Reactivity of triruthenium thiophyne and furyne clusters: competitive S-C and P-C bond cleavage reactions and the generation of highly unsymmetrical alkyne ligands

The synthesis and reactivity of the thiophyne and furyne clusters [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, O) is reported. Addition of P(C4H3E)3 to [Ru3(CO)10(mu-dppm)] (1) at room temperature in the presence of Me3NO gives simple substitution products [Ru3(CO)9(mu-dppm)(P(C4H3E)3)] (E = S, 2; E = O, 3). Mild thermolysis in the presence of further Me3NO affords the thiophyne and furyne complexes [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 4; E = O, 6) resulting from both carbon-hydrogen and carbon-phosphorus bond activation. In each the C4H2E (E = S, O) ligand donates 4-electrons to the cluster and the rings are tilted with respect to the mu-dppm and the phosphido-bridged open triruthenium unit. Heating 4 at 80 degrees C leads to the formation of the ring-opened cluster [Ru3(CO)5(mu-CO)(mu-dppm)(mu3-eta3-SC4H3)(mu-P(C4H3S)2)] (5) resulting from carbon-sulfur bond scission and carbon-hydrogen bond formation and containing a ring-opened mu3-eta3-1-thia-1,3-butadiene ligand. In contrast, a similar thermolysis of 3 affords the phosphinidene cluster [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2O)(mu3-P(C4H3O))] (7) resulting from a second phosphorus-carbon bond cleavage and (presumably) elimination of furan. Treatment of 4 and 6 with PPh3 affords the simple phosphine-substituted products [Ru3(CO)6(PPh3)(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 8; E = O, 9). Both thiophyne and furyne clusters 4 and 6 readily react with hydrogen bromide to give [Ru3(CO)6Br(mu-Br)(mu-dppm)(mu3-eta2-eta1-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 10; E = O, 11) containing both terminal and bridging bromides. Here the alkynes bind in a highly unsymmetrical manner with one carbon acting as a bridging alkylidene and the second as a terminally bonded Fisher carbene. As far as we are aware, this binding mode has only previously been noted in ynamine complexes or those with metals in different oxidation states. The crystal structures of seven of these new triruthenium clusters have been carried out, allowing a detailed analysis of the relative orientations of coordinated ligands.     

Proton-induced lewis acidity of unsaturated iridium amides

Oxidation of Cp*Ir((rac-TsDPEN)H (DPEN = H2NCHPhCHPhNTs) with Cp2FePF6 or Ph3CPF6 in MeCN solution generates [Cp*Ir(TsDPEN)(NCMe)]PF6 ([1H(NCMe)]PF6) together with H2 and Ph3CH, respectively. Labeling studies revealed that the Ir-H was abstracted. The formation of a transient electrophilic species is implicated by the formation of a cyclometalated derivative. The labile species [1H(NCMe)]+ was also obtained by protonation of the diamido derivative Cp*Ir(TsDPEN-H) (1) in MeCN solution (BArF4- = B(C6H3-3,5-(CF3)2)4-). The unsaturated, "naked" cation [1H]BArF4 can be prepared by protonation of 1 with H(OEt2)2BArF4 in CH2Cl2 solution or by thermal elimination of MeCN from [1H(NCMe)]+. Crystallographic analysis confirms the structure of this 16e cation in [1H]BArF4. The formally unsaturated species 1 and [1H]BArF4 have strongly contrasting Lewis acidities, with the cation binding PPh3, CO, and NH3. 1 does not measurably bind these same ligands. [1H]BArF4 is reactive toward H2, at least in the absence of inhibiting donor ligands such as MeCN. [1H]BArF4 (CH2Cl2 solutions) catalyzes the addition of H2 to 1 by proton transfer from an apparent dihydrogen complex. This work demonstrates that the protonation activates the Lewis acidity of unsaturated Ir(III) amides, giving rise to novel organometallic Lewis acids.     

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.     

Formation of a dinuclear imido complex from the reaction of a ruthenium(VI) nitride with a ruthenium(II) hydride

The treatment of [Ru(L(OEt))(N)Cl(2)] (1; L(OEt)(-) = [Co(η(5)-C(5)H(5)){P(O)(OEt)(2)}(3)](-)) with Et(3)SiH affords [Ru(L(OEt))Cl(2)(NH(3))] (2), whereas that with [Ru(L(OEt))(H)(CO)(PPh(3))] (3) gives the dinuclear imido complex [(L(OEt))Cl(2)Ru(μ-NH)Ru(CO)(PPh(3))(L(OEt))] (4). The imido group in 4 binds to the two ruthenium atoms unsymmetrically with Ru-N distances of 1.818(6) and 1.952(6) ?. The reaction between 1 and 3 at 25 °C in a toluene solution is first order in both complexes with a second-order rate constant determined to be (7.2 ± 0.4) × 10(-5) M(-1) s(-1).     

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.     

Ruthenium complexes with tetraphenylimidodiphosphinate: syntheses, structures, and applications to catalytic organic oxidation

Treatment of Ru(PPh3)3Cl2 with K(tpip) (tpip(-)=[N(Ph2PO)2](-)) afforded Ru(tpip)(PPh3)2Cl (1), which reacted with 4- t-Bu-C6H4CN, SO2(g), and NH 3(g) to give Ru(tpip)(PPh3)2Cl(4- t-BuC6H4CN) (2), Ru(tpip)(PPh3)2Cl(SO2) (3), and fac-[Ru(NH3)3(PPh3)2Cl][tpip] (4), respectively. Reaction of [Ru(CO)2Cl2] x with K(tpip) in refluxing tetrahydrofuran (THF) led to isolation of the K/Ru bimetallic compound K 2Ru2(tpip)4(CO)4Cl2 (5). Photolysis of cis-Ru(tpip) 2(NO)Cl in MeCN and wet CH 2Cl 2 afforded cis-Ru(tpip) 2(MeCN)Cl ( 6) and cis-Ru(tpip)2(H2O)Cl (7), respectively. Refluxing 6 in neat THF yielded Ru(tpip) 2(THF)Cl (8). Treatment of Ru(CHR)Cl2(PCy3)2 (Cy=cyclohexyl) with [Ag(tpip)] 4 afforded cis-Ru(tpip)2(CHR)(PCy3) [R=Ph (9), OEt (10)]. Complex 9 is capable of catalyzing oxidation of alcohols and olefins with N-methylmorpholine N-oxide and iodosylbenzene, respectively. The crystal structures of 2-7 and 9 were determined.     

Homobinuclear cyanide-bridged linkage isomers containing the redox-active unit [(micro-XY)Ru(CO)2L(o-O2C6Cl4)] (XY=CN or NC)

The salts [NEt4][Ru(CN)(CO)2L(o-O2C6Cl4)] {L=PPh3 or P(OPh)3}, which undergo one-electron oxidation at the catecholate ligand to give neutral semiquinone complexes [Ru(CN)(CO)2L(o-O2C6Cl4)], react with the dimers [{Ru(CO)2L(micro-o-O2C6Cl4)}2] {L=PPh3 or P(OPh)3} to give [NEt4][(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] {L or L'=PPh3 or P(OPh)3}. The cyanide-bridged binuclear anions are, in turn, reversibly oxidised to isolable neutral and cationic complexes [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)] and [(o-O2C6Cl4)L(OC)2Ru(micro-CN)Ru(CO)2L'(o-O2C6Cl4)]+ which contain one and two semiquinone ligands respectively. Structural studies on the redox pair [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- and [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)] confirm that the C-bound Ru(CO)2(o-O2C6Cl4) fragment is oxidised first. Uniquely, [(o-O2C6Cl4){(PhO)3P}(OC)2Ru(micro-CN)Ru(CO)2(PPh3)(o-O2C6Cl4)]- is oxidised first at the N-bound fragment, indicating that it is possible to control the site of electron transfer by tuning the co-ligands. Crystallisation of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(micro-CN)Ru(CO)2{P(OPh)3}(o-O2C6Cl4)] resulted in the formation of an isomer in which the P(OPh)3 ligand is cis to the cyanide bridge, contrasting with the trans arrangement of the X-Ru-L fragment in all other complexes of the type RuX(CO)2L(o-O2C6Cl4).     

Two generalizable routes to terminal carbido complexes

Desulfurization of the thiocarbonyl ligand in square pyramidal [Ru(CS)Cl2(PCy3)2] (1-S) via sulfur atom abstraction using [Mo(H)(eta2-Me2CNAr)(N[i-Pr]Ar)2] forms [Ru(C)Cl2(PCy3)2] (1) cleanly over several hours in benzene; isolated yield is 55%. Complex 1 is also formed in 87% isolated yield upon reaction of [Ru(CHR)(PCy3)2Cl2] (R = p-C6H4Me, 2; Ph, 3) with vinyl acetate in dichloromethane. Complex 1-S is re-formed quantitatively from 1 upon treatment with elemental sulfur in CH2Cl2, but is prepared most conveniently by treatment of crude [Ru(CS)Cl2(PPh3)2(OH2)] with excess PCy3 in toluene. Nearly quantitative conversion of 1 to [Ru(CO)Cl2(PCy3)2] (1-O) occurs upon addition of dimethyldioxirane solution in acetone to 1 dissolved in CH2Cl2 at ca. -90 degrees C.     

Catalytic hydrogenation by triruthenium clusters: a mechanistic study with parahydrogen-induced polarization

The reactivity of the cluster family [Ru(3)(CO)(12-x)(L)(x)] (in which L=PMe(3), PMe(2)Ph, PPh(3) and PCy(3), x=1-3) towards hydrogen is described. When x=2, three isomers of [Ru(3)(H)(mu-H)(CO)(9)(L)(2)] are formed, which differ in the arrangement of their equatorial phosphines. Kinetic studies reveal the presence of intra- and inter-isomer exchange processes with activation parameters and solvent effects indicating the involvement of ruthenium-ruthenium bond heterolysis and CO loss, respectively. When x=3, reaction with H(2) proceeds to form identical products to those found with x=2, while when x=1 a single isomer of [Ru(3)(H)(mu-H)(CO)(10)(L)] is formed. Species [Ru(3)(H)(mu-H)(CO)(9)(L)(2)] have been shown to play a kinetically significant role in the hydrogenation of an alkyne substrate through initial CO loss, with rates of H(2) transfer being explicitly determined for each isomer. A less significant secondary reaction involving loss of L yields a detectable product that contains both a pendant vinyl unit and a bridging hydride ligand. Competing pathways that involve fragmentation to form [Ru(H)(2)(CO)(2)(L)(alkyne)] are also observed and shown to be favoured by nonpolar solvents. Kinetic data reveal that catalysis based on [Ru(3)(CO)(10)(PPh(3))(2)] is the most efficient although [Ru(3)(H)(mu-H)(CO)(9)(PMe(3))(2)] corresponds to the most active of the detected intermediates.     

Evidence for the formation of terminal hydrides by protonation of an asymmetric iron hydrogenase active site mimic

Treatment of [Fe2(mu-pdt)(CO)6] [pdt=S(CH2)3S] with dppe (Ph2PCH2CH2PPh2) in refluxing toluene affords the asymmetric complex [Fe2(mu-pdt)(CO)4(dppe)] (1). Protonation of 1 with HBF4-Et2O in CH2Cl2 gives at room temperature the mu-hydrido derivative [Fe2(mu-pdt)(CO)4(dppe)(mu-H)](BF4) (2). Monitoring the reaction by 1H, 31P, and 13C NMR at low temperature reveals unambiguously that the process of the protonation of 1 implies terminal hydride intermediates.     

Dithiocarboxylate complexes of ruthenium(II) and osmium(II)

The ruthenium(II) complexes [Ru(R)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh) are formed on reaction of IPr·CS(2) with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] (BTD = 2,1,3-benzothiadiazole) or [Ru(C(C≡CPh)=CHPh)Cl(CO)(PPh(3))(2)] in the presence of ammonium hexafluorophosphate. Similarly, the complexes [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)](+) are formed in the same manner when ICy·CS(2) is employed. The ligand IMes·CS(2) reacts with [Ru(R)Cl(CO)(BTD)(PPh(3))(2)] to form the compounds [Ru(R)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) (R = CH=CHBu(t), CH=CHC(6)H(4)Me-4, C(C≡CPh)=CHPh). Two osmium analogues, [Os(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) and [Os(C(C≡CPh)=CHPh)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+) were also prepared. When the more bulky diisopropylphenyl derivative IDip·CS(2) is used, an unusual product, [Ru(κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IDip)Cl(CO)(PPh(3))(2)](+), with a migrated vinyl group, is obtained. Over extended reaction times, [Ru(CH=CHC(6)H(4)Me-4)Cl(BTD)(CO)(PPh(3))(2)] also reacts with IMes·CS(2) and NH(4)PF(6) to yield the analogous product [Ru{κ(2)-SC(H)S(CH=CHC(6)H(4)Me-4)·IMes}Cl(CO)(PPh(3))(2)](+)via the intermediate [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IMes)(CO)(PPh(3))(2)](+). Structural studies are reported for [Ru(CH=CHC(6)H(4)Me-4)(κ(2)-S(2)C·IPr)(CO)(PPh(3))(2)]PF(6) and [Ru(C(C≡CPh)=CHPh)(κ(2)-S(2)C·ICy)(CO)(PPh(3))(2)]PF(6).     

Cyanide-bridged linkage isomers with catecholateruthenium(II) centres bound to Mn(I) or M(alkyne) units

Two series of stable cyanide-bridged linkage isomers, namely [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)] (XY = CN or NC, L = CNBu(t) or CNXyl) and [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC-CPh)Tp'] {M = Mo or W, L = PPh3 or P(OPh)3, Tp' = hydrotris(3,5-dimethylpyrazolyl)borate} have been synthesised; pairs of isomers are distinguishable by IR spectroscopy and cyclic voltammetry. The molecular structure of [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-NC)Mo(CO)(PhC-CPh)Tp'] has the catecholate-bound ruthenium atom cyanide-bridged to a Mo(CO)(PhC[triple band]CPh)Tp' unit in which the alkyne acts as a four-electron donor; the alignment of the alkyne relative to the Mo-CO vector suggests the fragment (CN)Ru(CO)2(PPh3)(o-O2C6Cl4) acts as a pi-acceptor ligand. The complexes [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)Mn(NO)L(eta-C5Me5)] undergo three sequential one-electron oxidation processes with the first and third assigned to oxidation of the ruthenium-bound o-O2C6Cl4 ligand; the second corresponds to oxidation of Mn(I) to Mn(n). The complexes [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp'] are also first oxidised at the catecholate ligand; the second oxidation, and one-electron reduction, are based on the M(CO)(PhC[triple band]CPh)Tp' fragment. Chemical oxidation of [(o-O,C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)] with [Fe(eta-C5H4COMe)(eta-C5H5)][BF4], or of [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp'] with AgBF4, gave the paramagnetic monocations [(o-O2C6Cl4)(Ph3P)(OC)2Ru(mu-XY)MnL(NO)(eta-C5Me5)]+ and [(o-O2C6Cl4)L(OC)2Ru(mu-XY)M(CO)(PhC[triple band]CPh)Tp']+, the ESR spectra of which are consistent with ruthenium-bound semiquinone ligands. Linkage isomers are distinguishable by the magnitude of the 31P hyperfine coupling constant; complexes with N-bound Ru(o-O2C6Cl4) units also show small hyperfine coupling to the nitrogen atom of the cyanide bridge.     

Strong agostic-type interactions in ruthenium benzylidene complexes containing 7-azaindole based scorpionate ligands

The complexes [Ru(Tai)Cl{=C(H)Ph}(PCy(3))] (4) and [Ru((Ph)Bai)Cl{=C(H)Ph}(PCy(3))] (5) [where Tai = HB(7-azaindolyl)(3) and (Ph)Bai = Ph(H)B(7-azaindolyl)(2)] have been prepared and structurally characterised. The borohydride unit is located in the coordination site trans to the chloride ligand in both complexes. The degree of interaction between the borohydride group and the metal centre was found to be significantly large in both cases. Thermolysis reactions involving complex 4 led to a dehydrogenation reaction forming [Ru(Tai)Cl{PCy(2)(η(2)-C(6)H(9))}] (6) where the benzylidene group acts as a hydrogen acceptor.     

New synthetic routes to biscarbonylbipyridinerhenium(I) complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)n+ (X2bpy = 4,4'-X2-2,2'-bipyridine) via photochemical ligand substitution reactions, and their photophysical and electrochemical properties

Photochemical ligand substitution of fac-[Re(X2bpy)(CO)3(PR3)]+ (X2bpy = 4,4'-X2-2,2'-bipyridine; X = Me, H, CF3; R = OEt, Ph) with acetonitrile quantitatively gave a new class of biscarbonyl complexes, cis,trans[Re(X2bpy)(CO)2(PR3)(MeCN)]+, coordinated with four different kinds of ligands. Similarly, other biscarbonylrhenium complexes, cis,trans-[Re(X2bpy)(CO)2(PR3)(Y)]n+ (n = 0, Y = Cl-; n = 1, Y = pyridine, PR'3), were synthesized in good yields via photochemical ligand substitution reactions. The structure of cis,trans-[Re(Me2bpy)(CO)2[P(OEt)3](PPh3)](PF6) was determined by X-ray analysis. Crystal data: C38H42N2O5F6P3Re, monoclinic, P2(1/a), a = 11.592(1) A, b = 30.953(4) A, c = 11.799(2) A, V = 4221.6(1) A3, Z = 4, 7813 reflections, R = 0.066. The biscarbonyl complexes with two phosphorus ligands were strongly emissive from their 3MLCT state with lifetimes of 20-640 ns in fluid solutions at room temperature. Only weak or no emission was observed in the cases Y = Cl-, MeCN, and pyridine. Electrochemical reduction of the biscarbonyl complexes with Y = Cl- and pyridine in MeCN resulted in efficient ligand substitution to give the solvento complexes cis,trans-[Re(X2bpy)(CO)2(PR3)(MeCN)]+.     

The remarkable reactivity of high oxidation state ruthenium and osmium polypyridyl complexes

There is a remarkable redox chemistry of higher oxidation state M(IV)-M(VI) polypyridyl complexes of Ru and Os. They are accessible by proton loss and formation of oxo or nitrido ligands, examples being cis-[RuIV(bpy)2(py)(O)]2+ (RuIV=O2+, bpy=2,2'-bipyridine, and py=pyridine) and trans-[OsVI(tpy)(Cl)2(N)]+ (tpy=2,2':6',2' '-terpyridine). Metal-oxo or metal-nitrido multiple bonding stabilizes the higher oxidation states and greatly influences reactivity. O-atom transfer, hydride transfer, epoxidation, C-H insertion, and proton-coupled electron-transfer mechanisms have been identified in the oxidation of organics by RuIV=O2+. The Ru-O multiple bond inhibits electron transfer and promotes complex mechanisms. Both O atoms can be used for O-atom transfer by trans-[RuVI(tpy)(O)2(S)]2+ (S=CH3CN or H2O). Four-electron, four-proton oxidation of cis,cis-[(bpy)2(H2O)RuIII-O-RuIII(H2O)(bpy)2]4+ occurs to give cis,cis-[(bpy)2(O)RuV-O-RuV(O)(bpy)2]4+ which rapidly evolves O2. Oxidation of NH3 in trans-[OsII(tpy)(Cl)2(NH3)] gives trans-[OsVI(tpy)(Cl)2(N)]+ through a series of one-electron intermediates. It and related nitrido complexes undergo formal N- transfer analogous to O-atom transfer by RuIV=O2+. With secondary amines, the products are the hydrazido complexes, cis- and trans-[OsV(L3)(Cl)2(NNR2)]+ (L3=tpy or tpm and NR2-=morpholide, piperidide, or diethylamide). Reactions with aryl thiols and secondary phosphines give the analogous adducts cis- and trans-[OsIV(tpy)(Cl)2(NS(H)(C6H4Me))]+ and fac-[OsIV(Tp)(Cl)2(NP(H)(Et2))]. In dry CH3CN, all have an extensive multiple oxidation state chemistry based on couples from Os(VI/V) to Os(III/II). In acidic solution, the OsIV adducts are protonated, e.g., trans-[OsIV(tpy)(Cl)2(N(H)N(CH2)4O)]+, and undergo proton-coupled electron transfer to quinone to give OsV, e.g., trans-[OsV(tpy)(Cl)2(NN(CH2)4O)]+ and hydroquinone. These reactions occur with giant H/D kinetic isotope effects of up to 421 based on O-H, N-H, S-H, or P-H bonds. Reaction with azide ion has provided the first example of the terminal N4(2-) ligand in mer-[OsIV(bpy)(Cl)3(NalphaNbetaNgammaNdelta)]-. With CN-, the adduct mer-[OsIV(bpy)(Cl)3(NCN)]- has an extensive, reversible redox chemistry and undergoes NCN(2-) transfer to PPh3 and olefins. Coordination to Os also promotes ligand-based reactivity. The sulfoximido complex trans-[OsIV(tpy)(Cl)2(NS(O)-p-C6H4Me)] undergoes loss of O2 with added acid and O-atom transfer to trans-stilbene and PPh3. There is a reversible two-electron/two-proton, ligand-based acetonitrilo/imino couple in cis-[OsIV(tpy)(NCCH3)(Cl)(p-NSC6H4Me)]+. It undergoes reversible reactions with aldehydes and ketones to give the corresponding alcohols.     

Synthesis,structural characterization,and reactions of cyclic organohydroborate half-zirconocene compounds

Cyclic organohydroborate complexes of zirconium monocyclopentadienyl CpZr[(mu-H)(2)BC(5)H(10)](3), 1, and CpZr[(mu-H)(2)BC(8)H(14)](3), 2, were prepared from the reaction of CpZrCl(3) with 3 mol of K[H(2)BC(5)H(10)] and K[H(2)BC(8)H(10)], respectively, in diethyl ether. Compounds 1 and 2 react with the hydride ion abstracting agent B(C(6)F(5))(3) to form the same salt [CpZr(OEt)(OEt(2))(mu-OEt)](2)[HB(C(6)F(5))(3)](2), 5. The complexes CpZr(Cl)[(mu-H)(2)BC(8)H(14)](2), 3, and CpZr(Cl)[(mu-H)(2)BC(8)H(14)](2) [where Cp = C(5)(CH(3))(5)], 4, were prepared from the reaction of CpZrCl(3) and CpZrCl(3) with K[H(2)BC(8)H(10)] in 1:2 molar ratios, respectively. An alpha-hydrogen of a BC(8)H(14) unit forms an agostic interaction with Zr in compound 3 but not in 4. All of the compounds were characterized by single-crystal X-ray diffraction analysis.     

Olefin metatheses in metal coordination spheres: versatile new strategies for the construction of novel monohapto or polyhapto cyclic, macrocyclic, polymacrocyclic, and bridging ligands

The broad applicability of the title reaction is established through studies of neutral and charged, coordinatively saturated and unsaturated, octahedral and square planar rhenium, platinum, rhodium, and tungsten complexes with cyclopentadienyl, phosphine, and thioether ligands which contain terminal olefins. Grubbs' catalyst, [Ru(=CHPh)(PCy3)2(Cl)2], is used at 2-9 mol% levels (0.0095-0.00042 M, CH2-Cl2). Key data are as follows: [(eta5-C5H4(CH2)6CH=CH2)Re(NO)(PPh3)-(CH3)], intermolecular metathesis (95 %); [(eta5-C5H5)Re(NO)(PPh3)(E(CH2CH=CH2)2)]+ TfO (E=S, PMe, PPh), formation of five-membered heterocycles (96-64%; crystal structure E = PMe); [(eta5-C5Me5)Re(NO)(PPh((CH2)6CH=CH2)2)(L)]n+ nBF4-(L/n = CO/1, Cl/0), intramolecular macrocyclization (94-89%; crystal structure L= Cl); fac-[(CO)3Re(Br)(PPh2(CH2)6CH=CH2)2] and cis-[(Cl)2Pt(PPh2(CH2)6CH=CH2)2], intramolecular macrocyclizations (80-71%; crystal structures of each and a hydrogenation product); cis-[(Cl)2Pt(S(R)(CH2)6CH= CH2)2], intra-/intermolecular macrocyclization (R=Et, 55%/24%; tBu, 72%/ <4%); trans-[(Cl)(L)M(PPh2(CH2)6CH=CH2)2] (M/L = Rh/CO, Pt/C6F5) intramolecular macrocyclization (90-83%; crystal structure of hydrogenation product, M=Pt); fac-[W(CO)3(PPh((CH2)6CH=CH2)2)3], intramolecular trimacrocyclization (83 %) to a complex mixture of triphosphine, diphosphine/ monophosphine, and tris(monophosphine) complexes, from which two isomers of the first type are crystallized. The macrocycle conformations, and basis for the high yields, are analyzed.     

Synthesis, Characterization, and Comparative Properties of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)

The reaction of [PPN](2)[Re(6)C(CO)(19)] with Mo(CO)(6) and Ru(3)(CO)(12) under sunlamp irradiation provided the new mixed-metal clusters [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] and [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)], which were isolated in yields of 85% and 61%, respectively. The compound [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] crystallizes in the monoclinic space group P2(1)/c with a = 20.190 (7) ?, b = 16.489 (7) ?, c = 27.778 (7) ?, beta = 101.48 (2) degrees, and Z = 4 (at T = -75 degrees C). The cluster anion is composed of a Re(6)C octahedral core with a face capped by a Mo(CO)(4) fragment. There are three terminal carbonyl ligands coordinated to each rhenium atom. The four carbonyl ligands on the molybdenum center are essentially terminal, with one pair of carbonyl ligands (C72-O72 and C74-O74) subtending a relatively large angle at molybdenum (C72-Mo-C74 = 147.2(9) degrees ), whereas the remaining pair of carbonyl ligands (C71-O71 and C73-O73) subtend a much smaller angle (C71-Mo-C73 = 100.5(9) degrees ). The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows signals for four sets of carbonyl ligands at -40 degrees C, consistent with the solid state structure, but the carbonyl ligands undergo complete scrambling at ambient temperature. The (13)C NMR spectrum of (13)CO-enriched [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] at 20 degrees C is consistent with the expected structure of an octahedral Re(6)C(CO)(18) core capped by a Ru(CO)(3) fragment. The visible spectrum of [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)] shows a broad, strong band at 670 nm (epsilon = 8100), whereas all of the absorptions of [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)] are at higher energy. An irreversible oxidation wave with E(p) at 0.34 V is observed for [PPN](2)[Re(6)C(CO)(18)Mo(CO)(4)], whereas two quasi-reversible oxidation waves with E(1/2) values of 0.21 and 0.61 V (vs Ag/AgCl) are observed for [PPN](2)[Re(6)C(CO)(18)Ru(CO)(3)]. The molybdenum cap in [Re(6)C(CO)(18)Mo(CO(4))](2-) is cleaved by heating in donor solvents, and by treatment with H(2), to give largely [H(2)Re(6)C(CO)(18)](2-). In contrast, [Re(6)C(CO)(18)Ru(CO)(3)](2-) shows no tendency to react under similar conditions.     

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.     

New triruthenium clusters as photoinduced DNA-binding and cleaving agents

1-Hydroxybenzotriazole and 1-hydroxypyridine-2-thione were incorporated as ligands with the cluster Ru3(CO)10 (NCMe)2 to give [(mu-H)Ru3(CO)10(mu2-2,3-eta2-NNN(O)C6 H4)] and [(mu-H)Ru3(CO)9(mu2-eta1 : eta2-C5H4N(O)S)], respectively. Irradiation of these two new triruthenium metal clusters individually with 350 nm UV light in a phosphate buffer (pH 6.0) containing form I DNA resulted in single-strand cleavage. Cluster [(mu-H)Ru3(CO)10(mu2-2,3--eta2-NNN (O)C6H4)] was also found to bind to calf thymus DNA upon UV irradiation.