Synthesis of [SnPh2(SR)2] SR = SC6F4-4-H, SC6F5: Reactivity towards group 10 transition metal complexes

The organometallic tin(IV) complexes [SnPh₂(SR^F)₂] SR^F = ⁻SC₆F₄-4-H (1), ⁻SC₆F₅ (2), were synthesized and their reactivity with [MCl₂(PPh₃)₂] M = Ni, Pd and Pt explored. Thus, transmetallation products were obtained affording polymeric [Ni(SR^F)(μ-SR^F)]_n, monomeric cis-[Pt(PPh₃)₂(SC₆F₄-4-H)₂] (3) and cis-[Pt(PPh₃)₂(SC₆F₅)₂] (4) and dimeric species [Pd(PPh₃)(SC₆F₄-4-H)(μ-SC₆F₄-4-H)]₂ (5) and [Pd(PPh₃)(SC₆F₅)(μ-SC₆F₅)]₂ (6) for Ni, Pt and Pd, respectively. The crystal structures of complexes 1, 2, 3, 4 and 6 were determined.     

Quantification of cis and trans influences in [PtX(PPh3)3] complexes. A P NMR study

In [PtX(PPh₃)₃]⁺ complexes (X = F, Cl, Br, I, AcO, NO₃, NO₂, H, Me) the mutual cis and trans influences of the PPh₃ groups can be considered constants in the first place, therefore the one bond Pt-P coupling constants of P_(cis) and P_(trans) reflect the cis and trans influences of X. The compounds [PtBr(PPh₃)₃](BF₄) (2), [PtI(PPh₃)₃](BF₄) (3), [Pt(AcO)(PPh₃)₃](BF₄) (4), [Pt(NO₃)(PPh₃)₃](BF₄) (5), and the two isomers [Pt(NO₂-O)(PPh₃)₃](BF₄) (6a) and [Pt(NO₂-N)(PPh₃)₃](BF₄) (6b) have been newly synthesised and the crystal structures of 2 and 4·CH₂Cl₂·0.25C₃H₆O have been determined. From the ¹J_PtP values of all compounds we have deduced the series: I > Br > Cl > NO₃ > ONO > F > AcO > NO₂ > H > Me (cis influence) and Me > H > NO₂ > AcO > I > ONO > Br > Cl > F > NO₃ (trans influence). These sequences are like those obtained for the (neutral) cis- and trans-[PtClX(PPh₃)₂] derivatives, showing that there is no dependence on the charge of the complexes. On the contrary, the weights of both influences, relative to those of X = Cl, were found to depend on the charge and nature of the complex.     

Comparative reactivity of triorganosilanes, HSi(OEt)3 and HSiEt3, with IrCl(CO)(PPh3)2. Formation of IrCl(H)2(CO)(PPh3)2 or Ir(H)2(SiEt3)(CO)(PPh3)2 depending on the substituents at Si

Reaction of HSi(OEt)₃ with IrCl(CO)(PPh₃)₂ (5:1 molar ratio) at room temperature for 1 h gives IrCl(H){Si(OEt)₃}(CO)(PPh₃)₂ (1), which is observed by the ¹H and ³¹P{¹H} NMR spectra of the reaction mixture. The same reaction, but in 20:1 molar ratio at 50 °C for 24 h produces IrCl(H)₂(CO)(PPh₃)₂ (2) rather than the expected product Ir(H)₂{Si(OEt)₃}(CO)(PPh₃)₂ (3) that was previously reported to be formed by this reaction. Accompanying formation of Si(OEt)₄, (EtO)₃SiOSi(OEt)₃, and (EtO)₂HSiOSi(OEt)₃ is observed. On the other hand, trialkylhydrosilane HSiEt₃ reacts with IrCl(CO)(PPh₃)₂ (10:1 molar ratio) at 80 °C for 84 h to give Ir(H)₂(SiEt₃)(CO)(PPh₃)₂ (4) in a high yield, accompanying with a release of ClSiEt₃.     

Synthesis and characterization of three group 10 complexes containing nido-carborane diphosphine: [MCl(PPh3){7,8-(PPh2)2-7,8-C2B9H10}] (M = Ni, Pd, Pt)

Three group 10 complexes containing nido-carborane diphosphine, [NiCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] (1), [PdCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 1.25CH₂Cl₂ (2) and [PtCl(PPh₃){7,8-(PPh₂)₂-7,8-C₂B₉H₁₀}] · 2.5CH₂Cl₂ (3) have been synthesized by the reactions of [M(PPh₃)₂Cl₂] (M = Ni, Pd, Pt) with closo carborane diphosphine 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ in ethanol. For complex 3, it could also be obtained under solvothermal condition. All three complexes were characterized by elemental analysis, FT-IR, ¹H and ¹³C NMR spectroscopy and X-ray structure determination. Single crystal structures show that their structures are similar to each other. In each complex, the nido [7,8-(PPh₂)₂-7,8-C₂B₉H₁₀]⁻, which resulted from the degradation of the initial closo ligand 1,2-(PPh₂)₂-1,2-C₂B₁₀H₁₀ during the reaction process, was coordinated bidentately through the P atoms to M(II) ion, and this resulted in a stable five-membered chelating ring between the bis-diphosphine ligand and the metal. The coordination mode of the metal can be described as a slightly distorted square-planar, in which the remaining two positions were occupied by one Cl⁻ and one PPh₃ group.     

Synthesis and structural characterization of dinuclear iridium hydrido complex with 3,6-bis(2-pyridyl)tetrazine, [Ir2(H)4(PPh3)4(bptz)](PF6)2 · 4CH2Cl2

Reaction of the precursor Ir complex [Ir(H)₂(PPh₃)₂(Me₂CO)₂]PF₆ with 3,6-bis(2-pyridyl)tetrazine (bptz) in CH₂Cl₂ gave a novel dinuclear Ir hydrido complex [Ir₂(H)₄(PPh₃)₄(bptz)](PF₆)₂ · 4CH₂Cl₂. Crystallographic study described an interesting coordination environment having a π-π interaction and ¹H NMR study showed unique upfield shifts of pyridyl rings that are likely induced by the ring current effect of neighboring PPh₃ ligands.     

Kinetics study of the substitution reaction of fac-[Fe(CN)2(CO)3I] with PPh3

Substitution reaction of fac-[Fe^II(CN)₂(CO)₃I]⁻ with triphenylphosphine (PPh₃) produced mono phosphine substituted complex cis-cis-[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻. Crystal structure of the product showed that carbonyl positioned trans- to iodide was replaced by PPh₃. The substitution reaction was monitored by quantitative infrared spectroscopic method, and the rate law for the substitution reaction was determined to be rate = k[[Fe^II(CN)₂(CO)₂(PPh₃)I]⁻][PPh₃]. Transition state enthalpy and entropy changes were obtained from Eyring equation k = (k_BT/h)exp(−ΔH^≠/RT + ΔS^≠/R) with ΔH^≠ = 119(4) kJ mol⁻¹ and ΔS^≠ = 102(10) J mol⁻¹ K⁻¹. Positive transition state entropy change suggests that the substitution reaction went through a dissociative pathway.     

Synthesis, characterization and catalytic evaluation in the Heck coupling reactions of S-P-S pincer complexes of the type [Pd{PhP(C6H4-2-S)2}(PAr3)]

A series of palladium complexes of the type [Pd(phPS₂)(PAr₃)] (phPS₂) = [PhP(C₆H₄-2-S)₂]²⁻ have been synthesized in good yields and their crystal structures determined. Heck coupling reactions were carried out using the [Pd(phPS₂)(PPh₃)] (1), [Pd(phPS₂){P(C₆H₄-4-Cl)₃}] (2), [Pd(phPS₂){P(C₆H₄-4-F)₃}] (3), [Pd(phPS₂){P(C₆H₄-4-CF₃)₃}] (4), [Pd(phPS₂){P(C₆H₄-4-Me)₃}] (5) and [Pd(phPS₂){P(C₆H₄-4-OMe)₃}] (6) complexes as catalyst precursors in order to examine the potential effect of the para-substituted triarylphosphines in the reaction of bromobenzene and styrene.     

Photocatalytical decomposition of hydrazine in K4[Mo(CN)8] solution: X-ray crystal structure of (PPh4)2[Mo(CN)4O(NH3)] · 2H2O

Ligand-field photolysis of K₄[Mo(CN)₈] · 2H₂O in 98% N₂H₄ · H₂O yields the catalytical decomposition of N₂H₄ into NH₃ and N₂. From irradiated solutions of octacyanomolybdate(IV) both in NH₃(aq) and 98% N₂H₄ · H₂O(l) as solvents, the salt of the formula (PPh₄)₂[Mo(CN)₄O(NH₃)] · 2H₂O was isolated. The salt is not formed by direct ligand replacement in tetracyanooxomolybdate(IV) ions derived from K₃Na[Mo(CN)₄O₂] · 6H₂O as the solute in similar conditions. The X-ray crystal structure and spectral properties of (PPh₄)₂[Mo(CN)₄O(NH₃)] · 2H₂O are described. The improved method of the synthesis of K₄[Mo(CN)₈] · 2H₂O is also presented.     

Reaction of [MCl2(CH3CN)2] (M = Pd(II), Pt(II)) compounds with N1-alkylpyridylpyrazole-derived ligands

Palladium(II) and platinum(II) complexes with N-alkylpyridylpyrazole-derived ligands, 2-(1-ethyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L¹) and 2-(1-octyl-5-phenyl-1H-pyrazol-3-yl)pyridine (L²), cis-[MCl₂(L)] (M = Pd(II), Pt(II)), have been synthesised. Treatment of [PdCl₂(L)] (L = L¹, L²) with excess of ligand (L¹, L²), pyridine (py) or triphenylphosphine (PPh₃) in the presence of AgBF₄ and NaBPh₄ produced the following complexes: [Pd(L)₂](BPh₄)₂, [Pd(L)(py)₂](BPh₄)₂ and [Pd(L)(PPh₃)₂](BPh₄)₂. All complexes have been characterised by elemental analyses, conductivity, IR and NMR spectroscopies. The crystal structures of cis-[PdCl₂(L²)] (2) and cis-[PtCl₂(L¹)] (3) were determined by a single crystal X-ray diffraction method. In both complexes, the metal atom is coordinated by one pyrazole nitrogen, one pyridine nitrogen and two chlorine atoms in a distorted square-planar geometry. In complex 3, π-π stacking between pairs of molecules is observed.     

Long-range superexchanged magnetic interaction observed in heterometallic complex: {[Fe(Tpms)(CN)3][Mn(H2O)2(DMF)2]} · DMF

A new tri-cyanometalate building block for heterometallic complexes, [PPh₄]₂[Fe^II(Tpms)(CN)₃] (2) (PPh₄ = tetraphenylphosphonium; Tpms = tris(pyrazolyl) methanesulfonate), has been prepared. Using it as a building block, a one-dimensional chain compound, {[Fe^II(Tpms)(CN)₃][Mn^II(H₂O)₂( DMF)₂]} · DMF (3), has been synthesized and structurally characterized. The magnetic properties of 3 correspond to a ferromagnetic chain with weak long-range superexchanged magnetic interaction between the high-spin manganese(II) ions.     

Half-sandwich ruthenium thiocarbonate complexes: Structures of CpRu(PPh3)2SCO2Bu, CpRu(dppe)SCO2Bu and CpRu(PPh3)(CO)SCO2Bu

Thiocarbonate ruthenium complexes of the form CpRu(L)(L′)SCO₂R (L = L′ = PPh₃ (1), 1/2 dppe (2), L = PPh₃, L′ = CO (3); R = Et (a), Buⁿ (b), C₆H₅ (c), 4-C₆H₄NO₂ (d)) have been synthesized by the reaction of the corresponding sulfhydryl complexes, CpRu(L)(L′)SH, with chloroformates, ROCOCl, at low temperature. The bis(triphenylphosphine) complexes 1 can be converted to 3 under CO atmosphere. The crystal structures of CpRu(PPh₃)₂SCO₂Buⁿ (1b), CpRu(dppe)SCO₂Buⁿ (2b), and CpRu(PPh₃)(CO)SCO₂Buⁿ (3b) are reported.     

Stereochemistry of the reaction products of the oxidative addition reaction of methyl iodide to [Rh((C4H3S)COCHCOR)(CO)(PPh3)]: A NMR and computational study. R = CF3, C6H5, C4H3S

A NMR study of the reaction mixture of the square planar [Rh((C₄H₃S)COCHCOR)(CO)(PPh₃)] complex and CH₃I, where R = CF₃, C₆H₅ or C₄H₃S, revealed that two types of alkyl and one (R = CF₃) or two (R = C₆H₅ or C₄H₃S) types of acyl species exist in the system. Two isomers of each species with an unsymmetrical β-diketonato ligand were observed. ¹H-¹H NOESY NMR unambiguously showed that the PPh₃ group is in the apical position in the more stable Rh^III-alkyl product. Theoretical computations of the equilibrium geometry of the possible reaction products, consistent with experimental observations, revealed that the first alkyl product results from trans addition to Rh^I and that the second thermodynamic alkyl product adopts an octahedral geometry with the PPh₃ group and the iodide above and below the square planar plane. Theoretical computations also revealed that the thermodynamic acyl product adopts a square-pyramidal geometry with the COCH₃ group in the apical position.     

Facile synthesis and reactivity study of mixed phosphane-isocyanide Pd(II) and Pd(0) complexes

The reaction between an equimolecular mixture of isocyanide CNR (CNR = di-methylphenyl isocyanide (DIC), tert-butyl isocyanide (TIC), triphenyl phosphane (PPh₃) and a dechlorinated solution of the palladium allyl dimers [Pd(η³-allyl)Cl]₂ (allyl = 2-Meallyl, 1,1-Me₂allyl) in stoichiometric ratio yields the mixed derivative [Pd(η³-allyl)(CNR)(PPh₃)] only. Apparently, the mixed derivative represents the most stable species among all the possible ones that might be formed under those experimental conditions. Theoretical calculations are in agreement with the experimental observation and the energy stabilization of the mixed species with respect to the homoleptic derivatives is traced back to an overall push-pull effect exerted by the isocyanide and the phosphane acting synergically. Similar behavior is observed in the case of the synthesis of the palladacyclopentadienyl complexes [Pd(C₄(COOMe)₄)(CNR)(PPh₃)] and of the palladium(0) olefin complexes whose synthesis invariably yields the mixed [Pd(η²-olefin)(CNR)(PPh₃)] derivatives. The paper includes studies on the reactivity toward allylamination in the case of the palladium(II) allyl complexes. A diffractometric investigation on the solid state structures of four different palladium isocyanide-phosphane complexes is also included.     

Time-resolved infrared study of reactive species produced by flash photolysis of the hydroformylation catalyst precursor Co2(CO)6(PMePh2)2

Flash photolysis with time-resolved infrared (TRIR) spectroscopy was used to elucidate the photochemical reactivity of the hydroformylation catalyst precursor Co₂(CO)₆(PMePh₂)₂. Depending on reaction conditions, the net products of photolysis varied significantly. A model is presented that accounts for the net reactivity with two initial photoproducts, the 17-electron species Co(CO)₃(PMePh₂) and the coordinatively unsaturated dimer Co₂(CO)₅(PMePh₂)₂. No evidence was found for photochemical formation of Co₂(CO)₆(PMePh₂). Time-resolved spectroscopic studies allowed for the direct observation of transient species and for kinetics studies of certain reactions; for example, the reactions of Co(CO)₃PMePh₂ with CO and with PMePh₂ gave the respective rate constants 1.5 × 10⁵ and 1.2 × 10⁷ M⁻¹ s⁻¹, while the analogous reactions with Co₂(CO)₅(PMePh₂)₂ gave the rate constants of 2.6 × 10⁶ M⁻¹ s⁻¹ and 3.9 × 10⁷ M⁻¹ s⁻¹.     

Syntheses and structures of the heterometallic clusters [(Ph3PAu)3Re(CO)4], [(Ph3PAu)4Re(CO)4], [(Ph3PAu)6AuRe2(CO)8], and [(Ph3PAu)6Re(CO)3]

The reaction of [HRe₃(CO)₁₂]²⁻ with an excess of Ph₃PAuCl in CH₂Cl₂ yields [(Ph₃PAu)₄Re(CO)₄]⁺ as the main product, which crystallizes as [(Ph₃PAu)₄Re(CO)₄]PF₆ · CH₂Cl₂ (1 · CH₂Cl₂) after the addition of KPF₆.The crystal structure determination reveals a trigonal bipyramidal Au₄Re cluster with the Re atom in equatorial position.If [(Ph₃PAu)₄Re(CO)₄]⁺ is reacted with PPh₄Cl, a cation [Ph₃PAu]⁺ is eliminated as Ph₃PAuCl, and the neutral cluster [(Ph₃PAu)₃Re(CO)₄] (2) is formed.It combines with excess [(Ph₃PAu)₄Re(CO)₄]⁺ to afford the cluster cation, [(Ph₃PAu)₆AuRe₂(CO)₈]⁺. It crystallizes from CH₂Cl₂ as[(Ph₃PAu)₆AuRe₂(CO)₈]PF₆ · 4CH₂Cl₂ (3 · 4CH₂Cl₂). In [(Ph₃PAu)₃Re(CO)₄] the metal atoms are arranged in form of a lozenge while in [(Ph₃PAu)₆AuRe₂(CO)₈]⁺ two Au₄Re trigonal bipyramids are connected by a common axial Au atom.The treatment of [(Ph₃PAu)₄Re(CO)₄]⁺ with KOH and Ph₃PAuCl in methanol yields the cluster cation [(Ph₃PAu)₆Re(CO)₃]⁺, which crystallizes with from CH₂Cl₂ as [(Ph₃PAu)₆Re(CO)₃]PF₆ · CH₂Cl₂ (4 · CH₂Cl₂). The metal atoms in this cluster form a pentagonal bipyramid with the Re atom in the axial position.     

Synthesis and characterisation of palladium(II) iodo complexes containing water soluble phosphine ligands. Crystal structures of [PdI2(PTA-H)2][PtI3(PTA)]2 · 2H2O and trans-[PdI2(PTA)2]

The aqueous solution behaviour of the equilibrium related cis-[PdCl₂(PTA)₂] and [PdCl(PTA)₃]Cl complexes has been investigated in the presence of acid and iodide ions. Several of the resulting species were identified and a reaction scheme accounting for identified complexes is proposed. The crystal structures of trans-[PdI₂(PTA-H)₂][PdI₃(PTA)]₂ · 2H₂O (1) (PTA-H⁺ = protonated form of PTA) and trans-[PdI₂(PTA)₂] (2) are reported. The geometry around the Pd(II) metal centre in 1 (for both the cation and anion) and 2 is distorted square planar. The PTA ligands occupy a trans orientation in the cation of 1 and in complex 2. Compound 1 represents a rare example of a Pd(II) system wherein the cation:anion pair, in a 1:2 ratio, are both coordination complexes. It is the first d⁸ Ni-triad square planar complex containing only one PTA ligand and only the second platinum group metal complex. For the cation in 1, the bond distances and angles are Pd(1)-P(1) = 2.2864(16) Å, Pd(1)-I(1) = 2.6216(7) Å, P(1)-Pd(1)-P(1)′ = 180.00(7)° and P(1)-Pd(1)-I(1) = 87.62(4)°, while in the anion the bond distances are Pd(2)-P(2) = 2.2377(15) Å, Pd(2)-I(4) = 2.5961(13) Å, Pd(2)-I(2) = 2.6328(13) Å, Pd(2)-I(3) = 2.6513(8) Å, while the angles are P(2)-Pd(2)-I(4) = 90.00(5)°, P(2)-Pd(2)-I(2) = 89.69(5)°, I(4)-Pd(2)-I(2) = 179.57(2)°, P(2)-Pd(2)-I(3) = 175.19(4)°, I(4)-Pd(2)-I(3) = 90.29(4)° and I(2)-Pd(2)-I(3) = 90.05(4)°. Bond distances and angles of the coordination polyhedron in 2 are Pd-P = 2.327(3) Å, Pd-I = 2.5916(10) Å, P-Pd-I = 89.13(7)° and P-Pd-P = 180.00(13)°. The average effective- and Tolman cone angles for the two ligands, calculated from the crystallographic data, are 115° and 117° for PTA and PTA-H, respectively.     

Synthesis and characterization of complexes of the type [Pt(amine)4]I2 and trans-[Pt(CH3NH2)2(H3CNC(CH3)2)2]I2 by crystallography and multinuclear magnetic resonance spectroscopy

Complexes of the type [Pt(amine)₄]I₂ were synthesized and characterized mainly by multinuclear (¹⁹⁵Pt, ¹H and ¹³C) magnetic resonance spectroscopy. The compounds were prepared with different primary amines, but not with bulky amines, due to steric hindrance. In ¹⁹⁵Pt NMR, the signals were observed between −2715 and −2769 ppm in D₂O. The coupling constant ³J(¹⁹⁵Pt-¹H) for the MeNH₂ complex is 42 Hz. In ¹³C NMR, the average values of the coupling constants ²J(¹⁹⁵Pt-¹³C) and ³J(¹⁹⁵Pt-¹³C) are 18 and 30 Hz, respectively. The crystal structure of [Pt(EtNH₂)₄]I₂ was determined by X-ray diffraction methods. The Pt atom is located on an inversion center. The structure is stabilized by H-bonding between the amines and the iodide ions. The compound with n-BuNH₂ was found by crystallographic methods to be [Pt(n-BuNH₂)₄]₂I₃(n-BuNHCOO). The crystal contains two independent [Pt(CH₃NH₂)₄]²⁺ cations, three iodide ions and a carbamate ion formed from the reaction of butylamine with CO₂ from the air. When the compound [Pt(CH₃NH₂)₄]I₂ was dissolved in acetone, crystals identified as trans-[Pt(CH₃NH₂)₂(H₃CNC(CH₃)₂)₂]I₂ were isolated and characterized by crystallographic methods. Two trans bonded MeNH₂ ligands had reacted with acetone to produce the two N-bonded Schiff base Pt(II) compound.     

New aryl phosphinite ligands avoiding ortho-metallation: Synthesis and molecular structures of trans-[PdCl2(PPh2OR)2] and trans-[Rh(CO)Cl(PPh2OR)2] (R = 2,4,6-Me3C6H2; 2,6-Ph2C6H3)

The new aryl phosphinites PPh₂OR (R = 2,4,6-Me₃C₆H₂, 1; R = 2,6-Ph₂C₆H₃, 2) have been prepared from chlorodiphenylphosphine and the corresponding phenols. In these ligands, the ortho-positions of the aromatic phosphite function are blocked by methyl and phenyl substituents, which allows coordination to metal centres without ortho-metallation. Thus, reaction with [PdCl₂(cod)] leads to the complexes trans-[PdCl₂(PPh₂OR)₂] (R = 2,4,6-Me₃C₆H₂, 3; R = 2,6-Ph₂C₆H₃, 4), while the reaction with [Rh₂(CO)₄Cl₂] gives trans-[Rh(CO)Cl(PPh₂OR)₂] (R = 2,4,6-Me₃C₆H₂, 5; R = 2,6-Ph₂C₆H₃, 6). The single-crystal X-ray structure analyses of 3 and 5 confirm the trans-coordination of the new ligands in these square-planar complexes.     

Coordination chemistry of the metalloligand [Pt2(μ-S)2(PPh3)4] with nickel(II) complexes - an electrospray mass spectrometry directed synthetic study

The reactivity of [Pt₂(μ-S)₂(PPh₃)₄] towards a range of nickel(II) complexes has been probed using electrospray ionisation mass spectrometry coupled with synthesis and characterisation in selected systems. Reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [Ni(NCS)₂(PPh₃)₂] gives [Pt₂(μ-S)₂(PPh₃)₄Ni(NCS)(PPh₃)]⁺, isolated as its BPh₄ ⁻ salt; the same product is obtained in the reaction of [Pt₂(μ-S)₂(PPh₃)₄] with [NiBr₂(PPh₃)₂] and KNCS. An X-ray structure determination reveals the expected sulfide-bridged structure, with an N-bonded thiocyanate ligand and a square-planar coordination geometry about nickel. A range of nickel(II) complexes NiL₂, containing β-diketonate, 8-hydroxyquinolinate, or salicylaldehyde oximate ligands react similarly, giving [Pt₂(μ-S)₂(PPh₃)₄NiL]⁺ cations.     

Synthesis and characterization of Pd(II) and Pt(II) complexes with triazolopyrimidine derivatives: The crystal structure of [Pd2L2Cl4] where L = 5,7-dimethyl-1,2,4-triazolo[1,5-a]pyrimidine

The Pd(II) and Pt(II) complexes with triazolopyrimidine C-nucleosides L¹ (5,7-dimethyl-3-(2′,3′,5′-tri-O-benzoyl-β-d-ribofuranosyl-s-triazolo)[4,3-a]pyrimidine), L² (5,7-dimethyl-3-β-d-ribofuranosyl-s-triazolo[4,3-a]pyrimidine) and L³ (5,7-dimethyl[1,5-a]-s-triazolopyrimidine), [Pd(en)(L¹)](NO₃)₂, [Pd(bpy)(L¹)](NO₃)₂, cis-Pd(L³)₂Cl₂, [Pd₂(L³)₂Cl₄] · H₂O, cis-Pd(L²)₂Cl₂ and [Pt₃(L¹)₂Cl₆] were synthesized and characterized by elemental analysis and NMR spectroscopy. The structure of the [Pd₂(L³)₂Cl₄] · H₂O complex was established by X-ray crystallography. The two L³ ligands are found in a head to tail orientation, with a Pd?Pd distance of 3.1254(17) Å. L¹ coordinates to Pd(II) through N8 and N1 forming polymeric structures. L² coordinates to Pd(II) through N8 in acidic solutions (0.1 M HCl) forming complexes of cis-geometry. The Pd(II) coordination to L² does not affect the sugar conformation probably due to the high stability of the C-C glycoside bond.