Bis(diphenylphosphino)Alkane / Co(II)/Tetrahydroborate and Cyanotrihydroborate Reactions: Formation of Unusual Bis(diphenylphosphino)methane Complexes and the Influence of Carbon Monoxide

Abstract

Reactions between Co(II), bis(diphenylphosphino)methane (dppm) and either NaBH₄ or NaBH₃CN have been studied. They follow pathways which are in marked contrast to those followed by Ph₂P(CH₂)nPPh₂ (n=2?6) in the presence of NaBH₄ in which the final product is normally CoH(phosphine)₂ although binuclear BH₄-bridged complexes may sometimes be obtained. The products obtained with dppm are Co₂X₃(dppm)₂ (X=Cl,Br) (I), CoCl(dppm)₃ (II), {CoHX(dppm)₂}Y (X=Cl, Br, I, BH₃CN; Y=Cl,BH₃CN,BPh₄,Clo₄) (III), and Co₂H₂(dppm)₃ (IV). While a binuclear A-frame structure can be proposed for the Co(I)-Co(II) species (I), crystal twinning has so far prevented an X-ray determination. However, X-ray studies on (II) and (IV) have shown that (II) contains tetrahedral Co(I) to which one chloro and three monodentate dppm ligands are attracted while (IV) is a binuclear species containing bridging dppm ligands and two terminal hydrides. The compounds (III) are octahedral Co(III) complexes. Possible mechanisms for the formation of these in strongly reducing environments will be discussed.     

Synthesis, Structure and Spectroscopy of Clathrate Inclusion Compounds of Cobalt(II), Cadmium(II) and Zinc(II) trans-4-styrylpyridine nitrates as Host with trans-4-styrylpyridine as Guest (2 : 1)

New clathrate inclusion compounds with the general formula,MA₃X₂ 1/2G (M = Co(II)(1),Cd(II)(2), and Zn(II)(3), X = NO₃ ^- andA and G = trans-4-styrylpyridine), differing from the usualWerner clathrates, MA₄X₂ 2G, have been prepared and characterized by elemental and thermal analyses,IR and electronic spectroscopy and X-ray crystallography. Tworepresentative compounds [Co(stpy)₃(NO₃)₂] 1/2stpy (1) and [Cd(stpy)₃(NO₃)₂] 1/2 stpy (2)are investigated by single crystal X-ray diffraction. Compound (1)crystallizes in the triclinic space group P¯1 with a = 10.966(2),b = 12.802(4), c = 16.063(5) Å = 83.38(3), = 71.30(2), = 76.88(3) °,Z = 2. The structure is made up of discretemolecules of [Co(stpy)₃(NO₃)₂]. The central Co(II) issurrounded by three stpy nitrogen atoms and four oxygen atoms of twoasymmetrically coordinated bidentate nitrate ligands. One of the oxygensis semicoordinated leading to a distorted octahedral geometry for Co(II).Compound (2) crystallizes in the monoclinic space group P2₁/nwith a = 15.597(3), b = 18.313(5), c = 16.188(3) Å = 115.998(14)° and Z = 4. The structure consists of neutralmolecules of [Cd(stpy)₃(NO₃)₂]. The geometry aroundCd(II) is best described as pentagonal bipyramid with four oxygen atomsfrom symmetrical bidentate nitrate groups and one stpy nitrogen atom inthe equatorial positions. Two other nitrogen atoms from stpy ligands occupythe axial positions. The guest stpy molecules are trapped in the centrosymmetricalcavities in lattices of both 1 and 2. Compound 3is found to beisomorphous with 2. A large splitting of the symmetric and asymmetricNO₂ stretching vibrations reveals the presence of bidentate nitrate ligands.Thermogravimetric and DTA studies on the Cd(II) compound, show it to be athermally stable inclusion compound.     

Polarity and Conformatios of Phosphorylethylenes and Phosphorylacetates in Solution

Abstract

A series of derivatives R¹R²P(X)R³, where R¹=R²=Ph. R³= -CH=CH-Me, X=O(I); R¹=Me, R²=Ph, R³= -CH=CH₂, X=O(II); R¹=R²=Ph, R³= -CH=CH₂, X=Se(III) and R¹R²P(O)-CH₂C(O)OX, where R¹=Ph, R²= -CH=CH₂, X=Ment?(IV); R¹=Ph-2-OMe, R²=Ph, X=Ment?(V); R¹=R²=CH₂Ph, X=Et(I), were investigated by means of dipole moments method. The problem of conjugation in phosphorylethylenes and conformation behaviour of phosphorylacetates was considered. DM (exp.) of (I-IV), determined in CC1₄ solution are 4.48(I), 4.27(II), 4.97(III), 4.21(IV), 5.21(V) and 4.02 D (VI). The intramolecular electronic interactions of phosphoryl group with unsaturated fragment did not displays in polarity properties of compounds (I-III). The experimental dipole moments of derivatives (I-III) are equal to the calculated values of DM. DM (IV-VI) is very sensitive to orientation of the P=O and C=O polar bonds. Because DM (exp.) of these compounds very sensitive to its orientation. DM (calc.) for cis- and trans- orientation of P=O and C=O dipoles are really different, that allows to drow the conclution that, in the contrast to the crystal state, the corresponded dipoles prefer an anti array in solution.     

Complexation Studies of Phosphorus Containing Bis and Tris (Benzocrown Ether) Moieties

The complexation behaviour between salts of Li⁺-Rb⁺ in CD₃CN and tris(benzocrown ether)s 2a,bX=P(NMeN=CH-B15C5)₃ (X = O, S) and tri[bis(benzocrown ether)][N=P(NMeN=CH-B15C5)₂]₃ 3 was investigated by ¹³ C NMR spectroscopy. Using the program RMNSTAB, the complexation constants for the different possible complexes (M₂L, ML andML₂ were L represents one benzo-15-crown-5) were obtained and were compared with those of the corresponding monomer material. A remarkable ``biscrown effect' for compounds 2a,b and 3 was found, especially for potassium and rubidium by the predominant formation of stable ML₂ complexes. The strong chelate effect make these ligands highly efficient extracting agents for alkali metal picrate salts of K⁺, Rb⁺ and Cs⁺,as shown by UV-Vis spectroscopy.     

Synthesis,characterization, structures,and DFT study of zinc(II) complexes with tributylphosphine chalcogenides

Four new zinc(II) complexes of the type [ZnCl₂(n-Bu₃PE)₂] (E=O (1), S (2), Se (3), or Te (4)) have been synthesized from zinc(II) chloride and the ligands n-Bu₃PE giving yields of 56–88%. The adducts were characterized by multinuclear (³¹P, ¹³C, and ⁷⁷Se) NMR, conductivity, IR spectroscopy and by X-ray analyses. Zinc complexes 1–4 are compriseS of two ligands coordinated to the metal center in a distorted tetrahedral arrangement. The P=E bond lengths of 1.497(7) (E=O), 2.000(4) (E=S), and 2.178(2) Å (E=Se) in these complexes are slightly elongated compared to those in the free ligand. In addition, a DFT/B3LYP theoretical study on the geometry optimization of the title ligands and their zinc complexes has been carried out in order to support and complement the experimental data and to further investigate the nature of the chalcogenide-metal interaction. The results show good agreement between the experimental and theoretical data.     

Structural studies on Ba(II) adducts of the cytosine nucleobase and its derivative 1-Methylcytosine*

Abstract

The use of the cytosine nucleobase or its 1-Methylcytosine derivative as ligands toward barium(II) cations led to the formation of three compounds, {[Ba(1-Mecyt)(H₂O)X₂]}_n [X=Cl (1), Br (2)], and {[Ba(cyt)₂(H₂O)(ClO₄)₂]}_n (3). Depending on the ligand and the counterion employed, 1–3 exhibit different architectures, which serve as a playground to study how the methyl substitution, together with the nature of the counterion are both significant in the self-assembling process of such species. The effect of the nature and size of the alkaline-earth metal ion on the final structural motif is also evident when comparing these structures with parent complexes of the Ca(II) ion.     

Synthesis and Characterization of Three Coordinate “T-Shaped” Complexes of Tellurium (II) Incorporating a Naphthyl Tellurium Fragment

Several new three coordinate tellurium(II) complexes have been prepared by the addition of dinaphthyl ditelluride (C₁₀H₇)₂Te₂ and a halogen (Br₂ or I₂) to various monodentate ligands known to coordinate through their terminal sulfur or selenium atoms to investigate possible electronic and steric effects associated with a large aryl group. Complexes of the type RTeX(L) are described here [R = naphthyl, X = Br, I, L = thiourea (I (X = Br), II (X = I)), tetramethylthiourea (III), selenourea (IV), tris(dimethylamino)phosphane selenide (V) and N-methylbenzothiazol-2(3H)-thione (VI)]. Evidence of the formation of new complexes is presented through microanalytical data and multinuclear NMR spectroscopy in addition to single crystal X-ray diffraction studies of (I) and (III). Structures are described in detail along with a comparison with related Te (II) complexes.     

COPPER(II) PROPIONATES Crystal and Molecular Structure of Bis(propionato)copper(II) Di(methyl-3-pyridylcarbamate)

Abstract

New copper(II) propionate compounds of composition Cu(prop)₂L (L =methyl-3-pyridylcarbamate or N, N-diethylnikotinamide) andau(prop)₂L₂ (L = methyl-3-pyr-idylcarbamate or2, 6-pyridinemethanole) have been prepared. The crystal and molecular structure of thetetrakis(μ-propionato)di(methyl-3-pyridinecarbamate) dicopper(II), Cu-₂(prop)₄(mpc)₂, was determined by direct method and Fouriertechniques. The compound crystallizes in the orthorhombic space group Pcab with four dimeric units in a cell withdimensions a = 19.350(4), b = 15.390(3), c = 10.725(2)Å. The structure was refined byfull-matrix least-squares methods to a R factor of 0.031, based on 3666 independent reflections. Thecompound is dimeric, with square-pyramidal geometry at each copper centre. The two copper atoms are bridgedby four carboxylate groups, while the apical ligands are methyl-3-pyridylcarbamate. The structural dataare compared with those found in similar copper(II) propionates. Spectral data of Cu(prop)₂L aretypical for dimeric copper(II) compounds. Both Cu(prop)₂L₂ compounds seem to possessoctahedral cop-per(II) stereochemistry with differing tetragonal distortion.     

Synthesis and chemistry of tris(2-pyridyl)phosphine and bis(2-pyridyl)phenylphosphine complexes of mercury(II) X (X = Br,Cl) and X-ray crystal structural determination of [HgBr2(PPh(2-py)2)2]

Mercury(II) halide complexes [HgX₂(P(2-py)₃)₂] (X?=?Br (1), Cl (2)) and [HgX₂(PPh(2-py)₂)₂] (X?=?Br (3), Cl (4)) containing P(2-py)₃ and PPh(2-py)₂ ligands (P(2-py)₃ is tris(2-pyridyl)phosphine and PPh(2-py)₂ is bis(2-pyridyl)phenylphosphine) were synthesized in nearly quantitative yield by reaction of corresponding mercury(II) halide and appropriate ligands. The synthesized complexes are fully characterized by elemental analysis, melting point determination, IR, ¹H, and ³¹P-NMR spectroscopies. Furthermore, the crystal structure of [HgBr₂(PPh(2-py)₂)₂] determined by X-ray diffraction is also reported.     

Zur Oxydation von Nickel(0)-Komplexen mit Halogenverbindungen des Kobalt(II), Kupfer(II) und Zink(II)

Oxidation of Nickel(0) Complexes by Halogen Compounds of Cobalt(II), Copper(II), and Zine(II) In aceton as a solvent Ni(PPh₃)₄ is oxidized by; cobalt(II) complexes of the type (Ph₃P)₂CoX₂ to nickel(I) compounds. In the case of X = Cl (Ph₃P)₃NiCl and (Ph₃P)₃CoCl separately crystallize, while for X = Br the lattice compound CoNi(PPh₃)₆Br₂ and for X = I CoNi(PPh₃)₅I₂ are formed. CuBr₂ and Ni(PPh₃)₄ react to (Ph₃P)₂NiBr and (Ph₃P)_nCuBr. With (Ph₃P)₂ZnCl₂ also (Ph₃P)₃NiCl is formed But in this case the oxidant is hydrogen chloride originating from hydrolysis. The magnetic moments of the new compounds were measured and their vis and fir spectra compared with those of the simple compounds (Ph₃P)_nNiX (n = 2, 3) and (Ph₃P)₃CoX. The M–X stretching frequencies are assigned. The cobalt (I) complexes (Ph₃P)₃CoCl have identical (distorted tetrahedral) structures, but most probably the nickel (I) complexes have not.     

The preparation and spectral properties of the new ‘mixed’ complexes [MI2(CO)3(py)L] (M = Mo and W; L = PPh3, AsPh3 and SbPh3)

Abstract

Seven-coordinate complexes of molybdenum(II) and tungsten(II) have become increasingly important as homogeneous catalysts. For example, the complexes [MX₂(CO)₃L₂] (M = Mo and W; X = Cl and Br; L = PPh₃ and AsPh₃) have been shown to be catalysts for the ring-opening polymerisation of norbornene.¹ Although a wide variety of complexes of the type [MX₂(CO)₃L₂] (M = Mo and W; X = Cl, Br and I; L = nitrogen, phosphorus, arsenic and antimony donor ligands)² have been reported, until now no examples of the mixed complexes [MX₂(CO)₃(py)L] have been prepared. In this communication we wish to describe the synthesis of the new mixed pyridine/L compounds [MI₂(CO)₃(py)L] (M = Mo and W; L = PPh₃, AsPh₃ and SbPh₃).     

Structural and Antimicrobial Studies of Some Divalent Transition Metal Complexes with Some New Symmetrical Bis (7-Formylanil Substituted-Sulfoxine) Schiff Base Ligands

Symmetrical bis (7-formyanil substituted-8-hydroxyquinoline-5-sulfonic acid), Schiff bases, react with Co(II), Ni(II) and Cu(II) ions to give M_nL (n=1, 2) complexes as established by conductometric titration in 1 : 1 DMF: H₂O. The complexes were identified by elemental analyses, molecular weight determination, thermal analysis, infrared, magnetic moments, electronic absorption, and electron spin resonance spectra. The suggested general geometry for these complexes may have a tetrahedral crystal structure and the general formula is [M₂L(OH₂4], where M(II) = Co, Ni and Cu and L = 7―X―H₂ L(―X―= dimethyl, p-phenyl, o-phenyl), while for the, trimethyl, ligand and the tetrahedral crystal structure has the general formula [M₂L(OH₂)₂].Antimicrobial activity of these ligands and their transition metal complexes has been investigated on some common fungi and bacteria. A considerable increase in the biocide acticity of these ligands has been observed on coordination with transition metal ions, therefore, these complexes can be used in the chemotherapy of candidiaces and other fungal skin diseases.     

Synthesis,Crystal Structures,Thermal and Magnetic Properties of New Selenocyanato Coordination Polymers with Pyrazine as Co‐Ligand

Reaction of iron(II), cobalt(II) and nickel(II) selenocyanate with pyrazine in water at room temperature leads to the formation of the isotypic new ligand‐rich 1:2 (1:2 = ratio between metal and co‐ligand) compounds [M(NCSe)₂(pyrazine)₂]_n (M = Fe ( 1 ), Co ( 2 ), Ni ( 3 )). The crystal structure of 2 was determined by X‐ray single crystal analysis and those of 1 and 3 were refined from X‐ray powder data with the Rietveld method. In their crystal structure the metal(II) cations are coordinated by four pyrazine co‐ligands, which connect them into layers, and two terminally N‐bonded selenocyanato anions in a distorted octahedral arrangement. The terminal coordination mode of the selenocyanato anions was further emphasized by IR spectroscopic investigations. On heating, all compounds decompose in a single heating step without the formation of ligand‐deficient intermediates like previously reported for related thiocyanato compounds. Magnetic measurements of compound 1 show a long‐range antiferromagnetic ordering with an ordering temperature of T_N = 6.7 K, which must be mediated by the aromatic π‐system of the pyrazine ligand, whereas 2 and 3 show only Curie–Weiss behavior with antiferromagnetic exchange interactions.     

Organoselenium/Tellurium-Bearing Macroacyclic and Cyclic Ligand Systems and Their Complexation Reactions

Abstract

A series of phenol-substituted acyclic Schiff bases, 2,6-{RE(CH₂) _n N═C(CH₃)}₂-C₆H₂(4-CH₃)(OH), (E = Te: R = C₆H₅, n = 2(L _a), 3(L _b); R = C₆H₄-4-OCH₃, n = 2(L _c), 3(L _d); E = Se: R = C₆H₅, n = 2(L _e), 3(L _f)), of the type E₂N₂O have been synthesized by condensation of 2,6-diacetyl-4-methylphenol with arylchalcogenoalkylamines. This ligand framework is useful for designing molecular complexes with a variety of coordination modes depending upon the nature of the central metal atom. The reactivity of the tellurium-bearing macroacyclics ligands towards Zn(II), Cd(II), and Hg(II) has been examined. The ligands L _a?L _d with Zn(II) and Cd(II), and only L _a and L _b with Hg(II) form complexes of composition M₂X₄L, (X = Cl or Br), whereas L _c and L _d with Hg(II) give products of composition HgBr₂L. The modes of ligand interaction with Zn(II) and Cd(II) are different than that with Hg(II).

Following a multistep reaction involving abstraction of bridged Br atoms and subsequent addition of more ligand, the mercury complex, Hg₂Br₄L has been used for developing metallocyclic system of the type [Hg₂Br₂L₂]²⁺. The latter has been found to encapsulate Zn(II) and Cd(II) to give multimetallic systems.     

Transition Metal Halide Salts and Complexes of 2-Aminopyrimidine: Cobalt(II) and Nickel(II) compounds,Crystal Structures of Bis(2-Aminopyrimidinium)MX4 [M = Co,Ni; X = Cl,Br] and 2-Aminopyrimidinium(+2) [NiBr2(H2O)4]Br2

The reaction of MX₂ (M = Co(II), Ni(II); X = Cl, Br) with 2-aminopyrimidine in aqueous acid yields compounds [(2-apmH)₂MX₄], (2-apmH)₂[MX₄], or (2-apmH₂) [MX₂(H₂O)₄]X₂ (2-apmH = 2-aminopyrimidinium; 2-apmH₂ = 2-aminopyrimidinium(2+)). All compounds have been characterized by single crystal X-ray diffraction. The compounds [(2-apmH)₂MX₄] with M = Co, X = Cl (1); M = Ni, X = Cl (3); and M = Ni, X = Br (4) are isomorphous and crystallize as nearly square planar MX₄ units with the 2-apmH cations coordinated in the axial sites through the unprotonated ring nitrogen. (2-ApmH)₂[CoBr₄] (2) crystallizes as the salt with a nearly tetrahedral CuBr₄ ^2- anion. (2-ApmH₂)[NiBr₂(H₂O)₄]Br₂ (5) forms as a cocrystal of the neutral, six-coordinate nickel complex and (2-ampH₂)Br₂, stabilized by extensive hydrogen bonding. Crystal data (1): monoclinic, P2₁/c, a = 7.540(4), b = 12.954(4), c = 7.277(3) Å, β = 110.09(6), V = 667.4(5) ų, Z = 2, D_calc = 1.955 Mg/m³, μ = 2.079 mm^-1, R = 0.0501 for [|I|≥2(I)]. For (2): triclinic, P-1, a = 7.720(2), b = 7.916(2), c = 14.797(3) Å, α = 97.264(3), β = 104.788(3), γ = 105.171(3)°, V = 825.3(3) ų, Z = 2, D_calc = 2.296 Mg/m³, μ = 10.715 mm^-1, R = 0.0308 for [|I|≥2(I)]. For (3): monoclinic, P2₁/c, a = 7.595(3), b = 12.891(4), c = 7.204(3) Å, β = 111.07(3)°, V = 658.2 ų, Z = 2, D_calc = 1.982 Mg/m³, μ = 2.279 mm^-1, R = 0.0552 for [|I|≥2(I)]. For (4): monoclinic, P2₁/c, a = 7.840(2), b = 13.358(4), c = 7.518(2) Å, β = 110.923(3)°, V = 938.6(3) ų, Z = 2, D_calc = 2.577 Mg/m³, μ = 12.18 mm^-1, R = 0.0280 for [|I|≥2(I)]. For (5): orthorhombic, Pnma, a = 16.776(6), b = 11.943(4), c = 7.079(3) Å, V = 1418.2(9) ų, Z = 4, D_calc = 2.564 Mg/m³, μ = 12.639 mm^-1, R = 0.0381 for [|I|≥2σ(I)].     

Polar bonds in π-complexes. Preparation and crystal structures of cyclopentadienylcarbonyl iron(II) and ruthenium(II) benzoates andp-fluorobenzoates

Complexes of Fe(II) and Ru(II) of the general formula Cp(OC)₂MOC(O)C₆H₄X-p, where M=Fe, X=H, F (1, 2) or M=Ru, X=H, F (3, 4) have been prepared by reactingp-XC₆H₄COOAg with [CpFe(CO)₂]₂ or CpRu(CO)₂I. The crystal structures of complexes1–3 have been determined using X-ray diffraction. Compounds1 and3 are isomorphous. The COO group in1–3 is coordinated as a monodentate ligand. As the latter and the CO ligands are electronically non-equivalent, the coordination of the Cp ligand to the metal is slightly asymmetric.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 395–399, February, 1993.     

Two cadmium compounds with adenine and carboxylate ligands: syntheses,structures and photoluminescence

Two cadmium(II) coordination compounds, [Cd₃(CH₃CO₂)₄(ad)₂(CH₃CN)₂]_n (1) and [Cd₃(5-SIP)₂(H-ad)₂(H₂O)₆]_n (2) (H-ad = adenine and 5-SIP = 5-sulfoisophthalate), were synthesized and characterized. Compound 1 features a two-dimensional (2-D) layered structure based on linear trinuclear [Cd₃(CH₃CO₂)₄] units bridged by monoanionic adenine ligands. In 2, the 5-SIP^3? ligands link Cd(II) ions to form a one-dimensional (1-D) ladder, which is further linked by neutral adenine ligands to give a 2-D layered structure. In both structures, the carboxylate ligands link Cd(II) ions to form low-dimensional structures, which are further connected by adenine ligands to give high-dimensional structures. Compounds 1 and 2 exhibit emissions centered at 382 and 416 nm, respectively, which can be attributed to the ligand centered π–π* transition.     

Synthesis and Characterization of Alkyltris(2-pyridyl)phosphonium Salts

Alkytris(2-pyridyl)phosphonium salts [(2-Py) ₃ PR]X 1 [1a, R = Et, X = Br; 1b, R = Pr, X = Br; 1c, R = Bu, X = Br; 1d, R = CH₂Ph, X = Br; 1e, R = CH ₂ Ph, X = Cl] were synthesised from (2-Py) ₃ P and an excess of RCl. 1c and 1e were found to rapidly decompose in hot acetone to 2,2′-bipyridinium(+1) bromide 2 and (2-Py)P(O)(CH ₂ Ph)C(OH)Me ₂ 3, respectively. A reaction mechanism for both products is proposed. All compounds were fully characterized, including X-ray crystallography for 1a and 3 with 1a being the first representative of this class of compounds characterized by this technique.     

Different Coordination Modes of Saccharin in the Complexes of Lead(II) with 2‐Pyridylmethanol and Pyridine‐2, 6‐dimethanol — Synthesis,Spectral and Structural Characterization

New lead(II)‐saccharin complexes, [Pb(sac)₂(pym)] (1) and [Pb(sac)₂(pydm)] (2) (sac = saccharinate anion; pym = 2‐pyridylmethanol; pydm = pyridine‐2, 6‐dimethanol) were synthesized and characterized by IR spectroscopy and single crystal X‐ray diffractometry. Complex 1 crystallizes in the monoclinic P2₁/c space group with Z = 4, while the crystals of complex 2 are extremely X‐ray sensitive and decompose by the X‐ray beam within one day. Pym and pydm act as bi‐ and tridentate ligands, respectively. Most important feature of the complexes is non‐equivalent coordination of the sac ligands to the lead(II) atom. In the complex 1 , the sac ligands coordinate to the lead(II) ion in two distinct manners. One sac ligand behaves as a bridge between the lead(II) atoms through its N and carbonyl O atoms, whereas the other sac ligand acts as a bidentate chelating ligand through its N and carbonyl O atoms which is bicoordinating and also bridges the metal atoms to achieve the seven‐coordination. The structure is built up of three‐dimensional chains formed by the bridging of the PbN₃O₂ units and also held intermolecular hydrogen bonds. The IR spectra of the complexes were discussed in detail.     

N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamato Complexes of Nickel(II) with Phosphorus Donor Ligands

Planar nickel(II) complexes involving N‐(2‐Hydroxyethyl)‐N‐methyldithiocarbamate, such as [NiX(nmedtc)(PPh₃)] (X = Cl, NCS; PPh₃ = triphenylphosphine), and [Ni(nmedtc)(P‐P)]ClO₄(P‐P = 1,1‐bis(diphenylphosphino)methane(dppm); 1,3‐bis(diphenylphosphino)propane (1,3‐dppp); 1,4‐bis(diphenylphosphino)butane(1,4‐dppb) have been synthesized. The complexes have been characterized by elemental analyses, IR and electronic spectroscopies. The increased νC–N value in all the complexes is due to the mesomeric drift of electrons from the dithiocarbamate ligands to the metal atom. Single crystal X‐ray structure of [Ni(nmedtc)(1,3‐dppp)]ClO₄·H₂O is reported. In the present 1,3‐dppp chelate, the P–Ni–P angle is higher than that found in 1,2‐bis(diphenylphosphino)ethane‐nickel chelates and lower than 1,4‐bis(diphenylphosphino)butane‐nickel chelates, as a result of presence of the flexible propyl back bone connecting the two phosphorus atoms of the complex.