Avi Bino

Several coordination modes of the pentadentate ligand 2,6-diacetylpyridinebis(thiosemicarbazone)

Abstract The reaction between Zn(II) salts and the pentadentate ligand 2,6-diacetylpyridinebis(thiosemicarbazone) (H 2 daptsc) produces various compounds, depending upon the H + ion concentration and the nature of the solvent from which the complex crystallizes. In the presence of nitric acid, the compound [Zn(H 2 daptsc)(H 2 O)2](NO 3 ) 2 ( 1 ) is obtained. The mononuclear complex in 1 possesses a pentagonal bipyramidal geometry with an almost planar, fully protonated, H 2 daptsc ligand and two axially bonded water ligands. Compound 2 , [Zn 2 (daptsc) 2 ]·2DMF, was prepared and crystallized from dimethylformamide. The dinuclear complex in 2 contains two fully deprotonated ligands which are coordinated to two Zn(II) ions with a distorted octahedral geometry. Compound 3 , [Zn 2 (daptsc) 2 ]·MeOH·H 2 o, was prepared and crystallized from methanol. The dinuclear unit in 3 is a structural isomer of complex 2 . The complex is asymmetric in which one zinc atom is six-coordinate and the other one is four-coordinate. Compound 1 is monoclinic, space group Cc with a = 21.930(3), b = 12.940(2), c = 7.345(1) A, β = 104.22(3)°, V = 2020(1) A 3 and Z = 4. Compound 2 is monoclinic, space group C 2/ c with a = 18.189(2), b = 15.716(2), c = 14.653(2) A, β = 115.86(2)°, V = 3769(1) A 3 and Z = 4. Compound 3 is monoclinic, space group P 1 with a = 10.666(2), b = 16.282(2), c = 10.458(2) A, α = 90.79(2), β = 117.94(2), γ = 80.70(2)°, V = 1579(1) A 3 and Z = 2.

Polynuclear chromium(III) carboxlylates: Part 2. Chromium(III) acetate — what's in it?

Abstract Chromium(III) acetate has been widely used in industry for decades. The commercial material is an ill-defined substance, which represents a large number of compounds having different compositions, physical properties and appearances. Several samples of Cr(III) acetate, from various commercial sources were examined by ion-exchange chromatography. All the samples were found to contain several species such as [Cr3O(O2CCH3)6(H2O)3]+ and other positively charged purple complexes. They also contain various amounts of the neutral violet complex [Cr8(OH)8(O2CCH3)16] (1) which crystallizes upon slow evaporation of its aqueous solution. 1 is a cyclic octanuclear complex with hydroxo and acetate ligands bridging the adjacent Cr(III) ions. The structure of a well-defined Cr(III) acetate, namely, [Cr(H2O)6](O2CCH3)3 (2) has been determined crystallographically and its decomposition products were examined by ion-exchange chromatography. Compound 2 decomposes under ambient conditions, releasing acetic acid and water producing neutral and charged polynuclear Cr(III) complexes.

Three coordination modes of the pentadentate ligand 2,6-diacetylpyridinedisemicarbazone

Abstract The pentadentate ligand 2,6-diacetylpyridinedisemicarbazone, DAPSC, reacts with Cr(NO 3 ) 3 ·9H 2 O and forms two kinds of complexes. At pH=3, the ligand is singly-deprotonated and crystals of [Cr- (DAPSCH)(H 2 O) 2 ](NO 3 ) 2 ·H 2 O ( Ia ) are obtained. Evaporation of a solution at pH=0, yields crystals of [Cr(DAPSC)(H 2 O) 2 ](NO 3 ) 3 ·2H 2 O ( II ) in which the ligand is fully protonated. The reaction of DAPSC with UO 2 (O 2 CCH 3 ) 2 in methanol, followed by crystallization of the product from DMSO yields crystals of [UO 2 (DAPSC2H)(H 2 O)]·2DMSO ( III ) in which the ligand is fully deprotonated. Compound Ia is monoclinic, space group P 2 1 / n with a =11.746(1), b =14.752(2), c =11.866(1) A,β=105.53(2)°, V = 1981(1) A 3 and Z =4. Compound II is monoclinic, space group, P 2 1 / n with a =38.000(3), b = 14.939(2), c =8.233(1) A, β=96.12(2)°, V = 4647(1) A and Z =8. Compound III is monoclinic, space group P 2 1 / n with a =18.048(2), b =15.207(2), c =8.842(1) A,β=97.72(2)°, V =2405(1) A 3 and Z =4. The structures were refined using 2084, 4169 and 2516 reflections to R values of 4.4%, 7.8% and 4.8% respectively.

Synthesis, structure and magnetic properties of an asymmetric dinuclear oxocitratovanadate(IV) complex

Abstract Evaporation of an aqueous solution containing VO2+, citric acid and neocuproine (2,9-dimethyl-1,10-phenanthroline=neo) produces blue crystals of (Hneo)3[(VO)2(cit)(Hcit)]·4H2O (1). An X-ray structural analysis showed that 1 consists of a discrete, asymmetric, dinuclear oxocitratovanadate(IV) complex and three neocuproinium cations. The complex contains one six-coordinate V(IV) atom with a distorted octahedral geometry and one five-coordinate V(IV) atom with a distorted square pyramidal geometry. The two metal atoms are bridged by two alkoxide oxygen atoms of one cit4− group and one Hcit3− group which has one protonated, non-coordinating carboxylic group. The V⋯V distance was found to be 2.949(1) A. Compound 1 is orthorhombic, space group Pca21, with a = 22.223(3), b = 10.499(1), c = 22.818(2) A , V = 5324(1) A 3 and Z = 4 . Magnetic susceptibility measurements of a powdered sample of 1 over the range 2–300 K showed a very strong antiferromagnetic coupling between the two d1 systems with −J value of 212 cm−1.

The structure of oxo-bridged trinuclear ruthenium and iridium hexacarboxylates

Abstract The reactions between ruthenium trichloride or iridium trichloride and carboxylic acids produce oxygen-centered triangular trinuclear complexes which are known as ‘basic’ carboxylates having the general formula [M3O(O2CR)6(H2O3]n+. Using ion-exchange chromatography, a variety of such complexes with different carboxylates and oxidation states were isolated and crystallized. The X-ray study of five compounds is reported. Compound 1, [Ru3O(O2CCH3)6(H2O)3]BF4·2H2O is monoclinic, space group P2/c with a=11.717(1), b=15.019(2), c=15.220(2) A, β=92.27(3)°, V=2676(1) A3 and Z=4. Compound 2, [Ru3O(O2CH)6(H2O)6]BF4·3H2O is orthorhombic, space group Pmn21 with a=11.362(1), b=6.676(1), c=14.447(2) A, V=1096(1) A3 and Z=2. Compound 3, [Ru3O(O2CCH3)6(H2O)3](ClO4)2·H2O is monoclinic, space group P21/n with a=17.226(2), b=15.532(2), c=11.117(1) A, β=91.68(2)°, V=2973(1) A3 and Z=4. Compound 4, [Ir3O(O2CCH3)6(H2O)3]BF4·4H2O is monoclinic space group I2/a with a=22.305(6), b=14.098(3), c=20.119(5) A, β=103.10(5)°, V=6162(5) A3 and Z=8. Compound 5, [Ir3O(O2CCH3)6(H2O)3](ClO3)1.667(ClO4)0.333 is rhombohedral, space group R 3 with a=11.173(4), c=40.621(10) A, V=4392(4) A3 and Z=6. The structural parameters, such as MO (central) distances, for the M(III,III,III) and M(III,III,IV) systems are almost identical. This indicates that the removal of a d-electron from a non-bonding level of the M3O system has a very little or no effect at all on this system.

Novel carboplatin analogs containing flexible and potentially intercalating ligands: preparation and X-ray crystal structures of di-2-pyridyl ketone cyclobutanedicarboxylate platinum(II) and of 2,3-bis(2-pyridyl)pyrazine cyclobutane dicarboxylate platinum(II)

Abstract The crystal structures of the cyclobutanedicarboxylate (ebde) platinum(II) complexes of di-2-pyridyl ketone (dpk) 1, [Pt(dpk)(ebde)] and of 2,3-bis(2-pyridyl)pyrazine (bpp) 2, [Pt(bpp)(cbdc)] · 2CH2Cl2 have been determined by X-ray crystallography. Crystal data are: 1, orthorhombic space group Pbcn, a = 16.164(3), b = 10.749(2), c = 18.601(3) A, V = 3232(1) A3 and Z = 8; 2, triclinic space group P1, a = 9.437(2), b = 15.424(3), c = 9.342(2) A, α = 107.45(2), β = 91.92(1), γ = 82.68(1), V = 1287(1) A3 and Z = 2. In the former structure, the dpk ligand did not undergo the metal promoted hydration reaction to yield a facial tridentate ligand. It binds the platinum in a bidentate fashion retaining the sp2 hybridization around the carbonyl carbon. The conformational strain is relieved by distortion of the planar ligand through rotation of the pyridyl rings around the bonds connecting them to the carbonyl group to yield a non-planar ligand. In the second structure (bpp complex), the ehelating pyrazine and pyridyl rings are coplanar and the non-ligating pyridyl ring is nearly perpendicular to them.

Oxalato complexes of the trinuclear aquo ion of molybdenum(IV), [Mo3O4]4+

The preparations and X-ray crystallographic structure determinations of two compounds containing the complex oxalato anion of Mo3O44+, viz., [Mo3O4(C2O4)3(H2O)3]−, are reported. Compound 1, Cs2[Mo3O4(C2O4)3(H2O)3]·4H2O·H2C2O4 forms monoclinic crystals (space group P21/n) with unit cell dimensions a = 12.82(2) A, b = 16.764(3) A, c = 12.529(2) A, β = 91.31(2)° and Z = 4. Compound 2, Cs3[Mo3O4(C2O4)3]CF3SO3·3H2O, forms hexagonal crystals (space group R3m) with a = 12.955(1) A, c = 14.738(2) A and Z = 3. The [Mo3O4(C2O4)3(H2O)3]2− ion has essentially the same dimensions in each case. In compound 1 no crystallographic symmetry is required while in 2C3v symmetry is imposed. Some important dimensions are the following where we give first the mean value (averaged according to C3v symmetry) for 1 and then the value for 2: MoMo, 2,486(1) A. 2,491(1) A; Mo(μ3-O), 2.0196(6) A, 2.01(1) A; Mo(μ2-O), 1.921(4) A, 1.908(7) A; MoO(H2O), 2.154(7) A, 2.15(1) A; MoO(oxalate), 2.091(4) A, 2.102(8) A; Mo(μ3-O)Mo, 76.0(1)°, 76.6(6)°, Mo(μ2-O)Mo, 80.6(1)°, 81.5(4)°.

Models of the oxidized forms of polyiron oxo proteins: synthetic routes to (μ-oxo)bis(μ-carboxylato)diiron(III) complexes with neutral monodentate and bidentate capping ligands

Two (μ-oxo)bis(μ-carboxylato)diiron(III) complexes with neutral monodentate and bidentate terminal ligands have been prepared that incorporate features of the diiron oxo centers in the non-heme iron proteins hemerythrin (Hr) and the B2 subunit of ribonucleotide reductase (RRB2) that were not previously modeled. [Fe 2 O(OH 2 ) 2 (O 2 CCH 2 Cl) 2 (bpy) 2 ](NO 3 ) 2 ( 1 ) and [Fe 2 O(CH 3 OH) 2 (O 2 CCH 3 ) 2 (BIPhMe) 2 ](NO 3 ) 2 ( 2 ) were synthesized from the appropriate basic iron carboxylate, ferric nitrate and the bidentate nitrogen ligand bpy or BIPhMe. The molecular structures, as determined by X-ray crystallography, and the electronic spectral, Mossbauer and magnetic properties of 1 and 2 reproduce many of the physical properties of the met forms of Hr and RRB2. A singly-bridged (μ-oxo)diiron(III) complex, [Fe 2 O(NO 3 ) 4 (bpy) 2 ] ( 3 ), was also prepared from ferric nitrate and bpy. The chelating bpy and nitrate ligands afford seven-coordinate ferric centers in the centrosymmetric compound. Complex 3 serves as a synthon for the (μ-oxo)bis(μ-carboxylato)diiron(III) core, for the reaction of 3 with excess chloroacetic acid gives 1 .

Polymeric and monomeric forms of metalphosphinates

Abstract Diphenylphosphinic acid reacts with Mn 2+ in the presence of dimethylformamide and two kinds of compounds are formed. Compound 1, {Mn[O 2 P(C 6 H 5 ) 2 ] 2 (DMF)}·DMF, consists of one-dimensional, infinite centrosymmetric chains of Mn(II) atoms connected by double phosphinate bridges. Each manganese atom is coordinated to four phosphinate oxygen atoms and one DMF molecule in a trigonal bipyramidal geometry with three equatorial angles of 123.7(6), 116.8(5) and 117.4(6)° and an axial— metal—axial angle of 173.3(7)°. The M…M separation is 4.583 A. Compound 2, {Mn[O 2 P(C 6 H 5 ) 2 ] 2 [HO 2 P(C 6 H 5 ) 2 ] 2 - (DMF) 2 } cocrystallizes with 1 under the same conditions. The manganese atom is coordinated to two phosphinate ions, to two phosphinic acid molecules and to two DMF molecules in an octahedral geometry. Two very strong, intramolecular hydrogen bonds are formed between the POH group of one ligand and the PO − group of another ligand with O…O separation of 2.444(3) A. Compound 3 is the Co(II) analogue of 2, {Co[O 2 P(C 6 H 5 ) 2 ] 2 [HO 2 P(C 6 H 5 ) 2 ] 2 (DMF) 2 }. The O…O separation in the intramolecular hydrogen bond in 3 is 2.422(4) A. Compound 1: triclinic, space group P 1 with a = 13.174(2), b = 13.364(2), c = 9.995(1) A, α = 96.05(3), β = 110.23(3), γ = 104.54(2)°, V = 1562(1) A 3 and Z = 2. Compound 2: triclinic, space group P 1 with a = 12.019(1), b = 12.390(1), c = 9.479(1) A, α = 94.90(3), β = 101.71(2), γ = 102.65(3)°, V = 1336(1) A 3 and Z = 1. Compound 3: monoclinic, space group P 2 1 / c with a = 12.552(2), b = 9.921(1), c = 21.558(3) A, β = 101.88(3)°, V = 2627(1) A 3 and Z = 2.

Synthesis, structure and magnetic properties of a chromium(III)nicotinamide complex [Cr3O(O2CCH3)6(na)3]+ (na=nicotinamide)

Abstract The reaction between [Cr 3 O(O 2 CCH 3 ) 7 (H 2 O)] (‘basic chromium acetate’) and an excess of nicotinamide (na) at 120°C, followed by dissolution of the mixture in water and addition of PF 6  − , led to the isolation of the first Cr(III)nicotinamide complex [Cr 3 O(O 2 CCH 3 ) 6 (na) 3 ] + ( 1 ). Crystals of the compound 1 ·PF 6 ·3CH 3 CN were subjected to a detailed X-ray structural analysis. The three N-bonded na ligands, which occupy axial positions at the corners of the triangular basic chromium acetate, are nearly co-planar with the Cr 3 O system. The three CrN(na) bond distances are in the range 2.121(8)–2.128(8) A. Two of the na ligands on each cluster form four hydrogen bonds with two ligands from a neighboring cluster, via their amide ends with N⋯O distances of 2.88(1)–2.92(1) A. Magnetic susceptibility measurements of a powdered sample of 1 ·PF 6 ·3CH 3 CN over the range 2–300 K showed that the three Cr(III) ions were antiferromagnetically coupled with J =−10.4 cm −1 . There was no evidence for intermolecular magnetic exchange between the two Cr 3 O centers which are connected via hydrogen bonds.