A convenient route to dinuclear chloro-bridged platinum(II) derivatives via nitrile complexes

The syntheses of the complexes [PtCl(2)(NCR)L] [R = Me, Et; L = PPh(3); R = Et, L = Py, CO] and [PtCl{(κ(2)-P,C)P(OC(6)H(4))(OPh)(2)}(NCEt)] are described starting from the easily available [PtCl(2)(NCR)(2)]. The stability of the products under different experimental conditions is discussed as well as their use as precursors to dinuclear complexes [Pt(μ-Cl)ClL](2). The crystal and molecular structures of cis-[PtCl(2)(NCEt)(PPh(3))], [SP-4-2]-[PtCl{(κ(2)-P,C)P(OC(6)H(4))(OPh)(2)}(NCEt)] and trans-[Pt(μ-Cl){(κ(2)-P,C)P(OC(6)H(4))(OPh)(2)}](2) are reported.     

Reactivity of RuCl(2)(CO)(P(t)()Bu(2)Me)(2) toward H(2) and Brønsted Acids: Aggregation Triggered by Protonation and Phosphine Loss

Reaction of H(2) with RuCl(2)(CO)L(2) (L = P(t)()Bu(2)Me) in benzene forms RuHCl(CO)L(2) and HCl. The latter reacts with RuCl(2)(CO)L(2) to give [LH][Ru(2)Cl(5)(CO)(2)L(2)] and [LH]Cl. The Ru(2)Cl(5)(CO)(2)L(2)(-) ion is detected (NMR) as several isomers, and is shown by X-ray diffraction to have a face-shared bioctahedral structure: LCl(OC)Ru(&mgr;-Cl)(3)Ru(CO)ClL(-). The loss of phosphine from Ru(II) is triggered by electrophilic attack, but not directly on P or on the Ru-P bond. It is shown (low-temperature NMR studies) that HCl reacts with RuHCl(CO)L(2) to give initially RuCl(2)(H(2))(CO)L(2), in which H(2) is trans to Cl. From this study, and also direct observation of the reaction of HCl with RuCl(2)(CO)L(2) to produce Ru(2)Cl(5)(CO)(2)L(2)(-), the Br?nsted basicity of chloride in RuCl(2)(CO)L(2) is established. This accounts for its reaction with PhC(2)H and NEt(3) to give Ru(C(2)Ph)Cl(CO)L(2). Crystallographic data (-173 degrees C) for [P(t)()Bu(2)MeH][Ru(2)Cl(5)(CO)(2)(P(t)()Bu(2)Me)(2)]: a = 16.418(2)?, b = 12.578(2)?, c = 20.044(3)?, beta = 103.38(1) degrees with Z = 4 in space group P2(1)/a.     

Use of the tetrahydroborate ligand as "gate-keeper" and protected hydride ligand: preparation and study of alkyl hydride and acyl hydride complexes of ruthenium(II)

Complex 3, [Ru(eta2-BH4)(CO)(Et)L2] (L = PMe2Ph) can be converted by nucleophiles L' {a, PMe2Ph; b, P(OMe)3; c, Me3CNC; d, CO} to alkyl and acyl complexes [Ru(eta1-BH4)(CO)(Et)L2L'] (4a), [Ru(eta2-BH4)(COEt)L2L'] (5a-d), and [Ru(eta1-BH4)(COEt)L2L'2] (7d and isomers 7c and 10c). Deprotection can then be achieved under conditions mild enough to allow study of the resulting alkyl hydride complexes [Ru(CO)(Et)HL2L'] (1a, 1b) and acyl hydride complexes [Ru(COEt)HL2L'2] (8c, 8d) prior to elimination of ethane and propanal respectively, with formation of ruthenium(0) complexes [Ru(CO)L2L'2] (6a, 6b, 6d). With Me3CNC, however, the final product is (depending on the solvent used) [Ru(CNCMe3)2{C(H)NCMe3}(COEt)L2] (9c) or [Ru(CNCMe3)3(COEt)L2]+ (11c). Successive treatment of [Ru(eta2-BH4)(CO)HL2], , with ethene and then CO yields propanal, but turning this into a catalytic cycle is hindered by the greater readiness of to yield propanal non-catalytically (reacting with CO) than catalytically (reacting with H2).     

Coordination complexes containing multidentate ligands : V. The reactions between trans-carbonylchlorobis(triphenylphosphine)iridium and trans-carbonylchloro(triphenylarsine)iridium and some tridentate group VB ligands

Bis[3-(dimethylarsino)propyl]phenylarsine, (tas), reacts with trans-Ir(CO)(EPh₃)₂ X (E = P, As; X = F, Cl, Br, I) to yield the (Ir(CO)(tas)] X complexes. In contrast, the similar ligand bis[3-(dimethylarsino)propyl]phenylphosphine, (dap), reacts with trans-Ir(CO)(EPh₃)₂X (E = P, As; X = Cl, Br, I) to yield a mixture of [Ir(CO)(dap)X] and [Ir(CO)(dap)]X, and with trans Ir(CO)(EPh₃)₂F (E = P, As) to yield solely [Ir(CO)(dap)F]. The cations [Ir(CO)(L)]⁺ (L = tas, dap) readily yield tetraphenylborate derivatives, [Ir(CO)(L)]BPh₄. The oxygenation of [Ir(CO)(tas)]⁺ in solution proceeds almost to completion after 15 h, whereas [Ir(CO)(dap)]⁺ does not appear to undergo oxygenation.     

A new [2 + 1] mixed ligand concept based on [99(m)Tc(OH2)3(CO)3]+: a basic study

Mixed ligand fac-tricarbonyl complexes of the general formula [M(L1)(L2)(CO)3](M = Re, 99(m)Tc, L1= imidazole, benzyl isocyanide, L2 = 1H-imidazole-4-carboxylic acid, pyridine-2,4-dicarboxylic acid, pyridine-2,5-dicarboxylic acid) have been prepared starting from the precursors [M(OH2)3(CO)3]+. The complexes can be obtained in good yield and purity in a two-step procedure by first attaching the bidentate ligand followed by addition of the monodentate. 99mTc compounds can also be prepared at the tracer level in one-pot procedures with L1 and L2 being concomitantly present. This [2 + 1] approach allows the labeling of bioactive molecules containing a monodentate or a bidentate donor site. Examples given in here are N-(tert-butoxycarbonyl)glycyl-N-(3-(imidazol-1-yl)propyl)phenylalaninamide, 5-((3-(imidazol-1-yl)propyl)aminomethyl)-2'-deoxyuridine and 4-(5-isonitrilpentyl)-1-(2-methoxyphenyl)-piperazine as L1 and N-((6-carboxypyridine-3-yl)methyl)glycylphenylalanine as L2. The corresponding second ligand can be used to influence the physico-chemical properties of the conjugate. The crystal structures of [99Tc(OH2)(imc)(CO)3], [Re(OH2)(2,4-dipic)(CO)3], [Re(bic)(2,4-dipic)(CO)3] and [Re(im)(2,5-dipic)(CO)3] are reported.     

Oxacalix[3]arene complexes with the ReI(CO)3 fragment

Oxacalix[3]arenes p-methyloxacalix[3]arene (L(1)), p-isopropyloxacalix[3]arene (L2), and p-ethoxycarbonyloxacalix[3]arene (L3) are able to bind the Re(I)(CO)3 moiety with two of their three phenol-O atoms and one of their ether-O atoms. The monoanionic complexes were isolated in the salts (DBUH)[Re(CO)3(L1H-2)].L1 (1) and (NEt4)[Re(CO)3(L2H-2)].L2.0.5 MeCN (2) (DBU = 1,8-diazabicyclo[5.4.0]undec-7-ene). Over the course of its reaction with (NEt4)(2)[Re(CO)3Br(3)] and DBU, p-ethoxycarbonyloxacalix[3]arene decomposes to form [{Re(CO)3(L4H-2)}2] (3) {L4 = 1-(5-ethoxycarbonyl-2-hydroxy-3-hydroxymethyl-benzyl)-2,3,4,6,7,8,9,10-octahydro-pyrimido[1,2-a]azepin-1-ium. The expected monoanion [Re(CO)3(L3H-2)]- (4) was identified by 13C NMR and mass spectra.     

Cluster expansion reactions of group 6 and 8 metallaboranes using transition metal carbonyl compounds of groups 7-9

The reinvestigation of an early synthesis of heterometallic cubane-type clusters has led to the isolation of a number of new clusters which have been characterized by spectroscopic and crystallographic techniques. The thermolysis of [(Cp*Mo)(2)B(4)H(4)E(2)] (1: E = S; 2: E = Se; Cp* = η(5)-C(5)Me(5)) in presence of [Fe(2)(CO)(9)] yielded cubane-type clusters [(Cp*Mo)(2)(μ(3)-E)(2)B(2)H(μ-H){Fe(CO)(2)}(2)Fe(CO)(3)], 4 and 5 (4: E = S; 5: E = Se) together with fused clusters [(Cp*Mo)(2)B(4)H(4)E(2)Fe(CO)(2)Fe(CO)(3)] (8: E = S; 9: E = Se). In a similar fashion, reaction of [(Cp*RuCO)(2)B(2)H(6)], 3, with [Fe(2)(CO)(9)] yielded [(Cp*Ru)(2)(μ(3)-CO)(2)B(2)H(μ-H){Fe(CO)(2)}(2)Fe(CO)(3)], 6, and an incomplete cubane cluster [(μ(3)-BH)(3)(Cp*Ru)(2){Fe(CO)(3)}(2)], 7. Clusters 4-6 can be described as heterometallic cubane clusters containing a Fe(CO)(3) moiety exo-bonded to the cubane, while 7 has an incomplete cubane [Ru(2)Fe(2)B(3)] core. The geometry of both compounds 8 and 9 consist of a bicapped octahedron [Mo(2)Fe(2)B(3)E] and a trigonal bipyramidal [Mo(2)B(2)E] core, fused through a common three vertex [Mo(2)B] triangular face. In addition, thermolysis of 3 with [Mn(2)(CO)(10)] permits the isolation of arachno-[(Cp*RuCO)(2)B(3)H(7)], 10. Cluster 10 constitutes a diruthenaborane analogue of 8-sep pentaborane(11) and has a structural isomeric relationship to 1,2-[{Cp*Ru}(2)(CO)(2)B(3)H(7)].     

Substitution and derivatization reactions of a water soluble iron(II) complex containing a self-assembled tetradentate phosphine ligand

Facile substitution reactions of the two water ligands in the hydrophilic tetradentate phosphine complex cis-[Fe{(HOCH2)P{CH2N(CH2P(CH2OH)2)CH2}2P(CH2OH)}(H2O)2](SO4) (abbreviated to [Fe(L1)(H2O)2](SO4), 1) take place upon addition of Cl-, NCS-, N3(-), CO3(2-) and CO to give [Fe(L1)X2] (2, X = Cl; 4, X = NCS; 5, X=N3), [Fe(L1)(kappa2-O(2)CO)], 6 and [Fe(L1)(CO)2](SO4), 7. The unsymmetrical mono-substituted intermediates [Fe(L1)(H2O)(CO)](SO(4)) and [Fe(L(1))(CO)(kappa(1)-OSO(3))] (8/9) have been identified spectroscopically en-route to 7. Treatment of 1 with acetic anhydride affords the acylated derivative [Fe{(AcOCH2)P{CH2N(CH2P(CH2OAc)2)CH2}2P(CH2OAc)}(kappa2-O(2)SO2)] (abbreviated to [Fe(L2)(kappa2-O(2)SO2)], 10), which has increased solubility over 1 in both organic solvents and water. Treatment of 1 with glycine does not lead to functionalisation of L1, but substitution of the aqua ligands occurs to form [Fe(L(1))(NH(2)CH(2)CO(2)-kappa(2)N,O)](HSO(4)), 11. Compound 10 reacts with chloride to form [Fe(L(2))Cl(2)] 12, and 12 reacts with CO in the presence of NaBPh4 to form [Fe(L2)Cl(CO)](BPh4) 13b. Both of the chlorides in 12 are substituted on reaction with NCS- and N3(-) to form [Fe(L2)(NCS)2] 14 and [Fe(L2)(N3)2] 15, respectively. Complexes 2.H2O, 4.2H2O, 5.0.812H2O, 6.1.7H2O, 7.H2O, 10.1.3CH3C(O)CH3, 12 and 15.0.5H2O have all been crystallographically characterised.     

Comparative studies of substitution reactions of rhenium(I) dicarbonyl-nitrosyl and tricarbonyl complexes in aqueous media

The ligand substitution behavior of [ReBr3(CO)3](NEt4)2 (1) and [ReBr3(CO)2(NO)]NEt4 (2) in aqueous media was compared. Ligand exchange reactions were performed with multidentate chelating systems such as picolylaminediacetic acid (L1; N,N',O,O'), nitrilotriacetic acid (L2; N,O,O',O'), iminodiacetic acid (L3; N,O,O'), and bis(2-pyridyl)methane (L4; N,N'). The products of the substitution reactions were isolated and characterized by means of IR, NMR, MS, and X-ray structure analysis. NMR and crystallographic analyses confirmed the formation of single structural isomers in all cases with a ligand-to-metal ratio of 1:1. With ligands L1 and L2 and precursor 1 the tridentately coordinated complexes [Re(L1)(CO)3] (7) and [Re(L2)(CO)3]2- (8) were formed. With precursor 2 the same ligands unexpectedly coordinated tetradentately after displacing a CO ligand, yielding complexes [Re(L1)(CO)(NO)] (3) and [Re(L2)(CO)(NO)]- (4). In both complexes NO was found to be coordinated trans to the carboxylate group. Time-dependent IR spectra of the reaction of 2 with ligand L1 and L2 confirmed the loss of one CO during the reaction. The product of the reaction of 2 with L3 was identified as the neutral complex [Re(L3)(CO)2(NO)] (5), again, with the nitrosyl coordinated trans to the carboxylate. With 1, ligand L3 formed the anionic complex [Re(L3)(CO)3]- (9). Finally the reactions with L4 yielded the complexes [ReBr(L4)(CO)2(NO)]Br (6) and [ReBr(L4)(CO)3] (10), in which bromide was found to be coordinated trans to the NO and CO, respectively. The X-ray structures of 3, 5-7, and 10 are discussed: 3, monoclinic P2(1)/n, with a = 14.6071(6) A, b = 8.0573(3) A, c = 24.7210(11) A, beta = 107.117(5) degrees, and Z = 4; 5, triclinic P1, with a = 6.9091(5) A, b = 9.8828(7) A, c = 14.2834(10) A, alpha = 89.246(9) degrees, beta = 89.420(9) degrees, gamma = 86.196(9) degrees, and Z = 4; 6, triclinic P1, with a = 9.8236(8) A, b = 10.0949(8) A, c = 12.5346(10) A, alpha = 108.679(9) degrees, beta = 111.992(9) degrees, gamma = 95.426(10) degrees, and Z = 2; 10, monoclinic P2(1)/c, with a = 12.7491(12) A, b = 13.3015(13) A, c = 9.0112(9) A, beta = 107.195(2) degrees, and Z = 7.     

Synthesis and coordination behavior of planar-chiral ferrocene alkenylphosphines

A series of planar-chiral ferrocene alkenylphosphines, (S(p))-2-(diphenylphosphino)-1-vinylferrocene (2), (S(p))-2-(diphenylphosphino)-1-(prop-1-en-1-yl)ferrocene (3; as a mixture of Z and E isomers in ca. 5:1 ratio), and (E,S(p))-2-(diphenylphosphino)-1-(2-phenylethen-1-yl)ferrocene ((E)-4), was obtained by Wittig and Horner-Wadsworth-Emmons reactions from the common precursor, (S(p))-2-(diphenylphosphino)ferrocene-1-carboxaldehyde (1). Coordination properties of these novel ferrocene donors were studied in their palladium(II) and tungsten(0)-carbonyl complexes. The reaction between 2 and [{Pd(mu-Cl)(L(NC))}2] (5, L(NC) = 2-{(dimethylamino)methyl-kappaN}phenyl-kappaC(1)) gave the bridge-cleavage product [PdCl(L(NC))(2-kappaP)] (6) while the reaction with [Pd(L(NC))(MeCN)2]ClO4 (7) yielded the cationic bis(chelate) [Pd(L(NC))(2-eta2:kappaP)]ClO4 (8). Chelate complexes of the type [W(CO)4(L-eta2:kappaP)] (9 with L = 2; (Z/E)-10 with L = (Z/E)-3) were obtained by reacting [W(CO)4(cod)] (cod = eta2:eta2-cycloocta-1,5-diene) with the appropriate phosphinoalkene in refluxing toluene while a similar reaction with (E)-4 yielded mixtures of [W(CO)5(4-kappaP)] ((E)-11) and [W(CO)4(4-eta2:kappaP)] ((E)-12). All compounds were characterized by spectral methods (multinuclear NMR, IR, MS, and CD), and the structures of 1, 2, 8, 9, (Z/E)-10, and (E)-11 were corroborated by X-ray diffraction analysis. Ligands 2 and (E)-4 as well as their complexes 6, 8, 9, (E)-11, and (E)-12 were further studied by electrochemical methods.     

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.     

C-C coupling reactions in the coordination sphere of rhodium(I) and rhodium(III): New routes for the di- and trimerization of terminal alkynes

The alkynyl(vinylidene)rhodium(I) complexes trans-[Rh(C[triple bond, length as m-dash]CR)(=C=CHR)(PiPr3)2] 2, 5, 6 react with CO by migratory insertion to give stereoselectively the butenynyl compounds trans-[Rh{eta1-(Z)-C(=CHR)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-7-9, of which (Z)-7 (R=Ph) and (Z)-8 (R=tBu) rearrange upon heating or UV irradiation to the (E) isomers. Similarly, trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CPh}(CO)(PiPr3)2] 12 and trans-[Rh{eta1-(Z)-C(=CHCO2Me)C[triple bond, length as m-dash]CR}(CO)(PiPr3)2](Z)-15, (Z)-16 have been prepared. At room temperature, the corresponding "non-substituted" derivative trans-[Rh{eta1-C(=CH2)C[triple bond, length as m-dash]CH}(CO)(PiPr3)2] 18 is in equilibrium with the butatrienyl isomer trans-[Rh(eta1-CH=]C=C=CH2)(CO)(PiPr3)2] 19 that rearranges photochemically to the alkynyl complex trans-[Rh(C[triple bond, length as m-dash]CCH=CH2)(CO)(PiPr3)2] 20. Reactions of (Z)-7, (E)-7, (Z)-8 and (E)-8 with carboxylic acids R'CO2H (R'=CH3, CF3) yield either the butenyne (Z)- and/or (E)-RC[triple bond, length as m-dash]CCH=CHR or a mixture of the butenyne and the isomeric butatriene, the ratio of which depends on both R and R'. Treatment of 2 (R=Ph) with HCl at -40 degrees C affords five-coordinate [RhCl(C[triple bond, length as m-dash]CPh){(Z)-CH=CHPh}(PiPr3)2] 23, which at room temperature reacts by C-C coupling to give trans-[RhCl{eta2-(Z)-PhC[triple bond, length as m-dash]CCH=CHPh}(PiPr3)2](Z)-21. The related compound trans-[RhCl(eta2-HC[triple bond, length as m-dash]CCH=CH2)(PiPr3)2] 27, prepared from trans-[Rh(C[triple bond, length as m-dash]CH)(=C=CH2)(PiPr3)2] 17 and HCl, rearranges to the vinylvinylidene isomer trans-[RhCl(=C=CHCH=CH2)(PiPr3)2] 28. While stepwise reaction of 2with CF3CO2H yields, via alkynyl(vinyl)rhodium(III) intermediates (Z)-29 and (E)-29, the alkyne complexes trans-[Rh(kappa1-O2CCF3)(eta2-PhC[triple bond, length as m-dash]CCH=CHPh)(PiPr3)2](Z)-30 and (E)-30, from 2 and CH3CO2H the acetato derivative [Rh(kappa2-O2CCH3)(PiPr3)2] 33 and (Z)-PhC[triple bond, length as m-dash]CCH=]CHPh are obtained. From 6 (R=CO2Me) and HCl or HC[triple bond, length as m-dash]CCO2Me the chelate complexes [RhX(C[triple bond, length as m-dash]CCO2Me){kappa2(C,O)-CH=CHC(OMe)=O}(PiPr3)2] 34 (X=Cl) and 35 (X=C[triple bond, length as m-dash]CCO2Me) have been prepared. In contrast to the reactions of [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE)(CH=CHE)(PiPr3)2] 37(E=CO2Me) with chloride sources which give, via intramolecular C-C coupling, four-coordinate trans-[RhCl{eta2-(E)-EC[triple bond, length as m-dash]CCH=CHE}(PiPr3)2](E)-36, treatment of 37with HC[triple bond, length as m-dash]CE affords, via insertion of the alkyne into the rhodium-vinyl bond, six-coordinate [Rh(kappa2-O2CCH3)(C[triple bond, length as m-dash]CE){eta1-(E,E)-C(=CHE)CH=CHE}(PiPr3)2] 38. The latter reacts with MgCl2 to yield trans-[RhCl{eta2-(E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE}(PiPr3)2] 39, which, in the presence of CO, generates the substituted hexadienyne (E,E)-EC[triple bond, length as m-dash]CC(=CHE)CH=CHE 40.     

Rhodium(I) carbonyl complexes of triphenylphosphine chalcogenides and their catalytic activity

Rhodium(I) carbonyl complexes [Rh(CO)₂ClL] where L = Ph₃PO, Ph₃PS and Ph₃PSe, were synthesized and characterized by elemental analysis, i.r. and by ¹H-, ¹³C- and ³¹P-n.m.r. spectroscopy. The vBD;(CO) band frequencies in the complexes follow the order: Ph₃PO > Ph₃PS > Ph₃PSe, in keeping with the hard/soft nature of the interactions. The complexes undergo oxidative additions with electrophiles such as MeI, PhCH₂Cl and I₂ to give, e.g. [Rh(CO)(COMe)ClIL] which react with PPh₃ to give trans-[Rh(CO)Cl(PPh₃)₂]. The catalytic activity of the [Rh(CO)₂ClL] complexes in carbonylation of MeOH is higher than that of the well-known [Rh(CO)₂I₂]⁻ species. This revised version was published online in June 2006 with corrections to the Cover Date.     

Electronic structures of ruthenium and osmium complexes of 9,10-phenanthrenequinone

The reaction of 9,10-phenanthrenequinone (PQ) with [M(II)(H)(CO)(X)(PPh(3))(3)] in boiling toluene leads to the homolytic cleavage of the M(II)-H bond, affording the paramagnetic trans-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 1; M = Os, X = Br, 3) and cis-[M(PQ)(PPh(3))(2)(CO)X] (M = Ru, X = Cl, 2; M = Os, X = Br, 4) complexes. Single-crystal X-ray structure determinations of 1, 2·toluene, and 4·CH(2)Cl(2), EPR spectra, and density functional theory (DFT) calculations have substantiated that 1-4 are 9,10-phenanthrenesemiquinone radical (PQ(?-)) complexes of ruthenium(II) and osmium(II) and are defined as trans-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (1), cis-[Ru(II)(PQ(?-))(PPh(3))(2)(CO)Cl] (2), trans-[Os(II)(PQ(?-))(PPh(3))(2)(CO) Br] (3), and cis-[Os(II)(PQ(?-))(PPh(3))(2)(CO)Br] (4). Two comparatively longer C-O [average lengths: 1, 1.291(3) ?; 2·toluene, 1.281(5) ?; 4·CH(2)Cl(2), 1.300(8) ?] and shorter C-C lengths [1, 1.418(5) ?; 2·toluene, 1.439(6) ?; 4·CH(2)Cl(2), 1.434(9) ?] of the OO chelates are consistent with the presence of a reduced PQ(?-) ligand in 1-4. A minor contribution of the alternate resonance form, trans- or cis-[M(I)(PQ)(PPh(3))(2)(CO)X], of 1-4 has been predicted by the anisotropic X- and Q-band electron paramagnetic resonance spectra of the frozen glasses of the complexes at 25 K and unrestricted DFT calculations on 1, trans-[Ru(PQ)(PMe(3))(2)(CO)Cl] (5), cis-[Ru(PQ)(PMe(3))(2)(CO)Cl] (6), and cis-[Os(PQ)(PMe(3))(2)(CO)Br] (7). However, no thermodynamic equilibria between [M(II)(PQ(?-))(PPh(3))(2)(CO)X] and [M(I)(PQ)(PPh(3))(2)(CO)X] tautomers have been detected. 1-4 undergo one-electron oxidation at -0.06, -0.05, 0.03, and -0.03 V versus a ferrocenium/ferrocene, Fc(+)/Fc, couple because of the formation of PQ complexes as trans-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (1(+)), cis-[Ru(II)(PQ)(PPh(3))(2)(CO)Cl](+) (2(+)), trans-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (3(+)), and cis-[Os(II)(PQ)(PPh(3))(2)(CO)Br](+) (4(+)). The trans isomers 1 and 3 also undergo one-electron reduction at -1.11 and -0.96 V, forming PQ(2-) complexes trans-[Ru(II)(PQ(2-))(PPh(3))(2)(CO)Cl](-) (1(-)) and trans-[Os(II)(PQ(2-))(PPh(3))(2)(CO)Br](-) (3(-)). Oxidation of 1 by I(2) affords diamagnetic 1(+)I(3)(-) in low yields. Bond parameters of 1(+)I(3)(-) [C-O, 1.256(3) and 1.258(3) ?; C-C, 1.482(3) ?] are consistent with ligand oxidation, yielding a coordinated PQ ligand. Origins of UV-vis/near-IR absorption features of 1-4 and the electrogenerated species have been investigated by spectroelectrochemical measurements and time-dependent DFT calculations on 5, 6, 5(+), and 5(-).     

Substitution, cage functionalization, and oxidation of the charge-compensated triruthenium monocarbollide cluster complex [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)6}-closo-2,1-RuCB10H8

The compound [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)6}-closo-2,1-RuCB10H8] 1a reacts with PMe3 or PCy3(Cy = cyclo-C6H11) to give the structurally different species [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)5(PMe3)}-closo-2,1-RuCB10H8] 4 and [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(CO)5(PCy3)}-closo-2,1-RuCB10H8]5, respectively. A symmetrically disubstituted product [1-SMe2-2,2-(CO)2-7,11-(mu-H)2-2,7,11-{Ru2(CO)4(PMe3)2}-closo-2,1-RuCB10H8] 6 is obtained using an excess of PMe3. In contrast, the chelating diphosphines 1,1'-(PPh2)2-Fe(eta-C5H4)2 and 1,2-(PPh2)2-closo-1,2-C2B10H10 react with 1a to yield oxidative-insertion species [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(micro-[1',1'-(PPh2)2-Fe(eta-C5H4)2])(CO)4}-closo-2,1-RuCB10H8] 7 and [1-SMe2-2,2-(CO)2-11-(mu-H)-2,7,11-{Ru2(mu-H)(CO)4(1',2'-(PPh2)2-closo-1',2'-C2B10H10)}-closo-2,1-RuCB10H8] 8, respectively. In toluene at reflux temperatures, 1a with Bu(t)SSBu(t) gives [1-SMe2-2,2-(CO)2-7-(mu-SBu(t))-11-(mu-H)-2,7,11-{Ru2(mu-H)(mu-SBu(t))(CO)4}-closo-2,1-RuCB10H8] 9, and with Bu(t)C [triple bond] CH gives [1-SMe2-2,2-(CO)2-7-{mu:eta2-(E)-CH=C(H)Bu(t)}-11-{mu:eta2-(E)-CH=C(H)Bu(t)}-2,7,11-{Ru2(CO)5}-closo-2,1-RuCB10H8] 10. In the latter, two alkyne groups have inserted into cage B-H groups, with one of the resulting B-vinyl moieties involved in a C-H...Ru agostic bond. Oxidation of 1a with I2 or HgCl2 affords the mononuclear ruthenium complex [1-SMe2-2,2,2-(CO)3-closo-2,1-RuCB10H10] 11.     

Betaine-induced assembly of neutral infinite columns and chains of linked silver(I) polyhedra with embedded acetylenediide

Ten polymeric silver(I) double salts containing embedded acetylenediide: [(Ag2C2)2(AgCF3CO2)9(L1)3] (1), [(Ag2C2)2(AgCF3CO2)10(L2)3]H2O (2), [(Ag2C2)(AgCF3CO2)4(L3)(H2O)]0.75 H2O (3), [(Ag2C2)(1.5)(AgCF3CO2)7(L4)2] (4), [(Ag2C2)(AgCF3CO2)7(L5)2(H2O)] (5), [(Ag2C2) (AgC2F5CO2)7(L1)3(H2O)] (6), [(Ag2C2)(AgCF3CO2)7(L1)3(H2O)]2 H2O (7), [(Ag2C2)(AgC2F5CO2)6(L3)2] (8), [(Ag2C2)2(AgC2F5CO2)12(L4)2(H2O)4]H2O (9), and [(Ag2C2)(AgCF3CO2)6(L3)2(H2O)]H2O (10) have been isolated by varying the types of betaines, the perfluorocarboxylate ligands employed, and the reaction conditions. Single-crystal X-ray analysis has shown that 1-4 all have a columnar structure composed of fused silver(I) double cages, with C2(2-) species embedded in its stem and an exterior coat comprising anionic and zwitterionic carboxylates. For 5 and 6, single silver(I) cages are linked into a beaded chain through both types of carboxylate ligands. In 7, two different coordination modes of L1 connect the silver(I) polyhedra into a chain. For 8, the mu(2)-O,O' coordination mode of L3 connects the silver(I) double cages into a chain. Compound 9 exhibits a two-dimensional architecture generated from the cross-linkage of double cages by C2F5CO2-, L4, and [Ag2(C2F5CO2)2] units. Similar to 9, 10 is also a two-dimensional structure, which is formed by connecting the chains of linked double cages through [Ag2(CF3CO2)2] bridging.     

Diruthenium dithiolato cyanides: basic reactivity studies and a post hoc examination of nature's choice of Fe versus Ru for hydrogenogenesis

The reaction of Ru2(S2C3H6)(CO)6 (1) with 2 equiv of Et4NCN yielded (Et4N)2[Ru2(S2C3H6)(CN)2(CO)4], (Et4N)2[3], which was shown crystallographically to consist of a face-sharing bioctahedron with the cyanide ligands in the axial positions, trans to the Ru-Ru bond. Competition experiments showed that 1 underwent cyanation >100x more rapidly than the analogous Fe2(S2C3H6)(CO)6. Furthermore, Ru2(S2C3H6)(CO)6 underwent dicyanation faster than [Ru2(S2C3H6)(CN)(CO)5]-, implicating a highly electrophilic intermediate [Ru2(S2C3H6)(mu-CO)(CN)(CO)5]-. Ru2(S2C3H6)(CO)6 (1) is noticeably more basic than the diiron compound, as demonstrated by the generation of [Ru2(S2C3H6)(mu-H)(CO)6]+, [1H]+. In contrast to 1, the complex [1H]+ is unstable in MeCN solution and converts to [Ru2(S2C3H6)(mu-H)(CO)5(MeCN)]+. (Et4N)2[3] was shown to protonate with HOAc (pKa = 22.3, MeCN) and, slowly, with MeOH and H2O. Dicyanide [3]2- is stable toward excess acid, unlike the diiron complex; it slowly forms the coordination polymer [Ru2(S2C3H6)(mu-H)(CN)(CNH)(CO)4]n, which can be deprotonated with Et3N to regenerate [H3]-. Electrochemical experiments demonstrate that [3H]- catalyzes proton reduction at -1.8 V vs Ag/AgCl. In contrast to [3]2-, the CO ligands in [3H]- undergo displacement. For example, PMe3 and [3H]- react to produce [Ru2(S2C3H6)(mu-H)(CN)2(CO)3(PMe3)]-. Oxidation of (Et4N)2[3] with 1 equiv of Cp2Fe+ gave a mixture of [Ru2(S2C3H6)(mu-CO)(CN)3(CO)3]- and [Ru2(S2C3H6)(CN)(CO)5]-, via a proposed [Ru2]2(mu-CN) intermediate. Overall, the ruthenium analogues of the diiron dithiolates exhibit reactivity highly reminiscent of the diiron species, but the products are more robust and the catalytic properties appear to be less promising.     

Site selectivity in the reactions of the hexanuclear platinum cluster [Pt6(mu-PtBu2)4(CO)6][CF3SO3]2

The previously reported hexanuclear cluster [Pt(6)(mu-PtBu(2))(4)(CO)(6)](2+)[Y](2) (1-Y(2): Y=CF(3)SO(3) (-)) contains a central Pt(4) tetrahedron bridged at each of the opposite edges by another platinum atom; in turn, four phosphido ligands bridge the four Pt-Pt bonds not involved in the tetrahedron, and, finally, one carbonyl ligand is terminally bonded to each metal centre. Interestingly, the two outer carbonyls are more easily substituted or attacked by nucleophiles than the inner four, which are bonded to the tetrahedron vertices. In fact, the reaction of 1-Y(2) with 1 equiv of [nBu(4)N]Cl or with an excess of halide salts gives the monochloride [Pt(6)(mu-PtBu(2))(4)(CO)(5)Cl](+)[Y], 2-Y, or the neutral dihalide derivatives [Pt(6)(mu-PtBu(2))(4)(CO)(4)X(2)] (3: X=Cl; 4: X=Br; 5: X=I). Moreover, the useful unsymmetrically substituted [Pt(6)(mu-PtBu(2))(4)(CO)(4)ICl] (6) was obtained by reacting equimolar amounts of 2 and [nBu(4)N]I, and the dicationic derivatives [Pt(6)(mu-PtBu(2))(4)(CO)(4)L(2)](2+)[Y](2) (7-Y(2): L=(13)CO; 8-Y(2): L=CNtBu; 9-Y(2): L=PMe(3)) were obtained by reaction of an excess of the ligand L with 1-Y(2). Weaker nitrogen ligands were introduced by dissolving the dichloride 3 in acetonitrile or pyridyne in the presence of TlPF(6) to afford [Pt(6)(mu-PtBu(2))(4) (CO)(4)L(2)](2+)[Z](2) (Z=PF(6) (-), 10-Z(2): L=MeCN; 11-Z(2): L=Py). The "apical" carbonyls in 1-Y(2) are also prone to nucleophilic addition (Nu(-): H(-), MeO(-)) affording the acyl derivatives [Pt(6)(mu-PtBu(2))(4)(CO)(4)(CONu)(2)] (12: Nu=H; 13: Nu=OMe). Complex 12 is slowly converted into the dihydride [Pt(6)(mu-PtBu(2))(4)(CO)(4)H(2)] (14), which was more cleanly prepared by reacting 3 with NaBH(4). In a unique case we observed a reaction involving also the inner carbonyls of complex 1, that is, in the reaction with a large excess of the isocyanides R-NC, which form the corresponding persubstituted derivatives [Pt(6)(mu-tPBu(2))(4)(CN-R)(6)](2+)[Y](2), (15-Y(2): R=tBu; 16-Y(2) (2-): R=-C(6)H(4)-4-C triple bond CH). All complexes were characterized by microanalysis, IR and multinuclear NMR spectroscopy. The crystal and molecular structures of complexes 3, 5, 6 and 9-Y(2) are also reported. From the redox viewpoint, all complexes display two reversible one-electron reduction steps, the location of which depends both upon the electronic effects of the substituents, and the overall charge of the original complex.     

Bis-phosphites and bis-phosphinites based on distally-functionalised calix[4]arenes: coordination chemistry and use in rhodium-catalysed, low-pressure olefin hydroformylation

Six calix[4]arenes each bearing two non-cyclic PR2 units attached at distal phenolic oxygen atoms, p-Bu t-calix[4]arene-25,27-(OPR2)2-26,28-(OR')2(R = OPh; R'= Prn, L1; R = OPh; R'= CH2CO2Et, L2; R= OPh; R'= CO2 cholesteryl, L3; R = Ph; R'= Prn, 4; R = Ph; R'= CH2CO2Et, L5; R = Ph; R'= CO2cholesteryl, L6) have been synthesized and their coordinative properties investigated. The diphosphites L1-L3, where the P centres are separated by 12 bonds, readily form chelate complexes provided the complexation reaction is achieved either by using a starting complex that possesses good leaving groups or by operating under high dilution in order to avoid oligomer formation. Thus, the cationic complexes [Rh(COD)L1]BF4 and [Rh(COD)L3]BF4 were both formed in high yield by reacting the appropriate diphosphite with either [Rh(COD)(THF)2]BF4 or [Rh(COD)2]BF4. At high dilution, reaction of L3 with the neutral complex [PdCl2(COD)] afforded the chelate complex [PdCl2L3] in 90% yield. The reaction of one equiv. of L1 with [Rh(acac)(CO)2] resulted in the formation of [Rh(acac)L1] without requiring high dilution conditions. When the latter reaction was carried out with 0.5 equiv. of L1, the bimetallic complex [{Rh(acac)(CO)}2(eta]1-P,eta1-P'-L1)] was formed instead. Reaction at high dilution of with the cyclometallated complex [Pd(o-C6H4CH2NMe2)(THF)2]BF4 gave the expected chelate complex [Pd(o-C6H4CH2NMe2)]BF4. The latter slowly converts in solution to an oligomer in which the ligand behaves as a (eta1-P,eta1-P') bridging ligand, thus leading to a less strained structure. All six ligands, when mixed with [Rh(acac)CO2], effectively catalyse the hydroformylation of octene and styrene. In the hydroformylation of octene, the linear aldehyde selectivities observed with L2 and L3 are significantly higher (linear : branched =ca. 10) than those obtained with the other 4 ligands of this study and also with respect to PPh3. Molecular modelling shows that the lower rim substituents of and form tighter pockets about the metal centre than do the other ligands and so sterically favour the formation of Rh(n-alkyl) intermediates over that of Rh(i-alkyl) ones. In styrene hydroformylation, all ligands result in the formation of unusually high amounts of the linear aldehyde, the b : l ratios being all close to 65 : 35. The highest activities were found when using an L/Rh ratio of 1/1.     

Organometallic building blocks with amino-substituted cyclopentadienyl and boratabenzene ligands for the synthesis of heterometallic complexes and clusters

A comparative study of the reactivity of isolobal rhenium and molybdenum carbonylmetallates containing a borole, in [Re(eta5-C4H4BPh)(CO)3]- (2), a boratanaphthalene, in [Mo(eta5-2,4-MeC9H6BMe)(CO)3]- (4a) and [Mo(eta5-2,4-MeC9H6BNi-Pr2)(CO)3]- (4b), a boratabenzene, in [Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3]- (6) or a dimethylaminocyclopentadienyl ligand, in [Mo(eta5-C5H4NMe2)(CO)3]- (7), toward palladium(II), gold(I), mercury(II) and platinum(II) complexes has allowed an evaluation of the role of these pi-bonded ligands on the structures and unprecedented coordination modes observed in the resulting metal-metal bonded, heterometallic complexes. The new metallate 6 was reacted with [AuCl(PPh3)], and with 1 or 2 equiv. HgCl2, which afforded the new heterodinuclear complexes [Au{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}(PPh3)] (Mo-Au) (10) and [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}Cl] (Hg-Mo) (11) and the heterometallic chain complex [Hg{Mo(eta5-3,5-Me2C5H3BNi-Pr2)(CO)3}2] (Mo-Hg-Mo) (12), respectively. Reactions of the new metallate 7 with HgCl2, trans-[PtCl2(CNt-Bu)2] and trans-[PtCl2(NCPh)2] yielded the heterodinuclear complex [Hg{Mo(eta5-C5H4NMe2)(CO)3}Cl] (Mo-Hg) (15), the heterotrinuclear chain complexes trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(CNt-Bu)2] (Mo-Pt-Mo) (16) and trans-[Pt{Mo(eta5-C5H4NMe2)(CO)3}2(NCPh)2] (Mo-Pt-Mo) (17), the mononuclear complex [Mo(eta5-C5H4NMe2)(CO)3Cl] (18), the lozenge-type cluster [Mo2Pt2(eta5-C5H4NMe2)2(CO)8] (19) and the heterodinuclear complex [[upper bond 1 start]Pt{Mo(eta5-C5H4N[upper bond 1 end]Me2)(CO)3}(NCPh)Cl](Mo-Pt) (20), respectively. The complexes 11, 16, 17.2THF, 18 and 20 have been structurally characterized by X-ray diffraction and 20 differs from all other compounds in that the dimethylaminocyclopentadienyl ligand forms a bridge between the metals.