An intramolecular N-H...(mu-H)Re2 dihydrogen bond and a novel mu 3-eta 2 coordination mode of the pyrazolate anion on a triangular cluster face

The quantitative addition of pyrazole (Hpz) to the 44 valence-electron, triangular cluster anion [Re3(mu 3-H)-(mu-H)3(CO)9]- gives the novel unsaturated anion [Re3(mu-H)4(CO)9(Hpz)]- (1, 46 valence electrons), which contains a pyrazole molecule that is terminally coordinated on a cluster vertex. Solidstate X-ray and IR analyses reveal a rather weak hydrogen-bonding interaction between the NH proton and one of the hydrides bridging the opposite triangular cluster edge (delta H degree = -3.1 kcal mol-1 from the Iogansen equation). Both IR and NMR data indicate that such a proton-hydride interaction is maintained in the major conformer present in CD2Cl2, but also provide evidence of the presence of minor conformers of 1 in which the NH proton is involved in an intermolecular hydrogen bond with the solvent. The mu-H...HN bond length evaluated in solution through the T1 minimum value (2.07 A) and that determined in the solid state by X-ray diffraction (2.05 A) are in good agreement. NMR experiments show that, in acetone, intermolecular N-H...solvent interactions replace the intramolecular dihydrogen bond. At room temperature in CH2Cl2, the pyrazole ligand in 1 is labile and 1 slowly "disproportionates" to [Re3(mu 3-H)-(mu-H)3(CO)9]- and [Re3(mu-H)3(CO)9-(mu-eta 2-pz)(Hpz)]-, with H2 evolution. Slow H2 evolution also leads to the formation of the anion [Re3(mu-H)3-(CO)9(pz)]- (5), in which the pyrazolate anion adopts a novel mu 3-eta 2-coordination mode, as revealed by a single-crystal X-ray analysis. The analysis of the bond lengths indicates that the pyrazolate anion in 5 acts as a six-electron donor, with loss of the aromaticity. The formation of 5 from 1 is much faster in solvents with a high dielectric constant, such as acetone or DMF. Anion 5 was also obtained from the reaction of pyrazole with [Re3(mu-H)3(CO)9(mu 3-CH3)]- through the intermediate formation of two isomeric addition derivatives and following CH4 evolution.     

A meso-helical coordination polymer from achiral dinuclear [Cu2(H3CCN)2(micro-pydz)3][PF6]2 and 1,3-bis(diphenylphosphanyl)propane-synthesis and crystal structure of 1 to infinity Cu(mu-pydz)2][PF6 (pydz=pyridazine)

Reaction of achiral [Cu2(H3CCN)2(mu-pydz)3][PF6]2 (1) (pydz = pyridazine) with bidendate 1,3-bis(diphenylphosphanyl)propane (2) in acetonitrile at room temperature in a 1:1 ratio yielded the mononuclear copper(I) complex [Cu[CH2(CH2PPh2)2]2][PF6] (3) together with new one-dimensional coordination polymer 1 to infinity[[Cu(mu-pydz)2][PF6]] (4). Air-sensitive single crystals of 4, suitable for X-ray structure determination, were grown from a mixture of dichloromethane/ hexane [crystal system: monoclinic; space group: C2/c: a = 21.910(3), b = 12.130(2), c = 25.704(3) A,beta = 110.08(10) degrees, V = 6416.65(16) A3]. The one-dimensional coordination polymer 1 to infinity[[Cu(mu-pydz)2][PF6]] (4) exhibits as outstanding feature the rare structure of a meso-helix.     

Synthesis and structural characterization of a series of high-hydride content osmium-rhodium carbonyl complexes by the hydrogenation of arene-coordinated clusters

The reaction of [Os3Rh(mu-H)3(CO)12] with an excess amount of 4-vinylphenol (as hydride acceptor) in refluxing m-xylene, chlorobenzene or benzene yielded the three new clusters [Os5Rh2(mu-CO){eta6-C6H4(CH3)2}(CO)16] 1, [Os5Rh2(mu-CO)(eta6-C6H5Cl)(CO)16] 2 and [Os5Rh2(mu-CO)(eta6-C6H6)(CO)16] 3. The treatment of [Os3Rh(mu-H)3(CO)12] 4 in refluxing toluene with an excess amount of 4-vinylphenol afforded a new complex, [Os4Rh(mu-H)(eta6-C6H5CH3)(CO)12], which was isolated as a brown complex in 20% yield together with two known compounds, [Os5Rh2(eta6-C6H5CH3)(mu-CO)(CO)16] in 10% yield and [Os3Rh4(mu3-eta1:eta1:eta1-C6H5CH3)(CO)13] in 5% yield. Complexes 1-4 were fully characterized by IR, 1H NMR spectroscopy, mass spectroscopy, elemental analysis and X-ray crystallography. The molecular structures of compounds 1-3 are isomorphous, and only differ in the arene-derivatives that attach to the same metal core. Their metal cores can be viewed as a monocapped octahedral, in which an osmium atom caps one of the Os-Os-Os triangular faces of the Os4Rh2 metal framework. Complex 4 has a trigonal-bipyramidal metal core with a C6H5Me ligand that is terminally bound to the Rh atom that lies in the trigonal plane of the metal core. The hydrogenation of [Os5Rh2(eta6-C6H5CH3)(mu-CO)(CO)16] with [Os3(mu-H)2(CO)10] in chloroform under reflux resulted in two hydrogen-rich compounds: [Os7Rh3(mu-H)11(CO)23] 5 and [Os5Rh3Cl(mu-H)8(CO)18] 6, both in moderate yields. The reaction of [Os5Rh2(eta6-C6H5CH3)(mu-CO)(CO)16] with hydrogen in refluxing chloroform yielded a new cluster compound, [Os5Rh(mu-H)5(CO)18] 7, in 20% yield, together with a known osmium-rhodium cluster, [Os6Rh(mu-H)7(mu-CO)(CO)18], as a major compound. Clusters 5, 6, and 7 have been fully characterized by both spectroscopic and crystallographic methods. Additionally, a deuterium-exchange experiment was performed on [Os7Rh3(mu-H)11(CO)23] 5 and [Os5Rh3Cl(mu-H)8(CO)18] 6. Both the compounds proved to be able to exchange the H atom with D in the presence of D2SO4, and the absence of the hydride signal in the 1H NMR spectrum is consistent with this. Therefore, clusters 5 and 6 may serve as appropriate new hydrogen storage models.     

Hydrogenation and carbon-sulfur bond hydrogenolysis of benzothiophene promoted by Re2(CO)10 and H4Re4(CO)12

In the search for metal complexes that promote the cleavage of C-S bonds in thiophenes, we observe that the reaction of Re(2)(CO)(10) and benzothiophene (BT) under a hydrogen atmosphere gives the trinuclear cluster Re(3)(mu-H)(2)(mu(3)-S-2-EtC(6)H(4))(mu-2,3-DHBT)(CO)(9) (1), which contains a hydrogenated BT ligand and a thiolate ligand resulting from the hydrogenation and cleavage of a C-S bond in BT. A detailed study of the reaction shows that Re(2)(CO)(10) initially reacts with H(2) to give H(3)Re(3)(CO)(12), which subsequently converts to H(4)Re(4)(CO)(12), which finally reacts with BT to give 1.     

Unexpected ferromagnetic interaction in a new tetranuclear copper(II) complex: synthesis, crystal structure, magnetic properties, and theoretical studies

The new tetranuclear carbonate complex [Cu2L)2(CO3)] x 8H2O (1 x 8H2O) (H3L = (2-(2-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) has been obtained by two different synthetic routes and fully characterized. Recrystallization of 1 x 8H2O in methanol yields single crystals of {[(Cu2L)2(CO3)]}2 x 12H2O (1 x 6H2O), suitable for X-ray diffraction studies. The crystal structure of 1 x 6H2O shows two crystallographically different tetranuclear molecules in the asymmetric unit, 1a and 1b. Both molecules can be understood as self-assembled from two dinuclear [Cu2L]+ cations, joined by a mu4-eta(2):eta(1):eta(1) carbonate ligand. The copper atoms of each crystallographically different [(Cu2L)2(CO3)] molecule present miscellaneous coordination polyhedra: in both 1a and 1b, two metal centers are in square pyramidal environments, one displays a square planar chromophore and the other one has a geometry that can be considered as an intermediate between square pyramid and trigonal bipyramid. Magnetic studies reveal net intramolecular ferromagnetic coupling between the metal atoms. Density functional calculations allow the assignment of the different magnetic coupling constants and explain the unexpected ferromagnetic behavior, because of the presence of an unusual NCN bridging moiety and countercomplementarity of the phenoxo (or carbonate) and NCN bridges.     

1,2,3,4-Tetraphenyl-1,2,3,4-tetraphospholane,a highly versatile cyclocarbaphosphine ligand: reactions with activated triosmium clusters and characterization of the products

Reaction of 1,2,3,4-tetraphenyl-1,2,3,4-tetraphospholane (I) with [Os(3)(CO)(11)(NCMe)] at ambient temperature affords substituted clusters: the monosubstituted trinuclear cluster [Os(3)(CO)(11)[(PPh)(4)CH(2)]] (1) and the isomeric linked bis-trinuclear clusters [[Os(3)(CO)(11)](2)[mu-1,4-eta(2)-(PPh)(4)CH(2)]] (2) and [[Os(3)(CO)(11)](2)[mu-1,3-eta(2)-(PPh)(4)CH(2)]] (3). Clusters 2 and 3 can also be prepared by further reaction of 1 with [Os(3)(CO)(11)(NCMe)]. The reaction at 100 degrees C gives, apart from cluster 2, the disubstituted 1,4-bridged trinuclear cluster [Os(3)(CO)(10)[mu-1,4-eta(2)-(PPh)(4)CH(2)]] (4). The conversion of 1 into 4 can be achieved through the pyrolysis of a solution of 1. When 1 reacts with an equimolar amount of [Os(3)(CO)(10)(mu-H)(2)] at 100 degrees C in toluene, the 1,2,4-linked bis-trinuclear cluster [Os(3)(CO)(11)[mu(3)-1,2,4-eta(3)-(PPh)(4)CH(2)]Os(3)(CO)(8)(mu-H)(2)] (5) is obtained. When I reacts with a 2-fold molar amount of [Os(3)(CO)(10)(mu-H)(2)], the 1,2,3,4-linked bis-trinuclear hydride cluster [[Os(3)(CO)(8)(mu-H)(2)](2)[mu(4)-1,2,3,4-eta(4)-(PPh)(4)CH(2)]] (6) is obtained. Cluster 1 exists as two conformational isomers (1y and 1r) in the crystalline state, due to different conformational arrangements of pseudoaxial carbonyls in the cluster. Cluster 3 shows two interconvertible conformers (3y and 3r) due to the inversion of the configuration of the uncoordinated outer phosphorus atom, and a pair of enantiomers exists in 3r. All of the new compounds obtained have been characterized by spectroscopic and analytical techniques, and their structures have been established by X-ray crystallography.     

Photoreversible multiple additions of hydrogen to a highly unsaturated platinum-rhenium cluster complex

The compound Pt3Re2(CO)6(PBut3)3, 1, was obtained from the reaction of Re2(CO)10 with Pt(PBut3)2 in octane solvent at reflux. Compound 1 consists of a trigonal bipyramidal cluster of five metal atoms with three platinum atoms in the trigonal plane and the two rhenium atoms in the apical positions. The metal cluster is formally unsaturated by 10 electrons. Compound 1 sequentially adds 3 equiv of hydrogen at room temperature/1 atm to form the series of compounds Pt3Re2(CO)6(PBut3)3(mu-H)2, 2, Pt3Re2(CO)6(PBut3)3(mu-H)4, 3, and Pt3Re2(CO)6(PBut3)3(mu-H)6, 4. A small but significant kinetic isotope effect was observed, kH/kD = 1.3. The rate of addition of hydrogen is unaffected by the presence of a 20-fold excess of free PBut3 in solutions of 1. Compounds 2-4 each consist of a trigonal bipyramidal cluster of three platinum and two rhenium atoms similar to that of 1. The hydrido ligands in 2-4 bridge the platinum-rhenium bonds and are arranged to give structures having overall C2v symmetry for 2 and 3 and approximate D3h symmetry for 4. Some of the hydrido ligands were expelled from 4 in the form of hydrogen upon exposure of solutions to UV-vis irradiation to yield compound 3 and then 2 in reasonable yields, but the elimination of all hydrido ligands to yield 1 was achieved only under the most forcing UV irradiation and then only with a major loss of the complex due to decomposition. The electronic structures of 1-4 were investigated by DFT calculations. Additional DFT calculations have suggested some mechanisms for the activation of hydrogen at multicenter metal sites without ligand eliminations prior to the hydrogen additions.     

Redox-induced coordination isomerization of a phosphoniobenzophospholide

1-Triphenylphosphoniobenzo[c]phospholide 1 reacts with [M(CO)(5)Br] (M = Mn, Re) and [Mn(CO)(3)(naphthalene)][BF(4)] to give complexes cis-[M(CO)(4)(1)Br] (5 a,b) and [Mn(CO)(3)(1)][BF(4)] (6 a[BF(4)]), respectively, featuring eta(1)(P)- and eta(5)(pi)-coordination of the phosphole ring. The corresponding reactions with [M(2)(CO)(10)] proceed with conservation of the metal-metal bond and yield, depending on the reaction temperature, dinuclear complexes [M(2)(CO)(8)(1)] (M=Mn, 7 a) or [M(2)(CO)(6)(1)(2)] (M=Mn, Re, 8 a,b) with mu(2)-bridging eta(1)(P):eta(2)(Pdbond;C) coordination of the phosphole moiety. All complexes formed were characterized by spectroscopic data; 5 b, 6 a[BF(4)], and 8 a,b were characterized by X-ray diffraction studies as well. The structural and (31)P NMR data of the dinuclear manganese complex 8 a suggest that the interaction between the metal atoms and the eta(2)-bound Pdbond;C double bond moieties is dominated by the L-->M charge-transfer contribution; this hints at a very low back-donation ability of the central M(2)(CO)(6) fragment. Investigation of the reactions of the Mn complexes 6 a and 8 a with Mg or ferrocenium hexafluorophosphate ([Fc][PF(6)]), respectively, revealed that the chemically reversible mutual interconversion between both species was feasible. Likewise, oxidation of the rhenium complex 8 b with [Fc][PF(6)] gave spectroscopic evidence for the formation of a Re analogue of 6 a. Electrochemical studies suggested that the oxidation 8 a-->2 6 a involves two consecutive single-electron-transfer steps, the first of which is electrochemically reversible and produces a metastable radical cation that is detectable by ESR spectroscopy. The mutual interconversion between 6 a and 8 a represents the first case of a reversible coordination isomerization of a phosphaarene that is triggered by a redox process and might stimulate further studies directed at the use of dinuclear phosphaarene complexes in redox-catalysis.     

新型Mo-Pb-S异四核簇合物 [Mo~3(PbI~3)S~4(dtp)~3(C~3H~4N~2)~3][(CH~3) ~2CO]~2 的合成和晶体结构

由[Mo~3(μ~3-O)(μ-S)~3(dtp)~4(H~2O)和PbI~3^-在咪唑存在下反应获得异四核混合簇[Mo~3(PbI~3)S~4(dtp)~3(C~3H~4N~2)~3][(CH~3)~2CO]~2(2)[dtp=S~2P(OC~2H~5)~2^-]。簇合物属斜方晶系,空间群P~b~c~a(No.61),晶胞参数为a=2.3590(3),b=1.9161(5),c=2.6458(9)nm,V=11.959(6)nm^3,Z=8。结构最终偏离因子R=0.067。此四核簇分子具有[Mo~3PbS~4]类立方烷簇芯,簇分子整体对称性接近C~3~v。在同一不对称单元中,簇分子的咪唑环以(NH)和溶剂丙酮分子的氧原子形成O---H---N氢键。     

High nuclearity ruthenium-tin clusters from the reactions of triphenylstannane with pentaruthenium carbonyl carbido cluster complexes

The reaction of Ru(5)(CO)(15)(mu(5)-C), 1, with Ph(3)SnH in the presence of UV irradiation has yielded the Ph(3)SnH adduct Ru(5)(CO)(15)(SnPh(3))(mu(5)-C)(mu-H), 3, by SnH bond activation and cleavage of one Ru-Ru bond in the cluster of 1. The reaction of 1 with Ph(3)SnH at 127 degrees C yielded the high nuclearity cluster compound Ru(5)(CO)(10)(SnPh(3))(mu-SnPh(2))(4)(&mu(5)-C)(mu-H), 4, that contains five tin ligands. Four of these are SnPh(2) groups that bridge each edge of the base of the Ru(5) square pyramidal cluster. The reaction of Ph(3)SnH with the benzene-substituted cluster Ru(5)(CO)(12)(C(6)H(6))(mu(5)-C), 2, at 68 degrees C yielded two products: Ru(5)(CO)(11)(SnPh(3))(C(6)H(6))(mu(5)-C)(mu-H), 5, and Ru(5)(CO)(10)(SnPh(3))(2)(C(6)H(6))(mu(5)-C)(mu-H)(2), 6. Both contain square pyramidal Ru(5) clusters with one and two SnPh(3) groups, respectively. At 127 degrees C, the reaction of 2 with an excess of Ph(3)SnH has led to the formation of two new high-nuclearity cluster complexes: Ru(5)(CO)(8)(mu-SnPh(2))(4)(C(6)H(6))(mu(5)-C), 7, and Ru(5)(CO)(7)(mu-SnPh(2))(4)(SnPh(3))(C(6)H(6))(mu-H), 8. Both compounds contain square pyramidal Ru(5) clusters with SnPh(2) groups bridging each edge of the square base. Compound 8 contains a SnPh(3) group analogous to that of compound 4. When treated with CO, compound 8 is converted to 4. When heated to 68 degrees C, compound 5 was converted to the new compound Ru(5)(CO)(11)(C(6)H(6))(mu(4)-SnPh)(mu(3)-CPh), 9, by loss of benzene and the shift of a phenyl group from the tin ligand to the carbido carbon atom to form a triply bridging benzylidyne ligand and a novel quadruply bridging stannylyne ligand.     

Di-, tri-, and tetranuclear zinc hydroxamate complexes as structural models for the inhibition of zinc hydrolases by hydroxamic acids

Attempts to produce Zn analogues of the structural model complexes [M2(mu-O2CR)2(O2CR)2(mu-H2O)(tmen)2] (M = Ni, Co, Mn; R = CH(3), C(CH3)3, CF3) by the reaction of a series of zinc carboxylates with N,N,N',N'-tetramethylethylenediamine (tmen), resulted in the mononuclear complexes [Zn(OAc)(2)(tmen)] (1) and [Zn(crot)2(tmen)].(0.5)H2O (2) for R = CH3 and (CH)2CH3, respectively, and the dinuclear complexes [Zn(2)(mu-piv)(2)(piv)(2)(mu-H2O)(tmen)2] (3) and [Zn2(mu-OAc(F))2(OAc(F))2(mu-H2O)(tmen)2] (4) for R = C(CH3)3 and CF3, respectively. In contrast to the analogous imidazole series, i.e., [M2(mu-O2CR)2(O2CR)2(mu-H2O)(Im)4] (M = Ni, Co, Mn; R = CH3, C(CH3)3, CF3), zinc carboxylates react with imidazole to give only the mononuclear complexes [Zn(OAc)2(Im)2] (5), [Zn(crot)2(Im)2].H2O (6), [Zn(piv)2(Im)2].(0.5)H2O (7), and [Zn(OAc(F))2(Im)2] (8). Reaction of 1, 2, and 3 with either acetohydroxamic acid (AHA) or benzohydroxamic acid (BHA) gives the dinuclear complexes [Zn2(O2CR)3(R'A)(tmen)], where R'A = acetohydroxamate (AA) (9, 10, 11) or benzohydroxamate (BA) (13, 14, 15). In these complexes, the zinc atoms are bridged by a single hydroxamate and two carboxylates, with a capping tmen ligand on one zinc and a monodentate carboxylate bonded to the second zinc atom. This composition models closely the observed structure of the active site of the p-iodo-d-phenylalanine hydroxamic acid inhibited Aeromonas proteolyticaaminopeptidase enzyme. In contrast, 4 reacts with AHA to give [Zn2(OAc(F))3(tmen)2(AA)] (12) with an additional tmen ligand so that both Zn atoms are 6-coordinate, whereas reaction with BHA gives the trinuclear complex [Zn3(OAc(F))4(tmen)2(BA)2] (16). Reactions of 3 and 4 with glutarodihydroxamic acid (GluH2A2) produce the tetranuclear complexes [Zn4(piv)6(tmen)4(GluA2)] (18) and [Zn4(OAc(F))6(tmen)4(GluA2)] (19).     

Carbidohexarhenate cluster cores bicapped by mercury with acetate or thiolate ligands

The reaction of [PPh4]3[Re7C(CO)21] (1) with 1 or more equiv of Hg(OAc)2 in dichloromethane provides the monomercury derivative [PPh4]2[Re7C(CO)21HgOAc] (2) in high yield. However, in the presence of methanol the reaction of 1 with 2 equiv of Hg(OAc)2 yields the dimercury hexarhenium cluster compound [PPh4]2[Re6C(CO)18(HgOAc)2] (3) together with the dirhenium complex [PPh4][Re2(CO)6(mu-OMe)2(mu-OAc)] (4). The dimercury compound 3 reacts with various thiols HS-Z to form thiolate-substituted derivatives [PPh4]2[Re6C(CO)18(HgSZ)2] [Z = C6H4Br (5); C5H4N (6); C2H4COOH (7)]. All new compounds have been characterized by a combination of analytical and spectroscopic data, and the molecular structures of compounds 3-6 have been determined by X-ray crystallography.     

Addition of palladium and platinum tri-tert-butylphosphine groups to Re-Sn and Re-Ge bonds

The reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3SnH at 68 degrees C yielded the new compound Re2(CO)8(mu-SnPh2)2 (10) which contains two SnPh2 ligands bridging two Re(CO)(4) groups, joined by an unusually long Re-Re bond. Fenske-Hall molecular orbital calculations indicate that the bonding in the Re2Sn2 cluster is dominated by strong Re-Sn interactions and that the Re-Re interactions are weak. The 119Sn M?ssbauer spectrum of 10 exhibits a doublet with an isomer shift (IS) of 1.674(12) mm s(-1) and a quadrupole splitting (QS) of 2.080(12) mm s(-1) at 90 K,characteristic of Sn(IV) in a SnA2B2 environment. The IS is temperature dependent, -1.99(14) x 10(-4) mm s(-1) K(-1); the QS is temperature independent. The temperature-dependent properties are consistent with the known Gol'danskii-Kariagin effect. The germanium compound Re2(CO)8(mu-GePh2)2 (11) was obtained from the reaction of Re2(CO)8[mu-eta2-C(H)=C(H)Bu(n)](mu-H) with Ph3GeH. Compound 11 has a structure similar to that of 10. The reaction of 10 with Pd(PBu(t)3)2 at 25 degrees C yielded the bis-Pd(PBu(t)3) adduct, Re2(CO)8(mu-SnPh2)2[Pd(PBu(t)3)]2 (12); it has two Pd(PBu(t)3) groups bridging two of the four Re-Sn bonds in 10. Fenske-Hall molecular orbital calculations show that the Pd(PBu(t)3) groups form three-center two-electron bonds with the neighboring rhenium and tin atoms. The mono- and bis-Pt(PBu(t)3) adducts, Re2(CO)8(mu-SnPh2(2)[Pt(PBu(t)3)] (13) and Re2(CO)8(mu-SnPh2)2[Pt(PBu(t)3)]2 (14), were formed when 10 was treated with Pt(PBu(t)3)2. A mono adduct of 11, Re2(CO)8(mu-GePh2)2[Pt(PBu(t)3)] (15), was obtained similarly from the reaction of 11 with Pt(PBu(t)3)2.     

New rhenium-tin cluster adds palladium phosphine groups across Re-Sn bonds

The new rhenium-tin complex Re2(CO)8(mu-SnPh2)2, 1 was obtained in 52% yield from the reaction of Re2(CO)8(mu-H)[mu-C(H)C(H)Bu] with Ph3SnH. Compound 1 contains two SnPh2 groups bridging a long Re-Re single bond, Re-Re = 3.1971(4) A [3.1902(4) A], Re-Sn = 2.7429(4) A [2.7445(4) A], and 2.7675(4) [2.7682(5) A]. A bis-Pd(PBut3) adduct of 1, Pd2Re2(CO)8(mu-SnPh2)2(PBut3)2, 2 was obtained from the reaction of 1 with Pd(PBut3)2. Compound 2 contains Pd(PBut3) groups bridging two of its four Re-Sn bonds. The Re-Re bond and the unbridged Re-Sn bonds in 2 are significantly longer than those in 1, 3.245(1) A and 2.8167(14) A, respectively. Fenske-Hall molecular orbital calculations on 1 and 2 have been performed to explain the metal-metal bonding in these unusual mixed-metal polynuclear metal complexes.     

Pyrazole complexes as anion receptors: effects of changing the metal, the pyrazole substitution pattern, and the number of pyrazole ligands

Compound cis,fac-[Mo(eta3-allyl)(CO)2(Hdmpz)3]BAr'4 (1) (Hdmpz = 3,5-dimethylpyrazole, Ar' = 3,5-bis(trifluoromethyl)phenyl) undergoes rapid substitution of one of the pyrazole ligands by anions, including the low nucleophilic ReO4-, a reaction that afforded [Mo(OReO3)(eta3-allyl)(CO)2(Hdmpz)2] (2), structurally characterized by X-ray diffraction. The new compounds fac-[Mn(CO)3(Hdmpz)3]BAr'4 (4a) and fac-[Mn(CO)3(HtBupz)3]BAr'4 (4b) (HtBupz = 3(5)-tert-butylpyrazole) also undergo pyrazole substitution with most anions, and the product from the reaction with nitrate was crystallographically characterized. Compounds 4a,b were found to be substitutionally stable toward perrhenate, and the adducts [Mn(CO)3(Hdmpz)3].[ReO4] (7a) and [Mn(CO)3(HtBupz)3].[ReO4].[Bu4N].[BAr'4] (7b), crystallographically characterized, display hydrogen bonds between one of the perrhenate oxygens and the N-H groups of two of the pyrazole ligands. The structurally similar adduct [Re(CO)3(Hdmpz)3].[ReO4] (8) was found to result from the interaction of [Re(CO)3(Hdmpz)3]BAr'4 with perrhenate. The reaction of [Re(OTf)(CO)5] with 3,5-dimethylpyrazole (Hdmpz) afforded [Re(CO)5(Hdmpz)]OTf (9). The reaction of 9 with Hdmpz and NaBAr'4 yielded [Re(CO)4(Hdmpz)2]BAr'4 (10), which was found to be unstable toward chloride anion. In contrast, the new compound fac,cis-[Re(CO)3(CNtBu)(Hdmpz)2]BAr'4 (11) is stable in solution in the presence of different anions. Binding constants for 11 with chloride, bromide, and nitrate are 1-2 orders of magnitude lower than those found for these anions and rhenium tris(pyrazole) hosts, indicating that the presence of the third pyrazole ligand is crucial. Compounds fac-[Re(CO)3(HPhpz)3]BAr'4 (14) (HPhpz = 3(5)-phenylpyrazole) and fac-[Re(CO)3(HIndz)3]BAr'4 (15) (HIndz = indazole) are, in terms of anion binding strength and selectivity, inferior to those with dimethylpyrazole or tert-butylpyrazole ligands.     

Two stereoisomers of an S-bridged RhIII2PtII2 tetranuclear complex [{Pt(NH3)2}2{Rh(aet)3}2]4+ that lead to a discrete and a 1D RhIII2PtII2AgI structures by reacting with AgI (aet = 2-aminoethanethiolate)

An S-bridged RhIII2PtII2 tetranuclear complex having two nonbridging thiolato groups, [{Pt(NH3)2}2{Rh(aet)3}2]4+ ([1]4+), in which two fac(S)-[Rh(aet)3] units are linked by two trans-[Pt(NH3)2]2+ moieties, was synthesized by the 1:1 reaction of fac(S)-[Rh(aet)3] (aet = 2-aminoethanethiolate) with trans-[PtCl2(NH3)2] in water. Complex [1]4+ gave both the meso (DeltaLambda) and racemic (DeltaDelta/LambdaLambda) forms, which were separated by fractional crystallization. Of two possible geometries, syn and anti, which arise from the arrangement of two nonbridging thiolato groups, the meso and racemic forms of [1]4+ selectively afforded the anti and syn geometries, respectively. The DeltaLambda-anti and DeltaDelta/LambdaLambda-syn isomers of [1]4+ reacted with Ag+ using two nonbridging thiolato groups to produce a {RhIII2PtII2AgI}n) polymeric complex, {[Ag{Pt(NH3)2}2{Rh(aet)3}2]5+}n) ([2]5+), and a RhIII2PtII2AgI pentanuclear complex, [Ag{Pt2(mu-H2O)(NH3)2}{Rh(aet)3}2]5+ ([3]5+), respectively, which contain octahedral RhIII, square-planar PtII, and linear AgI centers. In [2]5+, each DeltaLambda-anti-[{Pt(NH3)2}2{Rh(aet)3}2]4+ tetranuclear unit is bound to two AgI atoms to form a one-dimensional zigzag chain, indicating the retention of the parental S-bridged structure in DeltaLambda-anti-[1]4+. In [3]5+, two Delta- or Lambda-fac(S)-[Rh(aet)3] units are linked by a [Pt2(mu-H2O)(NH3)2]4+ dinuclear moiety, together with an AgI atom, indicating that two NH3 molecules in [1]4+ have been replaced by a water molecule that bridges two PtII centers, while the parental DeltaDelta/LambdaLambda-syn configuration is retained. The complexes obtained were characterized on the basis of electronic absorption, CD, and NMR spectra, along with single-crystal X-ray analyses.     

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-cluster-mediated activation of all bonds of a methyl group of 6,6'-dimethyl-2,2'-bipyridine and 2,9-dimethyl-1,10-phenanthroline: transformation of the latter into a 2-alkenyl-9-methyl-1,10-phenanthroline ligand

The treatment of [Ru3(CO)12] with 6,6'-dimethyl-2,2'-bipyridine (Me2bipy) or 2,9-dimethyl-1,10-phenanthroline (Me2phen) in THF at reflux temperature gives the trinuclear dihydride complexes [Ru3(mu-H)2(mu3-L1)(CO)8] (L1 = HCbipyMe 1 a, HCphenMe 1 b), which result from the activation of two C-H bonds of a methyl group. The hexa-, hepta-, and pentanuclear derivatives [Ru6(mu3-H)(mu5-L2)(mu-CO)3(CO)13] (L2 = CbipyMe 2 a, CphenMe 2 b), [Ru7(mu3-H)(mu5-L2)(mu-CO)2(CO)16] (L2 = CbipyMe 3 a, CphenMe 3 b), and [Ru5(mu-H)(mu5-C)(mu-L3)(CO)13] (L3 = bipyMe 4 a, phenMe 4 b) can also be obtained by treating 1 a and 1 b with [Ru3(CO)12]. Compounds 2 a and 2 b have a basal edge-bridged square-pyramidal metallic skeleton with a carbyne-type C atom capping the four Ru atoms of the pyramid base. The structures of 3 a and 3 b are similar to those of 2 a and 2 b, respectively, but an additional Ru atom now caps a triangular face of the square-pyramidal fragment of the metallic skeleton. The most interesting feature of 2 a, 2 b, 3 a, and 3 b is that their carbyne-type C atoms were originally bound to three hydrogen atoms in Me2bipy or Me2phen and, therefore, they arise from the unprecedented activation of all three C-H bonds of C-bound methyl groups. The pentanuclear compounds 4 a and 4 b contain a carbide ligand surrounded by five Ru atoms in a distorted trigonal-bipyramidal environment. They are the products of a series of processes that includes the activation of all bonds (three C-H and one C-C) of organic methyl groups, and are the first examples of complexes having carbide ligands that arise from C-bonded methyl groups. The alkenyl derivatives [Ru5(mu5-C)(mu-p-MeC6H4CHCHphenMe)(CO)13] (5 b), [Ru5(mu-H)(mu5-C)(mu-p-MeC6H4CHCHphenMe)(p-tolC2)(CO)12] (6 b), and [Ru5(mu-H)(mu5-C)(mu-PhCHCHphenMe)(PhC2)(CO)12] (7 b) have been obtained by treating 4 b with p-tolyl- and phenylacetylene, respectively. Their heterocyclic ligands contain an alkenyl fragment in the position that was originally occupied by a methyl group. Therefore, these complexes are the result of the formal substitution of an alkenyl group for a methyl group of 2,9-dimethyl-1,10- phenanthroline.     

Fine-tuning of metallaborane geometries: chemistry of iridaboranes derived from the reaction of

From reaction of [(Cp*Ir)2HxCl(4-x)] (x=1, 0) and LiBH4, arachno-[[Cp*IrH2]B3H7](1) is produced in moderate yield concurrently with [Cp*IrH4]. In contrast, reaction of [(Cp*Ir)2H2Cl2] with LiBH4 results in arachno-[[Cp*IrH]2(mu-H)B2H5] (3) in high yield at room temperature but a mixture of 1 and [[Cp*IrH]2(mu-H)BH4] (2) at 0 degrees C. BH3 x THF converts 1 to arachno-[(Cp*IrHB4H9] (4) and 2 to 3 with 1 as a minor product. Further, reaction of 3 with excess of BH3 x THF results in formation of nido-[[Cp*Ir]2-(mu-H)B4H7] (6) formed by loss of H2 from the intermediate arachno-[[Cp*IrH]2B4H8] (5). Reaction of 1 with [Co2(CO)8] permits the isolation of two metallaboranes, arachno-[[Cp*Ir(CO)]-B3H7] (7) and nido-[1-[Cp*Ir]-2,3-Co2-(CO)4(mu-CO)B3H7] (8). Treatment of 4 with [Co2(CO)8] gives only one single mixed-metal metallaborane nido-[1-[Cp*Ir]-2-Co(CO)3B4H7 (9) in high yield. Finally, pyrolysis of 8 results in loss of hydrogen and formation of pileo-[1-[Cp*Ir]-2,3-Co2(CO)5B3H5] (10) with a BH-capped square-pyramidal structure. With kinetic control rational synthesis of a variety metallaboranes has been achieved by varying the number of chlorides in the monocyclopentadienylmetal halide dimer, reaction temperature, types of monoborane, and metal fragment sources.     

Dihydrogen activation by a diruthenium analogue of the Fe-only hydrogenase active site

The photochemical reaction of Ru2(S2C3H6)(CO)4(PCy3)2 (1) and H2 gives the dihydride Ru2(S2C3H6)(mu-H)(H)(CO)3(PCy3)2 (2). NMR and crystallographic studies reveal mutually trans basal phosphine ligands and both bridging and terminal hydrides. Ru2(S2C2H4)(CO)4(PCy3)2 behaves similarly. Other HX substrates undergo photoaddition to 1, affording Ru2(S2C3H6)(mu-H)(X)(CO)3(PCy3)2 for X = OTs (3a), Cl (3b), and SPh (3c). Treatment of Ru2(S2C3H6)(mu-H)(H)(CO)3(PCy3)2 with [H(OEt2)]BArF4 (ArF = B(C6H3-3,5-(CF3)2) in CD2Cl2 gives [Ru2(S2C3H6)(mu-H)(CO)3(PCy3)2(H2)]+ (4), which catalyzes H2-D2 exchange. The reaction of 2 with [D(OEt2)]BArF4 gave [Ru2(S2C3H6)(mu-H)(CO)3(PCy3)2(HD)]+ (JH-D = 31 Hz). These studies provide the first models for the Fe-only hydrogenases that bear dihydrogen and terminal hydrido ligands.