Different coordination modes of the dimethyldisulfide ligand in trimethylplatinum(IV) complexes

The reaction of [PtMe₃(bpy)(Me₂CO)](BF₄) (2) (prepared from [PtMe₃I(bpy)] (1) plus Ag(BF₄)) with MeSSMe resulted in the formation of [PtMe₃(bpy)(MeSSMe-κS)](BF₄) (3). A single-crystal X-ray diffraction analysis revealed in the octahedral Pt(IV) complex (configuration index: OC-6-33), a conformation of the monodentately κS bound MeSSMe ligand (C–S–S–C 92.7(4)°) being very close to that in non-coordinated MeSSMe, thus allowing some hyperconjugative interaction stabilizing the S–S bond. The reaction of [K(18C6)][(PtMe₃)₂(μ-I)(μ-pz)₂] (4; 18C6 = 18-crown-6, Hpz = pyrazole) with Ag(BF₄) and MeSSMe resulted in the formation of dinuclear complexes [(PtMe₃)₂(μ-pz)₂(μ-MeSSMe)] existing at room temperature in acetone solution as different fast interconverting isomers. At –40 °C, two isomers with a μ-1κS:2κS (5a) and a μ-1κS:2κS′ (5b) coordinated MeSSMe ligand in the ratio 2:1 could be identified ¹H NMR spectroscopically. DFT calculations of type 5 complexes revealed the existence of two conformers with a μ-MeSSMe-1κS:2κS ligand, which differ mainly in the C–S–S–C dihedral angle (66.4 vs. 180.0° 6a/6a′). They have essentially the same energy and a very low activation barrier in acetone as solvent (1.3 kcal/mol) for their mutual interconversion. A further equilibrium structure was identified to be an isomer having a μ-MeSSMe-1κS:2κS′ ligand (6b) that proved to be only 1.9 kcal/mol higher in energy than 6a/6a′.     

Reactivity of diacetylplatinum(II) complexes: Oxidative addition of halogens and hydrogen halides

Diacetylplatinum(II) complexes [Pt(COMe)₂()] ( = bpy, 3a; 4,4′-t-Bu₂-bpy, 3b), obtained by the reaction of [Pt(COMe)₂X(H)()] with NaOH in CH₂Cl₂/H₂O, were found to undergo oxidative addition reactions with halogens (Br₂, I₂) yielding the platinum(IV) complexes (trans, OC-6-13)/(cis, OC-6-32) [Pt(COMe)₂X₂()] ( = bpy, X = Br, 4a/4b; I, 4c/4d;  = 4,4′-t-Bu₂-bpy, X = Br, 4e/4f; I, 4g/4h). The diastereoselectivity of the reactions proved to be strongly dependent on the solvent. The oxidative addition of (SCN)₂ resulted in the formation of (OC-6-13)-[Pt(COMe)₂(SCN)₂()] ( = bpy, 4i; 4,4′-t-Bu₂-bpy, 4j). In a reaction the reverse of their formation, the diacetylplatinum(II) complexes 3 underwent oxidative addition with anhydrous HX (X = Cl, Br, I), prepared in situ from Me₃SiX/H₂O, yielding diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)₂X(H)()] ( = bpy, X = Cl, 5a; Br, 5b; I, 5c;  = 4,4′-t-Bu₂-bpy, X = Cl, 5d; Br, 5e; I, 5f). Furthermore, diacetyldihaloplatinum complexes 4 were found to undergo reductive elimination reactions in boiling methanol yielding acetylplatinum(II) complexes [Pt(COMe)X()] ( = bpy, X = Br, 6b; I, 6c;  = 4,4′-t-Bu₂-bpy, X = Br, 6e; I, 6f). All complexes were characterized by microanalysis, IR and ¹H and ¹³C NMR spectroscopy. Additionally, the bis(thiocyanato) complex 4j was characterized by single-crystal X-ray diffraction analysis.     

Insertion of tin(II) bromide into Pt–X (X = Cl,Br) bond of dimethylplatinum(IV) complexes: A novel polymorphic form of [PtBr2(bpy)]

The platinum(II) complex [PtMe₂(bpy)] (bpy = 2,2′-bipyridine) reacted with a large excess of dihaloalkanes X(CH₂)_nX (n = 1, X = Cl; n = 4, X = Br) to form the platinum(IV) complexes [PtMe₂X{(CH₂)_nX}(bpy)] (n = 1, X = Cl, 1a; n = 4, X = Br, 1b). The reaction of complexes 1a and 1b with SnBr₂ resulted in insertion of SnBr₂ into Pt–X (X = Cl, Br) bond to afford the trihalostannyl complexes [PtMe₂(SnBr₂X){(CH₂)_nX}(bpy)] (n = 1, X = Cl, 2a; n = 4, X = Br, 2b). The synthesis of such trihalostannylplatinum(IV) complexes is reported for the first time. The complex 2a was decomposed in CH₂Cl₂ solution and single crystals of [PtBr₂(bpy)] (3a) were obtained. The X-ray structure determination of 3a revealed a new polymorphic form of [PtBr₂(bpy)]. The molecules undergo a remarkable stacking along the b-axis to form a zigzag Pt?Pt?Pt chain containing both short (3.799 Å) and long (5.175 Å) Pt?Pt separations through the crystal. The crystal structure is compared to that of the yellow modification of [PtBr₂(bpy)].     

N-(1-亚氨基乙基)乙脒铂配合物合成、结构和性质

四氯合铂酸钾分别与邻、间、对磺基苯甲酸在乙腈和水中利用水热合成获得了3个铂的N-(1-亚氨基乙基)乙脒配合物:[Pt(NIA)₂]·(2-sb)·2H₂O(1),[Pt(NIA)₂]·(3-sb)·3H₂O(2)和[Pt(NIA)₂]·(1,4-dsb)·2H₂O(3)(NIA=N-(1-亚氨基乙基)乙脒,2-sb^2-=2-磺基苯甲酸二价阴离子、3-sb^2-=3-磺基苯甲酸二价阴离子、1,4-dsb^2-=1,4-二磺基苯二价阴离子)。合成过程中发生了乙氰三聚以及4-sb^2-转变为1,4-dsb^2-的反应。对配合物进行了元素分析、红外、紫外、荧光、热重和粉末X射线衍射表征,并利用单晶X射线衍射测定了配合物的晶体结构。3个配合物为阳离子-阴离子物种,阳离子为[Pt(NIA)₂]²⁺,中心金属离子四配位平面构型;阴离子与阳离子、水形成氢键,组成一个三维网络结构,但3个配合物的氢键模式不同。配合物在热稳定性、荧光性质上有一定差异。     

Structural studies of seven homoisoflavonoids, six thiohomoisoflavonoids, and four structurally related compounds

¹H and ¹³C NMR chemical shifts have been determined and assigned based on PFG ¹H, ¹³C HMQC, and HMBC experiments for 3-(4′-X-benzyl)-4-chromenones (Ia, X = CN and Ib, X = NO₂), 3-(4′-X-benzyl)-4-thiochromenones (IIa, X = Cl and IIb, X = Br), (E)-3-(4′-X-benzylidene)-4-chromanones (IIIa–IIIe, X = OCH₃, CH₃, Cl, N(CH₃)₂, Br), (Z)-3-(4′-X-benzylidene)4-thiochromanones (IVa–IVd, X = Cl, Br, F, OCH₃), 2-benzyl-1,2,3,4-tetrahydro-1-naphthol (V), 2-benzyl- and (E)-2-benzylidene-1-tetralones (VI and VII), and (E)-2-benzylidene-1-benzosuberol (VIII). The crystal structures have been determined for the following seven compounds: derivatives of 4-chromanones (IIIa–IIId), 1-tetrahydronaphtol (V), and 1-tetralones (VI and VII). The molecular features and intermolecular interactions in crystal state have been discussed.     

Heterometallic Pt-Ag and Pt2Ag transition metal complexes

Complexes of type {cis-[Pt](μ-σ,π-CCPh)₂}AgX (3a, [Pt] = (bipy′)Pt, X = FBF₃; 3b, [Pt] = (bipy′)Pt, X = FPF₅; 3c, [Pt] = (bipy)Pt, X = OClO₃; 3d, [Pt] = (bipy′)Pt, X = BPh₄; bipy′ = 4,4′-dimethyl-2,2′-bipyridine; bipy = 2,2′-bipyridine) are accessible by combining cis-[Pt](CCPh)₂ (1a, [Pt] = (bipy′)Pt; 1b, [Pt] = (bipy)Pt) with equimolar amounts of [AgX] (2a, X = BF₄; 2b, X = PF₆; 2c, X = ClO₄; 2d, X = BPh₄). In 3a-3d the platinum(II) and silver(I) ions are connected by σ- and π-bonded phenyl acetylide ligands. When the molar ratio of 1 and 2 is changed to 2:1 then trimetallic [{cis-[Pt](μ-CCPh)₂}₂Ag]X (8a, [Pt] = (bipy)Pt, X = BF₄; 8b, [Pt] = (bipy′)Pt, X = PF₆; 8c, [Pt] = (bipy)Pt, X = BF₄) is produced. The solid state structure of 8a was determined by single X-ray crystal structure analysis. In 8a the silver(I) ion is embedded between two parallel oriented cis-[Pt](CCPh)₂ units. Within this structural arrangement the phenyl acetylides of individual [Pt](CCPh)₂ entities possess a μ-bridging position between Pt(II) and Ag(I). In addition, a very weak dative Pt → Ag interaction is found (Pt-Ag 2.8965(3) Å). The respective silver carbon distances Ag-C_α (2.548(7), 2.447(7) Å) and Ag-C_β (3.042(7), 2.799(8) Å)(PtC_αC_βPh) confirm this structural motif.Complexes 8a-8c isomerize in solution to form trimetallic [{cis-[Pt](μ-σ,π-CCPh)₂}₂Ag]X (9a, [Pt] = (bipy)Pt, X = BF₄; 9b, [Pt] = (bipy′)Pt, X = PF₆; 9c, [Pt] = (bipy)Pt, X = ClO₄). In the latter molecules the organometallic cation [{cis-[Pt](μ-σ,π- CCPh)₂}₂Ag]⁺ is set-up by two nearly orthogonal positioned [Pt](CCPh)₂ entities which are hold in close proximity by the group-11 metal ion. Within this assembly all four PhCC units are η²-coordinated to silver(I). A possible mechanism for the formation of 9 is presented.     

Oxygen- versus carbon-coordination of the alpha-stabilized phosphorus ylide Ph<Subscript>3</Subscript>P=C(H)R in palladacycles bearing secondary amines

The ortho-metalated complex [Pd(x){κ ² (C,N)-[C₆H₄CH₂NRR′ (Y)}] (2a–4a and 2b–3b) was prepared by refluxing in benzene equimolecular amounts of Pd(OAc)₂ and secondary benzylamine [a, EtNHCH₂Ph; b, t-BuNHCH₂Ph followed by addition of excess NaCl. The reaction of the complexes [Pd(x){κ ² (C,N)-[C₆H₄CH₂NRR′ (Y)}] (2a–4a and 2b–3b) with a stoichiometric amount of Ph₃P=C(H)COC₆H₄-4-Z (Z = Br, Ph) (ZBPPY) (1:1 molar ratio), in THF at low temperature, gives the cationic derivatives [Pd(OC(Z-4-C₆H₄C=CHPPh₃){κ ² (C,N)-[C₆H₄CH₂NRR′(Y)}] (5a–9a, 4b–6b, and 4b′–6b′), in which the ylide ligand is O-coordinated to the Pd(II) center and trans to the ortho-metalated C(6)H(4) group, in an “end-on carbonyl”. Ortho-metallation, ylide O-coordination, and C-coordination in complexes (5a–9a, 4b–6b, and 4b′–6b′) were characterized by elemental analysis as well as various spectroscopic techniques.     

N-(1-亚氨基乙基)乙脒铂配合物合成、结构和性质

四氯合铂酸钾分别与邻、间、对磺基苯甲酸在乙腈和水中利用水热合成获得了3个铂的N-(1-亚氨基乙基)乙脒配合物:[Pt(NIA)_2]·(2-sb)·2H_2O(1),[Pt(NIA)_2]·(3-sb)·3H_2O(2)和[Pt(NIA)_2]·(1,4-dsb)·2H_2O(3)(NIA=N-(1-亚氨基乙基)乙脒,2-sb~2-=2-磺基苯甲酸二价阴离子、3-sb~2-=3-磺基苯甲酸二价阴离子、1,4-dsb~2-=1,4-二磺基苯二价阴离子)。合成过程中发生了乙氰三聚以及4-sb~2-转变为1,4-dsb~2-的反应。对配合物进行了元素分析、红外、紫外、荧光、热重和粉末X射线衍射表征,并利用单晶X射线衍射测定了配合物的晶体结构。3个配合物为阳离子-阴离子物种,阳离子为[Pt(NIA)_2]~(2+),中心金属离子四配位平面构型;阴离子与阳离子、水形成氢键,组成一个三维网络结构,但3个配合物的氢键模式不同。配合物在热稳定性、荧光性质上有一定差异。     

Syntheses,structures, and properties of two mononuclear cobalt(III) azido complexes containing a tetradentate N-donor Schiff base as end-capping ligand

Two hexacoordinated mononuclear Co(III) compounds of the type cis-[Co(L)(N₃)₂] X [1, X = ClO₄; 2, X = PF₆; L = N,N′-(bis(pyridine-2-yl)benzylidine)-1,4-butanediamine] have been synthesized and characterized by physicochemical and spectroscopic methods. The crystal structures of complexes 1 and 2 both have distorted octahedral geometry with two terminal azides in mutual cis orientations. In the crystalline state, two mononuclear units of 1 are associated by weak C–H…π interactions to produce a dimeric unit, which packs through C–H…O hydrogen bonds and π…π interactions leading to a 2-D continuum. The mononuclear units in 2 are engaged in weak cooperative intermolecular C–H…π interactions and multiple C–H…F hydrogen bonds giving rise to a 3-D network structure. These diamagnetic compounds are redox active and show luminescence in DMF solutions.     

Synthesis and characterization of half-sandwich iridium(III) and rhodium(III) complexes bearing organochalcogen ligands

Reactions of [Cp*M(μ-Cl)Cl]₂ (M = Ir, Rh; Cp* = η⁵-pentamethylcyclopentadienyl) with bi- or tri-dentate organochalcogen ligands Mbit (L1), Mbpit (L2), Mbbit (L3) and [Tm^Me]⁻ (L4) (Mbit = 1,1′-methylenebis(3-methyl-imidazole-2-thione); Mbpit = 1,1′-methylene bis (3-iso-propyl-imidazole-2-thione), Mbbit = 1,1′-methylene bis (3-tert-butyl-imidazole-2-thione)) and [Tm^Me]⁻ (Tm^Me = tris (2-mercapto-1-methylimidazolyl) borate) result in the formation of the 18-electron half-sandwich complexes [Cp*M(Mbit)Cl]Cl (M = Ir, 1a; M = Rh, 1b), [Cp*M(Mbpit)Cl]Cl (M = Ir, 2a; M = Rh, 2b), [Cp*M(Mbbit)Cl]Cl (M = Ir, 3a; M = Rh, 3b) and [Cp*M(Tm^Me)]Cl (M = Ir, 4a; M = Rh, 4b), respectively. All complexes have been characterized by elemental analysis, NMR and IR spectra. The molecular structures of 1a, 2b and 4a have been determined by X-ray crystallography.     

Synthesis and characterization of thiosemicarbazone derivatives of 2-chloro-4-hydroxy-benzaldehyde and their rhenium(I) complexes

N-Thioamide thiosemicarbazone derived of 2-chloro-4-hydroxy-benzaldehyde (R = H, HL¹; R = Me, HL² and R = Ph, HL³) have been prepared and their reaction with fac-[ReX(CO)₃(CH₃CN)₂] (X = Br, Cl) in chloroform gave the adducts [ReX(CO)₃(HL)] (1a X = Cl, R = H; 1a′ X = Br, R = H; 1b X = Cl, R = CH₃; 1b′ X = Br, R = CH₃; 1c X = Cl, R = Ph; 1c′ X = Br, R = Ph) in good yield. Complexes 1a′ and 1b’ were also obtained by the reaction of HL¹ and HL³ with [ReBr(CO)₅] in toluene.All the compounds have been characterized by elemental analysis, mass spectrometry (FAB), IR and ¹H NMR spectroscopic methods. Moreover, the structures of HL², HL³ and 1a·H₂O were also established by X-ray diffraction. In 1a, the rhenium atom is coordinated by the sulphur and the azomethine nitrogen atoms, forming a five-membered chelate ring, as well as three carbonyl carbon and chloride atoms. The resulting coordination polyhedron can be described as a distorted octahedron.The study of the crystals obtained by slow evaporation of methanol and DMSO solutions of the adducts 1a′ and 1b, respectively, showed the formation of dimer structures based on rhenium(I) thiosemicarbazonates [Re₂(L¹)₂(CO)₆]·3H₂O (2a)·3H₂O and [Re₂(L²)₂(CO)₆]·(CH₃)₂SO (2b)·2(CH₃)₂SO. Amounts of these thiosemicarbazonate complexes [Re₂(L)₂(CO)₆] (2) were obtained by reaction of the corresponding free ligands with [ReCl(CO)₅] in dry toluene.In 2a·3H₂O and 2b·2(CH₃)₂SO the dimer structures are established by Re–S–Re bridges, where S is the thiolate sulphur from a N,S-bidentate thiosemicarbazonate ligand. In both structures the rhenium coordination sphere is similar; the dimers are in the same diamond Re₂S₂ face.     

From platina-β-diketones to diacetylplatinum(II) complexes - Synthesis, characterization and structural features

The reaction of the electronically unsaturated platina-β-diketone [Pt₂{(COMe)₂H}₂(μ-Cl)₂] (1a) with N^?N donors led to the formation of diacetyl(hydrido)platinum(IV) complexes [Pt(COMe)₂Cl(H)(N^?N)] (2). By the reaction of these complexes with NaOH in a two-phase system (H₂O/CH₂Cl₂) diacetylplatinum(II) complexes [Pt(COMe)₂(N^?N)] (N^?N = bpy, 4a; 4,4′-Me₂-bpy, 4b; 4,4′-t-Bu₂-bpy, 4c; 4,4′-Ph₂-bpy, 4d; 4,4′-t-Bu₂-6-n-Bu-bpy, 4e; bpym, 4f; bpyr, 4g; phen, 4h; 4-Me-phen, 4i; 5-Me-phen, 4j) were obtained. All complexes were characterized by microanalysis, IR and ¹H and ¹³C NMR spectroscopy. Additionally, complexes 4a, 4c, 4d and 4e were characterized by single-crystal X-ray diffraction analysis. The observed variety of packing patterns resulting from π-π stacking and hydrogen bonding is discussed.     

Synthesis and Crystal Structures of Two Zinc(II) Complexes with the Tripodal Ligand Tris(2-Benzimidazolymethyl)Amine

This article reports the synthesis and crystal structures of two new mononuclear Zinc(II) complexes, [Zn₂(NTB)₂(N₃)₂](NO₃)₂·2CH₃OH (1) and [Zn₂(NTB)₂(SCN)₂](NO₃)₂·2CH₃OH·H₂O (2). Complex 1 crystallizes in the triclinic system, space group P&1macr;, a=13.743(4), b=14.374(4), c=14.443(5) Å; α=77.053(5), β=81.824(5), γ=88.959(6)°; Z=2; R1=0.0418, wR2=0.0889. Complex 2 also crystallizes in the triclinic system, space group P&1macr;, a=12.203(10), b=14.430(12), c=18.541(15)Å; α=72.712(15), β=85.039(15), γ=73.610(14); Z=2; R1=0.0771, wR2=0.1288. In both cases the central zinc(II) metal ions are coordinated to the four nitrogen atoms of NTB and a nitrogen atom of N^- ₃(1) or SCN^-(2) to form distorted trigonal bipyramidal coordination spheres.     

Iodo Derivatives of Bimetallic Fe—Pd and Fe—Pt Complexes. Crystal Structures of

Summary.  Iodo derivatives of diphosphine-bridged heterobimetallic Fe—Pd and Fe—Pt complexeshave been prepared in which an alkoxysilyl ligand bridges the two metals in a μ₂−η²-SiO manner. In the course of their synthesis by halide exchange from (dppx = dppm (Ph₂ PCH₂ PPh₂) or dppa (Ph₂PNHPPh₂); M = Pd or Pt), loss of the alkoxysilyl ligand occurred resulting in the formation of complexes in which a bridging iodide has replaced, as a 3e⁻-donor, the bridging alkoxysilyl ligand. These complexes of formula (M = Pd, Pt are better prepared by reaction of with [MI₂(cod)]. The crystal structures of (2a), (2b), and  · CH₂Cl₂ (3b · CH₂Cl₂) have been determined by X-ray diffraction. Received January 24, 2001. Accepted February 12, 2001     

Different orientations of C=O versus P=O in P(O)NHC(O) skeleton: the first study on an aliphatic diazaphosphorinane with a gauche orientation

Different orientations of P(O) versus C(O) in P(O)NHC(O) skeleton have been discussed in two new phosphorus(V)-nitrogen compounds with formula XP(O)Y and XP(O)Z₂ where X = NHC(O)C₆H₄(4-F) and Y = NHCH₂C(CH₃)₂CH₂NH (1), Z = NHC₆H₄(4-CH₃) (2). Compound 1 is the first example of an aliphatic diazaphosphorinane with a gauche orientation which has been studied by X-ray crystallography; the P=O bond is in the equatorial position of the ring. Both compounds show ⁿ J(F,C) and ^m J(F,H) coupling constants (n = 1, 2, 3 and 4; m = 3 and 4) and ³ J(P,C) > ² J(P,C). Quantum chemical calculations were performed with HF and Density Functional Theory (DFT) methods using 6−31+G(d,p) basis set. A tentative assignment of the observed vibrational bands for these molecules is discussed. Compound 1 shows a deshielded C atom of the carbonyl moiety (in ¹³C NMR spectrum) relative to that of 2, which is supported by IR spectroscopy in which the considerably lower C=O frequency is observed for 1. Comparing the X-ray crystallography and IR spectra of 1 and 2 shows that the acyclic compound 2, containing P=O and C=O bonds in an anti position, are involving in a stronger N–H···O=P hydrogen bond in crystal network. This leads to a weaker P=O and N_C(O)NHP(O)–H bonds and stronger N···O interaction. The N_amide–H is involved in an intramolecular N–H···O hydrogen bond.     

Supramolecular self-assembly of two Cu(II) complexes with 1,2,4-triazole derivatives: syntheses,crystal structures and magnetic properties

Two two-dimensional coordination complexes, {[Cu₄(BTM)₆(OPA)₄] · 4DMF · 3H₂O} _n (1) and {[Cu(BDTM)(OH)](ClO₄) · 2H₂O} _n (2) (BTM = bis(1,2,4-triazol-1-yl)methane, BDTM = bis(3,5-dimethyl-1,2,4-triazol-1-yl)methane, OPA²⁻ = ortho-phthalic dianion, DMF = N,N-dimethylformamide), were synthesized and structurally characterized. Each Cu(II) ion locates in a distorted square pyramidal geometry in 1, in which OPA²⁻ ligands bridge Cu²⁺ ions along a axis to form a magnetic transmission chain and BTM ligands act as flexible spacers to construct the two-dimensional layer structure. In 2, each Cu²⁺ ion adopts tetra-coordination geometry to two hydroxyl groups and two triazolyl nitrogen atoms from two different BDTM ligands. Two hydroxyl groups bridge two Cu²⁺ ions to form a rhombic diamond, and four BDTM ligands connect four diamonds to form a 36-membered macrocyclic structure with large channels along a axis. Magnetic properties revealed that both OPA²⁻ and OH⁻ mediate anti-ferromagnetic interactions between Cu²⁺ ions with J = − 0.06(3) and −301.9(2) cm⁻¹ for 1 and 2, respectively. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Alanine- and taurine-salicylal Schiff base complexes of magnesium

The complexes of α-alanine-salicylal Schiff base of magnesium (α-ASSM), β-alanine-salicylal Schiff base of magnesium (β-ASSM) and taurine-salicylal Schiff base of magnesium (TSSM) were synthesized. The formulae of the complexes are Mg[OC₆H₄CHNCH(CH₃)COO]·2H₂O, Mg[OC₆H₄CHNCH₂CH₂COO]·2H₂O and Mg[OC₆H₄CHNCH₂CH₂SO₃]·2H₂O. The crystal structure belongs to orthorhombic system with the lattice parameters: a=1.6954 nm, b=2.0873 nm and c=2.3037 nm for the β-ASSM, to orthorhombic system with the lattice parameters: a=1.5586 nm, b=1.8510 nm and c=2.6240 nm for the β-ASSM, to monoclinic system with the lattice parameters: a=1.3232 nm, b=1.4960 nm, c=2.1543 nm and β=98.04° for the TSSM, respectively. The results of the thermal decomposition processes and infrared spectra of the complexes show that the complexes may possess different coordination structures.     

Cationic tris(pyrazolyl)borate bipyrimidine complexes

The cationic complexes, [Tp^RNi(bpym)]⁺ {Tp^R = tris(3,5-diphenylpyrazolyl)borate, R = Ph₂ 1; tris(3-phenyl-5-methylpyrazolyl)borate, R = Ph,Me 2} were synthesized by reacting [Tp^RNiBr] (R = Ph₂; Ph,Me) with bipyrimidine followed by subsequent addition of KPF₆ in CH₂Cl₂. The green solids have been characterized by IR, UV–Vis and ¹H NMR spectroscopy. Crystallographic studies of [Tp^Ph,MeNi(bpym)]PF₆ reveal a five-coordinate square pyramidal nickel centre with a κ³-coordinated Tp^Ph,Me ligand and a chelating bipyrimidine ligand. Cyclic voltammetric studies show irreversible reduction with the degree of reversibility dependent on the type of Tp^R ligand.     

DNA-binding properties of ruthenium(II) complexes with the bidentate ligand 5-chloro-2-(phenylazo)pyridine

A bidentate ligand, 5-chloro-2-(phenylazo)pyridine (Clazpy), and its two polypyridyl ruthenium(II) complexes, [Ru(Clazpy)₂bpy]Cl₂·7H₂O (1) and [Ru(Clazpy)₂phen]Cl₂·8H₂O (2), were synthesized and characterized. The DNA-binding properties of these complexes with DNA, the breast cancer susceptibility gene 1 (BRCA1), and the pBIND plasmid DNA were probed by photocleavage, electronic absorption titration, ethidium bromide quenching, and thermal denaturation. Both complexes were found to bind to the BRCA1 fragment through the intercalative mode into the base pairs of DNA, and the DNA-binding constants (K_b) for 1 and 2 were 7.0 × 10⁴ M⁻¹ and 5.1 × 10⁵ M⁻¹, respectively. In addition, both complexes enhanced the single-stranded cleavage of the plasmid DNA. Under comparable experimental conditions, 2 cleaved DNA more effectively than 1, in a dose–response manner. The data indicated that the binding affinity of these two complexes to DNA was dependent on the aromatic planarity and hydrophobicity of the intercalative polypyridyl ligand.     

Palladium(II)/allylpalladium(II) complexes with xanthate ligands: Single-source precursors for the generation of palladium sulfide nanocrystals

In an effort to find simple and common single-source precursors for palladium sulfide nanostructures, palladium(II) complexes, [Pd(S₂X)₂] (X = COMe (1), COⁱPr (2)) and η³-allylpalladium complexes with xanthate ligands, [(η³-CH₂C(CH₃)CR₂)Pd(S₂X)] (R = H, X = COMe (3); R = H, X = COEt (4); R = H, X = COⁱPr (5); R = CH₃, X = COMe (6)), have been investigated. The crystal structures of [Pd(S₂X)₂] (X = COMe (1), CoⁱPr (2)) and [(η³-CH₂C(CH₃)CH₂)Pd(S₂COMe)] (3) have been established by single crystal X-ray diffraction analysis. The complexes, 1, 2 and 3 all contain a square planar palladium(II) centre. In the allyl complex 3, this is defined by the two sulfurs of the xanthate and the outer carbons of the 2-methylallyl ligand, while in the complexes, 1 and 2 it is defined by the four sulfur atoms of the xanthate ligand. Thermogravimetric studies have been carried out to evaluate the thermal stability of η³-allylpalladium(II) analogues. The complexes are useful precursors for the growth of nanocrystals of PdS either by furnace decomposition or solvothermolysis in dioctyl ether. The solvothermal decomposition of complexes in dioctyl ether gives a new metastable phase of PdS which can be transformed to the more stable tetragonal phase at 320 °C. The nanocrystals obtained have been characterized by PXRD, SEM, TEM and EDX.