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The synthesis and characterization of [Pt{4′-(p-tolyl)trpy}Cl]SbF6 is described where trpy is 2,2′:6′,2″-terpyridine. A single crystal X-ray structure determination at 100 K shows that the cations are stacked in columns that comprise cations arranged in a staircase motif. Successive cations within a column are linked by π(trpy)–π(phenyl) stabilizing interactions; and each cation in one column is linked to a cation in an adjacent column by a weakly stabilizing Pt···Pt interaction. The Pt···Pt distance is 3.434(1) A. The metrics governing non-covalent interactions between [Pt{4′-(aryl)trpy}Cl]+ cations have been analyzed for the present structure and related structures in the CSD (Cambridge Structural Database). Cation dimers cluster into three distinct groups based on their lateral shifts and, to a lesser extent, the angular parameters governing their relative displacements; the dominant grouping exhibits Pt···Pt and π(trpy)–π(trpy) stabilizing interactions. An emission spectrum recorded at 77 K on a solid sample of the compound is best interpreted as arising from the decay of three photoexcited states: a 3MLCT (MLCT = metal-to-ligand charge transfer) state; a 3MMLCT (MMLCT = metal–metal-to-ligand charge transfer) state, and an excimeric 3π–π∗ state.

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 [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.

An investigation of the effects of solvent, temperature and the bulk of the silyl and carbamate functionalities on the stereoselective synthesis of substituted vinyl carbamates from α-silyl benzyl carbamates is described.

Imidazolinylidene and thiazolinylidene complexes of gold in acetonitrile have been investigated by cyclic voltammetry. No Au(II) intermediate was observed during the redox reactions and Au(III) compounds form only by oxidative addition of halogens.

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.

A new neolignan, which differs from ocobullenone at a single chiral centre, and a neolignan ketone, possibly a precursor of the ocobullenones, have been isolated from the stem bark of Ocotea bullata .

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 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.

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.

Hexahydro-3a, 7a-dihydroxy-3,7,7-trimethyl-2-phenyl-4H-furo [3,2-c]pyran-4-one 6 has been obtained from the reaction between tetrahydro-4, 4-dimethyl-2-oxo-3-furanyl propanoate 4 , benzaldehyde and base. The product is the result of a modified benzilic acid rearrangement.

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 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.

(−)(R,R)-2-Amino-1-(4-nitrophenyl)propan-1,3-diol 3 has been used to resolve racemic 3-hydroxy-2-methylene-3-phenylpropanoic acid 1a. Conversion of the laevorotatory enantiomer into anti and syn methyl 3-hydroxy-2-methyl-3-phenylpropanoate, 2a and 2b respectively, was achieved with Pd/H2. Correlation of the specific rotations of 2a and 2b with isomers of known configuration established the absolute configuration of 4a as R. This was confirmed independently by X-ray crystallography.

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.

From the root bark of Cassine transvaalensis a new peltogynoid,(+)-11,11-dimethyl-1,3,8,10-tetrahydroxy-9-methoxypeltogynan was obtained along with three pentacyclic triterpenes, canophyllol, canophyllal and 6β-hydroxy-lup-20(30)-en-3-one. The latter was fully characterized by X-ray analysis and high resolution NMR. The carbohydrate galactitol was also present in unusually high concentration.

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.

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.

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.

Bis- and, in particular, tetra-substituted ditertiary phosphine and diphosphazane derivatives of [Fe2(CO)9] and [Ru2(CO)9], readily synthesised by reaction of the appropriate bidentate ligand with [Fe2(CO)9] and [Ru3(CO)12], respectively, are very susceptible to electrophilic attack by reagents such as halogens and protons; the solid state structure of one of the products [Fe2(μ-Br)(CO)4 {μ-(PhO)2PN(Et)P(OPh)2}2]PF6 has been determined by X-ray crystallography.

Treatment of [M(η-C5H5)(CO)32] (M = Mo or W) with diiodine in ethanol at O°C in the presence of Na[B(C6H5)4] produces the iodine-bridged derivative [(M(η-C5H5)(CO)32(μ-I)] [B(C6H5)4] [IV-B(C6H5)4]. IV is an intermediate in the formation of [M(η-C5H5)(CO)3I] from [(M(η-C5H5)(CO)32] and I2 in dichloromethane as shown by monitoring with IR and, consistent with this, iodide attack on this bridged species gives [M(η-C5H5)(CO)3I]. IV is also susceptible to nucleophilic attack by neutral donors such as acetone, pyridine, P(C6H5)3 and P(OCH3)3. The reaction of the substituted derivatives [Mo(η-C5H5)(CO)2P(OCH3)32] with an equimolar amount of diiodine in ethanol in the presence of Na(B(C6H5)4] also affords a bridged iodo product, viz. [Mo(η-C5H5)(CO)2P(OCH3)3 2(μ-I)[B(C6H5)4] although if an excess of diiodine is employed the molybdenum (IV) species [Mo(η-C5H5)(CO)P(OCH3)3I3] is formed. Bromination and chlorination of [(M(η-C5H5)(CO)32] and [Mo(η-C5H5)(CO)2P(OCH3)32] always gives rise to molybdenum (IV) derivatives, [M(η-C5H5)(CO)2X3] or [Mo(η-C5H5)(CO)P(OCH3)3X3], as well as the molybdenum (II) products [M(η-C5H5)(CO)3X] or [Mo(η-C5H5)(CO)2 P(OCH3)3X] (X = Br or Cl), irrespective of the molar ratios employed. The tertiary phosphinemolybdenum (IV) compounds [Mo(η-C5H5)(CO)LX3] L = P(C2H5)3 or P(CH3)2C6H5, L ≠ P(C6H5)3; X = Cl Br or I are produced by treatment of the corresponding molybdenum (II) derivatives [Mo(η-C5H5)(CO)2LX] with the appropriate dihalogen. A mechanism for the halogenation of [(M(η-C5H5)(CO)2L2] (L = CO or P(OCH)3)3) is proposed.

The synthesis of [Mo(η-C 5 H 5 )(CO) 2 LI] (L = CO or P(OCH 3 ) 3 ) and [W(η-C 5 H 5 )(CO) 3 I] by iodination of [{Mo(η-C 5 H 5 )(CO) 2 L} 2 ] and [{W(η-C 5 H 5 )(CO) 5 } 2 ], respectively, is shown to proceed via iodide bridged intermediates, [{M(η-C 5 H 5 )(CO) 2 L} 2 I] + (M = Mo or W); treatment of [Mo(η-C 5 H 5 )(CO) 2 LX] {X = CI, Br or I; L =CO, P(C 2 H 5 ) 3 , P(CH 3 ) 2 C 6 H 5 or P(OCH 3 ) 3 ; L ≠ P(C 6 H 5 ) 3 } with excess halogen leads to the formation of the molybdenum(IV) derivatives, [Mo(η-C 5 H 5 )(CO)LX 3 ].

Reaction of [Fe 2 (CO) 9 ] with a half molar amount of R 2 PYPR 2 (Y = CH 2 , R = Ph, Me, OMe or OPr i ; Y = N(Et), R = OPh, OMe or OCH 2 ; Y = N(Me), R = OPr i or OEt) leads to the ready formation of a product which on irradiation with ultraviolet light rapidly decarbonylates to the heptacarbonyl derivative [Fe 2 (μ-CO)(CO) 6 {μ-R 2 PYPR 2 }]. Treatment of the latter with a slight excess of the appropriate ligand results, under photochemical conditions, in the formation of the dinuclear pentacarbonyl complex [Fe 2 (μ-CO)(C)) 4 {μ-R 2 PYPR 2 } 2 ] but under thermal conditions in the formation of the mononuclear species [Fe(CO) 3 {R 2 PYPR 2 }]. Reaction of [Ru 3 (CO) 12 ] with an equimolar amount of (RO) 2 PN(R′)P(OR) 2 (R′ = Me, R = Pr i or Et; R′ = Et, R = Ph or Me) under either thermal or photochemical conditions produces [Ru 3 (CO) 10 {μ-(RO) 2 PN(OR) 2 }] which reacts further with excess (RO) 2 PN(R′)P(OR) 2 on irradiation with ultraviolet light to afford the dinuclear compound [Ru 2 (μ-CO)(CO 4 {μ-(RO) 2 PN(R′)P(OR) 2 } 2 ]. The molecular structure of [Ru 2 (μ-CO)(CO) 4 {μ-(MeO) 2 PN(Et)P(OMe) 2 } 2 ], which has been determined by X-ray crystallography, is described.

Protonation of the dinuclear compounds [M 2 (μ-CO)(CO) 4 (μ-R 2 PYPR 2 ) 2 ] by HBF 4 or HPF 6 leads to the formation of crystalline cationic hydrido products [M 2 H(CO) 5 (μ-R 2 PYPR 2 ) 2 ]X and [M 2 (μ-H)(μ-CO)(CO) 4 (μ-R 2 PYPR 2 ) 2 ]X (X = BF 4 or PF 6 ) in which the hydride ligand is terminal for M = Ru, Y = N(Et) and R = OMe or OPr i and bridging for M = Fe, Y = CH 2 and R = Me or Ph, for M = Fe, Y = N(Et) and R = OMe, OEt, OPr i or OPh and for M = Ru, Y = CH 2 and R = Ph; the fluxional behaviour of [Ru 2 H(CO) 5 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] + (R = Me or Pr i ) in solution is described.

The reaction of [Ru3(CO)12] with an equimolar amount of PPhH2 under reflux leads not only to the formation of trinuclear products such as [Ru3(μ2-H)(μ2-PPhH)(CO)10] and [Ru3(μ2-H)2(μ3-PPh)(CO)9] but to pentanuclear [Ru4(μ4-PPh)2(μ2-CO)(CO)10] and to pentanuclear Ru5(μ4-PPh)(CO)15]; the X-ray crystal structure of (Ru4(μ4-PPh)2(μ2-CO)(CO)10] described.

The polymer [OsCl 2 (COD)] x ( 1 ; COD = cycloocta-1,5-diene; x > 2) and the appropriate hydrazine have been used to prepare the salts [OsCl(COD)(N 2 H 4 ) 3 ]BPh 4 ( 2 ), [Os(COD)(N 2 H 4 ) 4 ][BPh 4 ] 2 ( 3 ) and [OsCl(COD)(NH 2 NMe 2 ) 3 ]PF 6 ( 4 ). Treatment of 3 with t-butyl isocyanide produced mer -[Os(CNBu t ) 3 (N 2 H 4 ) 3 ][BPh 4 ] 2 ( 5 ) and trans -[Os(CNBu t ) 4 (N 2 H 4 ) 2 ][BPh 4 ] 2 ( 6 ) from refluxing ethanol and the hydrazone complex [Os(COD)(CNBu t ) 2 (NH 2 N:CMe 2 ) 2 ][BPh 4 ] 2 ( 7 ) from refluxing acetone. Reactions of 3 and L {L = CNxylyl, P(OMe) 3 , and P(OMe) 3 Ph; xylyl = 2,6-dimethylphenyl} in acetone gave trans -[Os(NH 2 N:CMe 2 ) 2 L 4 ][BPh 4 ] 2 ( 8 ). The crystal structure of [Os(COD)(CNBu t ) 2 (NH 2 N:CMe 2 ) 2 ][BPh 4 ] 2 ·(Acetone) 2 ( 7 ) has been determined from three-dimensional X-ray counter data and refined to a final R (on F ) of 0.090 based on 3014 reflections. The compound crystallizes in the monoclinic space group C 2/ c with four formula units in a cell of dimensions a 24.60(2), b 13.31(1), c 24.12(2) A and β 111.51(2)°. The cation has a crystallographically imposed C 2 symmetry, with octahedral coordination of the osmium atom, assuming that the COD ligand occupies two adjacent coordination sites. Coordination of the mutually trans hydrazone ligands to the osmium atom is through the amino-N atoms rather than through the less basic, more sterically hindered, imino-N atoms. relevant bond distances are: Os-N 2.19(2) (mean), Os-C(COD) 2.19(2) and 2.29(2), and Os-C(isocyanide) 1.93(2) (mean) A.

[Ru4(μ4-PPh)2(μ2-CO)(CO)10], in which an essentially square planar array of ruthenium atoms is capped by two phenylphosphinidene groups, readily and reversibly adds carbon monoxide to afford the tridecacarbonyl derivative [Ru4(μ3-PPh)2 (CO)13] ; crystal structure determinations on this compound and its arsenic analogue reveal that the CO addition is accompanied by a re arrangement of the cluster framework, and that these compounds can be considered as dirivatives of [Ru3(μ3-XPh)2(CO)9] (X  P or As) in which an Ru(CO)4 unit has been inserted into one of the three RuP or RuAs bonds.

Reaction of [Ru 2 (μ-CO)(CO) 4 {μ-(RO) 2 PN(Et)(OR) 2 } 2 ] (R = Me or Pr i ) with the protonic acids HCl, HBr, HNO 3 , H 2 BO 2 F, CF 3 COOH, PhSH/HPF 6 , and H 2 CO 3 /HPF 6 produces [Ru 2 A(CO) 5 {μ-(RO) 2 PN(Et)(OR) 2 } 2 ] + and/or [Ru 2 (μ-A)(CO) 4 {μ-(RO) 2 PN(Et)(OR) 2 } 2 ] + (A = Cl, Br, ON(O)O, OB(F)OH, OC(CF 3 )O, SPh, and OC(OH)O) via [Ru 2 H(CO) 5 {μ-(RO) 2 PN(Et)(OR) 2 } 2 ] + as intermediate; the structure of [Ru 2 {μ-OB(F)OH}(CO) 4 {-(Pr i O) 2 PN(Et)P(OPr i ) 2 }] + has been established X-ray crystallographically.

The diphosphazane ligand (CH 2 O) 2 PN(Et)P(OCH 2 ) 2 reacts readily with [Co 2 (CO) 8 ] to form the red-black complex [Co 2 (CO) 4 μ-(CH 2 O) 2 PN(Et)P(OCH 2 ) 2 2 ]. A single crystal X-ray diffraction study of this complex shows the two cobalt atoms linked by a metalmetal bond of length 2.635(2) A, and by two bridging diphosphazane ligands. Both cobalt atoms are five-coordinate with an identical set of ligands, comprising the other cobalt atom, two carbonyl groups and two phosphorus donor atoms. However, one cobalt atom has near trigonal-bipyramidal coordination while the other has highly distorted square-pyramidal coordination, the apical positions in both cases being occupied by phosphorus atoms. Significantly, the different coordination at each cobalt atom is achieved by the twisting of each diphosphazane ligand about the CoCo bond; the CoPPCo torsion angles are 29 and 40°. Indeed, in solution, rapid twisting of the diphosphazane ligands renders the phosphorus atoms equivalent on the NMR time scale, as evidenced by a single peak in the 31 P 1 H NMR spectrum of the molecule. The solution and solid state structures of the title compound are compared with those previously reported for teh closely-related complex [Co 2 (CO) 4 μ-(MeO) 2 PN(Et)P(OMe) 2 2 ].

Reaction of [Ru 3 (CO) 12 ] with an equimolar amount of PPh 2 H affords a range of products including an octaruthenium species [Ru 8 (μ 8 -P)(μ 2 -η 1 ,η 6 -CH 2 C 6 H 5 )(μ 2 -CO) 2 (CO) 17 ], in which, as established X-ray crystallographically, a phosphorus atom is encapsulated in a square anti-prism of ruthenium atoms and a benzyl group is coordinated to two of these rutheniums through all seven carbon atoms.

Reaction of [Ru 3 (CO) 12 ] with a two molar proportion of (RO) 2 PN(Et)P(OR) 2 (R = Me or Pr i ) in benzene under reflux affords a number of products including [Ru 3 (CO) 10 {μ-(RO) 2 PN(Et)P(OR) 2 }], [Ru 3 (CO) 9 {μ-(RO) 2 PN(Et)P(OR) 2 }{η 1 -(RO) 2 PN(Et)P(OR) 2 }] and, as the major species, the tetranuclear derivative [Ru 4 (μ 3 -η 2 -CO)(CO) 9 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]. An X-ray diffraction study of [Ru 4 (μ 3 -η 2 -CO)(CO) 9 {μ-(MeO) 2 PN(Et)P(OMe) 2 } 2 ] has revealed that the skeletal framework adopts a butterfly structure and that one of the carbonyl groups functions as a triply bridging four-electron donor ligand capping the two wing-tip and one of the hinge ruthenium atoms.

Reaction of [Ru3(CO)12] with a three-fold molar amount of PPhH2 in toluene under reflux affords a range of products including two hexaruthenium species, [Ru6(μ4-PPh)2(μ3-PPh)2(CO)12] and [Ru6(μ4-PPh)3(μ3-PPh)2(CO)12], established X-ray crystallographically to have distorted trigonal prismatic skeletal geometries.

Treatment of [M 2 (μ-CO)(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] (M  Fe or Ru; R  Me, Pr i or Ph) with halogens gives [M 2 X(CO) 5 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]X (X  Cl, Br or I) which can be readily decarbonylated to [M 2 (μ-X)(CO) 4 {μ-(RO) 2 -PN(Et)(OR) 2 } 2 ]X (M  Fe or Ru), [M 2 (μ-X)X(CO) 3 {μ-(RO) 2 PN(Et)-P(OR) 2 } 2 ] (M  Ru) and [M 2 (μ-X) 2 (CO) 2 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] (M  Ru) under appropriate reaction conditions; the structures of [Fe 2 I(CO) 5 {μ-(MeO) 2 PN(Et)P(OMe) 2 }]PF 6 and [Ru 2 (μ-I)I(CO) 3 {μ-(Pr i O) 2 PN(Et)P(OPr i ) 2 } 2 ] have been established X-ray crystallographically.

Dissolution of [Fe 2 (μ-CO)(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] (R = Me, Pr i or Ph) and [Ru 2 (μ-CO)(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ](R = Me or Pr i ) in CCl 4 leads to the rapid formation of [Fe 2 (μ-Cl)(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]Cl and [Ru 2 Cl 2 (CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ], respectively, with the latter isomerising in dichloromethane or chloroform solution to [Ru 2 (μ-Cl)(Cl(CO) 4 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]Cl, which in turn decarbonylates to [Ru 2 (μ-Cl)Cl(CO) 3 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]; the structure of [Ru 2 Cl 2 (CO) 4 {μ-(MeO) 2 PN(Et)P(OMe) 2 } 2 ] has been established X-ray crystallographically.

Cyclic voltammetric studies in acetone and benzonitrile show that the oxidation of [M2(η-CO)(CO)4(η-R2PYPR2)2] (M  Fe, Y  CH2, R  Ph or Me; M  Fe, Y  NEt, R  OMe, PRri or OEt; M  Ru, Y  NEt, R  OPri) generally proceeds via an EEC mechanism, whereas oxidation of [Ru2(η-CO)(CO)4 {η-(MeO)2PN(Et)-P(OMe)2}2] proceeds via an ECE mechanism, for which removal of the second electron is easier than the first, giving rise to an overall 2e-transfer reaction. In both mechanisms the chemical step involves solvent attack.

Treatment of [Ru4(μ4-PPh)2(μ2-CO)(CO)10] with NaBH4 leads to the formation of [Ru4(μ4-PPh)2(μ2-H)(μ2-CO)2(CO)8]− which readily adds protons and carbon monoxide to produce [Ru4(μ3-PPh)2(μ2-H)2(CO)12]; X-ray crystallographic studies have revealed that while the Ru4P2 framework adopts a closo octahedral geometry in [Ru4(μ4-PPh)2(μ2-H)(μ2-CO)2(CO)8]−, it adopts a closo trigonal prismatic one in [Ru4(μ3-PPh)2(μ2-H)2(CO)12]

Treatment of closo -[Ru 4 (μ 4 -PPh) 2 (μ 2 -CO)(CO) 10 ] with acetylene under ambient conditions leads to the insertion of the acetylene into the skeletal framework of the cluster and the formation of [Ru 4 (μ 4 -PPh){μ 4 -η 3 -P(Ph)CHCH}(μ 2 -CO)(CO) 10 ], the structure of which has been determined X-ray crystallographically.

The salts, [OsCl(cod)(NH2NR2)3]X (R = H, X = BPh4; R = Me, X = PF6) and [Os(cod)(NH2NH2)4](BPh4)2, formed from [OsCl2(cod)]x and hydrazines, can be converted into a range of hydrazine- and hydrazone-osmium(II) complexes with isocyanides and tertiary phosphorus ligands. The crystal structure of [Os(cod)(CNBut)2(NH2NCMe2)2](BPh4)2·(acetone)2 has been elucidated.

The ditertiary arsine cis -(CH 3 ) 2 AsC(CF 3 )C(CF 3 )As(CH 3 ) 2 reacts ith M 2 (CO) 10 to give compounds of formulae C 16 H 18 As 3 F 5 O 6 Mn 2 and C 11 H 8 AsF 6 O 5 Re. The former contains a fluorinated π-allyl group bonded to one Mn atom and the latter a CH 2 O fragment σ-bonded to rhenium