Experimental and theoretical studies on ferromagnetically coupled metal complexes with imino nitroxides

Copper(II), zinc(II), and nickel(II) complexes with tridentate imino nitroxyl diradicals, [CuCl(bisimpy)(MeOH)](PF(6)) (1), [ZnCl(2)(bisimpy)] (2), and [NiCl(bisimpy)(H(2)O)(2)]Cl x 2H(2)O (3) (bisimpy = 2,6-bis(1'-oxyl-4',4',5',5'-tetramethyl-4',5'-dihydro-1'H-imidazol-2'-yl)pyridine), were prepared, and their magnetic properties were studied. In 1, the Cu(II) ion has a square pyramidal coordination geometry, of which the equatorial coordination sites are occupied by three nitrogen atoms from the bisimpy and a chloride ion. The coordination geometry of the Zn(II) ion in 2 can be described as a trigonal bipyramid, with two chloride ions and a bisimpy. In 3, the Ni(II) ion has a distorted octahedral coordination geometry, of which four coordination sites are coordinated by the bisimpy and chloride ion, and two water molecules occupy the remaining cis positions. Magnetic susceptibility and EPR measurements revealed that in 1 and 3 the Cu(II) and Ni(II) ions with imino nitroxyl diradicals were ferromagnetically coupled, with the coupling constants J (H = -2J(ij) summation operator S(i)S(j)) of +165(1) and 109(2) cm(-1), respectively, and the intraligand ferromagnetic interactions in 1-3 were very weak. DFT molecular orbital calculations were performed on the diradical ligand, 1, and 2 to study the spin density distribution before and after coordination to the metal ions.     

Synthesis and reactivity of ruthenium tetrazolate complexes containing a tris(pyrazolyl)borato (Tp) ligand

Facile ligand substitutions are observed when the neutral ruthenium cyclopropenyl complex (PPh₃)[Ru]-CC(Ph)CHCN (1, [Ru] = Tp(PPh₃)Ru) is treated with MeCN and pyrazole yielding the nitrile substituted ruthenium cyclopropenyl complex (MeCN)[Ru]-CC(Ph)CHCN (4a) and the ruthenium metallacyclic pyrazole complex (C₃H₃NN)[Ru]-CC(Ph)CH₂CN (7a), respectively. The reactions of Me₃SiN₃ with 1, 4a and 7a are investigated. Treatment of 1 with Me₃SiN₃ affords in high yield the cationic N-coordinated nitrile complex {(PPh₃)[Ru]NCCH(Ph)CH₂CN}N₃ (3). Interestingly, the reaction of 4a with Me₃SiN₃ in CH₂Cl₂ in the presence of NH₄PF₆ results in an insertion of four nitrogen atoms into the Ru-C_α bond to form a diastereomeric mixture of the bright yellow zwitterionic tetrazolate complex (MeCN)[Ru]-N₄CCH(Ph)CH₂CN (6a) in a 3:2 ratio. The reaction of 7a with Me₃SiN₃ gives the zwitterionic tetrazolate complex (C₃H₃NNH)[Ru]-N₄CCH(Ph)CH₂CN (9a). The two cationic tetrazolate complexes {(C₃H₃NNH)[Ru]-N₄(R)CCH(Ph)CH₂CN}⁺ (12a, R = CH₃, 12b, R = C₆H₅CH₂) are prepared by electrophilic addition of organic halides to 9a. All of the complexes are identified by spectroscopic methods as well as elemental analysis. Pathways for the synthesis of these compounds are proposed.     

ScorpoPhos: a novel phosphine-nitrogen ligand containing a tris(pyrazolyl)borate ligand core

A new tris(pyrazolyl)borate ligand bearing phosphine donor groups appended to the 3-position of the pyrazolyl rings is reported, and the hemilabile behaviour of this tris-N,P ligand in coordination with K+, Tl+ and Cu+ ions is investigated.     

Dinuclear oxovanadium(IV) thiolate complexes with ferromagnetically coupled interaction between vanadium centers

Two dinuclear oxovanadium(IV) thiolate complexes, [N(C5H11)4]2[VOL1]2 (1) and [N(C4H9)4][(VOL2)2(mu-OCH3)] (2) (where L1 = [(CH3)SiO(C6H4-2-S)2]3- and L2 = [(C6H5)PO(C6H4-2-S)2]2-), have been synthesized and characterized. The geometry of the anion in 1 can be classified to an edge-sharing bi-square-pyramid with a syn-orthogonal configuration. The one in 2 can be view as a face-sharing bioctahedron with two oxo groups in syn positions. Of note, these two complexes display intramolecular ferromagnetic interaction between two metal centers.     

Distorted pentacoordinate copper(II) complexes containing a tridentate ligand

Summary Copper(II) complexes with a tridentate chelating ligand within the general 2N, X (X = O or S) donor class, containing abis(benzimidazolyl) donor set, were prepared and characterized. X-band e.p.r. spectra of the complexes indicateg >g and the largeg and lowA have been interpreted in terms of a distorted basal plane. Superimposed on theg component are five SHF lines withA _N = 16±2G, supporting the interaction of two nitrogen atoms with the copper nucleus. Thus, the basal plane of the complex comprises 2N atoms, with the ligand hetero atom being axially coordinated.     

Allosteric anion recognition by metal complexation of tris(bipyridine-imidazolium) ligand

A new tripodal imidazolium ligand 2 comprising three 2,2′-bipyridine-imidazolium subunits connected through a mesityl spacer has been synthesized and 1:1 complexes of 2 with Fe(II) and Ru(II) ions have been prepared. ¹H NMR spectroscopy including NOE analysis and molecular modeling study established that the complexes exist as a pseudocryptand type twisted structure in solution. The Fe(II) and Ru(II) complexes show strong 1:1 binding of Cl⁻, Br⁻, and I⁻ anions in MeCN-d₃ with a large enhancement of the guest selectivity (Cl⁻ > Br⁻ > I⁻) upon metal complexation.     

Structural diversity in metal complexes with a dinucleating ligand containing carboxyamidopyridyl groups

The synthesis of a (carboxyamido)pyridinepyrazolate (H(5)bppap) dinucleating ligand is described. Bimetallic iron and cobalt complexes of H(5)bppap ([M(II)(2)H(2)bppap](+)) showed structural differences in both their primary and secondary coordination spheres. The binding of small molecules into the preorganized ligand cavity is verified by the hydration of [Fe(II)(2)H(2)bppap](+) and [Co(II)(2)H(2)bppap](+), leading to the formation of complexes [{Co(II)(OH)}Co(II)H(3)bppap](+) and [{Fe(II)(OH)}Fe(II)H(3)bppap](+), in which one of the metal centers has a terminal hydroxo ligand.     

Platinum(II) complexes containing the 3,3-dimethylglutarimidate ligand

Reaction of cis-[PtCl₂(PPh₃)₂] with excess 3,3-dimethylglutarimide (dmgH) and sodium chloride in refluxing methanol gives the mono-imidate complex cis-[PtCl(dmg)(PPh₃)₂], which was structurally characterized. The plane of the imidate ligand is approximately perpendicular to the platinum coordination plane which, coupled with restricted rotation about the Pt–N bond, results in inequivalent methyl groups and CH₂ protons of the dmg ligand in the room temperature ¹H NMR spectrum. These observations were corroborated by a theoretical study using density functional theory methods. The analogous bromide complex cis-[PtBr(dmg)(PPh₃)₂] can be prepared by replacing NaCl with NaBr in the reaction mixture.     

Mixed ligand complexes of platinum(0) containing diphosphines

The reaction of PtCl₂L (L = diphosphine) with the appropriate diphosphine L′ in ethanol followed by reduction with aqueous sodium borohydride leads to either disproportionation to give mixtures of the bis(diphosphine) complexes PtL₂ and PtL′₂ or to the formation of the mixed ligand complex PtLL′ depending on the diphosphines. Mixed ligand complexes are obtained when L=Ph₂P(CH₂)₂PPh₂, L′ = Ph₂P(CH₂PPh₂cis-Ph₂PCH CHPPh₂, Ph₂P(CH₂)₂AsPh₂, Ph₂- P(CH₂)₄PPh₂, o-Ph₂PC₆H₄PPh₂; and L=(C₆H₁₁)₂P(CH₂₂P(C₆H₁₁)₂, L′= Ph₂P(CH₂)PPh₂, Ph₂P(CH₂)₂PPh₂cis-Ph₂PCHCHPPh₂, (2S,3S)-Ph₂PCH- (CH₃)CH(CH₃)PPh₂, (R)-Ph₂PCH(CH₃)CH₂PPh₂. When L=Ph₂P(CH₂)₄PPh₂ L′= Ph₂P(CH₂₃PPh₂ or cis-Ph₂PCHCHRPh₂ the mixed ligand complexes are obtained but extensive disproportionation also occurs.     

The optical resolution of tris(pentane-2,4-dionato)metal(III) complexes

A facile large-scale optical resolution of neutral [M(pd)₃] complexes, M = Cr(III), Co(III), Ru(III), Rh(III) and Ir(III), through enantioselective complex formation with (2R, 3R)-(-)-dibenzoyltartaric acid, is described.     

Binuclear metal(II) complexes of a 30-membered hexa-aza macro-cyclic ligand

Summary Schiff base [2 + 2] condensation of p-phthalaldehyde with the triamine 1,7-diamino-4-azaheptane followed by reduction with NaBH₄ gives a 30-membered hexa-aza macrocyclic ligand. A series of binuclear copper(II), nickel(II) and zinc(II) complexes have been prepared and characterized, ¹H-n.m.r., u.v.-vis. and i.r. measurements are reported with associated magnetic and electrochemical studies.Author to whom all correspondence should be directed.     

Ruthenium hydride complexes of the hindered phosphine ligand tris(3-diisopropylphosphinopropyl)phosphine

The synthesis and characterization of the novel hindered tripodal phosphine ligand P(CH(2)CH(2)CH(2)P(i)Pr(2))(3) (P(3)P(3)(iPr)) (1) are reported, along with the synthesis and characterization of ruthenium chloro and hydrido complexes of 1. Complexes [RuCl(P(3)P(3)(i)Pr)][BPh(4)] (2[BPh(4)]), RuH(2)(P(3)P(3)(i)Pr) (3), and [Ru(H(2))(H)(P(3)P(3)(iPr))][BPh(4)] (4[BPh(4)]) were characterized by crystallography. Complex 2 is fluxional in solution, and low-temperature NMR spectroscopy of the complex correlates well with two dynamic processes, an exchange between stereoisomers and a faster turnstile-type exchange within one of the stereoisomers.     

Synthesis of ruthenium tris(2,2′-dipyridyl) complexes containing ethynyl substituents

A method was developed for the synthesis of Ru2+ tris(2,2′-dipyridyl) complexes where one of the ligands contains substituents with triple bonds conjugated with the dipyridyl system.     

Silver(I) carbonyl and silver(I) ethylene complexes of a B-protected fluorinated tris(pyrazolyl)borate ligand

B-methylated ligand [MeB(3-(C2F5)Pz)3]-enables the isolation of a lithium adduct [MeB(3-(C2F5)Pz)3]Li with fac-N3F3 coordination, and rare isolable silver carbon monoxide and silver ethylene complexes, [MeB(3-(C2F5)Pz)3]AgCO and [MeB(3-(C2F5)Pz)3]AgC2H4.     

Synthesis and characterization of some transition metal complexes containing a nitrogen-oxygen donor macrocyclic ligand

Summary The synthesis and characterization of some Co^II, Ni^II and Cu^II complexes with a nitrogen-oxygen donor macrocyclic ligand is reported. Analytical data, i.r. and visible spectra are compatible with an octahedral or distorted octahedral coordination around the metal. For each of the CoL(NCS)₂ and NiL(NCS)₂ complexes, two crystalline forms were obtained, having different i.r. absorptions for the thiocyanate groups and different x-ray powder diffraction spectra; the pairs of Co-Ni complexes appear to be isostructural.     

Base hydrolysis of tris(acetylacetonato)metal(III) complexes involving technetium and ruthenium

Irradiation of chloro- and bromoalkanes in solid cis-decalin-d₁₈ results in the selective formation (as major paramagnetic species) of alkyl radicals that are specific or the haloalkane solute, in addition to matrix radicals. The method offers a convenient and universal technique for generating, specific alkyl radicals and for examining their powder ESR spectrum. Examples of the generation of chain-end, penultimate and interior alkyl radicals are given. Computer calculations, in which spectra of penultimate and interior radicals are added, clearly demonstrate that quite extensive amounts of interior radicals can be present in a radical mixture, without considerably affecting the composite spectrum.