Synthesis and characterisation of ferrocene-containing β-diketonato complexes of rhodium(I) and rhodium(III)

The synthesis of new β-diketonato rhodium(I) complexes of the type [Rh(FcCOCHCOR)(CO)₂] and [Rh(FcCOCHCOR)(CO)(PPh₃)] with Fc=ferrocenyl and R=Fc, C₆H₅, CH₃ and CF₃ are described. ¹H, ¹³C and ³¹P NMR data showed that for each of the non-symmetric β-diketonato mono-carbonyl rhodium(I) complexes, two isomers exist in solution. The equilibrium constant, K_c, which relates these two isomers in an equilibrium reaction, are concentration independent but temperature and solvent dependent. Δ_rG, Δ_rH and Δ_rS values for this equilibrium have been determined and a linear relationship between solvent polarity on the Dimroth scale and K_c exists. The relationship between RhP bond lengths, d(RhP), and ³¹P NMR peak positions as well as coupling constants ¹J(³¹P¹⁰³Rh) has been quantified to allow calculation of approximate d(RhP) values. Variations in d(RhP) for [Rh(RCOCHCOR′)(CO)(PPh₃)] complexes have also been related to the group electronegativities (Gordy scale) of the terminal β-diketonato R groups trans to PPh₃. A measure of the electron density on the rhodium centre of [Rh(RCOCHCOR′)(CO)(PPh₃)] may be expressed in terms of the IR carbonyl stretching wave number, ν(CO), the sum of the group electronegativities of the R and R′ groups, (χ_R+χ_R′), or the observed pK_a^′ values of the free β-diketones RCOCH₂COR^′. An empirical relationship between ν(CO) and either pK_a^′ or (χ_R+χ_R′) has also been quantified.     

Organometallic nickel(II) complexes with dithiophosphate, dithiophosphonate and monothiophosphonate ligands

The hydroxo complex [NBu₄]₂[Ni₂(C₆F₅)₄(μ-OH)₂] reacts with ammonium O,O^′-dialkyldithiophosphates, O-alkyl-p-methoxyphenyldithiophosphonate acids and ammonium O-alkylferrocenyldithiophosphonates in dichloromethane under mild conditions to give, respectively, [NBu₄][Ni(C₆F₅)₂{S(S)P(OR)₂}] (R=Me (1), Et (2), ⁱPr (3)) and [NBu₄][Ni(C₆F₅)₂{S(S)P(OR)Ar}] (Ar=p-MeOC₆H₄, R=Me (4), Et (5), ⁱPr (6); Ar=ferrocenyl; R=Me (7), Et (8), ⁱPr (9)). The monothiophosphonate nickel complexes [NBu₄][Ni(C₆F₅)₂{S(S)P(OR)(ferrocenyl)}] (R=Et (10), ⁱPr (11)) are obtained by reaction of the hydroxo complex with O-alkylferrocenyldithiophosphonate acids. Analytical (C, H, N, S), conductivity, and spectroscopic (IR, ¹H, ¹⁹F and ³¹P NMR, and FAB-MS) data were used for structural assignments. A single-crystal X-ray diffraction study of [NBu₄][Ni(C₆F₅)₂{S(S)P(OMe)(p-MeOC₆H₄)}] (4) and [NBu₄][Ni(C₆F₅)₂{S(O)P(OEt)(ferrocenyl)}] (10) shows that in both cases the coordination around the nickel atom es essentially square planar with NiC₂S₂ and NiC₂SO central cores, respectively.     

1,2-Borotropic shifts and B-N bond cleavage reactions in molybdenum hydrotris(3-isopropylpyrazolyl)borate chemistry: Mixed-valence MoMo2 and pyrazole-rich oxo-Mo complexes

Red-black [Tp^iPr∗Mo^VO]₂(μ-O)(μ-Mo^VIO₄) (1, Tp^iPr∗ = hydrobis(3-isopropylpyrazolyl)(5-isopropylpyrazolyl)borate) has been isolated as a by-product in the synthesis of NEt₄[Tp^iPrMo(CO)₃] (Tp^iPr = hydrotris(3-isopropylpyrazolyl)borate) and characterized by spectroscopic and X-ray crystallographic techniques. The trinuclear, mixed-valence complex contains two distorted octahedral anti-Tp^iPr∗Mo^VO centers bridged by bent oxo (Mo-O-Mo av. 158.7°) and tetrahedral κO,κO′-molybdate ligands. The complex contains a six-membered, non-planar Mo₃(μ-O)₃ core and two 1,2-borotropically-shifted Tp^iPr∗ ligands (with the shifted pyrazolyl trans to Mo^V=O). Aerial decomposition of solid NEt₄[Tp^iPrMo(CO)₃] produces sky-blue, diamagnetic Tp^iPrMoO(ⁱPrpz)(ⁱPrpzH) (2, ⁱPrpz^- = 3-isopropylpyrazolate, ⁱPrpzH = 3-isopropyl-2H-pyrazole). Molecules of 2 feature a tridentate fac-Tp^iPr ligand and mutually cis terminal oxo (MoO = 1.665(2) Å) and monodentate ⁱPrpz⁻ and ⁱPrpzH ligands. The latter are formed by B-N bond cleavage of Tp^iPr. The complex can also be synthesized by reacting NEt₄[Tp^iPrMo(CO)₃] with excess 3-isopropylpyrazole and dioxygen at 100 °C. Cleavage of the B-N bond(s) of Tp^iPr was also observed in the formation of Tp^iPrMoO(SPh)(ⁱPrpzH) (3) as a by-product in the synthesis of Tp^iPrMoO₂(SPh). In the monohydrate, 3 exhibits a distorted octahedral geometry defined by a tridentate fac-Tp^iPr ligand and mutually cis terminal oxo (MoO = 1.676(3) Å) and monodentate SPh⁻ and ⁱPrpzH ligands. The pyrazole β-NH group is observed to participate in a hydrogen-bond to the lattice water molecule. The complex can be synthesized in high yield by reducing Tp^iPrMoO₂(SPh) by HSPh or PPh₃ in the presence of excess 3-isopropylpyrazole.     

Syntheses and crystal structures of the first iridium complexes with m- and p-terphenyl (tp). {[Ir2(p-tp)(cod)2](BF4)2 · 2CH2Cl2}3 and [Ir(m-tp)(η-C5Me5)](BF4)2

Novel two iridium terphenyl complexes were prepared and their structures were characterized crystallographically. The reaction of [Ir(cod)₂]BF₄ with p-terphenyl (p-tp) in CH₂Cl₂ was carried out to afford dinuclear Ir(I) complex {[Ir₂(p-tp)(cod)₂](BF₄)₂ · 2CH₂Cl₂}₃ (cod=1,5-cyclooctadiene) (1 · 2CH₂Cl₂), whereas the reaction of the intermediate [Ir(η⁵-C₅Me₅)(Me₂CO)₃]³⁺ in Me₂CO with m-terphenyl (m-tp) was done to provide mononuclear Ir(III) complex [Ir(m-tp)(η⁵-C₅Me₅)](BF₄)₂ (2). In complex 1 · 2CH₂Cl₂, two Ir atoms are η⁶-coordinated to both sides of terminal benzene rings from the upper and lower sides in the p-tp ligand, while one Ir atom is η⁶-coordinated to one side of the terminal benzene ring in the m-tp ligand in complex 2. Each crystal structure describes the first coordination mode found in metal complexes with the m- and p-tp ligands.     

Chloro and acetato complexes of platinum(II) with functionalized thioethers

The chloro complexes [PtCl₂(RSR′)₂] (1-10) (RSR′ = MeSCH₂C(O)OMe, 1; MeSCH₂C(O)OEt, 2; MeSCH₂C(O)Omenthyl(−), 3; MeSCH₂CH₂C(O)OMe, 4; , 5; EtSCH₂C(O)Me, 6; MeSCH(Me)C(O)Me, 7; MeSPh, 8; MeS-o-C₆H₄Me, 9; and MeS-o-C₆H₄Et, 10) are obtained in high yield (63-90%) by reaction of [PtCl₂(PhCN)₂] with the proper thioether in 1/2 molar ratio, in anhydrous chloroform, at reflux under argon for ca. 10 h. The X-ray crystal structure of [PtCl₂(MeS-o-C₆H₄Me)₂] (9) shows an almost regular trans square planar geometry (triclinic, space group , a 6.806(1), b 7.789(2), c 10.085(3) Å, α 101.80(2)°, β 69.55(2)°, γ 115.27(2)°, R(F_o) 0.023, ). The dichloro complexes react with silver acetate in a complex manner, which depends on the nature of the thioether, and only with RSR′ = MeSPh the simple diacetato complex [Pt(OAc)₂(RSR′)₂] is obtained as the major product.     

Main group derivatives of a cyclometallated iron carbonyl anion. Crystal structures of Fe(CO)2{P(OPh)3}{(PhO)2POC6H4}(SnPh3) and two isomers of Fe(CO)2{P(OPh)3}{(PhO)2POC6H4}(I)

The iron hydrido complex HFe(CO)₂{P(OPh)₃}{(PhO)₂POC₆H₄} (1), was rapidly deprotonated by DBU or [BzMe₃N][OH] in THF to afford the new carbonyl iron anion [Fe(CO)₂{P(OPh)₃}{(PhO)₂POC₆H₄}]⁻ ([2]⁻), containing an ortho-metallated triphenyl phosphite ligand. Complex [2]⁻ reacted with triorganostannyl and plumbyl salts and with halogens to give the octahedral Fe^II compounds Fe(CO)₂{P(OPh)₃}{(PhO)₂POC₆H₄}(X) (X=SnPh₃, 3; SnMe₃, 4; PbPh₃, 5; PbMe₃, 6; Cl, 7; Br, 8; I, 9). The Group 14 complexes 3-6 were obtained in one isomeric form in which the P^III-donor atoms are mutually cis, the carbonyl ligands are cis and the P(OPh)₃ and MR₃ (M=Sn, Pb; R=Ph, Me) groups are trans as determined by solution-state IR, ³¹P and ¹³C NMR spectroscopic data. This geometry was confirmed for 3 by a single crystal X-ray diffraction study. The halide complexes, however, were obtained as a mixture of isomers. The major isomer (7, X=Cl; 8a, X=Br; 9a, X=I) has cis P atoms, trans CO groups and the halide located trans to the phosphorus atom of the ortho-metallated phosphite ligand. The structure of 9a was confirmed by an X-ray diffraction study. Two other isomers, designated 8b (X=Br) and 9b (X=I), with cis P atoms and cis CO groups were isolated from the reactions of [2]⁻ with Br₂ and I₂, respectively. The structure of the latter was established by X-ray crystallography and is related to 9a by exchange of the P(OPh)₃ ligand and a carbonyl group such that the metal-bound C atom of the five-membered metallacycle is trans to CO. The stereo-geometry of 8b could not be unambiguously assigned from the spectroscopic data; however, two of the seven possible geometric isomers were suggested as plausible structures.     

Reactivity of platina-β-diketones towards chelating nitrogen and sulfur donors: formation of acyl(hydrido)platinum(IV) and acyl(chloro)platinum(II) complexes

The platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1) was found to react with chelating N,N-ligands 2(R^′NCR)C₅H₄N (R/R^′=Ph/OH, H/Ph, Me/Ph) to form acyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H){2-(R^′NCR)C₅H₄N}] (R/R^′=Ph/OH 2a; H/Ph 2b; Me/Ph (2c)). Reactions of complex 1 with chelating S,S- and N,S-donors (RS-CH₂-CH₂-SR, 2-(RSCH₂)C₅H₄N, R=Et, Ph, t-Bu) afforded acyl(chloro)platinum(II) complexes [Pt(COMe)Cl(RSCH₂CH₂SR)] (R=Et, 3a; Ph, 3b; t-Bu, 3c) and [Pt(COMe)Cl{2-(RSCH₂)C₅H₄N}] (R=Et, 4a; Ph, 4b; t-Bu, 4c), respectively. All complexes were fully characterized by microanalysis, IR and NMR (¹H, ¹³C) spectroscopy. Furthermore, molecular structures of complexes 3b and 4b were determined by single-crystal X-ray diffraction analyses revealing close to square-planar configuration. In complex 4b the acetyl ligand is trans to pyridine N atom (configuration index SP-4-2). The reactions are discussed in terms of consecutive oxidative addition and reductive elimination reactions.     

The mononuclear and dinuclear dimethoxyethane adducts of lanthanide trichlorides [LnCl3(DME)2]n, n=1 or 2, fundamental starting materials in lanthanide chemistry: preparation and structures

Some new dimethoxyethane (DME) adducts of lanthanide trichlorides of formula [LnCl₃(DME)₂]_n, n=1 or 2; (n=2, Ln=La, Ce, Pr, Nd; n=1, Ln=Eu, Tb, Ho, Tm, Lu) have been prepared by treating Ln₂O₃, or LnCl₃ · nH₂O, or Ln₂(CO₃)₃, in DME as medium, with thionyl chloride at room temperature, eventually in the presence of water in the case of Ln₂O₃ and Ln₂(CO₃)₃. The complexes from lanthanum to praseodymium included are chloro-bridged dimers. In the case of neodymium, the new results complement the literature data, showing that both the mononuclear and dinuclear species exist: neodymium can therefore be regarded as the turning element from dinuclear to mononuclear structures along the series. Only mononuclear complexes were isolated in the Eu-Lu sequence. The lanthanide contraction has been evaluated on the basis of the Ln-O and Ln-Cl bond distances on the isotypical series of the mononuclear complexes LnCl₃(DME)₂ covering a range of 12 atomic numbers.     

Triphos as a bidentate ligand: the reactivity of the dangling phosphorus in [PtMe2(triphos-P,P′)]

Complex [PtMe₂(triphos-P,P′)], (1) where the linear triphosphine triphos [=bis(diphenylphosphinoethyl)phenylphosphine] acts as a bidentate ligand, can be easily converted in a variety of new complexes due to the reactivity of the free phosphorus donor. The selective oxidation of the uncoordinated phosphorus gave [PtMe₂(triphosPO-P,P′)] whose X-ray crystal structure is here reported; from the reactions of 1 with platinum and non platinum precursors homotrimetallic [Pt₃Me₄XY(triphos)₂] (X=Y=Me, Cl, I, X=Me, Y=Cl) and heterotrimetallic ([Pt₂PdMe₄Cl₂(triphos)₂] and [Pt₂RhMe₄(cod)(triphos)₂]PF₆) complexes were obtained where triphos acts as a chelating/bridging ligand. When 1 was treated with triflic acid in the presence of a neutral electron donor L (L=SMe₂, pyridine, PPh₃), complexes [PtL(triphos)]²⁺ were rapidly recovered in high yields. The protonolysis of 1 in the presence of CO and methanol gave the new organometallic complex [Pt(COOMe)(triphos)]OTf.     

Synthesis and crystal structure of the low-spin iron(II) complex [Fe(bpz)3](ClO4)2 · H2O (bpz=2,2-bipyrazine)

The crystal structure of the title compound [Fe(bpz)₃](ClO₄)₂ · H₂O (bpz=2,2^′-bipyrazine) has been determined by a single crystal X-ray diffraction study at 293(2) K. The complex is monoclinic, P2₁/c, a=17.263(3), b=9.983(2), c=17.921(4) Å, β=107.94(3)°, V=2938.3(10) ų, Z=4, R=0.073 and R_w=0.118. The structure is made up of tris-chelated [Fe(bpz)₃]²⁺ cations, uncoordinated perchlorate anions and crystallization water molecules. The iron atom exhibits a FeN₆ distorted octahedral geometry with average Fe-N bond length and N-Fe-N bidentate angle of 1.962(5) Å and 81.6(2)°. The value of the Fe-N bond distance and that of the room temperature magnetic moment are in agreement with a singlet ¹A₁ ground state. The structure of 1 is compared to those of other tris-chelated iron(II) complexes with bidentate nitrogen heterocycles.     

Calix[4]arene supported group 5 imido complexes

The reaction of imidoyl chlorides [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and calix[4]arene methyl ether H₃Mecalix unexpectedly leads to the formation of the structurally characterized vanadium (IV) complex [VCl(Mecalix)] (4). Calix[4]arene methyl ether stabilized imido complexes of the type [V(NR)(Mecalix)] (R = Ph 7, Tol 8, tBu 9) were afforded from the reaction of [V(NR)Cl₃] (R = Ph 1, Tol 2, tBu 3) and the tris(lithium) or tris(sodium) salt of the calix[4]arene ether. The lithium salt [{Li₃(Mecalix)}₂] (5) is a dimer in the solid state, in which two monomeric trianions are bridged by lithium cations. Imido complexes [M(NR)(Mecalix)] (M = Nb: R = tBu, 12, R = Tol 13, R = Mes 14, R = Dipp 15; M = Ta: R = tBu 16, R = Tol 17) (Tol = 4-C₆H₄Me, Mes = 2,6-C₆H₃Me₂; Dipp = 2,6-C₆H₃iPr₂) have been prepared from structurally characterized [NbCl₂(Mecalix)] (10) and previously known [TaCl₂(Mecalix)] (11) via reaction with two equivalents of the appropriately metallated (Li, K) primary amine. The molecular structures of 13 and 15 confirm the mononuclear nature of these complexes.     

Isovalent and mixed-valent molybdenum complexes containing Mo(μ-E)(μ-S2)Mo (E = O, S) core units

The reactions of Tp^iPrMoO(SR)(NCMe) (Tp^iPr = hydrotris(3-isopropylpyrazolyl)borate) with propylene sulfide in toluene result in the formation of the diamagnetic, isovalent Mo(V) complex, [Tp^iPrMo^VO]₂(μ-S)(μ-S₂). This complex and its previously reported μ-oxo analog, [Tp^iPrMo^VO]₂(μ-O)(μ-S₂), react with cobaltocene to produce one-electron-reduced, mixed-valent complexes, [CoCp₂][{Tp^iPrMo^IV,VO}₂(μ-E)(μ-S₂)] (E = S or O, respectively). All complexes have been isolated and characterized by microanalysis, mass spectrometry, IR and ¹H NMR or EPR spectroscopies, and X-ray crystallography. Neutral [Tp^iPrMo^VO]₂(μ-S)(μ-S₂) exhibits a pseudo-C₂ symmetric structure, with distorted octahedral anti oxo-Mo(IV) centers coordinated by Tp^iPr and linked by μ-sulfido and μ-disulfido ligands. A similar structure is adopted by the anion in mixed-valent [CoCp₂][{Tp^iPrMo^IV,VO}₂(μ-S)(μ-S₂)]; this compound adopts a hexagonal, supramolecular structure with columns of tight ion-pairs with interactions, interconnected through weaker contacts to three neighboring columns. The structure contains large interstitial voids filled with lattice solvent molecules. EPR investigation of the mixed-valent complexes gave rise to unusually broad signals with no evident hyperfine splitting. The synthesis and characterization of a number of cis-dioxo-Mo(VI) precursors are also reported.     

Heteropolymetallic complexes containing 1,1′-diphenylphosphino-ferrocene

The paper explores the capability of [(dppf)Pt(H-nbu₂-DTO)]Cl (2) (dppf = 1,1′-diphenylphosphinoferrocene; H-nbu₂-DTO = di-nbutyl-dithioxamidate) to act as a starting module for heterometallic linear chains. Actually, the reaction of 2 with [RuCl₂(p-cymene)]₂ affords the heterotrimetallic complex [Cl(p-cymene) Ru(μ-nbu₂-DTO κ-N,N Ru κ-S,S Pt)Pt(dppf κ-P,P Pt) ]₂ (4). However 2, allowed to stand, provides a blue compound of formula [(dppf)Pt(H-nbu₂-DTO)]_nCl_n (3), the most reliable value of n being 6. The oxidation behavior of the new species 2-4 has also been investigated. In particular, the oxidation behavior of cyclic compound 3 is quite unusual, and suggests a large delocalization of the HOMO over the whole multicomponent molecule.     

Synthesis and characterization of iron and ruthenium complexes bearing P-N ligands based on 8-hydroxyquinoline

The synthesis of bidentate aminophosphine ligands (PN^quin) based on 8-hydroxyquinoline is described. These ligands react with cis-Fe(CO)₄Br₂ to give selectively octahedral complexes of the type cis,cis-Fe(PN^quin)(CO)₂Br₂. There is only one isomer formed where the two CO and the two bromide ligands adopt a cis configuration. The reaction of [RuCp(CH₃CN)₃]PF₆ with PN^quin ligands affords the halfsandwich complexes [RuCp(PN^quin)(CH₃CN)]PF₆ in high isolated yields. Likewise, treatment of [Ru(η⁶-p-cymene)(μ-Cl)Cl]₂ with PN^quin in the presence of AgCF₃SO₃ affords halfsandwich complexes of the type [Ru(η⁶-p-cymene)(PN^quin)Cl]CF₃SO₃. All ligands and complexes are characterized by NMR and IR spectroscopy. The X-ray structure of representative compounds is reported. In addition, the relative stability of isomeric structures and conformers of Fe(PN^quin-Ph)(CO)₂Br₂ is studied by means of DFT calculations.     

Curcuminoids as potential new iron-chelating agents: spectroscopic, polarographic and potentiometric study on their Fe(III) complexing ability

The pK_a values of curcumin and diacetylcurcumin are, here doubtless, determined by means of spectroscopic and potentiometric measurements, and the enolic proton is the more acidic one. The interaction of Fe³⁺ with curcumin and diacetylcurcumin, in water/methanol 1:1 solution, leads to the formation of the complex species [FeH₂CU(OH)₂] and [FeDCU(OH)₂] (H₂CU and DCU=curcumin or diacetylcurcumin monoanion, respectively) which prevails near pH 7. At more basic condition the prevailing species are [FeH₂CU(OH)₃]⁻ and [FeDCU(OH)₃]⁻, which prevent metal hydroxide precipitation. ¹H NMR data state that the dissociated β-diketo moiety of the ligands is involved in metal chelation. The pK_a value of the deprotonation reaction is strongly anticipated by the metal ion, as shown by UV spectral data. The stability constants, evaluated from potentiometric data, are near to that of desferrioxamine, which is, by now, the only iron-chelating agent for clinical use.     

Platinum allenylidene complexes and formation of platinum and palladium acetonitrile alkynyl complexes

The platinum(0) complex [Pt(PPh₃)₄] reacts with brominated propargylic amides and esters in benzene by oxidative addition to give trans-[Br(PPh₃)₂Pt-CC-C(O)R] complexes whereas no reaction occurs when halogenated solvents (CH₂Cl₂, CHCl₃) are used. The cis-ligands PPh₃ can be replaced by P(ⁱPr)₃ and the bromide by trifluoroacetate. O-Alkylation of those trans-[X(PR′₃)₂Pt-CC-C(O)R] complexes (X = Br, CF₃COO; R′ = Ph, ⁱPr) derived from propargylic amides with MeOTf or [Me₃O]BF₄ in CH₂Cl₂ gives the first cationic monoallenylidene complexes of platinum, trans-[X(PR′₃)₂PtCCC(OMe)NR₂]⁺Y⁻ (Y = OTf, BF₄). In contrast, trans-[Br(PPh₃)₂Pt-CC-C(O)OMenthyl] derived from a propargylic ester does not react with MeOTf in CH₂Cl₂. However, in acetonitrile instead of O-methylation the substitution of acetonitrile for the bromide ligand to yield the cationic acetonitrile alkynyl platinum complex trans-[MeCN(PPh₃)₂Pt-CC-C(O)OMenthyl]⁺OTf⁻ is observed. The related palladium complexes trans-[X(PR′₃)₂Pd-CC-C(O)OR] (X = Br, CF₃COO; R′ = Ph, ⁱPr, R = menthyl, Et) react with MeOTf or [Et₃O]BF₄ analogously affording trans-[MeCN(PR′₃)₂Pd-CC-C(O)OR]⁺Y⁻ (Y = OTf, BF₄).     

Synthesis and reactivity of five- and six-coordinate hydrido(vinyl) iridium(III) complexes

The reaction of the dihydrido iridium(III) precursor [IrH₂(Cl)(PiPr₃)₂] (5) with internal alkynes RCC(CO₂Me) (R = Me, CO₂Me) afforded the five-coordinate hydrido(vinyl) complexes [IrH(Cl){(E)-C(R)CH(CO₂Me)}(PiPr₃)₂] (6, 7), via insertion of the alkyne into one of the IrH bonds. Compounds 6 and 7 are also accessible by careful hydrogenation of the alkyne iridium(I) derivatives trans-[IrCl{RCC(CO₂Me)}(PiPr₃)₂] (9, 10), the latter being prepared from in situ generated trans-[IrCl(C₈H₁₄)(PiPr₃)₂] and RCC(CO₂Me). UV irradiation of 6 (R = CO₂Me) led to the formation of the isomer [IrH(Cl){κ²(C,O)-C(CO₂Me)CHC(OMe)O}(PiPr₃)₂] (3) having the vinyl ligand coordinated in a bidentate fashion. While 6 reacted with acetonitrile and CO to afford the six-coordinate iridium(III) compounds [IrH(Cl){(E)-C(CO₂Me)CH(CO₂Me)}(L′)(PiPr₃)₂] (11, 12), treatment of 6 with LiC₅H₅ gave the half-sandwich-type complex [(η⁵-C₅H₅)IrH{(E)-C(CO₂Me)CH(CO₂Me)}(PiPr₃)] (13) by, the loss of one PiPr₃. The reaction of 3 with CO under pressure resulted in the formation of [IrH(Cl){(Z)-C(CO₂Me)CH(CO₂Me)}(CO)(PiPr₃)₂] (14) in which, in contrast to the stereoisomer 12, the two CO₂Me substituents are trans disposed.     

Synthesis, crystal structure and solid state photoluminescence of [Pt(trpy)(CCPh)]SbF6 (trpy=2,2′:6′,2″-terpyridine)

The synthesis and characterisation of an orange polymorph of [Pt(trpy)(CCPh)]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) Å. The perpendicular distances between successive cation planes are constant along the stack at a value of 3.33 Å. 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)(CCPh)]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_z²(Pt)-d_z²(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.     

Synthesis and characterisation of pyrazolic palladium compounds containing alcohol functionality:: rotation around the Pd-N bond

The ligands 1-hydroxymethylpyrazole (hl¹), 1-(2-hydroxyethyl)pyrazole (hl²) and 1-(3-hydroxypropyl)pyrazole (hl³) react with [PdCl₂(CH₃CN)₂] to give trans-[PdCl₂(hl)₂] compounds. Due to a hindered rotation around the Pd-bond, these compounds present two different conformations in solution: anti and syn. The conformation presented depends on the relative disposition of the hydroxyalkylic chains of the two pyrazolic ligands. The present study was carried out on the basis of NMR experiments. The present paper reports the crystal structure of trans-[PdCl₂(hl²)₂]. The synthesis and characterisation of compounds [Pd(hl)₄](BF₄)₂ (hl = hl¹, hl² and hl³) starting from [Pd(CH₃CN)₄](BF₄)₂ and the corresponding chlorocomplexes trans-[PdCl₂(hl)₂] are also described.     

New palladacyclopentadiene complexes containing an N,P-donor setting. Crystal structure of [Pd{C4(COOMe)4}(o-Ph2PC6H4CHNPr)]

The synthesis of palladacyclopentadiene derivatives with the mixed-donor bidentate ligands o-Ph₂PC₆H₄CHNR (N^∧P) has been achieved. The new complexes of general formula [Pd{C₄(COOMe)₄}(o-Ph₂PC₆H₄CHNR)] [R=Me (1), Et (2), ⁱPr (3), ^tBu (4), NHMe (5)] have been prepared by reaction between the precursor [Pd{C₄(COOMe)₄}]_n and the corresponding iminophosphine. The polymer complex [Pd{C₄(COOMe)₄}]_n also reacts with pyridazine (C₄H₄N₂) to give the insoluble dinuclear complex [Pd{C₄(COOMe)₄}(μ-C₄H₄N₂)]₂ (6), which has been successfully employed as precursor in the synthesis of pyridazine-based palladacyclopentadiene complexes. The reaction of 6 with tertiary phosphines yielded complexes containing an N,P-donor setting of formula [Pd{C₄(COOMe)₄}(C₄H₄N₂)(L)] (L=PPh₃ (7), PPh₂Me (8), P(p-MeOC₆H₄)₃ (9), P(p-FC₆H₄)₃ (10)). The new complexes were characterized by partial elemental analyses and spectroscopic methods (IR, ¹H, ¹⁹F and ³¹P NMR). The molecular structure of complex 3 has been determined by a single-crystal diffraction study, showing that the iminophosphine acts as chelating ligand with coordination around the palladium atom slightly distorted from the square-planar geometry.