Synthesis and Chemical and Electrochemical Characterization of Fe-S Carbonyl Clusters. X-ray Crystal Structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)

A reinvestigation of the redox behavior of the [Fe(3)(&mgr;(3)-S)(CO)(9)](2)(-) dianion led to the isolation and characterization of the new [Fe(5)S(2)(CO)(14)](2)(-), as well as the known [Fe(6)S(6)(CO)(12)](2)(-) dianion. As a corollary, new syntheses of the [Fe(3)S(CO)(9)](2)(-) dianion are also reported. The [Fe(5)S(2)(CO)(14)](2)(-) dianion has been obtained by oxidative condensation of [Fe(3)S(CO)(9)](2)(-) induced by tropylium and Ag(I) salts or SCl(2), or more straightforwardly through the reaction of [Fe(4)(CO)(13)](2)(-) with SCl(2). The [Fe(6)S(6)(CO)(12)](2)(-) dianion has been isolated as a byproduct of the synthesis of [Fe(3)S(CO)(9)](2)(-) and [Fe(5)S(2)(CO)(14)](2)(-) or by reaction of [Fe(4)(CO)(13)](2)(-) with elemental sulfur. The structures of [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)] and [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)] were determined by single-crystal X-ray diffraction analyses. Crystal data: for [N(PPh(3))(2)](2)[Fe(5)S(2)(CO)(14)], monoclinic, space group P2(1)/c (No. 14), a = 24.060(5), b = 14.355(6), c = 23.898(13) ?, beta = 90.42(3) degrees, Z = 4; for [N(PPh(3))(2)](2)[Fe(6)S(6)(CO)(12)], monoclinic, space group C2/c (No. 15), a = 34.424(4), b = 14.081(2), c = 19.674(2) ?, beta = 115.72(1) degrees, Z = 4. The new [Fe(5)S(2)(CO)(14)](2)(-) dianion shows a "bow tie" arrangement of the five metal atoms. The two Fe(3) triangles sharing the central Fe atom are not coplanar and show a dihedral angle of 55.08(3) degrees. Each Fe(3) moiety is capped by a triply bridging sulfide ligand. The 14 carbonyl groups are all terminal; two are bonded to the unique central atom and three to each peripheral iron atom. Protonation of the [Fe(5)S(2)(CO)(14)](2)(-) dianion gives reversibly rise to the corresponding [HFe(5)S(2)(CO)(14)](-) monohydride derivative, which shows an (1)H-NMR signal at delta -21.7 ppm. Its further protonation results in decomposition to mixtures of Fe(2)S(2)(CO)(6) and Fe(3)S(2)(CO)(9), rather than formation of the expected H(2)Fe(5)S(2)(CO)(14) dihydride. Exhaustive reduction of [Fe(5)S(2)(CO)(14)](2)(-) with sodium diphenyl ketyl progressively leads to fragmentation into [Fe(3)S(CO)(9)](2)(-) and [Fe(CO)(4)](2)(-), whereas electrochemical, as well as chemical oxidation with silver or tropylium tetrafluoroborate, in dichloromethane, generates the corresponding [Fe(5)S(2)(CO)(14)](-) radical anion which exhibits an ESR signal at g = 2.067 at 200 K. The electrochemical studies also indicated the existence of a subsequent one-electron anodic oxidation which possesses features of chemical reversibility in dichloromethane but not in acetonitrile solution. A reexamination of the electrochemical behavior of the [Fe(3)S(CO)(9)](2)(-) dianion coupled with ESR monitoring enabled the spectroscopic characterization of the [Fe(3)S(CO)(9)](-) radical monoanion and demonstrated its direct involvement in the generation of the [Fe(5)S(2)(CO)(14)](n)()(-) (n = 0, 1, 2) system.     

NMR studies of Ru(3)(CO)(10)(PMe(2)Ph)(2) and Ru(3)(CO)(10)(PPh(3))(2) and their H(2) addition products: detection of new isomers with complex dynamic behavior

The clusters Ru(3)(CO)(10)L(2), where L = PMe(2)Ph or PPh(3), are shown by NMR spectroscopy to exist in solution in at least three isomeric forms, one with both phosphines in the equatorial plane on the same ruthenium center and the others with phosphines in the equatorial plane on different ruthenium centers. Isomer interconversion for Ru(3)(CO)(10)(PMe(2)Ph)(2) is highly solvent dependent, with DeltaH decreasing and DeltaS becoming more negative as the polarity of the solvent increases. The stabilities of the isomers and their rates of interconversion depend on the phosphine ligand. A mechanism that accounts for isomer interchange involving Ru-Ru bond heterolysis is suggested. The products of the reaction of Ru(3)(CO)(10)L(2) with hydrogen have been monitored by NMR spectroscopy via normal and para hydrogen-enhanced methods. Two hydrogen addition products are observed with each containing one bridging and one terminal hydride ligand. EXSY spectroscopy reveals that both intra- and interisomer hydride exchange occurs on the NMR time scale. On the basis of the evidence available, mechanisms for hydride interchange involving Ru-Ru bond heterolysis and CO loss are proposed.     

Metal scrambling in the trinuclear (Pt(2)Se(2)M)(M = Pt, Pd, Au) system using an electrospray mass spectrometry (ESMS) directed synthetic methodology; isolation and crystallographic characterization of (Pt(2)(mu(3)-Se)(2)(PPh(3))(4)[Pt(cod)])(PF(6))(2) and (Pt(mu(3)-Se)(2)(PPh(3))(2)[Pt(cod)](2))(PF(6))(2) (cod = cyclo-octa-1,5-diene)

Pt(2)(mu-Se)(2)(PPh(3))(4) reacts with PtCl(2)(cod) to give (Pt(2)(mu(3)-Se)(2)(PPh(3))(4)[Pt(cod)])(2+) and an unexpected cod-rich product that arises from metal scrambling, viz. (Pt(mu(3)-Se)(2)(PPh(3))(2)[Pt(cod)](2))(2+). The formation of these species was detected and followed by electrospray mass spectrometry (ESMS) and subsequently verified by batch synthesis and crystallographic characterization. Other metal-scrambled aggregate products were successfully detected.     

Re6Te8(CN)6][(Ir(CO)(PPh3)2)6](OTf)2 : a new Re6 cluster-supported iridium(I) compound

A new hexanuclear rhenium cluster encapsulated by six iridium complexes, [Re6Te8(CN)6][(Ir(CO)(PPh3)2)6](OTf)2 (3), which is effective in catalyzing the hydrogenation of p-CH3C6H4C[triple bond]CH to p-CH3C6H4CH=CH2 has been prepared.     

Redox-active polymers based on nonbridged metal-metal bonds. Electrochemical formation of [Os(bpy)(CO)(L)](n) (bpy = 2,2'-bipyridine; L = CO, MeCN) and of their reduced forms: a spectroelectrochemical study

IR, UV-vis, and EPR spectroelectrochemistry at variable temperatures and in different solvents were applied to investigate in situ the formation of electroactive molecular chains with a nonbridged Os-Os backbone, in particular, the polymer [Os(0)(bpy)(CO)(2)](n) (bpy = 2,2'-bipyridine), from a mononuclear Os(II) carbonyl precursor, [Os(II)(bpy)(CO)(2)Cl(2)]. The one-electron-reduced form, [Os(II)(bpy(.)(-))(CO)(2)Cl(2)](-), has been characterized spectroscopically at low temperatures. This radical anion is the key intermediate in the electrochemical propagation process responsible for the metal-metal bond formation. Unambiguous spectroscopic evidence has been gained also for the formation of [[Os(0)(bpy(*)(-))(CO)(2)](-)](n), the electron-rich electrocatalyst of CO(2) reduction. The polymer species are fairly well soluble in butyronitrile, which is important for their potential utilization in nanoscience, for example, as conducting molecular wires. We have also shown that complete solubility is accomplished for the monocarbonyl-acetonitrile derivative of the polymer, [Os(0)(bpy)(CO)(MeCN)(2)Cl](n).     

Structural characterization of metal-metal bonded polymer [Ru(L)(CO)(2)](n) (L = 2,2'-bipyridine) in the solid state using high-resolution NMR and DFT chemical shift calculations

The metal bonded ruthenium polymer [Ru(0)(bpy)(CO)(2)](n) (bpy = 2,2'-bipyridine) is known to be a very promising and efficient solid material for catalysis applications, such as carbon dioxide electroreduction in pure aqueous media and the water-gas shift reaction. It also exhibits potential application for molecular electronics as a conductive molecular wire. The insolubility and relative air-sensitivity of [Ru(0)(bpy)(CO)(2)](n) as well as the lack of monocrystals make its structural characterization very challenging. A first approach to determine the structure of this polymer has been obtained by ab initio X-ray powder diffraction, based on the known X-ray structure of [Ru(CO)(4)](n). In order to refine this structure, a non-conventional solid-state NMR study was performed. The results of this study are presented here. The comparison of high-resolution solid-state (13)C NMR spectra of the polymer with those of the corresponding monomeric [Ru(bpy)(CO)(2)Cl(2)] or dimeric [Ru(bpy)(CO)(2)Cl](2) precursor complexes has shown a clear shift and splitting of carbonyl ligand resonances, which turns out to be linearly correlated with the redox state of the Ru (ii, i or 0, respectively). Bipyridine resonances are also affected but in a non-trivial way. Finally, in the case of the dimer, it was found that the CO peak splitting (2.7 ppm) contains structural information, e.g. the ligand staggering angle. Based on DFT chemical shift calculations on corresponding model molecules (n = 1-2), all the described experimental observations could be reproduced. Moreover, upon extending these calculations to models of increasing length (n = 3-5), it turns out that information about the staggering angle between successive ligands is actually retained in the CO NMR computed peak splitting. Turning back to experiments, the CO broad signal measured for the wire could be decomposed into a major component (at 214.9 ppm) assigned to the internal CO ligands, and a minor doublet component (216.9 and 218.1 ppm) whose splitting (2.8 ppm) contains the staggering angle information. Finally, from the relative integrals of these three components, expected to be in the ratio 1?:?1?:?n-2, it was possible to tentatively estimate the length n of the polymetallic wire (n = 7).     

A tungsten-183NMR study of cis and trans isomers of [W(CO)4(PPh3)(PR3)](PR3 = phosphine, phosphite)

Tungsten-183 NMR data are reported for the complexes cis- and trans-[W(CO)4(PPh3)(PR3)] (PR3 = PnBu3, PMe3, PMe2Ph, PMePh2, PPh3, P(4-C6H4OMe)3, P(4-C6H4Me)3, P(4-C6H4F)3, P(OMe)3, P(OEt)3, P(OPh)3 and for PCy3, P(NMe2)3(trans isomer only). The 183W chemical shift (obtained by indirect detection using 31P) is found to be related to the PR3 ligand parameters nu and theta (Tolman electronic factor and cone angle, respectively) for the cis isomers and to nu (but only poorly to theta) for the trans isomers. The 183W-31P spin coupling constant is also related, less clearly for P-C than for P-N and P-O bonded ligands, to nu. Chemical shifts are referenced to an absolute frequency Xi (183W) = 4.15 MHz, which is proposed as a calibration standard for 183W NMR. The structures of cis-[W(CO)4(PPh3)(PMe3)] and cis-[W(CO)4(PPh3){P(4-C6H4F)3}] are reported.     

Small ring metallocycles : V. Crystal and molecular structure of hydrido-1,3-(1,1,3,3-tetramethyldisiloxanediyl)carbonylbis(triphenylphosphine)iridium(III), Me2SiOSiMe2Ir(H)(CO)(PPh3)2 · EtOH

The structure of the cyclo-metalladisiloxane, Me₂SiOSiMe₂Ir(H)(CO)(PPh₃)₂, has been determined by single crystal X-ray diffraction using Mo-K_α radiation. Data were collected to 20 = 45 ° giving 6060 unique reflections,of which 4582 had I ?3σ(I). The latter were used in the full-matrix refinement. Crystallographic data: space group, P$\text{1}$; cell constants: 12.604(7),12.470(4), 15.821(6) Å, 66.93(6)°, 105.34(7)°, 112.41(8)°;V 2095(3) ų; p(obs) 1.45 g/cm³; p(calc) 1.46g/cm³ (Z=2). The asymmetric unit consists of one iridium complex and one molecule of ethanol of salvation. The structure was solved by standard heavy atom methods and refined with all non-hydrogen atoms anisotrophic to final R factors, R₁ 0.034 and R₂ 0.042. The iridium metallocycle has approximate C_s symmetry with the mirror plane passing through the four-membered IrSiOSi ring. The average IrP, IrSi and SiO bond lengths are 2.38, 2.41, and 1.68 Å, respectively. The IrCO and CO bond lengths are 1.903(8) and 1.133(8). The H atom bonded to Ir was not located.The Ir atom is raised out of the basal, P₂Si₂ plane toward the carbonyl by about 0.26 Å. The most striking feature of the structure is the strain apparent in the four-membered ring. The internal angels are: 64.7 (SiIrSi), 96.8 (IrSiO), 97.8 (IrSiO), and 99.8 (SiOSi). In an unstrained molecule, the SiOSi angle is normally in the 130–150° range. It is proposed that the strain in the ring is consistent with the catalytic activity of the metallocycle.     

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.     

Facile oxidative addition of water at iridium: reactivity of trans-[Ir(4-C5NF4)(H)(OH)(PiPr3)2] towards CO2 and NH3

A reaction of trans-[Ir(4-C(5)NF(4))(η(2)-C(2)H(4))(PiPr(3))(2)] (1) with an excess of water in THF at room temperature affords the hydrido hydroxo complex trans-[Ir(4-C(5)NF(4))(H)(OH)(PiPr(3))(2)] (2). Treatment of 2 with CO furnishes trans-[Ir(4-C(5)NF(4))(H)(OH)(CO)(PiPr(3))(2)] (3). Reductive elimination of water from 3 leads to the formation of the iridium(I) carbonyl complex trans-[Ir(4-C(5)NF(4))(CO)(PiPr(3))(2)] (4). The insertion of CO(2) into the Ir-O bond of 2 forms the hydrido hydrogencarbonato complex trans-[Ir(4-C(5)NF(4))(H)(κ(2)-(O,O)-O(2)COH)(PiPr(3))(2)] (5). Treatment of 2 with NH(3) in C(6)D(6) yields trans-[Ir(4-C(5)NF(4))(H)(OH)(NH(3))(PiPr(3))(2)] (6). Storage of the reaction mixture at room temperature reveals the formation of the N-H activation product [Ir(4-C(5)NF(4))(H)(μ-NH(2))(NH(3))(PiPr(3))](2) (7).     

Synthesis and structural characterization of [kappa3-B,S,S-B(mimR)3]Ir(CO)(PPh3)H (R = Bu(t), Ph) and [kappa4-B(mim(Bu(t))3]M(PPh3)Cl (M = Rh, Ir): analysis of the bonding in metal borane compounds

A series of iridium and rhodium complexes that feature M-->B dative bonds, namely [kappa(3)-B,S,S-B(mim(R))3]Ir(CO)(PPh3)H (R = But, Ph) and [kappa4-B(mim(Bu)t)3]M(PPh3)Cl (M = Rh, Ir), has been synthesized via (i) the reactions of Ir(PPh3)2(CO)Cl with [Tm(Bu)t]Tl and [Tm(Ph)]Li and (ii) the reactions of (COD)M(PPh3)Cl with [Tm(Bu)t]K. The complexes have been structurally characterized by X-ray diffraction, thereby demonstrating the presence of a M-->B dative bond in each complex. The nature of the M-->B interaction in these complexes has been addressed by computational methods which indicate that the metal centers possess a d(6) configuration. The d(6) configuration is in accord with the value predicted by using a method that employs the valence to determine d(n)(), but is not in accord with the d8 configuration that is predicted using the oxidation number. Thus, even though B(mim(R))3 may be regarded as a neutral closed-shell ligand, coordination to a d(n) transition metal via the boron results in the formation of a complex in which the metal center possesses a d(n-2) configuration.     

Reactivity of [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (tim(Me) = 2-mercapto-1-methylimidazolyl) toward neutral substrates

The complex [Re[kappa(3)-H(mu-H)B(tim(Me))(2)](CO)(3)] (2a) (tim(Me) = 2-mercapto-1-methylimidazolyl) reacts with a variety of neutral substrates to afford new complexes featuring the dihydrobis(2-mercapto-1-methylimidazolyl)borate coordinated in a bidentate or unidentate fashion. By treating 2a with unidentate ligands, the mononuclear complexes [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)(L)] (L = imidazole (5), 4-(dimethylamino)pyridine (6), tert-butylisonitrile (7), triphenylphosphine (8)) were formed, upon replacement of the agostic B-H...Re bond by the correspondent unidentate ligand. With potentially bidentate substrates, 2a is transformed into mononuclear or dinuclear complexes, depending on the atom donor set of the reacting substrates. Reaction of compound 2a with ethylenediamine (en) gave the complex [Re[kappa(1)-H(2)B(tim(Me))(2)](CO)(3)(en)] (9), because of cleavage of the agostic interaction, dechelation of one mercaptoimidazolyl ring, and bidentate coordination of the amine. By contrast, 1,2-bis(diphenyl)phosphinoethane (dppe) is not able to replace the mercaptoimidazolyl ring, and the dimer [Re[kappa(2)-H(2)B(tim(Me))(2)](CO)(3)](2)(mu-dppe) (10) was formed. The novel Re(I) tricarbonyl complexes (5-10) have been fully characterized, including by X-ray diffraction analysis in the case of 6, 8, 9, and 10. The X-ray diffraction study confirmed the unprecedented unidentate coordination mode of the dihydrobis(2-mercapto-1-methylimidazolyl)borate in complex 9.     

Transformation of organic molecules on the low-valent [M(Ph(2)PCH(2)CH(2)PPh(2))(2)] moiety derived from trans-[M(N(2))(2)(Ph(2)PCH(2)CH(2)PPh(2))(2)] or related complexes (M = Mo, W)

A zero-valent [M(Ph(2)PCH(2)CH(2)PPh(2))(2)] moiety (M = Mo, W) generated in situ by dissociation of the N(2) ligands in trans-[M(N(2))(2)(Ph(2)PCH(2)CH(2)PPh(2))(2)] can activate pi-accepting organic molecules including isocyanides and nitriles, which undergo the electrophilic attack caused by a strong pi-donation from a zero-valent metal center. Cleavage of a variety of C-X bonds (X = H, C, N, O, P, halogen) also occurs at their electron-rich sites through oxidative addition to form reactive intermediates, which subsequently degradate to yield smaller molecules either bound to or dissociated from the metal center. The mechanism is substantiated unambiguously by isolation of numerous intermediate stages.     

Gold(I) Complexes with the nido-Diphosphino Ligand [7,8-(Ph(2)P)(2)-7,8-C(2)B(9)H(10)](-). Preparation of the First Metallocarborane Complex of this Ligand. Crystal Structures of [Au{(PPh(2))(2)C(2)B(9)H(10)}(PPh(3))].CH(2)Cl(2) and [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2){(PPh(2))(2)(CH(2))(3)}].3Me(2)CO

The reaction of [AuCl(PR(3))] with [1,2-(Ph(2)P)(2)-1,2-C(2)B(10)H(10)] in refluxing ethanol proceeds with partial degradation (removal of a boron atom adjacent to carbon) of the closo species to give [Au{(PPh(2))(2)C(2)B(9)H(10)}(PR(3))] [PR(3) = PPh(3) (1), PPh(2)Me (2), PPh(2)(4-Me-C(6)H(4)) (3), P(4-Me-C(6)H(4))(3) (4), P(4-OMe-C(6)H(4))(3) (5)]. Similarly, the treatment of [Au(2)Cl(2)(&mgr;-P-P)] with [1,2-(Ph(2)P)(2)-1,2-C(2)B(10)H(10)] under the same conditions leads to the complexes [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2)(&mgr;-P-P)] [P-P = dppe = 1,2-bis(diphenylphosphino)ethane (6), dppp = 1,3-bis(diphenylphosphino)propane (7)], where the dppe or dppp ligands bridge two gold nido-diphosphine units. The reaction of 1 with NaH leads to removal of one proton, and further reaction with [Au(PPh(3))(tht)]ClO(4) gives the novel metallocarborane compound [Au(2){(PPh(2))(2)C(2)B(9)H(9)}(PPh(3))(2)] (8). The structure of complexes 1 and 7 have been established by X-ray diffraction. [Au{(PPh(2))(2)C(2)B(9)H(10)}(PPh(3))] (1) (dichloromethane solvate) crystallizes in the monoclinic space group P2(1)/c, with a = 17.326(3) ?, b = 20.688(3) ?, c = 13.442(2) ?, beta = 104.710(12) degrees, Z = 4, and T = -100 degrees C. [Au(2){(PPh(2))(2)C(2)B(9)H(10)}(2)(&mgr;-dppp)] (7) (acetone solvate) is triclinic, space group P&onemacr;, a = 13.432(3) ?, b = 18.888(3) ?, c = 20.021(3) ?, alpha = 78.56(2) degrees, beta = 72.02(2) degrees, gamma = 73.31(2) degrees, Z = 2, and T = -100 degrees C. In both complexes the gold atom exhibits trigonal planar geometry with the 7,8-bis(diphenylphosphino)-7,8-dicarba-nido-undecaborate(1-) acting as a chelating ligand.     

Synthesis and molecular structure of [[(HBpz(3))Rh(PPh(3))(mu-Cl)(2)](2)Ag]BF(4) (Hpz = pyrazole), a heterotrinuclear Rh(2)Ag compound with square-planar silver(I)

Reaction of [(HBpz(3))RhCl(2)(PPh(3))] (Hpz = pyrazole) with silver salts AgA (A = BF(4), NO(3), SbF(6)) affords the unexpected heterotrinuclear compounds [[(HBpz(3))Rh(PPh(3))(mu-Cl)(2)](2)Ag]A (A = BF(4) (1), NO(3) (2), SbF(6) (3)). The compounds have been fully characterized by IR, (1)H, (31)P[(1)H], and (13)C[(1)H] NMR spectroscopy and FAB(+) mass spectrometry. The solid structure of compound 1 was determined by single-crystal X-ray diffraction. The cation consists of two (HBpz(3))RhCl(2)(PPh(3)) units bonded to a silver atom through two double mu-Cl bridges in an unusual distorted square-planar arrangement.     

Syntheses,reactivity, and crystal structures of molybdenum complexes with pyridine-2-thionate (pyS)-containing ligands: crystal structures of [Mo(eta(3)-C(3)H(5))(CO)(2)](2)(mu-eta(1),eta(2)-pyS)(2), exo-[Mo(eta(3)-C(3)H(5))(CO)(eta(2)-pyS)(eta(2)-dppe)], [Mo(CO)(3)(eta(1)-SC(5)H(4)NH)(eta(2)-dppm)], and [Mo(CO)(eta(2)-pyS)(2)(eta(2)-dppm)

The doubly bridged pyridine-2-thionate (pyS) dimolybdenum complex [Mo(eta(3)-C(3)H(5))(CO)(2)](2)(mu-eta(1),eta(2)-pyS)(2) (1) is accessible by the reaction of [Mo(eta(3)-C(3)H(5))(CO)(2)(CH(3)CN)(2)Br] with pySK in methanol at room temperature. Complex 1 reacts with piperidine in acetonitrile to give the complex [Mo(eta(3)-C(3)H(5))(CO)(2)(eta(2)-pyS)(C(5)H(10)NH)] (2). Treatment of 1 with 1,10-phenanthroline (phen) results in the formation of complex [Mo(eta(3)-C(3)H(5))(CO)(2)(eta(1)-pyS)(phen)] (3), in which the pyS ligand is coordinated to Mo through the sulfur atom. Four conformational isomers, endo,exo-complexes [Mo(eta(3)-C(3)H(5))(CO)(eta(2)-pyS)(eta(2)-diphos)] (diphos = dppm, 4a-4d; dppe, 5a-5d), are accessible by the reactions of 1 with dppm and dppe in refluxing acetonitrile. Homonuclear shift-correlated 2-D (31)P((1)H)-(31)P((1)H) NMR experiments of the mixtures 4a-4d have been employed to elucidate the four stereoisomers. The reaction of 4 and pySK or [Mo(CO)(3)(eta(1)-SC(5)H(4)NH)(eta(2)-dppm)] (6) and O(2) affords allyl-displaced seven-coordinate bis(pyridine-2-thionate) complex [Mo(CO)(eta(2)-pyS)(2)(eta(2)-dppm)] (7). All of the complexes are identified by spectroscopic methods, and complexes 1, 5d, 6, and 7 are determined by single-crystal X-ray diffraction. Complexes 1 and 5d crystallize in the orthorhombic space groups Pbcn and Pbca with Z = 4 and 8, respectively, whereas 6 belongs to the monoclinic space group C2/c with Z = 8 and 7 belongs to the triclinic space group Ponemacr; with Z = 2. The cell dimensions are as follows: for 1, a = 8.3128(1) A, b = 16.1704(2) A, c = 16.6140(2) A; for 5d, a = 17.8309(10) A, b = 17.3324(10) A, c = 20.3716(11) A; for 6, a = 18.618(4) A, b = 16.062(2) A, c = 27.456(6) A, beta = 96.31(3) degrees; for 7, a = 9.1660(2) A, b = 12.0854(3) A, c = 15.9478(4) A, alpha = 78.4811(10) degrees, beta = 80.3894(10) degrees, gamma = 68.7089(11) degrees.     

New tetrahedral cluster compounds of iridium. Synthesis of the anions [Ir4(CO)11X]− (X = Cl,Br, I,CN, SCN) and x-ray structure of [PPh4] [Ir4(CO)11Br]

[Ir₄(CO)₁₁X]^? anions are obtained by reaction of halide and pseudo-halide ions with Ir₄(CO)₁₂. X-ray determination of the structure of [Ir₄(CO)₁₁Br]^? shows that the carbonyl arrangement differs from that of the parent Ir₄(CO)₁₂, and is similar to that known for Co₄(CO)₁₂; one terminal CO group in the basal M₃(CO)₉ moiety is replaced by the bromide ligand, and two of the bridging CO groups become markedly asymmetric.     

Ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn): preparation,crystal structures,and electrochemical and spectroscopic properties of [Ru(bpy or phen)(3)(-)(n)(Me(2)Pqn)(n)](PF(6))(2) (bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline; n = 1, 2, or 3)

Several new ruthenium(II) complexes containing 8-(dimethylphosphino)quinoline (Me(2)Pqn) were synthesized, and their structures and electrochemical/spectroscopic properties have been investigated. In addition to the mono(Me(2)Pqn) complex [Ru(bpy or phen)(2)(Me(2)Pqn)](PF(6))(2) (1 or 1'; bpy = 2,2'-bipyridine; phen = 1,10-phenanthroline), the geometrical isomers trans(P)- and C(1)-[Ru(bpy)(Me(2)Pqn)(2)](PF(6))(2) (tP-2 and C(1)-2) and mer- and fac-[Ru(Me(2)Pqn)(3)](PF(6))(2) (m-3 and f-3) were also selectively synthesized and isolated. It was found that complexes tP-2 and m-3 were converted quantitatively to the corresponding C(1)-2 and f-3 isomers, respectively, by irradiation of light corresponding to the MLCT transition energy. The strong trans influence of the Me(2)P- donor group of Me(2)Pqn was confirmed by the X-ray structural analyses for 1, tP-2, m-3, and f-3. Cyclic voltammetry of a series of complexes, [Ru(bpy)(3)](PF(6))(2), 1, C(1)-2, and f-3, exhibited a reversible one-electron oxidation wave and two or three one-electron reduction waves. The oxidation potentials of the complexes gave a large positive shift with increasing number of coordinated Me(2)Pqn molecules, indicating a larger pi-acceptability of the Me(2)P- group compared with bpy or qn. Complex f-3 in EtOH/MeOH (4:1) glass at 77 K exhibited an intense long-lived (tau = 920 microseconds) emission arising from the quinoline-based (3)(pi-pi) excited state. In contrast, the mixed-ligand complexes 1, 1', and C(1)-2 showed a characteristic dual emission, giving a double-exponential emission decay, and the dual emission originates from both the bpy-based (3)MLCT and the quinoline-based (3)(pi-pi) emitting states.     

Synthesis and characterization of iridium 1,3,5-triaza-7-phosphaadamantane (PTA) complexes. X-ray crystal and molecular structures of [Ir(PTA)4(CO)]Cl and [Ir(PTAH)3(PTAH2)(H)2]Cl6

The first 1,3,5-triaza-7-phosphaadamantane (PTA) ligated iridium compounds have been synthesized. The reaction of PTA with [Ir(COD)Cl]2 (COD = 1,5-cyclooctadiene) under a CO atmosphere produces an inseparable mixture of [Ir(PTA)3(CO)Cl] (1) and the PTA analogue of Vaska's compound, [Ir(PTA)2(CO)Cl] (2). Compound 1 and [Ir(PTA)4(CO)]Cl (3) were prepared via ligand substitution reactions of PTA with Vaska's compound, trans-Ir(PPh3)2(CO)Cl, in absolute and 95% ethanol, respectively. Complex 3 crystallizes in the orthorhombic space group Pbca with a = 20.3619(4) A, b = 14.0345(3) A, c = 24.1575(5) A, and Z = 8. Single-crystal X-ray diffraction studies show that 3 has a trigonal bipyramidal structure in which the CO occupies an axial position. This is the first crystallographically characterized [IrP4(CO)]+ complex in which the CO is axially ligated. Compound 1 was converted into 3 by ligand substitution with 1 equiv of PTA in water. Interestingly, the reaction of 3 with excess NaCl did not result in the production of 1, but instead the formation of the dichloro species, [Ir(PTAH)2(PTA)2Cl2]Cl3 (4) (PTAH = protonated PTA). Dissolution of 1 or 3 in dilute HCl produced 4 and a dihydrido species, [Ir(PTAH)4(H)2]Cl5 (5), which were readily separated by inspection due to their different crystal habits. Compound 5 crystallizes in the triclinic space group P1 with a = 12.4432(9) A, b = 12.5921(9) A, c = 16.3231(12) A, alpha = 76.004(1) degrees, beta = 71.605(1) degrees, gamma = 69.177(1) degrees, and Z = 2. Complex 5 exhibits a distorted octahedral geometry with two hydride ligands in a cis configuration. A rationale consistent with these reactions is presented by consideration of the steric and electronic properties of the PTA ligand.