Aurophilic self-assembly of a Mo4Au2 phosphinidene complex with an unprecedented H-shaped planar metal core

The isomers [Mo2Cp2(mu-kappa(1):kappa(1),eta(6)-PR*)(CO)2] (1) and [Mo2Cp(mu-kappa(1):kappa(1),eta(5)-PC5H4)(CO)2(eta(6)-HR*)] (2) (Cp = eta(5)-C5H5; R* = 2,4,6-C6H2(t)Bu3) react with [AuCl(THT)] and with the cation [Au(THT)2](+) (THT = tetrahydrothiophene) to give phosphinidene-bridged Mo2Au complexes resulting from the addition of an AuCl or Au(THT)(+) electrophile to their multiple P-Mo bonds. Removal of the Cl(-) or THT ligand from these derivatives causes a dimerization of the trinuclear structures to give the cationic derivative [{AuMo2Cp(mu3-kappa(1):kappa(1):kappa(1),eta(5)-PC5H4)(CO)2(eta(6)-HR*)}2](2+), which displays a novel H-shaped metal core held by strong Mo-Au dative bonds [2.768(1) A] and an aurophilic interaction [Au-Au = 3.022(1) A].     

High yield synthesis and reactivity of a phosphinidene bridged dimolybdenum complex

Protonation of [Mo2Cp2(mu-H)(mu-PHR*)(CO)4] (Cp = eta5-C5H5, R* = 2,4,6-C6H2tBu3) with HBF4.OEt2 gives the hydridophosphinidene complex [Mo2Cp2(mu-H)(mu-PR*)(CO)4]BF4, which is easily deprotonated with H2O to give the known phosphinidene complex [Mo2Cp2(mu-PR*)(CO)4] in 95% yield. Reaction of the latter with I2 gives the unsaturated phosphinidene complex [Mo2Cp2I2(mu-PR*)(CO)2], which exhibits an intermetallic distance of 2.960(2) A. Irradiation of solutions of [Mo2Cp2(mu-PR*)(CO)4] with UV light gives a mixture of the triply bonded [Mo2Cp2(mu-PR*)(mu-CO)2] and the hydridophosphido derivative [Mo2Cp2(mu-H){mu-P(CH2CMe2)C6H2tBu2}(CO)4] as major species. The latter complex results from an intramolecular C-H bond cleavage from a tBu group and has been characterized by spectroscopy and an X-ray study. Irradiation in the presence of HCC(p-tol) results in the insertion of the alkyne into the Mo-P bond to give [Mo2Cp2{mu-eta1:eta2,kappa-C(p-tol)CHPR*}(CO)4] structurally characterized through an X-ray study.     

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)].     

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.     

Proton induced P-H and Mo-H bond activation at the phosphide bridged dimolybdenum complexes [Mo2Cp2(mu-H)(mu-PHR)(CO)4](R = Cy, 2,4,6-C6H2R'3; R'= H, Me, tBu)

The new hydride complexes [Mo2Cp2(mu-H)(mu-PHR)(CO)4] having bulky substituents (R = 2,4,6-C(6)H2tBu3= Mes*, R = 2,4,6-C6H2Me3= Mes) have been prepared in good yield by addition of Li[PHR] to the triply bonded [Mo2Cp2(CO)4] and further protonation of the resulting anionic phosphide complex [Mo2Cp2(mu-PHR)(CO)4]-. Protonation of the Mes* compound with either [H(OEt2)2][B{3,5-C6H3(CF3)2}4] or HBF4.OEt2 gives the cationic phosphinidene complex [Mo2Cp2(mu-H)(mu-PMes*)(CO)4]+ in high yield. In contrast, protonation of the analogous hydride compounds with Mes or Cy substituents on phosphorus give the corresponding unsaturated tetracarbonyls [Mo2Cp2(mu-PHR)(CO)4]+, which are unstable at room temperature and display a cis geometry. Decomposition of the latter give the electron-precise pentacarbonyls [Mo2Cp2(mu-PHR)(mu-CO)(CO)4]+, also displaying a cis arrangement of the metal fragments. In the presence of BF4- as external anion, fluoride abstraction competes with carbonylation to yield the neutral fluorophosphide hydrides [Mo2Cp2(mu-H)(mu-PFR)(CO)4]. Similar results were obtained in the protonation reactions of the hydride compounds having a Ph substituent on phosphorus. In that case, using HCl as protonation reagent gave the chloro-complex [Mo2ClCp2(mu-PHPh)(CO)4] in good yield. The structures and dynamic behaviour of the new compounds are analyzed on the basis of solution IR and 1H, 31P, 19F and 13C NMR data as well as the X-ray studies carried out on [Mo2Cp2(mu-H)(mu-PHMes)(CO)4](cis isomer), [Mo2Cp2(mu-H)(mu-PFMes)(CO)4](trans isomer), [Mo2Cp2(mu-PHCy)(mu-CO)(CO)4](BF4) and [Mo2ClCp2(mu-PHPh)(CO)4].     

Mechanistic investigation of CO2 hydrogenation by Ru(II) and Ir(III) aqua complexes under acidic conditions: two catalytic systems differing in the nature of the rate determining step

Ruthenium aqua complexes [(eta(6)-C(6)Me(6))Ru(II)(L)(OH(2))](2+) {L = bpy (1) and 4,4'-OMe-bpy (2), bpy = 2,2'-bipyridine, 4,4'-OMe-bpy = 4,4'-dimethoxy-2,2'-bipyridine} and iridium aqua complexes [Cp*Ir(III)(L)(OH(2))](2+) {Cp* = eta(5)-C(5)Me(5), L = bpy (5) and 4,4'-OMe-bpy (6)} act as catalysts for hydrogenation of CO(2) into HCOOH at pH 3.0 in H(2)O. The active hydride catalysts cannot be observed in the hydrogenation of CO(2) with the ruthenium complexes, whereas the active hydride catalysts, [Cp*Ir(III)(L)(H)](+) {L = bpy (7) and 4,4'-OMe-bpy (8)}, have successfully been isolated after the hydrogenation of CO(2) with the iridium complexes. The key to the success of the isolation of the active hydride catalysts is the change in the rate-determining step in the catalytic hydrogenation of CO(2) from the formation of the active hydride catalysts, [(eta(6)-C(6)Me(6))Ru(II)(L)(H)](+), to the reactions of [Cp*Ir(III)(L)(H)](+) with CO(2), as indicated by the kinetic studies.     

Chemistry of the phosphinidene oxide ligand

Reaction of [Mo2Cp2(mu-H)(mu-PHR*)(CO)4] with DBU followed by O2 gives the first anionic phosphinidene oxide complex (H-DBU)[MoCp{P(O)R*}(CO)2] (1) (DBU = 1,8-diazabicyclo [5.4.0] undec-7-ene; R* = 2,4,6-C6H2tBu3). This anion displays three different nucleophilic sites located at the O, P, and Mo atoms, as illustrated by the reactions reported. Thus, reaction of 1 with excess HBF4.OEt2 gave the fluorophosphide complex [MoCp(PFR*)(CO)2] via the hidroxophosphide intermediate [MoCp{PR*(OH)}(CO)2]. Related alkoxyphosphide compounds [MoCp{P(OR)R*}(CO)2] (R = Me, C(O)Ph) were prepared by reaction of 1 with [Me3O]BF4 and PhC(O)Cl, respectively, whereas reaction of 1 with MeI or C3H5Br gave the P,O-bound phosphinite complexes [MoCp(kappa2-OPRR*)(CO)2] (R = Me, C3H5). Metal-based electrophiles were found to bind at either O or Mo positions. Thus, reaction of 1 with [ZrCl2Cp2] gave the phosphinidene oxide bridged [MoCp{P(OZrClCp2)R*}(CO)2], whereas reaction with SnPh3Cl gave trans-[MoCp{P(O)R*}(CO)2(SnPh3)], an heterometallic complex having an intact terminal P(O)R* ligand.     

Transition metal complexes of the chelating phosphine borane ligand Ph2PCH2Ph2P.BH3

Chromium and ruthenium complexes of the chelating phosphine borane H(3)B.dppm are reported. Addition of H(3)B.dppm to [Cr(CO)(4)(nbd)](nbd = norbornadiene) affords [Cr(CO)(4)(eta1-H(3)B.dppm)] in which the borane is linked to the metal through a single B-H-Cr interaction. Addition of H(3)B.dppm to [CpRu(PR(3))(NCMe)(2)](+)(Cp =eta5)-C(5)H(5)) results in [CpRu(PR(3))(eta1-H(3)B.dppm)][PF(6)](R = Me, OMe) which also show a single B-H-Ru interaction. Reaction with [CpRu(NCMe)(3)](+) only resulted in a mixture of products. In contrast, with [Cp*Ru(NCMe)(3)](+)(Cp*=eta5)-C(5)Me(5)) a single product is isolated in high yield: [Cp*Ru(eta2-H(3)B.dppm)][PF(6)]. This complex shows two B-H-Ru interactions. Reaction with L = PMe(3) or CO breaks one of these and the complexes [Cp*Ru(L)(eta1-H(3)B.dppm)][PF(6)] are formed in good yield. With L = MeCN an equilibrium is established between [Cp*Ru(eta2-H(3)B.dppm)][PF(6)] and the acetonitrile adduct. [Cp*Ru (eta2-H(3)B.dppm)][PF(6)] can be considered as being "operationally unsaturated", effectively acting as a source of 16-electron [Cp*Ru (eta1-H(3)B.dppm)][PF(6)]. All the new compounds (apart from the CO and MeCN adducts) have been characterised by X-ray crystallography. The solid-state structure of H(3)B.dppm is also reported.     

Novel class of heterometallic cubane and boride clusters containing heavier group 16 elements

Thermolysis of an in situ generated intermediate, produced from the reaction of [Cp*MoCl(4)] (Cp* = η(5)-C(5)Me(5)) and [LiBH(4).THF], with excess Te powder yielded isomeric [(Cp*Mo)(2)B(4)TeH(5)Cl] (2 and 3), [(Cp*Mo)(2)B(4)(μ(3)-OEt)TeH(3)Cl] (4), and [(Cp*Mo)(4)B(4)H(4)(μ(4)-BH)(3)] (5). Cluster 4 is a notable example of a dimolybdaoxatelluraborane cluster where both oxygen and tellurium are contiguously bound to molybdenum and boron. Cluster 5 represents an unprecedented metal-rich metallaborane cluster with a cubane core. The dimolybdaheteroborane 2 was found to be very reactive toward metal carbonyl compounds, and as a result, mild pyrolysis of 2 with [Fe(2)(CO)(9)] yielded distorted cubane cluster [(Cp*Mo)(2)(BH)(4)(μ(3)-Te){Fe(CO)(3)}] (6) and with [Co(2)(CO)(8)] produced the bicapped pentagonal bipyramid [(Cp*MoCo)(2)B(3)H(2)(μ(3)-Te)(μ-CO){Co(3)(CO)(6)}] (7) and pentacapped trigonal prism [(Cp*MoCo)(2)B(3)H(2)(μ(3)-Te)(μ-CO)(4){Co(6)(CO)(8)}] (8). The geometry of 8 is an example of a heterometallic boride cluster in which five Co and one Mo atom define a trigonal prismatic framework. The resultant trigonal prism core is in turn capped by two boron, one Te, and one Co atom. In the pentacapped trigonal prism unit of 8, one of the boron atoms is completely encapsulated and bonded to one molybdenum, one boron, and five cobalt atoms. All the new compounds have been characterized in solution by IR, (1)H, (11)B, and (13)C NMR spectroscopy, and the structural types were unambiguously established by crystallographic analysis of 2 and 4-8.     

Trapping of hemiquinone radicals at Mo and P sites by phosphide-bridged dimolybdenum species: chemistry of complexes [Mo2(eta5-C5H5)2(OC6H4OH)(mu-PR2)(CO)4] and [Mo2(eta5-C5H5)2{mu-PR(OC6H4OH)}(CO)4]- (R = Cy, Ph)

The phosphide-bridged dimolybdenum complexes (H-DBU)[Mo2Cp2(mu-PR2)(CO)4] (R= Cy, Ph; DBU = 1,8-diazabicyclo[5.4.0.]undec-7-ene) react with p-benzoquinone to give the hemiquinone complexes [Mo(2)Cp2(OC6H4OH)(mu-PR2)(CO)4]. The latter experience facile homolytic cleavage of the corresponding Mo-O bonds and react readily at room temperature with HSPh or S2Ph2 to give the thiolate complexes [Mo2Cp2(mu-PCy2)(mu-SPh)(CO)4] or [Mo2Cp2(mu-PR2)(mu-SPh)(CO)2]. In contrast, PRH-bridged substrates experience overall insertion of quinone into the P-H bond to give the anionic compounds (H-DBU)[Mo(2)Cp2{mu-PR(OC6H4OH)}(CO)4], which upon acidification yield the corresponding neutral hydrides. The cyclohexyl anion experiences rapid nucleophilic displacement of the hemiquinone group by different anions ER- (ER = OH, OMe, OC4H5, OPh, SPh) to give novel anionic compounds (H-DBU)[Mo2Cp2{mu-PCy(ER)}(CO)4], which upon acidification yield the corresponding neutral hydrides. The structure of four of these hydride complexes [PPh(OC6H4OH), PCy(OH), PCy(OMe), and PCy(OPh) bridges] was determined by X-ray diffraction methods and confirmed the presence of cis and trans isomers in several of these complexes. In addition, it was found that the hydroxyphosphide anion [Mo2Cp2{mu-PCy(OH)}(CO)4]- displays in solution an unprecedented tautomeric equilibrium with its hydride-oxophosphinidene isomer [Mo2Cp2(mu-H){mu-PCy(O)}(CO)4]-.     

Dinuclear oxidative addition of N-H and S-H bonds at chromium. Reaction of (*)Cr(CO)(3)(C(5)Me(5)) with [o-(HA)C(6)H(4)S-Cr(CO)(3)(C(5)Me(5))] (A = S,NH) yielding [eta(2)-o-(mu-A)C(6)H(4)S-Cr(C(5)Me(5))](2) and H-Cr(CO)(3)(C(5)Me(5))

Reaction of the 17-electron radical (*)Cr(CO)(3)Cp* (Cp* = C(5)Me(5)) with 0.5 equiv of 2-aminophenyl disulfide [(o-H(2)NC(6)H(4))(2)S(2)] results in rapid oxidative addition to form the initial product (o-H(2)N)C(6)H(4)S-Cr(CO)(3)Cp*. Addition of a second equivalent of (*)Cr(CO)(3)Cp* to this solution results in the formation of H-Cr(CO)(3)Cp* as well as (1)/(2)[[eta(2)-o-(mu-NH)C(6)H(4)S]CrCp*](2). Spectroscopic data show that (o-H(2)N)C(6)H(4)S-Cr(CO)(3)Cp* loses CO to form [eta(2)-(o-H(2)N)C(6)H(4)S]Cr(CO)(2)Cp*. Attack on the N-H bond of the coordinated amine by (*)Cr(CO)(3)Cp* provides a reasonable mechanism consistent with the observation that both chelate formation and oxidative addition of the N-H bond are faster under argon than under CO atmosphere. The N-H bonds of uncoordinated aniline do not react with (*)Cr(CO)(3)Cp*. Reaction of the 2 mol of (*)Cr(CO)(3)Cp* with 1,2-benzene dithiol [1,2-C(6)H(4)(SH)(2)] yields the initial product (o-HS)C(6)H(4)S-Cr(CO)(3)Cp and 1 mol of H-Cr(CO)(3)Cp*. Addition of 1 equiv more of (*)Cr(CO)(3)Cp to this solution also results in the formation of 1 equiv of H-Cr(CO)(3)Cp*, as well as the dimeric product (1)/(2)[[eta(2)-o-(mu-S)C(6)H(4)S]CrCp*](2). This reaction also occurs more rapidly under Ar than under CO, consistent with intramolecular coordination of the second thiol group prior to oxidative addition. The crystal structures of [[eta(2)-o-(mu-NH)C(6)H(4)S]CrCp*](2) and [[eta(2)-o-(mu-S)C(6)H(4)S]CrCp*](2) are reported.     

Synthesis, characterisation, crystal structures, reactivity, and electrochemistry of ruthenium-nitrido, ruthenium-cobalt-imido and ruthenapyrrolidone carbonyl clusters containing alkyne ligands

Thermolysis of [Ru3(CO)9(mu3-NOMe)(mu3-eta2-PhC2Ph)] (1) with two equivalents of [Cp*Co(CO)2] in THF afforded four new clusters, brown [Ru5(CO)8(mu-CO)3(eta5-C5Me5)(mu5-N)(mu4-eta2-PhC2Ph)] (2), green [Ru3Co2(CO)7(mu3-CO)(eta5-C5Me5)2(mu3-NH)[mu4-eta8-C6H4-C(H)C(Ph)]] (3), orange [Ru3(CO)7(mu-eta6-C5Me4CH2)[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (4) and pale yellow [Ru2(CO)6[mu-eta3-PhC2(Ph)C(O)N(OMe)]] (5). Cluster 2 is a pentaruthenium mu5-nitrido complex, in which the five metal atoms are arranged in a novel "spiked" square-planar metal skeleton with a quadruply bridging alkyne ligand. The mu5-nitrido N atom exhibits an unusually low frequency chemical shift in its 15N NMR spectrum. Cluster 3 contains a triangular Ru2Co-imido moiety linked to a ruthenium-cobaltocene through the mu4-eta8-C6H4C(H)C(Ph) ligand. Clusters 4 and 5 are both metallapyrrolidone complexes, in which interaction of diphenylacetylene with CO and the NOMe nitrene moiety were observed. In 4, one methyl group of the Cp* ring is activated and interacts with a ruthenium atom. The "distorted" Ru3Co butterfly nitrido complex [Ru3Co(CO)5(eta5-C5Me5)(mu4-N)(mu3-eta2-PhC2Ph)(mu-I)2I] (6) was isolated from the reaction of 1 with [Cp*Co(CO)I2] heated under reflux in THF, in which a Ru-Ru wing edge is missing. Two bridging and one terminal iodides were found to be placed along the two Ru-Ru wing edges and at a hinge Ru atom, respectively. The redox properties of the selected compounds in this study were investigated by using cyclic voltammetry and controlled potential coulometry. 15N magnetic resonance spectroscopy studies were also performed on these clusters.     

One-step synthesis of alkenyl ketone complexes from Cp*RhCl2(PPh3), alkyne and H2O in the presence of KPF6

The reaction of Cp*RhCl2(PPh3) 1 with 1-alkyne and H2O in the presence of KPF6 afforded the alkenyl ketone complex [Cp*Rh(PPh3)(CPh=CHCOCH2R)](PF6) [R = p-tolyl (3a), R = Ph (3b)], whereas Cp*IrCl2(PPh3) 2 or [(eta 6-C6Me6)RuCl2(PPh3) gave the corresponding [Cp*IrCl(CO)(PPh3)](PF6) 5a and [(eta 6-C6Me6)RuCl(CO)(PPh3)](PF6).     

Parallel modes of C-H bond activation initiated by CpMo(NO)(CH2CMe3)(C6H5) at ambient temperatures

The molybdenum nitrosyl complex Cp*Mo(NO)(CH2CMe3)(C6H5) reacts at room temperature via elimination of neopentane or benzene to form the transient species Cp*Mo(NO)(=CHCMe3) and Cp*Mo(NO)(eta2-C6H4). These reactive intermediates effect the intermolecular activation of hydrocarbon C-H bonds via the reverse of the transformations by which they are generated. Thermolysis of Cp*Mo(NO)(CH2CMe3)(C6H5) in pyridine yields the adducts Cp*Mo(NO)(=CHCMe3)(NC5H5) and Cp*Mo(NO)(eta2-C6H4)(NC5H5), and the benzyne complex has been characterized by X-ray diffraction.     

Sulfur-bridged early-late heterobimetallics synthesized by incorporation of titanium,vanadium, and molybdenum into bis(hydrosulfido) templates of group 9 metals

Reactions of the bis(hydrosulfido) complexes [Cp*Rh(SH)(2)(PMe(3))] (1a; Cp* = eta(5)-C(5)Me(5)) with [CpTiCl(3)] (Cp = eta(5)-C(5)H(5)) and [TiCl(4)(thf)(2)] in the presence of triethylamine led to the formation of the sulfido-bridged titanium-rhodium complexes [Cp*Rh(PMe(3))(micro(2)-S)(2)TiClCp] (2a) and [Cp*Rh(PMe(3))(micro2-S)(2)TiCl(2)] (3a), respectively. Complex 3a and its iridium analogue 3b were further converted into the bis(acetylacetonato) complexes [Cp*M(PMe(3))(micro(2)-S)(2)Ti(acac)(2)] (4a, M = Rh; 4b, M = Ir) upon treatment with acetylacetone. The hydrosulfido complexes 1a and [Cp*Ir(SH)(2)(PMe(3))] (1b) also reacted with [VCl(3)(thf)(3)] and [Mo(CO)(4)(nbd)] (nbd = 2,5-norbornadiene) to afford the cationic sulfido-bridged VM2 complexes [(Cp*M(PMe(3))(micro2-S)(2))2V](+) (5a(+), M = Rh; 5b(+), M = Ir) and the hydrosulfido-bridged MoM complexes [Cp*M(PMe(3))(micro2-SH)(2)Mo(CO)(4)] (6a, M = Rh; 6b, M = Ir), respectively.     

Comparative bonding behavior of functional cyclopentadienyl ligands and boron-containing analogues in heterometallic complexes and clusters

The reactivity of isolobal molybdenum carbonylmetalates containing a 2-boratanaphthalene, [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (5a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (5b), a 1-boratabenzene, [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (8), or a functionalized cyclopentadienyl ligand, the new metalate [Mo(eta5-C5H4Ph)(CO)3]- (7) and [Mo(eta5-C5H4NMe2)(CO)3]- (9), toward palladium (I and II) or platinum (I and II) complexes, such as trans-[PdCl2(NCPh)2], [Pd2(NCMe)6](BF4)2, trans-[PtCl2(PEt3)2], and [N(n-Bu)4]2 [Pt2Cl4(CO)2], has been investigated, and this has allowed an evaluation of the influence of the pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal-bonded heterometallic clusters. The new 58 CVE planar-triangulated centrosymmetric clusters, [Mo2Pd2(eta5-C5H4Ph)2(CO)6(PEt3)2] (11), [Mo2Pd2(eta5-2,4-MeC9H6BNi-Pr2)2(CO)6] (12), [Mo(2)Pd(2)(eta5-3,5-Me2C5H3BNi-Pr2)2(CO)6] (13), [Mo2Pd2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (15), [Mo2Pt2(eta5-C5H4NMe2)2(CO)6(PEt3)2] (16), and [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (20), have been characterized by single-crystal X-ray diffraction. Their structural features were compared with those of the 54 CVE cluster [Re2Pd2(eta5-C4H4BPh)2(CO)6)] (4), previously obtained from the borole-containing metalate [Re(eta5-C4H4BPh)(CO)3]- (2), in which a 2e-3c B-C(ipso)-Pd interaction involving the pi-ring was observed. As an extension of what has been observed in 4, clusters 12 and 13 present a direct interaction of the boratanaphthalene (12) and the boratabenzene (13) ligands with palladium. In clusters 11, 15, 16, and 20, the pi-ring does not interact with the palladium (11 and 15) or platinum centers (16 and 20), which confers to these clusters a geometry very similar to that of [Mo2Pd2(eta5-C5H5)2(CO)6(PEt3)2] (3b). The carbonylmetalates [Mo(pi-ring)(CO)3]- are thus best viewed as formal four electron donors which bridge a dinuclear d9-d9 unit. The orientation of this building block in the clusters influences the shape of their metal cores and the bonding mode of the bridging carbonyl ligands. The crystal structure of new centrosymmetric complex [Mo(eta5-C5H4Ph)(CO)3]2 (10) was determined, and it revealed intramolecular contacts of 2.773(4) A between the carbon atoms of carbonyl groups across the metal-metal bond and intermolecular bifurcated interactions between the carbonyl oxygen atoms (2.938(4) and 3.029(4) A), as well as intermolecular C-H...pi(Ar)(C=C) interactions (2.334(3) and 2.786(4) A) involving the phenyl substituents.     

Reactivity of transition metal-phosphorus triple bonds towards triply bonded [{CpMo(CO)2}2]: formation of heteronuclear cluster compounds

Thermolysis of [Cp*P{W(CO)5}2] (1) in the presence of [{CpMo(CO)2}2] leads to the novel complexes [{(CO)2Cp*W}{CpMo(CO)2}(micro,eta2:eta1:eta1-P2{W(CO)5}2)] (6; Cp=eta5-C5H5, Cp*=eta5-C5Me5), [{(micro-O)(CpMoWCp*)W(CO)4}{micro3-PW(CO)5}2] (7), [{CpMo(CO)2}2{Cp*W(CO)2}{micro3-PW(CO)5}] (8) and [{CpMo(CO)2}2{Cp*W(CO)2}(micro3-P)] (9). The structural framework of the main products 8 and 9 can be described as a tetrahedral Mo2WP unit that is formed by a cyclisation reaction of [{CpMo(CO)2}2] with an [Cp*(CO)2W[triple chemical bond]P-->W(CO)5] intermediate containing a W--P triple bond and subsequent metal-metal and metal-phosphorus bond formation. Photolysis of 1 in the presence of [{CpMo(CO)2}2] gives 8, 9 and phosphinidene complex [(micro3-PW(CO)5){CpMo(CO)2W(CO)5}] (10), in which the P atom is in a nearly trigonal-planar coordination environment formed by one {CpMo(CO)2} and two {W(CO)5} units. Comprehensive structural and spectroscopic data are given for the products. The reaction pathways are discussed for both activation procedures, and DFT calculations reveal the structures with minimum energy along the stepwise Cp* migration process under formation of the intermediate [Cp*(CO)2W[triple chemical bond]P-->W(CO)5].     

Heterometallic cluster complexes (RhMo, RhW) containing bridging 1,2-dicarba-closo-dodecaborane-1,2-dichalocogenolato ligands

The 16-electron half-sandwich rhodium complex [Cp*Rh{E2C2(B10H10)}] [Cp* = eta5-C5Me5, E = S (1a), Se (1b)] [Cp*Rh{E2C2(B10H10)} = eta5-pentamethylcyclopentadienyl[1,2-dicarba-closo-dodecaborane(12)-dichalcogenolato]rhodium] reacted with Mo(CO)3(py)3 in the presence of BF3.Et2O in THF solution to afford the {Cp*Rh[E2C2(B10H10)]}2Mo(CO)2 (E = S (3a); Se (3b)), {Cp*Rh[S2C2(B10H10)]}{Mo(CO)2[S2C2(B10H10)]} (4). The voluminous di-tert-butyl substituted Cp half-sandwich rhodium complex [Cp'Rh{E2C2(B10H10)}] [E = S (2a), Se (2b)] [CpRh{E2C2(B10H10)} = eta5-(1,3-di(tert-butyl)cyclopentadienyl-[1,2-dicarba-closo-dodecaborane(12)-dichalcogenolato]rhodium) reacted with W(CO)3(py)3 in the presence of BF3.Et2O in THF solution to give the {Cp'Rh[S2C2(B10H10)]}{W(CO)2[S2C2(B10H10)]} (5) and {Cp'Rh[Se2C2(B10H10)]}(mu-CO)[W(CO)3] (6), respectively. The complexes have been fully characterized by IR and NMR spectroscopy as well as by elemental analyses. The X-ray crystal structures of the complexes 3-6 are reported.     

Synthesis and reactivity of the monomeric late-transition-metal parent amido complex [Ir(Cp*)(PMe3)(Ph)(NH2)

The late-transition-metal parent amido compound [Ir(Cp*)(PMe3)(Ph)(NH2)] (2) has been synthesized by deprotonation of the corresponding ammine complex [Ir(Cp*)(PMe3)(Ph)(NH3)][OTf] (6) with KN(SiMe3)2. An X-ray structure determination has ascertained its monomeric nature. Proton-transfer studies indicate that 2 can successfully deprotonate p-nitrophenylacetonitrile, aniline, and phenol. Crystallographic analysis has revealed that the ion pair [Ir(Cp*)(PMe3)(Ph)(NH3)][OPh] (8) exists as a hydrogen-bonded dimer in the solid state. Reactions of 2 with isocyanates and carbodiimides lead to overall insertion of the heterocumulenes into the N--H bond of the Ir-bonded amido group, demonstrating the ability of 2 to act as an efficient nucleophile. Intriguing reactivity is observed when amide 2 reacts with CO or 2,6-dimethylphenyl isocyanide. eta4-Tetramethylfulvene complexes [Ir(eta4-C5Me4CH2)(PMe3)(Ph)(L)] (L=CO (15), CNC6H3-2,6-(CH3)2 (16)) are formed in solution through displacement of the amido group by the incoming ligand followed by deprotonation of a methyl group on the Cp* ring and liberation of ammonia. Conclusive evidence for the presence of the Ir-bonded eta4-tetramethylfulvene moiety in the solid state has been provided by an X-ray diffraction study of complex 16.