John S. Field

Luminescence properties of salts of the [Pt(4′Ph-terpy)Cl]+ chromophore: crystal structure of the red form of [Pt(4′Ph-terpy)Cl]BF4 (4′Ph-terpy = 4′-phenyl-2,2′∶6′,2″-terpyridine)

The complexes [Pt(4′Ph-terpy)Cl]A (4′Ph-terpyxa0=xa04′-phenyl-2,2′:6′,2″-terpyridine; Axa0=xa0SbF6, 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·xa0·xa0·Pt distances of ca. 3.3 A within a tetramer and a Pt·xa0·xa0·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 (MLCTxa0=xa0metal-to-ligand charge-transfer) and 3IL (ILxa0=xa0intraligand) 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 (MMLCTxa0=xa0metal–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·xa0·xa0·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.

Oxidation of diphosphazane-bridged derivatives of diruthenium nonacarbonyl by silver(I) salts in protic solvents: synthesis, structural characterization and protonation of the adduct [Ru2{µ-η2-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri) involving a novel mode of co-ordination of carbon dioxide

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.

Tri-, tetra-, penta-, and hexa-nuclear phenylphosphinidene-capped products from the reaction of dodecacarbonyltriruthenium with phenylphosphine: crystal structures of [Ru4(µ4-PPh)2(µ-CO)(CO)10], [Ru5(µ4-PPh){µ-PPh(OPrn)}(µ-H)(CO)13], [Ru6(µ4-PPh)2(µ3-PPh)2(CO)12], and [Ru6(µ4-PPh)3(µ3-PPh)2(CO)12]

The reaction of [Ru3(CO)12] with PPhH2 in toluene under reflux affords a range of products, the nature and yields of which are dependent on the reaction times and the molar ratios employed. Compounds isolated and characterised include not only the trinuclear derivatives [Ru3(µ-PPhH)(µ-H)(CO)10], [Ru3(µ3-PPh)(µ-H)2(CO)9], and [Ru3(µ3-PPh)2(CO)9] but the tetra-, and penta-, and hexanuclear species [Ru4(µ4-PPh)2(µ-CO)(CO)10], [Ru4(µ4-PPh)2(µ-PPhH)2(CO)8], [Ru5(µ4-PPh)(CO)15], [Ru6(µ-PPh)2(CO)n](n= 14 or 15), [Ru6(µ4-PPh)2(µ3-PPh)2(CO)12], and [Ru6(µ4-PPh)3(µ3-PPh)2(CO)12] as well as the pentanuclear by-product [Ru5(µ4-PPh){µ-PPh(OPrn)}(µ-H)(CO)13]. Crystal-structure determinations have revealed that [Ru4(µ4-PPh)2(µ-CO)(CO)10] contains an approximately square-planar array of ruthenium atoms capped on both sides by phenylphosphinidene ligands, that [Ru6(µ4-PPh)2(µ3-PPh)2(CO)12] and [Ru6(µ4-PPh)3(µ3-PPh)2(CO)12] have distorted trigonal-prismatic skeletal geometries, and that the ruthenium atom framework in [Ru5(µ4-PPh){µ-PPh(OPrn)}(µ-H)(CO)13] adopts a square-pyramidal configuration with the basal plane being capped by a phenylphosphinidene ligand and a basal edge being bridged by a phosphido group.

Ready deprotonation of the protic solvento species [Ru2(CO)5(R′OH){µ-(RO)2PN(Et)P(OR)2}2]2+(R = Me or Pri; R′= H, Me, Et, etc.) and the formation of [Ru2{µ-OC(O)}(CO)4{µ-(RO)2PN(Et)P(OR)2}2] containing carbon dioxide in a bridging co-ordination mode

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.

‘Inverse cryptate’ structure of an exceptionally stable dicopper(I) semiquinonoid intermediate

Dinuclear diphosphinecopper(I) complexes of the bis(chelating)‘S-frame’ ligand di-tert-butyl azodiformate exhibit a remarkable kinetic and thermodynamic stability of the deep blue o-semiquinonoid intermediate as evident from its facile formation, stability towards air and protic media, and from the electrochemical potential range. The comproportionation constant of [CuI2{µ-N2[CO(OBut)]2}{µ-Ph2P(CH2)6PPh2}2]+ was established at 1019·7. The crystal structure of the tetraphenylborate salt has been determined. It shows an ‘inverse cryptate’ structure; two bridging diphosphine ligands span the two bridgehead copper(I) centres which are fixed at 4.82 A apart by the bis(chelating) azodicarboxylate anion radical. In contrast to the neutral (reduced) form of the complex, the dicationic oxidised state could only be spectroelectrochemically.

Synthesis and reactivity of the unsaturated diruthenium diphosphazane-bridged species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri)

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.

Synthesis and reactivity of the formally unsaturated diruthenium diphosphazane-bridged species [Ru2(CO)4{µ-(RO)2PN(Et)P(OR)2}2](R = Me or Pri)

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.

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.

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 ue5fb Fe or Ru; R ue5fb Me, Pr i or Ph) with halogens gives [M 2 X(CO) 5 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ]X (X ue5fb 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 ue5fb Fe or Ru), [M 2 (μ-X)X(CO) 3 {μ-(RO) 2 PN(Et)-P(OR) 2 } 2 ] (M ue5fb Ru) and [M 2 (μ-X) 2 (CO) 2 {μ-(RO) 2 PN(Et)P(OR) 2 } 2 ] (M ue5fb 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.