Trans --> cis isomerization of trans-[(dppm)2Ru(H)(L)][BF4] (L = P(OR)3) complexes: preparation of cis-[(dppm)2Ru(eta2-H2)(L)][BF4]2

A series of new dicationic dihydrogen complexes of ruthenium of the type cis-[(dppm)(2)Ru(eta(2)-H(2))(L)][BF(4)](2) (dppm = Ph(2)PCH(2)PPh(2); L = P(OMe)(3), P(OEt)(3), PF(O(i)Pr)(2)) have been prepared by protonating the precursor hydride complexes cis-[(dppm)(2)Ru(H)(L)][BF(4)] (L = P(OMe)(3), P(OEt)(3), P(O(i)Pr)(3)) using HBF(4).Et(2)O. The cis-[(dppm)(2)Ru(H)(L)][BF(4)] complexes were obtained from the trans hydrides via an isomerization reaction that is acid-accelerated. This isomerization reaction gives mixtures of cis and trans hydride complexes, the ratios of which depend on the cone angles of the phosphite ligands: the greater the cone angle, the greater is the amount of the cis isomer. The eta(2)-H(2) ligand in the dihydrogen complexes is labile, and the loss of H(2) was found to be reversible. The protonation reactions of the starting hydrides with trans PMe(3) or PMe(2)Ph yield mixtures of the cis and the trans hydride complexes; further addition of the acid, however, give trans-[(dppm)(2)Ru(BF(4))Cl]. The roles of the bite angles of the dppm ligand as well as the steric and the electronic properties of the monodentate phosphorus ligands in this series of complexes are discussed. X-ray crystal structures of trans-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], cis-[(dppm)(2)Ru(H)(P(OMe)(3))][BF(4)], and cis-[(dppm)(2)Ru(H)(P(O(i)Pr)(3))][BF(4)] complexes have been determined.     

Structure and H(2)-Loss Energies of OsHX(H(2))(CO)L(2) Complexes (L = P(t-Bu)(2)Me, P(i-Pr)(3); X = Cl, I, H): Attempted Correlation of (1)J(H-D), T(1min), and DeltaG()

1J(H-D), T(1min) and k(1) for H(2) dissociation from OsHX(H(2))(CO)L(2) have been measured for X = Cl, I, H (L = P(t-Bu)(2)Me or P(i-Pr)(3)), as well as for OsCl(2)(H(2))(CO)(P(i-Pr)(3))(2). For comparison, new data (including previously unobserved coupling constants) have been reported for W(HD)(CO)(3)(P(i-Pr)(3))(2). A comprehensive consideration of T(1min) data for over 20 dihydrogen complexes containing only 1-2 phosphines cis to H(2), together with a consideration of the shortest "conceivable" H-H distance for H(2) bound to a d(4) or d(6) metal, is used to argue that the "fast spinning" model is not appropriate for determining r(H-H) in such complexes. Regarding OsHX(H(2))(CO)L(2), the stronger electron-donor (lighter) halide, when cis to H(2), facilitates loss of H(2). The complete absence of pi-donor ability when X = H renders H(2) loss most difficult. However, a pi-donor trans to H(2) also makes H(2) loss unobservable. Within the series of isoelectronic, structurally analogous Os complexes, a longer H-H bond shows a larger DeltaG() for H(2) loss. However, this correlation does not continue to W(H(2))(CO)(3)(P(i-Pr)(3))(2), which has r(H-H) comparable to that of OsH(halide)(H(2))(CO)(P(i-Pr)(3))(2), but a significantly higher DeltaG(). This may originate from lack of a pi-donor ligand to compensate as H(2) leaves W.     

Dynamics of a cis-dihydrogen/hydride complex of iridium

Insertion of CS2 into one of the Ir-H bonds of [Ir(H)5(PCy3)2] takes place to afford the dihydrido dithioformate complex cis-[Ir(H)2(eta2-S2CH)(PCy3)2] accompanied by the elimination of H2. Protonation of the dithioformate complex using HBF4.Et2O gives cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] wherein the H atom undergoes site exchange between the dihydrogen and the hydride ligands. The dynamics was found to be so extremely rapid with respect to the NMR time scale that the barrier to exchange could not be measured. Partial deuteration of the hydride ligands resulted in a J(H,D) of 6.5 and 7.7 Hz for the H2D and the HD2 isotopomers of cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4], respectively. The H-H distance (d(HH)) for this complex has been calculated to be 1.05 A, which can be categorized under the class of elongated dihydrogen complexes. The cis-[Ir(H)(eta2-H2)(eta2-S2CH)(PCy3)2][BF4] complex undergoes substitution of the bound H2 moiety with CH(3)CN and CO resulting in new hydride derivatives, cis-[Ir(H)(L)(eta2-S2CH)(PCy3)2][BF4] (L = CH3CN, CO). Reaction of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] with electrophilic reagents such as MeOTf and Me3SiOTf afforded a new hydride aquo complex cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] via the elimination of CH4 and Me3SiH, respectively, followed by the binding of a water molecule (present in trace quantities in the solvent) to the iridium center. The X-ray crystal structures of cis-[Ir(H)2(eta2-S2CH)(PCy3)2] and cis-[Ir(H)(H2O)(eta2-S2CH)(PCy3)2][OTf] have been determined.     

Mixed phosphine and group-13 metal ligator complexes [(PR3)(a)M(ECp*)b] (M = Mo, Ni; E = Ga, Al; R = C6H5, cyclo-C6H11, CH3)

Treatment of [Mo(N(2))(PMe(3))(5)] with two equivalents GaCp* (Cp* = η(5)-C(5)(CH(3))(5)) leads to the formation of cis-[Mo(GaCp*)(2)(PMe(3))(4)] (1), while AlCp* did not react with this precursor. In addition, [Ni(GaCp*)(2)(PPh(3))(2)] (2a), [Ni(AlCp*)(2)(PPh(3))(2)] (2b), [Ni(GaCp*)(2)(PCy(3))(2)] (3a), [Ni(GaCp*)(2)(PMe(3))(2)] (3b), [Ni(GaCp*)(3)(PCy(3))] (4) and [Ni(GaCp*)(PMe(3))(3)] (5) have been prepared in high yields by a direct synthesis from [Ni(COD)(2)] and stoichiometric amounts of the ligands PR(3) and ECp* (E = Al, Ga), respectively. All compounds have been fully characterized by (1)H, (13)C, and (31)P NMR spectroscopy, elemental analysis and single crystal X-ray diffraction studies.     

Preparation and characterization of ruthenium(II) monophosphaferrocene complexes. Reactivity, dynamic solution behavior, and X-ray structure of [RuH(2)(eta(2)-H(2))(PCy(3))2(2-phenyl-3,4-dimethylphosphaferrocene)

The bis(dihydrogen) complex RuH(2)(H(2))(2)(PCy(3))(2) (1) reacts with 2-phenyl-3,4-dimethylphosphaferrocene (L(1)) to give RuH(2)(H(2))(PCy(3))(2)(L(1)) (2). This dihydride-dihydrogen complex has been characterized by X-ray crystallography and variable-temperature (1)H and (31)P NMR spectroscopy. The exchange between the dihydrogen ligand and the two hydrides is characterized by a DeltaG() of 46.2 kJ/mol at 263 K. H/D exchange is readily observed when heating a C(7)D(8) solution of 2 (J(H-D) = 30 Hz). The H(2) ligand in 2 can be displaced by ethylene or carbon monoxide leading to the corresponding ethylene or carbonyl complexes. The reaction of 1 with 2 equiv of 3,4-dimethylphosphaferrocene (L(2)) yields the dihydride complex RuH(2)(PCy(3))(2)(L(2))(2) (5).     

Preparation, spectroscopy, EXAFS, electrochemistry and pharmacology of new ruthenium(II) carbonyl complexes containing ferrocenylthiosemicarbazone and triphenylphosphine/arsine

A new series of new hetero-bimetallic complexes containing iron and ruthenium of the general formula [RuCl(CO)(B)(EPh3)(L)] (where E=P or As; B=PPh3, AsPh3, py or pip; L=ferrocene derived monobasic bidentate thiosemicarbazone ligand) have been synthesized by the reaction between ferrocene-derived thiosemicarbazones and ruthenium(II) complexes of the type [RuHCl(CO)(B)(EPh3)2] (where E=P or As; B=PPh3, AsPh3, py or pip). The new complexes have been characterized by elemental analyses, IR, electronic, NMR (1H, 13C and 31P), EXAFS (extended X-ray absorption fine structure spectroscopy) and cyclic voltammetric techniques. Antibacterial activity of the new complexes has been screened against Escherichia coli, Vibrio cholerae, and Pseudomonas aeruginosa species.     

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).     

Synthesis and spectroscopic properties of elongated ruthenium dihydrogen complexes: temperature and isotope dependence of H-H distances

Several dihydrogen complexes of ruthenium of the form [Cp/Cp*Ru(P-P)H(2)](+) (P-P = chelating diphosphine ligand) have been prepared by reaction of the corresponding neutral chloride complexes with H(2) in the presence of NaB(ArF)(4). Treatment with D(2) or T(2) gas leads to incorporation of deuterium or tritium in the dihydrogen ligand. Measurement of the resulting H-D and H-T couplings as a function of the temperature and magnetic field gives results consistent with computational studies which predict that the H-H bond distance will increase with temperature and will be significantly shortened by isotopic substitution. The degree of the observed temperature dependence is found to be a critical function of the ancillary ligand set.     

Preparation, structures and some reactions of novel diynyl complexes of iron and ruthenium

Reactions between HC triple bond CC triple bond CSiMe3 and several ruthenium halide precursors have given the complexes Ru(C triple bond CC triple bond CSiMe3)(L2)Cp'[Cp'= Cp, L = CO (1), PPh3 (2); Cp' = Cp*, L2= dppe (3)]. Proto-desilylation of 2 and 3 have given unsubstituted buta-1,3-diyn-1-yl complexes Ru(C triple bond CC triple bond CH)(L2)Cp'[Cp'= Cp, L = PPh3 (5); Cp'= Cp*, L2 = dppe (6)]. Replacement of H in 5 or 6 with Au(PR3) groups was achieved in reactions with AuCl(PR3) in the presence of KN(SiMe3)2 to give Ru(C triple bond CC triple bond CAu(PR3)](L2)Cp'[Cp' = Cp, L = PPh3, R = Ph (7); Cp' = Cp*, L2= dppe, R = Ph (8), tol (9)]. The asymmetrically end-capped [Cp(Ph3P)2Ru]C triple bond CC triple bond C[Ru(dppe)Cp*] (10) was obtained from Ru(C triple bond CC triple bond CH)(dppe)Cp* and RuCl(PPh3)2Cp. Single-crystal X-ray structural determinations of and are reported, with a comparative determination of the structure of Fe(C triple bond CC triple bond CSiMe3)(dppe)Cp* (4), and those of a fifth polymorph of [Ru(PPh3)2Cp]2(mu-C triple bond CC triple bond C) (12), and [Ru(dppe)Cp]2(mu-C triple bond CC triple bond C) (13).     

Cubane-type heterometallic sulfido clusters: incorporation of two metal fragments into a dinuclear ReS(mu-S)2ReS core affording bimetallic M2Re2(mu 3-S)4 clusters (M = Ru,Pt, Cu) or trimetallic MM'Re2(mu 3-S)4 clusters via incomplete cubane-type MRe2(mu 3-S)(mu 2-S)3 intermediates (M = Ru,Rh, Ir; M' = Mo,W, Pd,Ru, Rh)

Reactions of a dirhenium tetra(sulfido) complex [PPh(4)](2)[ReS(L)(mu-S)(2)ReS(L)] (L = S(2)C(2)(SiMe(3))(2)) with a series of group 8-11 metal complexes in MeCN at room temperature afforded either the cubane-type clusters [M(2)(ReL)(2)(mu(3)-S)(4)] (M = CpRu (2), PtMe(3), Cu(PPh(3)) (4); Cp = eta(5)-C(5)Me(5)) or the incomplete cubane-type clusters [M(ReL)(2)(mu(3)-S)(mu(2)-S)(3)] (M = (eta(6)-C(6)HMe(5))Ru (5), CpRh (6), CpIr (7)), depending on the nature of the metal complexes added. It has also been disclosed that the latter incomplete cubane-type clusters can serve as the good precursors to the trimetallic cubane-type clusters still poorly precedented. Thus, treatment of 5-7 with a range of metal complexes in THF at room temperature resulted in the formation of novel trimetallic cubane-type clusters, including the neutral clusters [[(eta(6)-C(6)HMe(5))Ru][W(CO)(3)](ReL)(2)(mu(3)-S)(4)], [(CpM)[W(CO)(3)](ReL)(2)(mu(3)-S)(4)] (M = Rh, Ir), [(Cp*Ir)[Mo(CO)(3)](ReL)(2)(mu(3)-S)(4)], [[(eta(6)-C(6)HMe(5))Ru][Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)], and [(Cp*Ir)[Pd(PPh(3))](ReL)(2)(mu(3)-S)(4)] (13) along with the cationic clusters [(Cp*Ir)(CpRu)(ReL)(2)(mu(3)-S)(4)][PF(6)] (14) and [(Cp*Ir)[Rh(cod)](ReL)(2)(mu(3)-S)(4)][PF(6)] (cod = 1,5-cyclooctadiene). The X-ray analyses have been carried out for 2, 4, 7, 13, and the SbF(6) analogue of 14 (14') to confirm their bimetallic cubane-type, bimetallic incomplete cubane-type, or trimetallic cubane-type structures. Fluxional behavior of the incomplete cubane-type and trimetallic cubane-type clusters in solutions has been demonstrated by the variable-temperature (1)H NMR studies, which is ascribable to both the metal-metal bond migration in the cluster cores and the pseudorotation of the dithiolene ligand bonded to the square pyramidal Re centers, where the temperatures at which these processes proceed have been found to depend upon the nature of the metal centers included in the cluster cores.     

Stoichiometric and catalytic reactivity of the N-heterocyclic carbene ruthenium hydride complexes [Ru(NHC)(L)(CO)HCl] and [Ru(NHC)(L)(CO)H(eta2-BH4)] (L=NHC, PPh3)

Thermolysis of [Ru(AsPh3)3(CO)H2] with the N-aryl heterocyclic carbenes (NHCs) IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IPr (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) or the adduct SIPr.(C6F5)H (SIPr=1,3-bis(2,6-diisopropylphenyl)-4,5-dihydroimidazol-2-ylidene), followed by addition of CH2Cl2, affords the coordinatively unsaturated ruthenium hydride chloride complexes [Ru(NHC)2(CO)HCl] (NHC=IMes , IPr , SIPr ). These react with CO at room temperature to yield the corresponding 18-electron dicarbonyl complexes . Reduction of and [Ru(IMes)(PPh3)(CO)HCl] () with NaBH4 yields the isolable borohydride complexes [Ru(NHC)(L)(CO)H(eta2-BH4)] (, L=NHC, PPh3). Both the bis-IMes complex and the IMes-PPh3 species react with CO at low temperature to give the eta1-borohydride species [Ru(IMes)(L)(CO)2H(eta1-BH4)] (L=IMes , PPh3), which can be spectroscopically characterised. Upon warming to room temperature, further reaction with CO takes place to afford initially [Ru(IMes)(L)(CO)2H2] (L=IMes, L=PPh3) and, ultimately, [Ru(IMes)(L)(CO)3] (L=IMes , L=PPh3). Both and lose BH3 on addition of PMe2Ph to give [Ru(IMes)(L)(L')(CO)H2](L=L'=PMe2Ph; L=PPh3, L'=PMe2Ph). Compounds and have been tested as catalysts for the hydrogenation of aromatic ketones in the presence of (i)PrOH and H2. For the reduction of acetophenone, catalytic activity varies with the NHC present, decreasing in the order IPr>IMes>SIMes.     

Mechanism of the copper-free palladium-catalyzed Sonagashira reactions: multiple role of amines

Amines used as bases in copper-free, palladium-catalyzed Sonogashira reactions play a multiple role. The oxidative addition of iodobenzene with [Pd(0)(PPh(3))(4)] is faster when performed in the presence of amines (piperidine>morpholine). Amines also substitute one ligand L in trans-[PdI(Ph)(L)(2)] (L=PPh(3), AsPh(3)) formed in the oxidative addition. This reversible reaction, which gives [PdI(Ph)L(R(2)NH)], is favored in the order AsPh(3)>PPh(3) and piperidine>morpholine. Two mechanisms are proposed for Sonogashira reactions, depending on the ligand and the amine. When L=PPh(3), its substitution by the amine in trans-[PdI(Ph)(PPh(3))(2)] is less favored than that of the alkyne. A mechanism involving prior coordination of the alkyne is suggested, followed by deprotonation of the ligated alkyne by the amine. When L=AsPh(3), its substitution in trans-[PdI(Ph)(AsPh(3))(2)] by the piperidine is easier than that by the alkyne, leading to a different mechanism: substitution of AsPh(3) by the amine is followed by substitution of the second AsPh(3) by the alkyne to generate [PdI(Ph)(amine)(alkyne)]. Deprotonation of the ligated alkyne by an external amine leads to the coupling product. This explains why the catalytic reactions are less efficient with AsPh(3) than with PPh(3) as ligand.     

Nature of the Rh-H(2) Bond in a Dihydrogen Complex Stabilized Only by Nitrogen Donors. Inelastic Neutron Scattering Study of Tp(Me)2RhH(2)(eta(2)-H(2)) (Tp(Me)2 = Hydrotris(3,5-dimethylpyrazolyl)borate)

The tunnel splitting of the librational ground state and the torsional frequencies of the dihydrogen ligand in Tp(Me)()2RhH(2)(eta(2)-H(2)) (Tp(Me)()2 = hydrotris(3,5-dimethylpyrazolyl)borate) were measured using inelastic neutron scattering spectroscopy. The barrier for the rotation of the H(2) ligand and its H-H separation, calculated from these data, are 0.56(2) kcal/mol and 0.94 ?, respectively. These values indicate that pi-back-donation from the Tp(Me)()2RhH(2) fragment to H(2) is relatively weak and/or the interaction between the coordinated dihydrogen molecule and the two cis-hydride ligands significantly lowers the barrier for H(2) rotation.     

Facile Ru-H2 heterolytic activation and intramolecular proton transfer assisted by basic N-centers in the ligands

The use of the phosphine PPh2py instead of PPh3 in complexes of the type [Cp*RuH(P)2] enormously alters the kinetic control of the proton-transfer reactions over this compound and its chemical behavior. The reaction at low temperature of [Cp*RuH(PPh2py)2], 2, with HBF4 gives as products the classical dihydride trans-[Cp*RuH2(PPh2py)2](BF4), 3 (1 equiv of HBF4) or the dihydrogen-bonded complex [Cp*RuHH(PPh2pyH)(PPh2py)](BF4)2, 4 (2 equiv of HBF4). These complexes exhibit very accessible intramolecular processes of proton transfer, and finally, a slow release of H2 takes place at room temperature. Derivatives 2 and 3 are active catalysts for the deuterium labeling of H2 using methanol-d4 as an isotopic source. This demonstrates that the release of hydrogen is reversible, that the heterolytic activation of H2 is an easy process, and that acid species participate in the intramolecular proton-transfer processes. These observations are supported by reaction-coordinate calculations at the DFT/B3LYP level that show the existence of a low-energy reaction path that easily transforms the classical trans dihydride complex into the nonclassical cis dihydrogen compound in a reversible way, through the involvement of hydrogen- and dihydrogen-bonded intermediates and the essential participation of the pyridine centers. The different energy minima of this reaction profile are very accessible through low-energy transition states, all of which have been located.     

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

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

Quasi-octahedral complexes of pentamethylcyclopentadienyliridium(III) bearing bis(diphenylphosphinomethyl)phenylphosphine (dpmp)

Reaction of [Cp*IrCl2]2 (1) with dpmp in the presence of KPF6 afforded a binuclear complex [Cp*IrCl(dpmp-P1,P2;P3)IrCl2Cp*](PF6) (2) (dpmp =(Ph2PCH2)2PPh). The mononuclear complex [Cp*IrCl(dpmp-P1,P2)](PF6) (4) was generated by the reaction of [Cp*IrCl2(BDMPP)](BDMPP =PPh[2,6-(MeO)2C6H3]2) with dpmp in the presence of KPF6. These mono- and binuclear complexes have four-membered ring structures with a terminal and a central P atom of the dpmp ligand coordinated to an iridium atom as a bidentate ligand. Since there are two chiral centers at the Ir atom and a central P2 atom, there are two diastereomers that were characterized by spectrometry. Complexes anti-4 and syn-4 reacted with [Cp*RhCl2]2 or [(C6Me6)RuCl2]2, giving the corresponding mixed-metal complexes, anti- and syn- [Cp*IrCl(dppm-P1,P2;P3)MCl2L](PF6) (6: M = Rh, L = Cp*; 7: M = Ru, L = C6Me6). Treatment with AuCl(SC4H8) gave tetranuclear complexes, anti- and syn-8 [[Cp*IrCl(dppm-P1,P2;P3)AuCl]2](PF6)2 bearing an Au-Au bond. Reaction of anti- with PtCl2(cod) generated the trinuclear complex anti-9, anti-[[Cp*IrCl(dppm-P1,P2;P3)]2PtCl2](PF6)2. These reactions proceeded stereospecifically. The P,O-chelated complex syn-[Cp*IrCl(BDMPP-P,O)] (syn-10)(BDMPP-P,O = PPh[2,6-(MeO)2C6H3][2-O-6-(MeO)C6H3]2) reacted with dpmp in the presence of KPF6, generating the corresponding anti-complex as a main product as well as a small amount of syn-complex, [Cp*Ir(BDMPP-P,O)(dppm-P1)](PF6) (11). The reaction proceeded preferentially with inversion. The reaction processes were investigated by PM3 calculation. anti- was treated with MCl2(cod), giving anti-[Cp*Ir(BDMPP-P,O)(dppm-P1;P2,P3)MCl2](PF6)(14: M = Pt; 15: M = Pd), in which the MCl2 moiety coordinated to the two free P atoms of anti-11. The X-ray analyses of syn-2, anti-2, anti-4, anti-8 and anti-11 were performed.     

Solution and solid-state dynamics of metal-coordinated white phosphorus

The dynamic behavior in solution of eight mono-hapto?tetraphosphorus transition metal-complexes, trans-[Ru(dppm)(2) (H)(η(1) -P(4) )]BF(4) ([1]BF(4) ), trans-[Ru(dppe)(2) (H)(η(1) -P(4) )]BF(4) ([2]BF(4) ), [CpRu(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([3]PF(6) ), [CpOs(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([4]PF(6) ), [Cp*Ru(PPh(3) )(2) (η(1) -P(4) )]PF(6) ([5]PF(6) ), [Cp*Ru(dppe)(η(1) -P(4) )]PF(6) ([6]PF(6) ), [Cp*Fe(dppe)(η(1) -P(4) )]PF(6) ([7]PF(6) ), [(triphos)Re(CO)(2) (η(1) -P(4) )]OTf ([8]OTf), and of three bimetallic Ru(μ,η(1:2) -P(4) )Pt species [{Ru(dppm)(2) (H)}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([1-Pt]BF(4) ), [{Ru(dppe)(2) (H)}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([2-Pt]BF(4) ), [{CpRu(PPh(3) )(2) )}(μ,η(1:2) -P(4) ){Pt(PPh(3) )(2) }]BF(4) ([3-Pt]BF(4) ), [dppm=bis(diphenylphosphanyl)methane; dppe=1,2-bis(diphenylphosphanyl)ethane; triphos=1,1,1-tris(diphenylphosphanylmethyl)ethane; Cp=η(5) -C(5) H(5) ; Cp*=η(5) -C(5) Me(5) ] was studied by variable-temperature (VT) NMR and (31) P{(1) H} exchange spectroscopy (EXSY). For most of the mononuclear species, NMR spectroscopy allowed to ascertain that the metal-coordinated P(4) molecule experiences a dynamic process consisting, apart from the free rotation about the M?P(4) axis, in a tumbling movement of the P(4) cage while remaining chemically coordinated to the central metal. EXSY and VT (31) P?NMR experiments showed that also the binuclear complex cations [1-Pt](+) -[3-Pt](+) are subjected to molecular motions featured by the shift of each metal from one P to an adjacent one of the P(4) moiety. The relative mobility of the metal fragments (Ru vs. Pt) was found to depend on the co-ligands of the binuclear complexes. For complexes [2]BF(4) and [3]PF(6) , MAS, (31) P?NMR experiments revealed that the dynamic processes observed in solution (i.e., rotation and tumbling) may take place also in the solid state. The activation parameters for the dynamic processes of complexes 1(+) , 2(+) , 3(+) , 4(+) , 6(+) , 8(+) in solution, as well as the X-ray structures of 2(+) , 3(+) , 5(+) , 6(+) are also reported. The data collected suggest that metal-coordinated P(4) should not be considered as a static ligand in solution and in the solid state.     

Connecting [NiFe]- and [FeFe]-Hydrogenases: Mixed-Valence Nickel-Iron Dithiolates with Rotated Structures

New mixed-valence iron-nickel dithiolates are described that exhibit structures similar to those of mixed-valence diiron dithiolates. The interaction of tricarbonyl salt [(dppe)Ni(pdt)Fe(CO)(3)]BF(4) ([1]BF(4), where dppe = Ph(2)PCH(2)CH(2)PPh(2) and pdt(2-) = -SCH(2)CH(2)CH(2)S-) with P-donor ligands (L) afforded the substituted derivatives [(dppe)Ni(pdt)Fe(CO)(2)L]BF(4) incorporating L = PHCy(2) ([1a]BF(4)), PPh(NEt(2))(2) ([1b]BF(4)), P(NMe(2))(3) ([1c]BF(4)), P(i-Pr)(3) ([1d]BF(4)), and PCy(3) ([1e]BF(4)). The related precursor [(dcpe)Ni(pdt)Fe(CO)(3)]BF(4) ([2]BF(4), where dcpe = Cy(2)PCH(2)CH(2)PCy(2)) gave the more electron-rich family of compounds [(dcpe)Ni(pdt)Fe(CO)(2)L]BF(4) for L = PPh(2)(2-pyridyl) ([2a]BF(4)), PPh(3) ([2b]BF(4)), and PCy(3) ([2c]BF(4)). For bulky and strongly basic monophosphorus ligands, the salts feature distorted coordination geometries at iron: crystallographic analyses of [1e]BF(4) and [2c]BF(4) showed that they adopt "rotated" Fe(I) centers, in which PCy(3) occupies a basal site and one CO ligand partially bridges the Ni and Fe centers. Like the undistorted mixed-valence derivatives, members of the new class of complexes are described as Ni(II)Fe(I) (S = (1)/(2)) systems according to electron paramagnetic resonance spectroscopy, although with attenuated (31)P hyperfine interactions. Density functional theory calculations using the BP86, B3LYP, and PBE0 exchange-correlation functionals agree with the structural and spectroscopic data, suggesting that the spin for [1e](+) is mostly localized in a Fe(I)-centered d(z(2)) orbital, orthogonal to the Fe-P bond. The PCy(3) complexes, rare examples of species featuring "rotated" Fe centers, both structurally and spectroscopically incorporate features from homobimetallic mixed-valence diiron dithiolates. Also, when the NiS(2)Fe core of the [NiFe]-hydrogenase active site is reproduced, the "hybrid models" incorporate key features of the two major classes of hydrogenase. Furthermore, cyclic voltammetry experiments suggest that the highly basic phosphine ligands enable a second oxidation corresponding to the couple [(dxpe)Ni(pdt)Fe(CO)(2)L](+/2+). The resulting unsaturated 32e(-) dications represent the closest approach to modeling the highly electrophilic Ni-SI(a) state. In the case of L = PPh(2) (2-pyridyl), chelation of this ligand accompanies the second oxidation.     

Heterolytic cleavage of dihydrogen promoted by sulfido-bridged tungsten-ruthenium dinuclear complexes

A series of sulfido-bridged tungsten-ruthenium dinuclear complexes Cp*W(mu-S)(3)RuX(PPh(3))(2) (4a; X = Cl, 4b; X = H), Cp*W(O)(mu-S)(2)RuX(PPh(3))(2) (5a; X = Cl, 5b; X = H), and Cp*W(NPh)(mu-S)(2)RuX(PPh(3))(2) (6a; X = Cl, 6b; X = H) have been synthesized by the reactions of (PPh(4))[Cp*W(S)(3)] (1), (PPh(4))[Cp*W(O)(S)(2)] (2), and (PPh(4))[Cp*W(NPh)(S)(2)] (3), with RuClX(PPh(3))(3) (X = Cl, H). The heterolytic cleavage of H(2) was found to proceed at room temperature upon treating 5a and 6a with NaBAr(F)(4) (Ar(F) = 3, 5-C(6)H(3)(CF(3))(2)) under atmospheric pressure of H(2), which gave rise to [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (7a) and [Cp*W(NHPh)(mu-S)(2)RuH(PPh(3))(2)](BAr(F)(4)) (8), respectively. When Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b) was treated with a Br?nstead acid, [H(OEt(2))(2)](BAr(F)(4)) or HOTf, protonation occurred exclusively at the terminal oxide to give [Cp*W(OH)(mu-S)(2)RuH(PPh(3))(2)](X) (7a; X = BAr(F)(4), 7b; X = OTf), while the hydride remained intact. The analogous reaction of Cp+W(mu-S)(3)Ru(PPh(3))(2)H (4b) led to immediate evolution of H(2). Selective deprotonation of the hydroxyl group of 7a or 7b was induced by NEt(3) and 4b, generating Cp*W(O)(mu-S)(2)Ru(PPh(3))(2)H (5b). Evolution of H(2) was also observed for the reactions of 7a or 7b with CH(3)CN to give [Cp*W(O)(mu-S)(2)Ru(CH(3)CN)(PPh(3))(2)](X) (11a; X = BAr(F)(4), 11b; X = OTf). We examined the H/D exchange reactions of 4b, 5b, and 7a with D(2) and CH(3)OD, and found that facile H/D scrambling over the W-OH and Ru-H sites occurred for 7a. Based on these experimental results, the mechanism of the heterolytic H(2) activation and the reverse H(2) evolution reactions are discussed.     

Ruthenium(II) hydrazone Schiff base complexes: synthesis, spectral study and catalytic applications

Ruthenium(II) hydrazone Schiff base complexes of the type [RuCl(CO)(B)(L)] (were B=PPh(3), AsPh(3) or Py; L=hydrazone Schiff base ligands) were synthesized from the reactions of hydrazone Schiff base ligand (obtained from isonicotinoylhydrazide and different hydroxy aldehydes) with [RuHCl(CO)(EPh(3))(2)(B)] (where E=P or As; B=PPh(3), AsPh(3) or Py) in 1:1 molar ratio. All the new complexes have been characterized by analytical and spectral (FT-IR, electronic, (1)H, (13)C and (31)P NMR) data. They have been tentatively assigned an octahedral structure. The synthesized complexes have exhibited catalytic activity for oxidation of benzyl alcohol to benzaldehyde and cyclohexanol to cyclohexanone in the presence of N-methyl morpholine N-oxide (NMO) as co-oxidant. They were also found to catalyze the transfer hydrogenation of aliphatic and aromatic ketones to alcohols in KOH/Isopropanol.