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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.

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...

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.

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.

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.

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.

[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.

The photochemical reactions of [Ru 3 (CO) 12 ] with the diphosphorus ligands Me 2 PCH 2 PME 2 , Ph 2 PCH 2 PPh 2 and Ph 2 PN(Et)PPh 2 have been found to give tri-, di- or mono-nuclear products, depending on the reaction conditions and the ligand involved. Products isolated include [Ru 3 (CO) 10 [μ-R 2 PYPR 2 ] (Y = CH 2 , R = Me or Ph; Y = N(Et), R = Ph), [Ru 3 (CO) 8 [μ-R 2 PYPR 2 ] 2 ] (Y = CH 2 , R = Me or Ph), [Ru 3 (CO) 6 [μ-R 2 PYPR 2 ] 3 ] (Y = CH 2 , R = Me or Ph), [Ru 2 (μ-CO)(CO) 4 [μ-Ph 2 PCH 2 PPh 2 ] 2 ] and [Ru(CO) 3 [Ph 2 PN(Et)PPh 2 ]. An X-ray crystallographic study has revealed that the diphosphazane ligand in [Ru 3 (CO) 10 [η-Ph 2 PN(Et)PPh 2 ] is coordinated equatorially and that the Ru-Ru edge which it bridges is ca. 0.06 A shorter than the average of the other two edges.

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 solid state structure of μ-ethylthio-μ′-carbonylbis(η-cyclopentadienylcarbonyliron) hexaflouroantimonate has been determined by a single crystal X-ray analysis. Crystals of this compound are monoclinic, space group c2/c with a = 18.111(6), b = 16.450(5), c = 13.292(4) A, β = 92.2(1)°, Z = 8. The determination was by Patterson and Fourier methods. A full matrix least-squares refinement resulted in a final R value of 0.044 for 1505 independent reflections. The two cyclopentadienyl groups are cis disposed with respect to the Fe—Fe vector while both the sulphur atom of the ethylthio group and the carbon atom of the bridging carbonyl group are equidistant from the two iron atoms. The latter are separated by a distance of 2.580(2) A corresponding to a two electron Fe—Fe bond. The solution IR and NMR data are consistent with the cation retaining its cis structure in solution.

The ditertiary phosphines (C6H5)2P(CH2)nP(C6H5)2 (n = 1 and 2), cis(C6H5)2PC2H2P(C6H5)2 and (C6H5)2PN(C2H5)P(C6H52 and the ditertiary arsines (C6H5)2As(CH2)nAs(C6H5)2 (n = 1 and 2) react with [Fe(CO)3SC6H5]2 to give a wide range of products, the nature of which depends on the reaction conditions and the ligand involved. Examples of the different types of comp isolated include, (i) Fe2(CO)5[(C6H5)2PCH2P(C6H5)2](SC6H5)2, in which the ligand acts as a monodentate, (ii) {[Fe(CO)2SC6H5]2[(C6H5)2PC2H4P(C6H5)2]}2, in which two [Fe(CO)2SC6H5]2 moieties are bridged by two diphosphine ligands, (iii) [Fe(CO)2SC6H5]2[(C6H5)2PN(C2H5)P(C6H5)2], in which the ligand bridges the two iron atoms, and (iv) Fe(CO)3(SC6H5)2Fe(CO)[(C6H5)2PC2H2P(C6H5)2], which contains the ligand chelated to a single iron atom. The tertiary phosphines PR3 (R=C2H5 and C6H5), phosphites P(OR′)3(R′ = CH3, C2H5, i-C3H7 and C6H5) and the stibine Sb(C6H5)3 bring about mono-, bis- or tris-substitution in [Fe(CO)3SC6H5]2 depending on the reaction conditions and the ligand involved. Whereas in solution [Fe(CO)2L(SC6H5)]2 [L = PR3 (R = C2H5 and C6H5), P(OC6H5)3 and Sb(C6H5)3] exist as a single isomer, [Fe(CO)2L′(SC6H5)]2 [L′=P(OR′)3 (R'=CH3, C2H5 and i-C3H7)] occur as a mixture of isomers.

The ligands L = P(OC 3 H 5 ) 3 , P(OC 3 H 5 ) 2 (C 6 H 5 ) and P(OC 3 H 5 )(C 6 H 5 ) 2 react with [π-C 5 H 5 Mo(CO) 3 ] 2 to yield ionic [π-C 5 H 5 Mo(CO) 2 L 2 ][π-C 5 H 5 Mo(CO) 3 ], neutral [π-C 5 H 5 Mo(CO) 2 L] 2 or neutral π-C 5 H 5 Mo(CO) 2 LL′ [L′ = P(O)(OC 3 H 5 ) 2 , P(O)(OC 3 H 5 )(C 6 H 5 ) or P(O)(C 6 H 5 ) 2 ] depending on the reaction conditions. The mechanism of the formation of π-C 5 H 5 Mo(CO) 2 LL′ via the ionic intermediate [π-C 5 H 5 Mo(CO) 2 L 2 ][π-C 5 H 5 Mo(CO) 3 ] is discussed.

The tertiary alkyl phosphites P(OR) 3 (R = CH 3 , C 2 H 5 , n-C 4 H 9 and C 3 H 5 ) react with π-C 5 H 5 Fe(CO) 2 Cl in benzene to give in addition to neutral π-C 5 H 5 Fe(CO)P(OR) 3 Cl and ionic [π-C 5 H 5 Fe(CO) 2 P(OR) 3 ]Cl complexes, neutral phosphonate derivatives of formula π-C 5 H 5 Fe(CO) 2 [P(O)(OR) 2 ] and π-C 5 H 5 Fe(CO)-[P(OR) 3 ][P(O)(OR) 2 ]. The corresponding reactions involving the tertiary phosphonite P(OC 3 H 5 ) 2 C 6 H 5 and the tertiary phosphinite P(OC 3 H 5 )(C 6 H 5 ) 2 yield similar type products. In contrast compounds of the type [π-C 5 H 5 Fe(CO)P(OR) 3 ]I are the sole products from the reactions of P(OR) 3 (R = CH 3 and C 2 H 5 ) with π-C 5 H 5 Fe(CO) 2 I. The formation of π-C 5 H 5 Fe(CO) 2 [P(O)(OR) 2 ] is shown to occur via [π-C 5 H 5 Fe(CO) 2 P(OR) 3 ]Cl as intermediate and to involve a Michaelis-Arbuzov rearrangement. The reactions of π-C 5 H 5 Fe(CO) 2 X (X = Cl and I) with the tertiary phosphines PR 3 (R = C 2 H 5 and C 4 H 9 ) are also described.

The ditertiary phosphine and arsine ligands L = (C6H5)2P(CH2)nP(C6H5)2 (n = 1,2,3), cis-(C6H5)2PC2H2P(C6H5)2, (C6H5)2PN(C2H5)P(C6H5)2 and (C6H5)2As(CH)2nAs(C6H5)2 (n = 1, 2) have been shown to react with tetracarbonyldi-π-cyclopentadienyldiiron in benzene when the solution is refluxed or irradiated with ultraviolet light at room temperature to afford derivatives of the type [π-C5H5Fe(CO)]2L. Analogous products are similarly obtained from the reactions of (C6H5)2-P(CH2)nP(C6H5)2 (n = 1, 2), cis-(C6H5)2PC2H2P(C6H5)2 and (C6H5)2PN(C2H5)P(C6H5)2 with [π-CH3C5H4Fe(CO)2]2. On the basis of infrared spectroscopic evidence it is shown that the two terminal carbonyl groups in [π-RC5H4Fe(CO)2]2(R = H, CH3) have been replaced by these donor ligands and a structure for the new products is proposed. The infrared and nuclear magnetic resonance spectra are discussed.

X-ray diffraction shows that [Rh 2 (CO) 3 {(PhO) 2 PN(Et)P(OPh) 2 } 2 ], synthesised by reduction of [{RhCl(CO)(PhO) 2 PN(Et)P(OPh) 2 } 2 ] with amalgamated zinc in the presence of carbon monoxide, has an unusual structure with one rhodium atom square planar and the other trigonal bipyramidal.

The structure of one isomer of [Rh 3 Fe{P(C 6 H 5 ) 2 } 3 (CO) 8 ], synthesised by treatment of [ {Rh(CO) 2 Cl} 2 ] with [Fe(CO) 4 {P(C 6 H 5 ) 2 H} ] in the presence of a base, has been determined by single crystal X-ray diffration. This species rearranges in solution to a second isomer whose structure has been elucidated by 31 P NMR spectral measurements. The reactions of these compounds with carbon monoxide are described.

The reaction of [{Rh(CO) 2 Cl} 2 ] with PPh 2 H in benzene in the presence of a base affords a green product [Rh 3 (μ-PPh 2 ) 3 (CO) 5 ], the structure of which has been determined by X-ray crystallography.

Reaction of [{Rh(μ-Cl)(CO)2}2] with PPh2H in CO-saturated ethanol yields [Rh3(μ-PPh2)3 (CO)6 (PPh2H)], a red trinuclear cluster of rhodium containing a near-planar six-membered Rh3P3 ring; this compound reversibly undergoes elimination of CO and PPh2H to afford [Rh3(μ-PPh2)3(CO)5].

[{Rh(CO)(MeO)2PNEtP(OMe)2Cl)}2], synthesised by reaction of [{Rh(CO)2Cl)}2] with (MeO)2PNEtP(OMe)2, has an unusual asymmetric structure in which one carbonyl group adopts a terminal position while the other is bridging; the two chlorines are both terminal.

In various metal carbonyl derivatives and platinum compounds. (RO)2PN(Et)P(OR)2 (R = Et or Ph) function as chelating bidentate ligands whereas (EtO)2POP(OEt)2 is monodentate or bridged bidentate.

The reaction of [Fe(π-C 5 H 5 )(CO) 2 ] 2 with the dialkyl disulphides R 2 S 2 (R = CH 3 , C 2 H 5 , t-C 4 H 9 or CH 2 C 6 H 5 ) affords, as well as dinuclear derivatives of the type [Fe(π-C 5 H 5 )(CO)SR] 2 , trinuclear species of formula [Fe 3 (π-C 5 H 5 ) 3 (CO) 2 (S)SR].