Clifford N. Sampson

Stabilisation of [Fe2(CO)9] and [Ru2(CO)9] bu substitution with bridging diphosphorus ligands

Abstract 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.

Substituted derivatives of [Fe2(CO)9] and [Ru2(CO)9] and their susceptibility to electrophilic attack: X-ray crystal structure of [Fe2(μ-Br)(CO)4{μ-(C6H5O)2PN(C2H5)P(OC6H5)2}2]PF6

Abstract 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.

Electrophilic attack on a series of dinuclear diphosphazane-bridged derivatives of iron by halogens. X-Ray crystal structures of [Fe2I(CO)5{µ-(MeO)2PN(Et)P(OMe)2}2]PF and [Fe2(µ-Br)(CO)4{µ-(PhO)2PN(Et)-P(OPh)2}2]PF6

Treatment of [Fe2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = CH2, Me, Pri, or Ph) with halogens results in the formation of [Fe2X(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+(X = Cl, Br, or I) which, on the basis of the structure established X-ray crystallographically for [Fe2l(CO)5{µ-(MeO)2PN(Et)P(OMe)2}2] PF6(A), contains an axially co-ordinated halogen. The iron atoms in these compounds are not only bridged by the two diphosphazane ligands but are also linked through a direct iron–iron bond [Fe–Fe = 2.787(3)A in (A)]. Compound (A), and presumably the others, adopts a staggered conformation but the extent of twisting about the iron–iron bond is small as reflected by the P(1)–Fe(1)–Fe(2)–P(2) torsion angle of 28.8°. These pentacarbonyl derivatives readily decarbonylate in solution to produce the halogeno-bridged species [Fe2(µ-X)(CO)4{µ-(RO)2PN(Et)-P(OR)2}2]+. On the basis of a single-crystal X-ray diffraction study on [Fe2(µ-Br)(CO)4{µ-(PhO)2-PN(Et)P(OPh)2)2]PF6(B), these tetracarbonyl compounds, in contrast to the pentacarbonyl species, adopt an eclipsed configuration with the plane containing the two iron and four phosphorus atoms being orthogonal to a plane containing the two iron atoms, the bridging halogen, and the four terminal carbonyl groups. Although these tetracarbonyl compounds do not add halide ions to produce [Fe2X2(CO)4{µ-(RO)2PN(Et)P(OR)2}]2 the tetramethoxydiphosphazane species [Fe2X(CO)5{µ-(MeO)2PN(Et)P(OMe)2}2]+ and [Fe2(µ-X)(CO)4{µ-(MeO)2PN(Et)-P(OMe)2}2]+ are very susceptible to halide ion attack affording the Michaelis–Arbuzov type rearrangement products [Fe2X{µ-(MeO)2PN(Et)P(O)(OMe)}(CO)5(µ-(MeO)2PN(Et)P(OMe)2}] and [Fe2(µ-X){µ-(MeO)2PN(Et)P(O)(OMe)}(CO)4{µ-(MeO)2PN(Et)P(OMe)2}] respectively. The reactions with other halogenation agents such as N-chloro- and N-bromo-succinimide, and mixed halogens (ICI) are also reported and a general mechanism for the halogenation of compounds of the type [Fe2(µ-CO)(CO)4{µ-(RO)2PYP(OR)2}2][R = alkyl or aryl group; Y = CH, or N(Et)] is proposed.

Protonation of a series of diphosphazane- and diphosphine-bridged derivatives of iron and ruthenium: dependence of the nature of the hydride ligand on the metal and the bridging diphosphorus ligand

Abstract 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.

Halogenation and stepwise decarbonylation of diphosphazane-bridged derivatives of iron and ruthenium nonacarbonyl. Crystal structures of [Fe2I(CO)5{μ-(MeO)2PN(Et)P(OMe)2}2][PF6] and [Ru2(μ-I)I(CO)3{μ-(PriO)2PN(Et)P(OPri)2}2]

Abstract 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.

Electrophilic attack on diphosphazane-bridged derivatives of diruthenium nonacarbonyl by halogens. Crystal structure of [Ru2(µ-I)I(CO)3{µ-(PriO)2PN(Et)P(OPri)2}2]

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.

Contrasting halogenating action of halogenoalkanes and halogens towards diphosphazane-bridged derivatives of iron and ruthenium nonacarbonyl. Crystal structure of [Ru2Cl2(CO)4{μ-(MeO)2PN(Et)P(OMe)2}2]

Abstract 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.

Kinetics of reactions of hydrogen with [Os3(CO)11(NCMe)] and [Os3(CO)10(NCMe)2]

The kinetics of reactions of [Os3(CO)11(NCMe)] with H2 and CO, and of [Os3(CO)10(NCMe)2] with H2, have been studied in the presence of free MeCN. The reactions involve slow dissociation of MeCN from the clusters and subsequent competition between MeCN and H2 or CO for the vacant co-ordination site on the intermediate cluster. Rate constants for nucleophilic attack on [Os3(CO)11] are in the order MeCN > PPh3≈ CO > H2 and temperature-dependence studies provide activation enthalpy and entropy differences. These, together with a value of 1.34 ± 0.03 for the deuterium kinetic isotope effect, are consistent with a simple three-centre transition state for reaction of [Os3(CO)11] with H2. The cluster [Os3H2(CO)10] reacts with MeCN to form [Os3H2(CO)10(NCMe)] and equilibrium data for this reaction have been obtained.

The formal umpolung behaviour of protonic acids containing coordinating anions towards diphosphazane-bridged derivatives of nonacarbonyldiruthenium

Abstract 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.

Protonation of diphosphazane ligand-bridged derivatives of diruthenium nonacarbonyl by protic acids with co-ordinating and non-co-ordinating conjugate bases

Protonation of the diphosphazane ligand-bridged derivatives [Ru2(µ-CO)(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) by HBF4 or HPF6 leads to the formation of the cationic hydrido products [Ru2H(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+ in which the hydride ligand is co-ordinated terminally. On the other hand protonation of these species with strong protic acids HA having conjugate bases A– with co-ordinating properties [A–= Cl–, Br–, NO3–, FB(O)OH– or CF3CO2–] gives rise to products of the type [Ru2A(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+ and/or [Ru2(µ-A)(CO)4{µ-(RO)2PN(Et)P(OR)2}2]+. Weak acids HA (A–= SPh– or HCO3–) also afford these types of products but the presence of a strong acid such as HPF6 is necessary. The structures of two of the products [Ru2{µ-OB(F)OH}(CO)4{µ-(PriO)2PN(Et)P(OPri)2}2]BF4 and [Ru2(µ-SPh)(CO)4{µ-(MeO)2PN(Et)P(OMe)2}2]PF6 have been established by X-ray crystallography and are discussed as is the fluxional behaviour of the hydrido species [Ru2H(CO)5{µ-(RO)2PN(Et)P(OR)2}2]+.