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An efficient and selective isomerization of 1-alkenes to their corresponding 2-alkenes is achieved by using binary metal carbonyls such as Ru-3(CO)(12) as catalysts. Possible mechanisms are discussed. Substituents on the 1-alkene have a significant effect on the isomerization. (C) 2008 Elsevier Ltd. All rights reserved.

The synthesis and characterisation of an orange polymorph of [Pt(trpy)(C CPh)]SbF6 is described where trpy = 2,2′:6′,2″-terpyridine. An X-ray crystal structure determination at 293 K reveals that the cations are planar and stacked head-to-tail with alternating Pt⋯Pt distances of 3.604(1) and 4.412(1) A. The perpendicular distances between successive cation planes are constant along the stack at a value of 3.33 A. Crystal structure determinations at 240 and 200 K show that reducing the temperature to 200 K has no significant effect on the cation arrangement. However, below 200 K there is a phase change that we have not been able to characterise, but which has an effect on the solid state photoluminescence exhibited by [Pt(trpy)(C CPh)]SbF6. Thus, whereas at temperatures of ⩾200 K, a broad peak with two components at ca. 566 and 597 nm is observed, below 200 K a longer wavelength peak develops that red-shifts as the temperature is lowered [λ(em)max = 637 nm at 80 K]. We assign the ⩾200 K emission as 3MLLCT in origin, since the X-ray data show that ligand–ligand (LL) and not metal–metal (MM) interactions are important at T ⩾ 200 K. On the other hand, the long wavelength emission observed below 200 K is typical of 3MMLCT emission, suggesting that the phase change leads to d z 2 ( Pt ) – d z 2 ( Pt ) orbital interactions. Of particular interest is that the cation exhibits 3MLCT emission in dichloromethane that maximizes at 619 nm, i.e., the high temperature solid state emission occurs at a shorter wavelength, an unexpected result since intermolecular interactions in the solid usually cause the emission to occur at longer wavelengths. A possible explanation for this unexpected result is given.

The synthesis and characterisation of the 4-(o-R-C6H4)pzbipy [R = H, CH3 or CF3; pzbipy = 6-(2″- pyrazinyl)-2,2′-bipyridyl] ligands are described. Reaction of the 4-(o-MeC6H4)pzbipy ligand with [Pt(PhCN)2Cl2] in the presence of AgSbF6 affords [Pt{4-(o-MeC6H4)pzbipy}Cl]SbF6 as a marooncoloured microcrystalline solid. The [Pt{4-(o-MeC6H4)pzbipy}Cl]+ cation exhibits low intensity photoluminescence in dichloromethane that maximises at 543 nm and which is assigned to a 3MLCT excited state (τ = 20 ns). The emission spectrum of the cation was also recorded in a frozen DME {1 : 5:5 (v/v) DMF / MeOH / EtOH} glass; a highly structured band is observed with vibrational spacings of ca. 1400 cm−1, indicating emission from an intraligand 3π-π∗ state (τ = 11 μs). Variable temperature solid emission spectra show maxima that occur at significantly lower energies than is observed in fluid solution and that shift to the red when the temperature is lowered; specifically, λ (em)max is 674 nm at 280 K (τ = 80 ns) and 723 nm at 80 K (τ = 1.3 μs). Emission behaviour of this type is typical of emission from a metal-metal-ligand charge transfer (MMLCT) excited state that has its origins in dz² (Pt)-dz² (Pt) orbital interactions in the crystal.

The synthesis and characterization of [Pt{4′-(R)trpy}(CN)]X (R = Ph, X = BF4 or SbF6; R = o-CH3C6H4, X = SbF6; R = o-ClC6H4, X = SbF6; or R = o-CF3C6H4, X = SbF6) are described where trpy = 2,2′:6′,2″-terpyridine. Single crystals of [Pt{4′-(Ph)trpy}(CN)]BF4·CH3CN were grown by vapour diffusion of diethyl ether into an acetonitrile solution of [Pt{4′-(Ph)trpy}(CN)]BF4. An X-ray crystal structure determination of the solvated complex confirms the near linear coordination of the cyanide ligand to the platinum centre. The cation is almost planar as evidenced by a twist of only 1.9° of the phenyl group out of the plane of the terpyridyl moiety. Cyclic voltammograms were recorded in DMF/0.1 M TBAH for the [Pt{4′-(R)trpy}(CN)]+ cations. Two quasi-reversible one-electron reduction (cathodic) waves are observed with E1/2 values that show the trend expected for an increasingly lower energy of the trpy-based LUMO of the complex i.e., [Pt{4′-(Ph)trpy}(CN)]+ ∼ [Pt{4′-(o-CH3C6H4)trpy}(CN)]+ < [Pt{4′-(o-ClC6H4)trpy}(CN)]+ < [Pt{4′-(o-CF3C6H4)trpy}(CN)]+. All the [Pt(4′-(R)trpy}(CN)]+ cations are photoluminescent in dichloromethane. Emission by [Pt{4′-(Ph)trpy}(CN)]+ is from an excited state with largely 3MLCT orbital parentage, but with some intraligand 3π–π* character mixed-in (τ = 0.1 µs). In contrast, the other three cations display emission that appears exclusively intraligand 3π–π* in origin (τ ∼ 0.8 µs). Emission spectra have been recorded in a low concentration frozen DME {1 : 5 : 5 (v/v) DMF–MeOH–EtOH} glass. For the R = o-CH3C6H4, o-ClC6H4 and o-CF3C6H4 cations the envelope of vibronic structure and energies of the vibrational components are essentially the same as that recorded in dichloromethane. However, for the [Pt{4′-(Ph)trpy}(CN)]+ cation, there is a blue-shift in the energies of the vibrational components as compared to that recorded in dichloromethane, as well as a change in the envelope of vibronic structure to a more “domed” pattern; this has been interpreted in terms of a higher percentage of intraligand 3π–π* character in the emitting state for the glass. Increasing the concentration of the glass invariably leads to aggregation of the cations and the consequent development of new low energy bands, such that at 0.200 mM broad peaks centred at ca. 650 and 700 nm dominate the spectrum; these bands are assigned to excimeric 3π–π* and 3MMLCT emission, respectively.

The synthesis and characterisation of [Pt{4′-(Np1)-trpy}(C CPh)]SbF 6 ( 1 ) and [Pt{4′-(Np1)-trpy}{C C(CH 2 ) 2 CH 3 }]SbF 6 ( 2 ) [4′-(Np1)-trpy = 4′-(1-naphthyl)-2,2:6′,2′-terpyridine] are described. Complexes 1 and 2 exhibit unimolecular 3 MLCT (MLCT = metal-to-ligand charge transfer) emission in acetonitrile and in a low concentration 77 K glass solution in butyronitrile. The high concentration glass emission as well as the emission in the solid state is from a 3 MMLCT (MMLCT, metal–metal-to-ligand charge transfer) excited state, reflecting the presence of d z 2 ( Pt ) – d z 2 ( Pt ) interactions in these media.

The selective in situ synthesis of trans and cis (CH 3 CN)-[Ru(bpy)(CO) 2 (CH 3 CN) 2 ] 2+ isomers from the same [Ru(CO) 2 (CH 3 CN) 3 ] 2 2+ dimer precursor but using either an electrochemical–chemical or chemical–electrochemical process is described.

Reaction of [Pt(bipy)Cl2] (bipy = 2,2′-bipyridine) with an excess of silver triflate in refluxing acetonitrile readily affords [Pt(bipy)(MeCN)2](CF3SO3)2 as a yellow, crystalline solid. A single crystal X-ray diffraction study shows that the cations are arranged in a zig-zag manner in rows parallel to the b axis of the monoclinic unit cell. Consideration of the crystal structures of related bipyridyl ligand complexes of platinum(II), leads to the conclusion that a stacked structure with intermolecular Pt…Pt interactions for the title compound is prevented by the electrostatic repulsion between adjacent cations that are doubly charged.

The synthesis and characterisation of 4′-(2‴-chlorophenyl)-2,2′:6′,2″-terpyridine [4′-(o-ClC6H4)trpy] and [Pt{4′-(o-ClC6H4)trpy}Cl]SbF6 are described. An X-ray crystal structure determination of the salt reveals columns of cations and anions with the cations stacked parallel and head-to-tail. At 295 K the Pt⋯Pt distances alternate between 3.374(1) and 3.513(1) A while the perpendicular separation between the mean planes comprising the platinum and three bonded nitrogen atoms remains constant at 3.35 A. As evidenced by crystal structure determinations at 260, 240 and 180 K, the shorter Pt⋯Pt distances become systematically shorter and the longer Pt⋯Pt distances become systematically longer as the temperature of the crystal is lowered. Structural evidence is presented that shows that this trend is a consequence of the more closely separated platinum atoms slipping into line with respect to a perpendicular to the above planes; at the same time the more widely separated platinum atoms fall out-of-line as the temperature is lowered. Emission spectra measured on a polycrystalline sample of the salt at 40 K intervals from 280 to 80 K comprise a single, asymmetric and featureless band [λmaxem = 609 nm at 280 K] that systematically increases in intensity as the temperature is lowered. There is a slight blue shift in the wavelength of the emission maximum as the temperature is lowered to 240 K but, below this temperature, the emission maximum gradually and systematically shifts to the red [λmaxem = 642 nm at 80 K]. This behaviour is rationalised in terms of 3MMLCT emission, the energy of which being determined by subtle changes in the extent of dz2−dz2 orbital overlap between adjacent platinum atoms separated by the shorter distance on one hand, and between platinum atoms separated by the longer distance on the other.

We report the synthesis and characterisation of eight molecules that have in common a diphenylphosphino group bonded to an α-carbon atom of a thienyl or pyridyl ring: 5,5′-bis(diphenylphosphino)-2,2′-bithiophene 1; diphenyl(2,2′-bithienyl-5-yl)phosphine 2; 5,5″-bis(diphenylphosphino)-2,2′:5′,2″-terthiophene 3; diphenyl(2,2′:5′,2″-terthienyl-5-yl)phosphine 4; diphenyl[5-(2′-pyridyl)-2-thienyl]phosphine 5; diphenyl[6-(2′-thienyl)-2-pyridyl]phosphine 6; diphenyl{5-[6′-(diphenylphosphino)-2′-pyridyl]-2-thienyl}phosphine 7; and 2,6-bis[5′-(diphenylphosphino)-2′-thienyl]pyridine 8. Methods used for their synthesis range from lithiation of the parent heterocycle and subsequent reaction with PPh2Cl to the use of coupling reactions catalysed by metal complexes to assemble the molecule from its subunits. The crystal and molecular structures of 1, 7 and 8 have been determined and show that the 2,2′-bithienyl moiety in 1 adopts an s-trans-conformation, while the 2-(2′-thienyl)pyridyl moieties in 7 and 8 adopt s-cis-conformations in the solid state. These compounds represent a new series of ligands that are expected to bond to metals through the phosphorus and/or nitrogen atoms rather than a sulfur atom, in view of the poor donor ability of a thiophene sulfur towards metals.

The synthesis and structure of the Ru(I) dimer [Ru(bpy)(CO)2(CH3CN)]2(PF6)2 (1; bpy = 2,2‘-bipyridine) are described. The electrochemical properties of this complex have been examined. The irrevers...

The complexes [Pt(4′Ph-terpy)Cl]A (4′Ph-terpy = 4′-phenyl-2,2′:6′,2″-terpyridine; A = SbF6, CF3SO3, or BF4) have been prepared by reaction of [Pt(PhCN)2Cl2] with the appropriate silver salt followed by addition of the 4′-phenyl-2,2′:6′,2″-terpyridyl ligand. The hexafluoroantimonate salt is yellow but, depending on the method of crystallisation, the triflate and tetrafluoroborate salts can be isolated in two forms, one yellow and the other red, the red forms only being stable at low temperatures. The crystal structure of red [Pt(4′Ph-terpy)Cl]BF4·CH3CN has been determined at 153 K by X-ray diffraction methods. The [Pt(4′Ph-terpy)Cl]+ cations are stacked face-to-face in an extended chain of stepped tetramers, with essentially equal Pt· · ·Pt distances of ca. 3.3 A within a tetramer and a Pt· · ·Pt distance of 4.680 A between successive tetramers. The spectroscopic and solid state emission properties of the salts have been recorded. The yellow salts are characterised by emission from an isolated chromophore in an excited state that reflects the admixture of 3MLCT (MLCT = metal-to-ligand charge-transfer) and 3IL (IL = intraligand) character. This assignment is supported by the presence of vibrational structure in the emission band as well as by a lifetime of ca. 1 µs for the emission. The red [Pt(4′Ph-terpy)Cl]BF4·CH3CN salt, in contrast, exhibits emission from a 3MMLCT (MMLCT = metal–metal–ligand charge-transfer) state as a consequence of the strong platinum dz2–dz2 orbital interactions. This assignment is consistent with the observation of a narrow, structureless and asymmetric band as well as an emission lifetime of ca. 0.1 µs. There is a systematic and substantial red-shift of 75 nm in the emission maximum on cooling the red salt from 280 to 80 K, an unexpected result since bathochromic shifts of this kind are normally associated with stacked structures with a uniform Pt· · ·Pt separation. The above assignments are further supported by measurements of the emission spectra of solutions of varying concentrations of the tetrafluoroborate salt in a dimethylformamide–methanol–ethanol glass at 77 K and by lifetime measurements. Interestingly, pressure in the form of grinding the salts modifies their luminescent properties. Thus, crushed samples of the yellow hexafluoroantimonate salt exhibit multiple emission at 80 K from both the 3MMLCT and the mixed parentage 3MLCT/3IL excited states, whereas at room temperature the emission spectrum is dominated by a broad band centred at 644 nm associated entirely with the 3MMLCT emission.

The crystal structure of [Pt(trpy)(MeCN)](SbF6)2, where trpy denotes 2,2‘:6‘,2‘‘-terpyridine, shows that the platinum complex packs as a monomer; however, the 3π−π* emission of the solid occurs at surprisingly long wavelengths at room temperature. At lower temperatures new, shorter-wavelength maxima appear. Of the known salts with the composition [Pt(trpy)Cl]A, the A = SbF6- system is the lone example that exhibits a temperature-independent emission maximum. In these platinum(II) terpyridines, energy migration to defects or trap sites is one of the phenomena responsible for the temperature dependence of the solid-state emission spectrum. If trap emission is evident, the low-temperature spectral data are most representative of the bulk material.

Treatment of [{Ru 2 [µ-η 2 -OC(R)O] 2 (CO) 4 } n ] or its acetonitrile adduct [Ru 2 {µ-η 2 -OC(R)O} 2 (CO) 4 (MeCN) 2 ] (R = H, Me or Et) with a two-fold molar equivalent of the phosphorus–nitrogen ligands 2-diphenylphosphinopyridine (dppy), 2-diphenylphosphinoquinoline (dpquin) and 6-diphenylphosphino-2,2′-bipyridine (dpbipy) in alcohol under reflux resulted in the formation of dinuclear products of the type [Ru 2 {µ-η 2 -OC(R)O} 2 (CO) 4 (PPh 2 R′) 2 ] (R′ = pyridyl, quinolyl or bipyridyl) in which the PPh 2 R′ ligands are monodentate, co-ordinating axially through the phosphorus donor atoms, as established X-ray crystallographically for [Ru 2 {µ-η 2 -OC(Me)O} 2 (CO) 4 (dppy) 2 ]. On the other hand reaction of [{Ru 2 [µ-η 2 -OC(R)O] 2 (CO) 4 } n ] with 2 molar equivalents of dppy or dpquin in toluene under reflux in the presence of NH 4 PF 6 and under a slight pressure of carbon monoxide afforded products of the type [Ru 2 {µ-η 2 -OC(R)O}(CO) 4 (µ-dppy) 2 ]PF 6 or [Ru 2 {µ-η 2 -OC(R)O}(CO) 4 (µ-dpquin) 2 ]PF 6 in which the dppy or dpquin ligands adopt the bridging co-ordination mode, this mode of co-ordination being confirmed through a crystal structure determination on [Ru 2 {µ-η 2 -OC(H)O}(CO) 4 (µ-dppy) 2 ]PF 6 . Reaction of [{Ru 2 [µ-η 2 -OC(R)O] 2 (CO) 4 } n ] with dpbipy in n-butanol under reflux likewise afforded products, isolated as their hexafluorophosphate salts, in which the phosphorus–nitrogen ligands are bridging, viz. [Ru 2 {µ-η 2 -OC(R)O}(CO) 2 (µ-dpbipy) 2 ]PF 6 , the structure of [Ru 2 {µ-η 2 -OC(Me)O}(CO) 2 (µ-dpbipy) 2 ]PF 6 being established X-ray crystallographically.

The high-pressure (1300 psi CO, 120°C) reactions of Ru3(CO)12 with the diphosphines R2PCH2PR2; R = CH3 (dmpm), C6H5 (dppm), and C6H11 (dcypm), are reported. In the case of dppm, the disphosphinebridged dinuclear ruthenium complex [Ru2(μ-dppm)2(μ-CO)(CO4] was obtained. The corresponding reaction with dcypm afforded the mononuclear chelated diphosphine complex [Ru(dcypm)(CO)3]. The mixed ligand system [Ru2(μ-dmpm)(μ-dmpm)(μ-CO)(CO)4] was obtained by employing a 1:1 mixture of dppm and dmpm. The crystal and molecular structures of [Ru2(μ-dppm)2(μ-CO)(CO)4] and [Ru(dcypm)(CO)3] were also determined.

Reaction of the electron-rich thiolate-bridged complex [Fe 2 (η-C 5 Me 5 ) 2 (µ- SEt) 2 (CO) 2 ] with 1 molar equivalent of the electron-acceptor compounds 7,7,8,8-tetracyanoquinodimethane (tcnq) and tetracyanoethylene (tcne) is accompanied by electron transfer and resulted in the formation of the dark green crystalline salts [Fe 2 (η-C 5 Me 5 ) 2 (µ- SEt) 2 (CO) 2 ] 2 [tcnq] 2 1 and [Fe 2 (η-C 5 Me 5 ) 2 (µ- SEt) 2 (CO) 2 ][tcne] 2 respectively. The crystal structures of these salts have been determined by X-ray diffraction methods and the cations thereof established to have very similar stereochemistries. The C 5 Me 5 ligands are cis disposed with respect to the Fe · · · Fe vector with the dihedral angles between their planes being 71 and 68° for 1 and 2 respectively. The Fe · · · Fe distances are respectively 3.077(2) and 3.069(2) A. Crystals of 1 consist of isolated units of composition D ˙+ (A) 2 2- D ˙ where D ˙+ denotes the cation and (A) 2 2- a (tcnq) 2 2- dimer, the planes of the tcnq moieties comprising the dimer and those of the adjacent C 5 Me 5 rings being virtually parallel. The compound is paramagnetic. Crystals of 2 consist of parallel rows of cations and tcne ˙- anions in the sequence · · · D ˙ A A ˙- D ˙+ A B ˙- D ˙+ A A ˙- D ˙+ A B ˙ - · · ·, where A A ˙- and A B ˙- label crystallographically independent anions. The two types of tcne ˙- anion are themselves approximately planar, but define different angles to the planes of the adjacent C 5 Me 5 rings of 4 and 72°. Magnetic susceptibility measurements for 2, in the range 5.0 to 310.0 K, suggest very little magnetic coupling between the unpaired spins on the cations and the tcne ˙- anions and thus this compound is also paramagnetic.

Treatment of [Cu(MeCN)4]PF6 in acetonitrile with 2,6-bis(diphenylphosphino)pyridine [(Ph2P)2py] afforded a colourless crystalline material characterised as [Cu2gm-(Ph2P)2PY3][PF612. An X-ray diffraction study confirmed that the three ligands bridge the two copper atoms bonding solely through the phosphorus atoms, each copper being trigonally coordinated; a cavity thus exists in the centre of the dinuclear dication bounded by the nitrogen donor atoms, the Cu… Cu distance and the diameter of the cavity being 4.744(2) and ca 4.9 A, respectively. Measurements of the solution emission spectra of [Cu2{μ-(Ph2P)2PY}3] [PF6]2 in the presence and absence of Cu+ and Ag+ ions suggest that these ions are trapped in the cavity on their addition to an acetonitrile solution of the complex. Addition of (Ph2P)2PY to [Cu(η2-bipy)(MeCN)2]PF6 (bipy = 2,2′-bipyridyl) in acetone afforded a yellow crystalline solid characterised as [Cu2{μ-(Ph2P)2py}2(η2-bipy)2][PF6]2. A crystal structure determination revealed that the two copper atoms are bridged by the two (Ph2P)2PY ligands bonding solely through the phosphorus atoms, with the irregular tetrahedral coordination at each copper being completed by the nitrogen atoms of the chelating bipyridyl ligands. The Cu… Cu distance is 6.806(2) A.

Protonation of the co-ordinatively unsaturated species [Ru2(µsb-CO)2(CO)2(µ-etipdp)2][sb = semi-bridging, etipdp =(PriO)2PNEtP(OPri)2] by acids of non-co-ordinating conjugate bases, e.g. HBF4·OEt2, produced [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]+ which, as established X-ray crystallographically for the PF6– salt, contains both a bridging carbonyl and a bridging hydride ligand. This cationic species is very susceptible to attack by both neutral and anionic nucleophiles affording a range of product types. For instance, its reactions with anions X– which are capable of functioning as monodentate bridging ligands and which preferentially adopt the closed bridging co-ordination mode, e.g. halide and hydrogensulfide ions, afforded products of the type [Ru2(µ-X)H(µsb-CO)(CO)2(µ-etipdp)2](X = Cl, Br, I, SH, etc.), resulting from the substitution of a carbonyl group by the nucleophile. On the other hand, anionic nucleophiles such as H– and CN– gave addition products of the type [Ru2HX(CO)4(µ-etipdp)2](X = H, CN, etc.) in which the hydride and the X– ligand occupy equatorial sites trans disposed with respect to each other, as established in a separate study for [Ru2H2(CO)4(µ-etipdp)2]. Carbon monoxide also afforded a simple addition product, viz.[Ru2H(CO)5(µ-etipdp)2]+, but the majority of the other neutral nucleophiles studied, particularly the unsaturated systems, yielded products resulting from formal insertion of the nucleophile into the Ru–H bond. Thus sulfur produced [Ru2(µ-SH)(CO)4(µ-etipdp)2]+, while unsaturated nucleophiles of general formula X′Y′, e.g. PhCN and RCCH (R = H, Ph, etc.), gave products of the type [Ru2{µ-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2{µ-NC(H)Ph}(CO)4(µ-etipdp)2]+ or of the type [Ru2{µ-η2-X′Y′(H)}(CO)4(µ-etipdp)2]+, e.g.[Ru2(µ-η1 : η2-CHCHR)(CO)4(µ-etipdp)2]+. Heterocumulenes X″Y″Z″ such as CS2 and PhNCS behaved similarly affording products of general formula [Ru2{µ-η2-X″Y″(H)Z″}(CO)4(µ-etipdp)2]+ containing five-membered RuX″Y″Z″Ru rings. The co-ordinatively saturated pentacarbonyl [Ru2H(CO)5(µ-etipdp)2]PF6 gave products similar to those afforded by [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6 on reaction with systems of the type X′Y′ and X″Y″Z″ except that, for terminal alkynes such as PhCCH, alkenylcarbonyl-bridged products, e.g.[Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6, are produced. The crystal structures of the following compounds were determined : [Ru2(µ-H)(µ-CO)(CO)3(µ-etipdp)2]PF6, [Ru2(µ-I)H(µsb-CO)(CO)2(µ-etipdp)2], [Ru2{µ-N(CHPh)}(CO)4(µ-etipdp)2]PF6, [Ru2(µ-η1 : η2-CHCH2)(CO)4(µ-etipdp)2]PF6, [Ru2{µ-η2-OC(CHCHPh)}(CO)4(µ-etipdp)2]PF6 and [Ru2{µ-η2-SC(H)NPh}(CO)4(µ-etipdp)2]PF6.

Reaction of the electron-rich sulfido-bridged complex [Fe2(η-C5Me5)2(µ-SEt)2(CO)2] with electron-acceptor N,N′-dicyano-p-benzoquinone diimines resulted in electron transfer and formation of crystalline 1 : 1 salts of general formula [donor cation][acceptor anion]. The crystal structures of [Fe2(η-C5Me5)2(η-SEt)2(CO)2] and [Fe2(η-C5Me5)2(µ-SEt)2(CO)2][dmdcnqi](dmdcnqi =N,N′-dicyano-2,5-dimethyl-p-benzoquinone diimine) have been determined by X-ray diffraction methods. The neutral donor molecule possesses exact C2 symmetry, the molecules stacking in linear chains in the crystal with the C5Me5 rings of adjacent molecules parallel to each other. The donor cations in the electron-transfer salt also possess exact C2 symmetry and, moreover, are arranged similarly in the crystal, but with the planar acceptor anions sandwiched between the C5Me5 rings and at an angle of 11.4° to these rings. The sequence along the rows is thus one of alternating donor cations (D˙+) and acceptor anions (A˙–), i.e.⋯ D˙+A˙–D˙+A˙–D˙+A˙–⋯. Consistent with the formation of radical cations and anions is a decrease in the Fe ⋯ Fe distance from 3.445(1)A in the neutral donor molecule to 3.083(2)A in the donor cation. However, the temperature dependence of the magnetic susceptibility of this salt, when fitted by the Curie–Weiss law, affords a Weiss constant (θ) of only 0.414 K, which suggests that there is little ferromagnetic coupling between the unpaired spins on the radical cations and anions.

Treatment of the formally unsaturated species [Ru2(µsb-CO)2(CO)2(µ-etipdp)2][sb = semi-bridging, etipdp =(PriO)2PNEtP(OPri)2] with silver(I) salts such as AgSbF6 or AgBF4 in MeCN or PhCN led directly to the formation of the disolvated species [Ru2(CO)4(RCN)2(µ-etipdp)2]X2(R = Me or Ph; X = SbF6 or BF4), with no intermediates being detected. In contrast, as established spectroscopically, oxidation of this complex with silver(I) salts in very weakly co-ordinating solvents such as acetone or methanol afforded silver adducts of the parent species. Also, reaction with the electron acceptor tcnq (7,7,8,8-tetracyano-p-quinodimethane) in tetrahydrofuran (thf) gave the electron-transfer salt [Ru2(η1-tcnq)(CO)4(thf)(µ-etipdp)2][tcnq], while with p-chloranil(tetrachloro-1,4-benzoquinone) produced [Ru2(µ-Cl)(CO)4(µ-etipdp)2][p-OC6Cl4O]2 as a consequence of the benzoquinone functioning as a chlorinating agent as well as an electron acceptor. Cyclic voltammograms of [Ru2(µsb-CO)2(CO)2(µ-etipdp)2] and [Ru2(CO)4(RCN)2(µ-etipdp)2][SbF6]2(R = Me or Ph) have been measured in both aceto- and benzo-nitrile and are readily interpreted in terms of the redox process [Ru2(µsb-CO)2(CO)2(µ-etipdp)2]+ 2RCN [graphic omitted] [Ru2(CO)4(RCN)2(µ-etipdp)2]2+. The structure of the acetonitrile species [Ru2(CO)4(MeCN)2(µ-etipdp)2][BF4]2·CH2Cl2 has been determined X-ray crystallographically.

Treatment of [Ru 2 (μ-CO)(CO) 4 (μ-etdp) 2 ] {etdp = (RO) 2 PN(Et)P(OR) 2 , R = Me or Pr i } with silver(I) carboxylates AgOC(O)R′ (R′ = Me, CF 3 or Ph) in acetone or tetrahydrofuran resulted in two electron oxidation and the formation of carboxylato species of the type [Ru 2 {μ-OC(R′)O}(CO) 4 (μ-etdp) 2 ] + for R′ = Me or Ph and [Ru 2 {η 1 -OC(O)R′}(CO) 5 (μ-etdp) 2 ] + for R′ = CF 3 . The acetate ligand in [Ru 2 {μ-OC(Me)O}(CO) 4 (μ-etdp) 2 ] + was displaced by other anionic ligands such as oxy-2-pyridinate or pyrazolate ions affording for these two ligands [Ru 2 (μ-NC 5 H 4 O)(CO) 4 (μ-etdp) 2 ] + and [Ru 2 (μ-N 2 C 3 H 3 )(η 1 -N 2 C 3 H 3 )(CO) 3 (μ-etdp) 2 ] respectively. The structures of [Ru 2 {μ-OC(Ph)O}(CO) 4 (μ-etipdp) 2 ]PF 6 {etipdp = (Pr i O) 2 PN(Et)P(OPr i ) 2 } and [Ru 2 (μ-NC 5 H 4 O)(CO) 4 (μ-etmdp) 2 ]PF 6 {etmdp = (MeO) 2 PN(Et)P(OMe) 2 } have been determined by X-ray crystallographically.

Reaction of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with equimolar quantities of metal-containing electrophiles such as [AuCl(PPh3)], silver(I) salts, [Cu(MeCN)4]PF6 and HgCl2 has afforded cationic products in which the metal substrate are co-ordinated either terminally as in [Ru2(σ-HgCl)(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+ or in the bridging mode as in [Ru2{µ-Au(PPh3)}(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+ and [Ru2(µ-AgLx)(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+(L = pyridine or MeCN, x= 1 or 2). The silver adducts readily rearrange in solution with the nature of the product(s) formed being dependent on the identity of the ligand L and/or the solvent employed For non-protic weakly co-ordinating ligands such as acetonitrile, the silver-bridged cations disproportionate in solution to the parent compound [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]and the solvento species [Ru2(CO)5(Solv){µ-(RO)2PN(Et)P(OR)2}2]2+ thereby establishing that the formation of [Ru2-(CO)5(Solv){µ-(RO)2PN(Et)P(OR)2}2]2+ by treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2] with a two-fold molar amount of silver(I) ions in non-protic weakly co-ordinating solvents occurs via an inner-sphere mechanism. In the case of the aqua and acetone solvento species [Ru2(CO)5(solv)-{µ-(RO)2PN(Et)P(OR)2}2]2+(solv = H2O or Me2CO), both the solvent molecule and the carbonyl groups are labile with one or both being readily displaced by a wide range of neutral and ionic nucleophiles including carbon monoxide, isonitriles, nitriles, pyridine, 4,4′-bipyridine, dimethyl sulfide and tetra-hydrothiophene, and halide, thiocyanate, benzenethiolate, trifluoroacetate, acetate and hydride ions. The crystal structures of [Ru2{µ-Au(PPh3)}(µ-CO)(CO)4{µ-(MeO)2PN(Et)P(OMe)2}2]SbF6, [Ru2-(CO)5(PhCN){µ-(PriO)2PN(Et)P(OPri)2}2][SbF6]2 and [Ru2(CO)5(SC4H8){µ-(PriO)2PN(Et)P(OPri)2};2]-[SbF6]2 have been determined.

Reaction of 6-diphenylphosphino-2,2′-bipyridine (Ph2Pbipy) with copper(I) precursors such as [Cu(MeCN)4]+ and [Cu(2,2′-bipy)(MeCN)2]+ affords dinuclear phosphorusbipyridyl ligand-bridged dicopper products and in particular [Cu2(μ-Ph2Pbipy)2 (MeCN)2]2+ (1 and [Cu2(2,2′-bipy)(μ-Ph2Pbipy)2]2+ (2), respectively. The ligand coordinates head-to-tail in 1, and head-to-head in 2, as established by single crystal X-ray diffraction studies.

Homochiral catalysts, [Rh (norbornadiene)-(homochiral diphosphine)]+ X−/H2, were tested to assess possible enantiocontrol in the aldol-type coupling of activated vinyl components with aldehydes. A related approach, via in situ rhodium silyl enolates, was also investigated.

Reaction of the di-iron heptacarbonyl compounds [Fe2(μ-CO)(CO)6(μ-R2PCH2PR2)2] (R = Me or Ph) with a range of diphosphorus or diarsenic ligands under photochemical conditions affords the ligand-bridged pentacarbonyl derivatives [Fe2(μ-CO)(CO)4(μ-Me2PCH2PMe2)(μ-L-L)] [L-L = (MeO)2PN(Et)P(OMe)2 or (EtO)2PN(Me) P(OEt)2] and [Fe2(μ-CO)(CO)4(μ-Ph2PCH2PPh2)(μ-L-L)] [L-L = Me2PCH2PMe2, Ph2PN(Et)PPh2, Ph2AsCH2AsPh2, (MeO)2PN(Et)P(OMe)2 and (EtO)2PN(Me)P(OEt)2] in good yield. Treatment of these mixed ligand-bridged complexes with the protic acids HBF4 · Et2O or CF3COOH leads exclusively to the formation of the hydride-bridged species [Fe2(μ-H)(μ-CO)(CO)4(μ-R2PCH2PR2)(μ-L-L)]+ isolated as the tetrafluoroborate salts. Hydride-bridged products are also obtained by protonation of [Fe2(μ-CO)(CO)4{μ-(R′O)2PN(R″)P(OR′)2}2] (R″ = Me, R′ = Et; R″ = Et, R′ = Me, Pri or Ph) and [Fe2(μ-CO)(CO)4(μ-R2PCH2PR2)2] (R = Me or Ph), but whereas the diphosphazane-bridged species [Fe2(μ-H)(μ-CO)(CO)4{μ-(R′O)2PN(R″)P(OR′)2}2]+ are only stable to deprotonation in the presence of excess acid, the ditertiary phosphine-bridged species [Fe2(μ-H)(μ-CO)(CO)4(μ-R2PCH2PR2)2]+ can only be deprotonated by strong bases such as NaBH4. The structure of [Fe2(μ-CO)(CO)4(μ-Ph2PCH2PPh2)2] has been established X-ray crystallographically. The two iron atoms, which are bridged by a carbonyl group as well as by the two ditertiary phosphine ligands, are separated by a distance of 2.742(4) A, corresponding to a formal iron-iron bond.

The reaction of ethyne with [Ru2(µ-CO)(CO)4{(RO)2PN(Et)P(OR)2}2] in toluene at 80 °C or with [Ru2(µsb-CO)2(CO)2{(RO)2PN(Et)P(OR)2}2](R = Me or Pri, sb = semi-bridging), in toluene at room temperature, affords almost exclusively the ethenediyl-bridged species [Ru2(µ-σ2-HCCH)(CO)4{(RO)2-PN(Et)P(OR)2}2] for R = Me and the vinylidene-bridged product [Ru2(µ-σ-CCH2)(CO)4{(RO)2-PN(Et)P(OR)2}2] for R = Pri; a second, minor product is also formed in each of these reactions and was identified as [Ru2(µ-σ-CCH2)(CO)4{(MeO)2PN(Et)P(OMe)2}2] and [Ru2(µ-σ2-HCCH)(CO)4-{(PriO)2PN(Et)P(OPri)2}2] respectively. The reactions of [Ru2(µ-CO)(CO)4{(RO)2PN(Et)P(OR)2}2] and [Ru2(µsb-CO)2(CO)2{(RO)2PN(Et)P(OR)2}2] with the terminal alkynes MeCCH, PhCCH and MeO2CCCH also afford mixtures of alkenediyl- and vinylidene-bridged products with the relative yields of these isomers being dependent on the identity of the alkyne and of the bridging diphosphazane ligand. On the other hand reaction with the internal alkyne MeO2CCCCO2Me gives solely the alkenediyl-bridged product [Ru2(µ-σ2-MeO2CCCCO2Me)(CO)4{(RO)2PN(Et)P(OR)2}2] irrespective of the diphosphazane ligand involved. Possible mechanisms for the formation of the two types of products are described. The crystal structure of [Ru2(µ-σ2-HCCH)(CO)4{(MeO)2PN(Et)P(OMe)2}2] is reported.

Thermolysis of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2], [Ru2H2(CO)4{µ-(RO)2PN(Et)P(OR)2}2] or [Ru2{µ-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) under appropriate reaction conditions affords the formally unsaturated species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2], which have been established by X-ray crystallography for both R = Me and R = Pri to contain two complementary semi-bridging carbonyl groups as well as two terminal carbonyls. These compounds are highly labile and react under mild conditions with a range of small molecule nucleophiles and electrophiles including carbon monoxide, isonitriles, nitrosyl ions, alkynes, sulfur, hydrogen sulfide, dioxygen, sulfur dioxide, tin(II) chloride, dihydrogen, protons, halogens and carbon tetrachloride. The compound [Ru2H2(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2], the product of the reaction involving dihydrogen and the tetraisopropoxy-diphosphazane derivative and in which, as determined by X-ray crystallography, the hydrogens are situated equatorially and trans to each other on different ruthenium atoms, is also highly reactive, typically reductively eliminating dihydrogen in its reactions with nucleophiles including alkynes.

Treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with AgSbF6 in methanol, ethanol or tetrahydrofuran–water resulted in the formation of the solvento species [Ru2(CO)5(R′OH){µ-(RO)2PN(Et)P(OR)2}2][SbF6]2 which is isolable for R′= H but which spontaneously deprotonates to the alkoxycarbonyl-bridged derivative [Ru2{µ-η2-OC(OR′)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2]SbF6 for R′= Me or Et. The aqua species [Ru2(CO)5(H2O){µ-(RO)2PN(Et)P(OR)2}2][SbF6]2 was readily deprotonated in consecutive steps by appropriate bases to afford respectively the hydroxycarbonyl-bridged species [Ru2{µ-η2-OC(OH)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2]SbF6 and the adduct [Ru2{µ-η2-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2] in which the carbon dioxide molecule adopts a novel bridging co-ordination mode; this deprotonation is reversible and treatment of the latter with HBF4·OEt2 leads to stepwise regeneration of the aqua species. The co-ordinated water molecule in [Ru2(CO)5(H2O){µ-(PriO)2PN(Et)P(OPri)2}2][SbF6]2 was readily displaced by acids HA derived from conjugate bases with potential co-ordinating properties such as thiolate ions R″S–(R″= H or Ph) or carboxylate ions R‴CO2–(R‴= H, Me, Ph or CF3), to produce monocationic pentacarbonyl species of the type [Ru2A(CO)5{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6; detection of an intermediate, presumably [Ru2(CO)5(HA){µ-(PriO)2PN(Et)P(OPri)2}2][SbF6]2, was possible for HA = HCO2H and MeCO2H. The sulfido derivatives [Ru2(SR″)(CO)5{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6(R″= H or Ph) rapidly decarbonylate in solution to afford the tetracarbonyl products [Ru2(µ-SR″)(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6 in which the sulfido group bridges the two ruthenium atoms. On the other hand the carboxylato derivatives [Ru2{OC(O)R‴}(CO)5{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6(R‴= H, Me, Ph or CF3) are stable to decarbonylation in solution at room or elevated temperatures but can be decarbonylated to the carboxylato-bridged products [Ru2{µ-η2-OC(R‴)O}(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6 by irradiation with ultraviolet light. The water molecule in [Ru2(CO)5(H2O){µ-(PriO)2PN(Et)P(OPri)2}2][SbF6]2 was also readily displaced by the conjugate bases of the above acids HA, but in contrast to that observed for the carboxylic acids R‴CO2H (R‴= H, Me or Ph), reaction of the aqua species with the corresponding carboxylate ions R‴CO2– led to direct formation of the carboxylato-bridged species [Ru2{µ-η2-OC(R‴)O}(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2]SbF6. Possible mechanisms for the formation of the various products are discussed as are the structures of [Ru2(CO)5(H2O){µ-(PriO)2PN(Et)P(OPri)2}2][SbF6]2·OCMe2, [Ru2{µ-η2-OC(OEt)}(CO)4{µ-(MeO)2PN(Et)P(OMe)2}2]SbF6, [Ru2{µ-η2-OC(Me)O}(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2]PF6 and [Ru2{µ-η2-OC(O)}(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2], established X-ray crystallographically.

We report the synthesis and characterisation of eight molecules that have in common a diphenylphosphino group bonded to an α-carbon atom of a thienyl or pyridyl ring: 5,5′-bis(diphenylphosphino)-2,2′-bithiophene 1; diphenyl(2,2′-bithienyl-5-yl)phosphine 2; 5,5″-bis(diphenylphosphino)-2,2′:5′,2″-terthiophene 3; diphenyl(2,2′:5′,2″-terthienyl-5-yl)phosphine 4; diphenyl[5-(2′-pyridyl)-2-thienyl]phosphine 5; diphenyl[6-(2′-thienyl)-2-pyridyl]phosphine 6; diphenyl{5-[6′-(diphenylphosphino)-2′-pyridyl]-2-thienyl}phosphine 7; and 2,6-bis[5′-(diphenylphosphino)-2′-thienyl]pyridine 8. Methods used for their synthesis range from lithiation of the parent heterocycle and subsequent reaction with PPh2Cl to the use of coupling reactions catalysed by metal complexes to assemble the molecule from its subunits. The crystal and molecular structures of 1, 7 and 8 have been determined and show that the 2,2′-bithienyl moiety in 1 adopts an s-trans-conformation, while the 2-(2′-thienyl)pyridyl moieties in 7 and 8 adopt s-cis-conformations in the solid state. These compounds represent a new series of ligands that are expected to bond to metals through the phosphorus and/or nitrogen atoms rather than a sulfur atom, in view of the poor donor ability of a thiophene sulfur towards metals.

The purple, phosphinidene-capped, phosphido-bridged triruthenium cluster [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 7 ] reacts readily with carbon monoxide, trimethylphosphite, sodium borohydride and diphenylacetylene under mild conditions to afford product mixtures from which [Ru 3 (μ-PPh)(μ 2 -PPh 2 ) 2 (CO) 7+ n ] ( n = 1, 2 or 3), [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 6 {P(OMe) 3 }], [Ru 3 (μ 3 -η 3 -PhPCPhCPh)(μ 2 -PPh 2 ) 2 (CO) 6 ], respectively, can be isolated. The structure of [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 6 {P(OMe) 3 }] has been established X-ray crystallographically.

Reaction of the diphosphazane-bridged diruthenium derivatives Ru 2 (μ-CO)(CO) 4 [μ-(RO) 2 PN(Et)P(OR) 2 ] 2 (R=Me, i Pr) with the electron acceptors TCNX (X=Q, E) affords products of the type {Ru 2 (CO) 5 [μ-(RO) 2 PN-(Et)P(OR) 2 ] 2 (η 1 -TCNX)}(TCNX) containing a TCNX radical anion in both the inner and outer coordination sphere of the cation

Reaction of the electron-rich diphosphazane-bridged diruthenium complexes [Ru 2 (μ-(CO)(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] (R = Me or i Pr) with the electron-acceptor ligands 7,7,8,8-tetracyano- p -quinodimethane, TCNQ, and tetracyanoethylene, TCNE, results in electron transfer and the formation of the charge transfer salts [Ru 2 (CO) 5 (TCNX) {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]TCNX (X  Q or E) containing the radical anion of the electron-acceptor ligand in both the inner and the outer coordination spheres.

Cyclic voltammetric studies in benzonitrile, dichloromethane and acetone show that the oxidation of the di-iron derivatives [Fe2(μ-CO)(CO)4(μ-R2PYPR2)2] (Y = CH2, R = Me or Ph; Y = NEt, R = OMe, OEt, OiPr or OPh) generally proceeds via an EEC mechanism, the only exception being the oxidation of the Y = CH2, R = Ph derivative in acetone, which proceeds via an EE mechanism. The chemical step in the EEC mechanism involves solvent attack at an iron atom with formation of a dicationic solvento species of the type [Fe2(CO)5(solvent)(μ-R2PYPR2)2]2+. The electrochemical oxidation of the diruthenium tetramethoxydiphosphazane ligand-bridged derivative [Ru2(μ-CO)(CO)4{μ-(MeO)2PN(Et)-P(OMe)2}2] only proceeds via an EEC mechanism in the very weakly coordinating solvent dichloromethane; in benzonitrile and acetone oxidation is via an ECE mechanism for which the potential required to remove the second electron is lower than that for the removal of the first electron giving rise to an overall 2e-transfer reaction. Again the end-product of the oxidation process is a dicationic solvento species. Electrochemical oxidation in all three solvents of the diruthenium tetraisopropoxydiphosphazane ligand-bridged derivative [Ru2(μ-CO)(CO)4{μ-(iPrO)2PN(Et)P(OiPr)2}2] is proposed to proceed via an ECEC mechanism for which the first chemical step involves a structural rearrangement and the second solvent attack at a ruthenium atom to form the dicationic solvento species. Significantly, the separation between the potentials required to remove the first and second electrons is small, i.e., < 0.5 V. Two pathways are utilized in the electrochemical oxidation of the mixed-ligand complex [Ru2(μ-CO)(CO)4{μ-(MeO)2PN(Et)P(OMe)2}{μ-(iPrO)2PN(Et)P(OiPr)2}], their nature being dependent on the choise of solvent. The ECE mechanism is adopted in all three solvents benzonitrile, acetone and dichloromethane; however, in the first solvent the second pathway is the EEC process whereas the second pathway adopted in acetone and dichloromethane is the ECEC process. Thus, the overall mechanism proposed for the electrochemical oxidation of the above derivatives of [Fe2(CO)9] and [Ru2(CO)9] allows for three pathways to a dicationic solvento species, the pathway adopted being dependent on the metal, the bridging ligand, in particular on its size, and on the coordinating ability of the solvent.

Reaction of [Ru3(CO)12] with PPhH2 in toluene under reflux affords a range of higher nuclearity as well as trinuclear products, two of which have been characterised as the π-toluene derivatives [Ru5(μ4-PPh)(CO)12(η6-C6H5Me)] and [Ru7(μ4-PPh)2(CO)15(η6-C6H5Me)]. Crystal structure determinations have revealed that the structures of these two compound are based on those of their parents, [Ru5(μ4-PPh)(CO)15] and [Ru7(μ4-PPh)2(CO)18], with three carbonyls on one of the ruthenium atoms of each cluster having been replaced by a π-toluene ring.

Treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with halogens results in the ready formation of [Ru2X(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+(X = Cl, Br or I) with the halogen atom co-ordinating terminally. These pentacarbonyl species, isolated as their hexafluorophosphate salts, decarbonylate in solution, rapidly in the presence of trimethylamine N-oxide dihydrate but slowly in the absence of this decarbonylating agent, to produce the tetracarbonyl species [Ru2(µ-X)(CO)4{µ-(RO)2PN(Et)p(OR)2}2]+ in which the halogen bridges the two ruthenium atoms. Substitution of the carbonyl groups in these tetracarbonyl species can be effected further by halide ions, either photochemically or by promoting the process using Me3NO·2H2O and thus reaction of [Ru2(µ-X)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+ with chloride, bromide or iodide ions in the presence of Me3NO·2H2O readily affords [Ru2(µ-X)X(CO)3{µ-(RO)2PN(Et)P(OR)2}2]. Significantly, treatment of [Ru2I(CO)5{µ-(RO)2PN(Et)P(OR)2}2]I3, or [Ru2I(CO)5{µ-(RO)2PN(Et)P(OR)2}2]PF6 in the presence of iodide ions, with an excess of Me3NO·2H2O leads solely to the neutral tetracarbonyl derivative [Ru2I2(CO)4{µ-(RO)2PN(Et)P(OR)2}2]. On the basis of an X-ray crystallographic study on [Ru2(µ-I)I(CO)3{µ-(PriO)2PN(Et)P(OPri)2}2], the tricarbonyl derivatives have structures related to that of [Ru2(µ-X)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+ with an axial carbonyl group having been replaced by a halide ion.

Reaction of the ligand-bridged derivatives [M3(CO)10{μ-(RO)2PN(Et)P(OR)2}] and [M3(CO)8{μ-(RO)2PN(Et)P(OR)2}2] (M = Ru or Os; R = Me or Pri) with halogens leads to the formation of cationic products [M3(μ-X)(CO)10{μ- (RO)2PN(Et)P(OR)2}]+ and [M3(μ-X)(CO)8{μ-(RO)2PN(Et)P(OR)2}2]+ (X = Cl, Br or I) in which the halogen bridges an opened edge of the metal atom framework; the crystal structure of [Ru3(μ-I)(CO)8{μ-(MeO)2PN(Et)P(OMe)2}2]PF6 is reported.

Treatment of [Ru2(μ-CO)(CO)4{μ-(RO)2PN(Et)P(OR)2}2] (R = Me or Pri), electron-rich derivatives of [Ru2(CO)9], with a twice molar amount of a silver(I) salt in aprotic, weakly co-ordinating solvents such as acetone, acetonitrile or benzonitrile leads to the formation of the solvento species [Ru2(CO)5(solvent)- {μ-(RO)2PN(Et)P(OR)2}2]2+. The structure of the benzonitrile derivative, [Ru2(CO)5(PhCN){μ-(PriO)2PN(Et)P(OPri)2}2](SbF6)2, has been established by X-ray crystallography. The acetone molecule in [Ru2(CO)5(acetone){μ- (RO)2PN(Et)P(OR)2}2]2+ is readily replaced by various nucleophiles to afford products of the type [Ru2(CO)5L{μ-(RO)2PN(Et)P(OR)2}2]2+, where L is a neutral ligand such as CO, Me2C6H3NC, PhCN, C5H5N, H2O, Me2S or SC4H8, [Ru2Y(CO)5{μ-(RO)2PN(Et)P(OR)2}2]2+, where Y− is an anionic ligand such as Cl−, Br−, I−, CN−, SCN−, MeCO2−, CF3CO2− or [Ru2(μ-Y)(CO)4{μ-(RO)2- PN(Et)P(OR)2}2]+ where Y− is an anionic ligand such as Cl−, Br−, I−, SPh−, S2CNEt2−, MeCO2− or CF3CO2−.

Thermolysis of [Ru 3 (μ 2 -PPh 2 )(μ 2 -H)(CO) 9 ], [Ru 3 (μ 2 -PPh 2 ) 2 (μ 2 -H) 2 (CO) 8 ], [Ru 3 (μ 2 -PPh 2 ) 3 (μ 2 -H)(CO) 7 ] and [Ru 3 (μ 2 -PPh 2 ) 3 (μ 2 -H)(CO) 6 (PPh 2 H)] in xylene under reflux gives a wide range of condensation and/or degradation products, including [Ru 2 (μ-PPh 2 ) 2 (CO) 6 ], [Ru 3 (μ 3 -PPh) 2 (CO) 9 ], [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 7 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh 2 )(μ 2 -PPh 2 ) 2 (μ 2 -H)(CO) 6 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh)(μ 2 -PPh 2 )(μ 2 -H)(CO) 7 ], [Ru 4 (μ 3 -PPh)(CO) 13 ], [Ru 4 (μ 4 -PPh) 2 (μ 2 -CO)(CO) 10 ], [Ru 5 (μ 4 -PPh)(CO) 15 ], [Ru 5 (μ 4 -PPh)(CO) 12 (η 6 -C 6 H 4 Me 2 )], [Ru 6 (μ 4 -PPh) 2 (μ 3 -PPh) 2 (CO) 12 ] and [Ru 7 (μ 4 -PPh) 2 (CO) 18 ]. The structures of the unusual trinuclear species [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 7 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh 2 )(μ 2 -PPh 2 ) 2 (μ 2 -H)(CO) 6 ] and [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh)(μ 2 -PPh 2 )(μ 2 -H)(CO) 7 ] and that of the hexanuclear derivative [Ru 6 (μ 4 -PPh) 2 (μ 3 -PPh) 2 (CO) 12 ] have been established by X-ray crystallography.

Reactions of [Ru2H(CO)5μ-(RO)2PN(Et)P(OR)22][PF6] (R = Me or Pri) with unsaturated compounds such as alkynes, nitriles and carbon disulphide give three-, four-, or five-membered dimetallocyclic species depending on the nature of the unsaturated system. The structures of [Ru2μ-η1-N(CHPh)(CO)4μ-(PriO)2PN(Et)P(OPri)22][PF6], 577 [Ru2μ-η2-OC(CHCHPh)(CO)4μ-(PriO)2PN(Et)P(OPri)22][PF6] 577 and [Ru2μ-η2-PhNC(H)S(CO)4μ-(PriO)2PN(Et)P(OPri)22] 577 [PF6] have been determined by X-ray crystallography.

Halogenation of [Co2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) by I2, Br2, or freshly distilled CCl4 affords the cations [Co2(µ-X)(µ-CO)(CO)2{µ-(RO)2PN(Et)P(OR)2}2]+(X = I, Br, or Cl respectively). A single-crystal X-ray diffraction study on [Co2(µ-I)(µ-CO)(CO)2{µ-(MeO)2PN(Et)P(OMe)2}2] BPh4 confirms that these cations have A-frame structures with a neutral ligand, CO, occupying a bridging site additional to the bridging halogen atom. For R = Me (only) the cations slowly undergo a Michaelis–Arbusov type rearrangement initiated by attack of halide ions at a co-ordinated phosphorus atom, to give the neutral complexes [Co2(µ-X)(µ-CO)(CO)2{µ-(MeO)2PN(Et)P(OMe)2}{µ-(MeO)2PN(Et)P(O)(OMe)}]. The latter could not be isolated but [Co2(µ-I)(µ-CO)(CO)2{µ-(PriO)2PN(Et)P(OPri)2}{µ-(PriO)2PN(Et)P(O)(OPri)}] is readily isolated from the reaction of [Co2(µ-I)(µ-CO)(CO)2{µ-(PriO)2PN(Et)P(OPri)2}2]+ with hydride ions. When undistilled (Analar grade) rather than freshly distilled CCl4 is used to chlorinate [Co2(CO)4{µ-(MeO)2PN(Et)P(OMe)2}2] an unexpected product, viz.[Co(CO)2{P(OMe)3}2{(MeO)2-PN(Et)P(OMe)2-κP}]+ is formed; this cation contains one cobalt atom bonded to two trimethyl phosphite ligands, two carbonyl ligands, and a pendant diphosphazane ligand, as confirmed X-ray crystallographically.

The reaction of [Ru3(CO)12] with PPh2H in toluene under reflux affords a range of products, the nature and yields of which depend on the reaction times and the molar ratios employed. Compounds isolated include not only the trinuclear species [Ru3(μ2-PPh2)2(μ2-H)2(CO)8], [Ru3(μ2-PPh2)3(μ2-H)(CO)7], [Ru3(μ2-PPh2)3(μ2-H)(CO)6(PPh2H)], [Ru3(μ3-PPh)(μ-H)2(CO)9] and [Ru3(μ-PPh)(μ-PPh2)2(CO)7] but also condensation products, such as [Ru4(μ4-PPh)2(μ2-CO)(CO)10], [Ru5(μ4-PPh)(CO)15], [Ru6(μ4-PPh)2(μ3-PPh)2(CO)12] and [Ru7(μ4-PPh)2(CO)18], previously isolated from the reaction of [Ru3(CO)12] with PPhH2, as well as the highly unusual octaruthenium derivative [Ru8(μ8-P)(μ2-η1,η6-CH2Ph)(μ2-CO)2(CO)17] and the fragmentation product [Ru2(μ-PPh2)2(CO)6]. The molecular stereochemistries of [Ru2(μ-PPh2)2(CO)6], [Ru3(μ2-PPh2)3(μ2-H)(CO)7], [Ru3(μ2-PPh2)3(μ2-H)(CO)6(PPh2H)] and [Ru8(μ8-P)(μ2-η1,η6-CH2Ph)(μ2-CO)2(CO)17] have been established by X-ray crystallography. The eight ruthenium atoms in the latter adopt a square antiprismatic geometry and encapsulate a phosphorus atom derived from the diphenylphosphine. The benzyl group in this compound exhibits an unusual mode of coordination with the benzene ring functioning as a hexahapto ligand towards one of the ruthenium atoms and with the benzylic carbon bonding directly to an adjacent ruthenium atom.

Treatment of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) with silver(I) salts in the presence of protic solvents of the type R′OH (R′= H, Me, Et, etc.) leads to the formation of the solvento species [Ru2(CO)5(R′OH){µ-(RO)2PN(Et)P(OR)2}2]2+ which is readily deprotonated and rearranges to afford [Ru2{µ-OC(OR′)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+; [Ru2{µ-OC(OH)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+ can be deprotonated further to give [Ru2{µ-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2] containing a bridging carbon dioxide group, confirmed X-ray crystallographically.

Protonation of [Co2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) proceeds without CO loss to give [Co2(µ-H)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+. Proton n.m.r. spectroscopic data, as well as an X-ray structure determination of [Co2(µ-H)(CO)4{µ-(MeO)2PN(Et)P(OMe)2}2]BPh4, confirm the presence of a bridging hydride ligand. Both cobalt atoms are trigonal bipyramidal but the overall conformation is staggered as evidenced by P–Co–Co–P torsion angles of 34.7(1) and 35.7(1)°. Attempts to form a dihydrido species by addition of H– merely served to deprotonate the cation with formation of the starting complex and H2.

The synthesis and characterization of [Pt{4'-(R)trpy}(CN)]X (R = Ph, X = BF(4) or SbF(6); R = o-CH(3)C(6)H(4), X = SbF(6); R = o-ClC(6)H(4), X = SbF(6); or R = o-CF(3)C(6)H(4), X = SbF(6)) are described where trpy = 2,2':6',2''-terpyridine. Single crystals of [Pt{4'-(Ph)trpy}(CN)]BF(4).CH(3)CN were grown by vapour diffusion of diethyl ether into an acetonitrile solution of [Pt{4'-(Ph)trpy}(CN)]BF(4). An X-ray crystal structure determination of the solvated complex confirms the near linear coordination of the cyanide ligand to the platinum centre. The cation is almost planar as evidenced by a twist of only 1.9 degrees of the phenyl group out of the plane of the terpyridyl moiety. Cyclic voltammograms were recorded in DMF/0.1 M TBAH for the [Pt{4'-(R)trpy}(CN)](+) cations. Two quasi-reversible one-electron reduction (cathodic) waves are observed with E(1/2) values that show the trend expected for an increasingly lower energy of the trpy-based LUMO of the complex i.e., [Pt{4'-(Ph)trpy}(CN)](+) approximately [Pt{4'-(o-CH(3)C(6)H(4))trpy}(CN)](+)[Pt{4'-(o-ClC(6)H(4))trpy}(CN)](+)[Pt{4'-(o-CF(3)C(6)H(4))trpy}(CN)](+). All the [Pt(4'-(R)trpy}(CN)](+) cations are photoluminescent in dichloromethane. Emission by [Pt{4'-(Ph)trpy}(CN)](+) is from an excited state with largely (3)MLCT orbital parentage, but with some intraligand (3)pi-pi* character mixed-in (tau = 0.1 micros). In contrast, the other three cations display emission that appears exclusively intraligand (3)pi-pi* in origin (tau approximately 0.8 micros). Emission spectra have been recorded in a low concentration frozen DME {1 : 5 : 5 (v/v) DMF-MeOH-EtOH} glass. For the R = o-CH(3)C(6)H(4), o-ClC(6)H(4) and o-CF(3)C(6)H(4) cations the envelope of vibronic structure and energies of the vibrational components are essentially the same as that recorded in dichloromethane. However, for the [Pt{4'-(Ph)trpy}(CN)](+) cation, there is a blue-shift in the energies of the vibrational components as compared to that recorded in dichloromethane, as well as a change in the envelope of vibronic structure to a more "domed" pattern; this has been interpreted in terms of a higher percentage of intraligand (3)pi-pi* character in the emitting state for the glass. Increasing the concentration of the glass invariably leads to aggregation of the cations and the consequent development of new low energy bands, such that at 0.200 mM broad peaks centred at ca. 650 and 700 nm dominate the spectrum; these bands are assigned to excimeric (3)pi-pi* and (3)MMLCT emission, respectively.

Pt(trpy)Cl+, where trpy denotes 2,2':6',2' '-terpyridine, is a versatile binding agent but has a limited photochemistry due to a short excited-state lifetime. However, this work shows that the introduction of aryl substituents at the 4' position of the trpy ligand drastically alters the picture. For the substituents phenyl, p-methoxyphenyl, 1-naphthyl, 2-naphthyl, 9-phenanthrenyl, and 1-pyrenyl, the ligand abbrevations are 4'-Ph-T, 4'-pMeOPh-T, 4'-Npl-T, 4'-Np2-T, 4'-Phe9-T, and 4'-Pyre1-T, respectively. Techniques utilized include electrochemistry as well as absorption and emission spectroscopies. While the lowest energy excited states of Pt(4'-Ph-T)Cl+ and the parent complex Pt(trpy)Cl+ exhibit mainly metal-to-ligand charge-transfer (MLCT) character, the emitting state takes on aryl-to-trpy intraligand charge-transfer (ILCT) character as the substituents become more electron-donating. Studies of Zn(trpy)Cl2, its aryl-substituted analogues, and the free ligands themselves provide information about the relative energies of participating ILCT and intraligand 3pi-pi excited states. Even though the emission energy decreases when larger aryl groups are present, the emission lifetime increases all the way from 85 ns for Pt(4'-Ph-T)Cl+ to 64 micros for Pt(4'-Pyre1-T)Cl+. (Data from deoxygenated, room-temperature dichloromethane solution.) Intraligand character appears to dominate in the case of Pt(4'-Pyre1-T)Cl+, which is unique in the series in that it exhibits singlet and triplet emissions in solution. In aerated solution the complex shows prompt as well as delayed fluorescence. Finally, studies in donor media establish that the introduction of intraligand character inhibits solvent-induced exciplex quenching.

Thermolysis of [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2] or [Ru2H2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) under appropriate reaction conditions affords the formally unsaturated species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2], which reacts spontaneously at room temperature with various substrates; the crystal structure of [Ru2(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2] as well as that of [Ru2H2(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2] is reported.

Treatment of [Fe2(η-C5H5)2(µ-CO)2{µ-Ph2PN(Et)PPh2}] with 7,7,8,8-tetracyano-p-quinodimethane, TCNQ, affords, on crystallization from acetonitrile, a charge-transfer salt, [Fe2(η-C5H5)2(µ-CO)2{µ-Ph2PN(Et)PPh2}]2(TCNQ)3·2MeCN, with a novel 2 : 3 Stoichiometry; the cations and anions in this species are distributed in segregated stacks, the TCNQ anions packing as trimers along the stack with an intratrimer separation of 3.24(1)A and an intertrimer separation of 3.39(1)A.

Thermolysis of [Ru 3 (μ 2 -PPh 2 )(μ 2 -H)(CO) 9 ], [Ru 3 (μ 2 -PPh 2 ) 2 (μ 2 -H) 2 (CO) 8 ], [Ru 3 (μ 2 -PPh 2 ) 3 (μ 2 -H)(CO) 7 ] and [Ru 3 (μ 2 -PPh 2 ) 3 (μ 2 -H)(CO) 6 (PPh 2 H)] in xylene under reflux gives a wide range of condensation and/or degradation products, including [Ru 2 (μ-PPh 2 ) 2 (CO) 6 ], [Ru 3 (μ 3 -PPh) 2 (CO) 9 ], [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 7 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh 2 )(μ 2 -PPh 2 ) 2 (μ 2 -H)(CO) 6 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh)(μ 2 -PPh 2 )(μ 2 -H)(CO) 7 ], [Ru 4 (μ 3 -PPh)(CO) 13 ], [Ru 4 (μ 4 -PPh) 2 (μ 2 -CO)(CO) 10 ], [Ru 5 (μ 4 -PPh)(CO) 15 ], [Ru 5 (μ 4 -PPh)(CO) 12 (η 6 -C 6 H 4 Me 2 )], [Ru 6 (μ 4 -PPh) 2 (μ 3 -PPh) 2 (CO) 12 ] and [Ru 7 (μ 4 -PPh) 2 (CO) 18 ]. The structures of the unusual trinuclear species [Ru 3 (μ 3 -PPh)(μ 2 -PPh 2 ) 2 (CO) 7 ], [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh 2 )(μ 2 -PPh 2 ) 2 (μ 2 -H)(CO) 6 ] and [Ru 3 (μ 3 -η 2 -PhPC 6 H 4 PPh)(μ 2 -PPh 2 )(μ 2 -H)(CO) 7 ] and that of the hexanuclear derivative [Ru 6 (μ 4 -PPh) 2 (μ 3 -PPh) 2 (CO) 12 ] have been established by X-ray crystallography.