (+) salt (R* = 2,4,6-C 6H 2 (t)Bu 3; Cp = eta (5)-C 5H 5) reacts with SnCl 2Ph 2 to give the neutral oxophosphinidene complex [MoCp{P(O)R*}(CO) 2(SnPh 2Cl)] in high yield. Basic hydrolysis of the latter complex occurs readily to yield the novel Mo-Sn metallocyclic derivatives [MoSn{mu- O, P-OP(OH)R*}CpPh 2(CO) 2] and [MoSn{mu- O, O, P-O 2PR*}CpPh(CO) 2] 2. These products display respectively hydrogenhypophosphite(1-) and hypophosphite(2-) anions coordinated through all of their O (to Sn) and P (to Mo) atoms.