Masakazu Hirotsu

Antiferromagnetism induced by successive protonation of terminal phenol groups of a bis(μ-phenoxide)-bridged dicopper(II,II) complex

The reaction of a tripodal ligand (H2L = nN,N-bis(2-hydroxybenzyl)-N′,N′-dimethylethylenediamine) with Cu(NO3)2·3H2O and Cu(ClO4)2·6H2O in methanol yielded [Cu2(HL)2](NO3)2·H2O (1) and [Cu2(HL)2](ClO4)2 n(1′), respectively. When H2L was allowed to react with CuSO4·5H2O in the presence of triethylamine (1 ∶ 1 ∶ 2) in methanol, the neutral dicopper(II,II) complex [Cu2(L)2] n(2) was obtained. The monopositive species [Cu2(L)(HL)]ClO4·CH3OH·H2O (3) crystallized on mixing 1′ and 2 n(1 ∶ 1) in methanol–dichloromethane. The crystal structures of 1, 2, and 3 were determined by X-ray crystallography. All of the complexes consist of a discrete dinuclear molecule with bis(μ-phenoxide)-bridges. The tripodal ligand functions as a tetradentate ligand and one of the phenolic oxygen atoms serves as a bridging ligand. Protonation/deprotonation takes place at the terminal phenol moiety and as the phenol group is deprotonated the coordination geometry changes from a distorted square pyramid to a distorted trigonal bipyramid. The two copper ions in 1–3 are antiferromagnetically coupled with 2J n= n−714 (1), −19.9 (2), and −277 cm−1 n(3). The results clearly demonstrate that protonation/deprotonation causes a change in coordination geometry, which in turn drastically affects magnetic exchange interactions.

Preparation and properties of dinuclear dioxomolybdenum(VI) complexes with ONO–ONO-type hexadentate Schiff base ligands

Abstract Preparation and properties of dinuclear cis- dioxomolybdenum(VI) complexes containing ONO–ONO-type hexadentate Schiff bases derived from 2,5-dihydroxyterephthalaldehyde and aminoalcohols in a 1:2 molar ratio are reported. When 2-amino-2-methyl-1,3-propanediol was used as the aminoalcohol, the 1 H NMR spectrum of the complex showed two sets of resonances, indicating the presence of two isomers. The origin of the isomerism was elucidated by variable-temperature 1 H NMR spectroscopy and by comparing the 1 H NMR spectrum with those of the analogous dinuclear complexes derived from (1 R ,2 S )- and (1 S ,2 R )-norephedrine and with those of the corresponding mononuclear complexes. The Schiff base ligand derived from 2,5-dihydroxyterephthalaldehyde and 2-amino-2-methyl-1,3-propanediol contains two prochiral carbon atoms, which become chiral ( R and S ) upon coordination. The combination of these two chiral centers generates three stereoisomers, RR , SS , and RS (= SR ), and the NMR characteristics were accounted for by these isomers.

Spontaneous reduction of gold(III) to gold(I) by forming sulfur-bridged polynuclear structure with octahedral tris(thiolato) complexes

Abstract The reaction of fac(S)-[RhIII(aet)3] (aet = 2-aminoethanethiolate) with [AuIIICl4]− in water gave an S-bridged pentanuclear complex [AuI 3{RhIII-(aet)3}2]3+(1), accompanied by the spontaneous reduction of AuIII to AuI. The crystal structure of 1(NO3)3·4H2O was determined by X-ray crystallography. In 1 two octahedral fac(S)-[Rh(aet)3] units are linked by three linear AuI atoms to form a trigonal-bipyramid-type RhIII 2AuI 3 pentanuclear structure with an averaged AuI-AuI distance of 3.083(5) Å. The two RhIII 2AuI 3 cations contact with each other through one AuI-AuI interaction with a distance of 3.311(3) Å. The optically active δδ-1 was derived from ΔΔΔΔ-[Zn3(OH){Rh(aet)3}4]5+ by reacting with [AuCl4]− in water.

Linkage of [Cr(aet) 3 ] or [Cr( D -pen- N , O , S ) 2 − Octahedral Units by Forming S-Bridged Structures with AG I or Au I Ions (aet=2-aminoethanethiolate, D -pen= D -penicillaminate)

The reaction of [Cr(aet) 3 ] (aet=2-aminoethanethiolate) with Ag I in water gave an S-bridged Cr III 2 Ag 3 I pentanuclear complex [Ag 3 {Cr(aet) 3 } 2 ] 3+ ([1] 3+ ). The crystal structure of [1](NO 3 ) 3 2H 2 O was determined by X-ray analysis, which established that two fac ( S )-[Cr(aet) 3 ] units are linked by three Ag I ions through S atoms (average Cr-S=2.387(5), Ag-S= 2.403(5) Å). The three Ag I ions in [ 1 3+ were replaced by Au I ions to form the corresponding Cr 2 III Au 3 I pentanuclear complex [Au 3 {Cr(aet) 3 } 2 ] 3+ ([ 2 ] 3+ ). Treatment of [Cr( D -pen- N, O, S ) 2 ] m ( D -pen= D -penicillaminate) with Ag I in water produced an S-bridged Cr 3 III Ag 3 I hexanuclear complex [Ag 3 {Cr( D -pen- N, O, S ) 2 } 3 ] ([ 3 ]), which has a cyclic structure composed of three trans ( O )-[Cr( D -pen- N, O, S ) 2 ] m units. Variable-temperature magnetic susceptibility data indicated the weak antiferromagnetic interaction for [ 1 3+ ] ( J = m 0.84 cm m 1 ) while the very weak ferromagnetic interaction for [ 3 ] ( J =0.05 cm m 1 ). chromium(III) silver(I) gold(I) S-bridge

An unexpected chelate conformation in trans-[(R)-N,N′-bis(α-phenyl­salicyl­idene)­propane-1,2-diaminato(2–)]­bis(1-methyl-1H-imidazole-κN3)­cobalt(III) perchlorate

The title compound, [Co(C 29 H 24 N 2 O 2 )(C 4 H 6 N 2 ) 2 ]ClO 4 , contains an optically active tetradentate Schiff base ligand in an equatorial plane and two 1-methylimidazole ligands at apical positions. The central N-C-C-N chelate ring of the Schiff base ligand has an envelope structure with a λ conformation, which is different from the solution structure predicted from circular dichroism and H NMR spectra.

(2-Aminoethanethiolato-N, S)bis-(ethylenediamine-N, N')cobalt(III) dinitrate

In the title compound, [Co(C(2)H(6)NS)(C(2)H(8)N(2))(2)](NO(3))(2), the Co(III) atom has a slightly distorted octahedral geometry, coordinated by one 2-aminoethanethiolate and two ethylenediamine ligands. The three five-membered chelate rings adopt a gauche conformation with the unfavoured (lel)(2)(ob) form, which is ascribed to hydrogen bonds between the amine groups in the complex cation and the nitrate counter-anions [N.O 2.900 (3)-3.378 (3) A].

Sulfur-Bridged Co III Pt II Co III Trinuclear Complex Acting as an S-Donating Complex-Ligand

The reaction of fac(S) -[Co(aet) 3 ] (aet=H 2 NCH 2 CH 2 S m ) with [PtCl 2 {Co(aet) 2 (en)}] + gave an S-bridged Co III Pt II Co III trinuclear complex, [Pt{Co(aet) 3 }{Co(aet) 2 (en)}] 3+ ([ 1 ] 3+ ). The crystal structure of [ 1 ]Cl 3 was determined by X-ray crystallography. In [ 1 ] 3+ , the central Pt II atom is coordinated by four thiolato S atoms from octahedral C 2 - cis(S) -[Co(aet) 2 (en)] + and mer(S) -[Co(aet) 3 ] units in a square-planar geometry, giving a linear-type S-bridged trinuclear structure with a non-bridging thiolato group. Treatment of [ 1 ] 3+ with linear Au I produced an S-bridged Co III 4 Pt II 2 Au I heptanuclear complex, [Au{Pt[Co(aet) 3 ][Co(aet) 2 (en)]} 2 ] 7+ ([ 2 ] 7+ ), which indicated that [ 1 ] 3+ acts as a new class of S-donating trinuclear complex-ligand. polynuclear complexes cobalt platinum gold S ligands

Rhodium(III) complexes with thiolate and thioether ligands derived from fac(S)-[Rh(aet)3] (aet = 2-aminoethanethiolate): selective formation, characterization and properties

Alkylation of fac(S)-[Rh(aet)3] (aet = NH2CH2CH2S−) with use of 1,2-dibromoethane in N,N-dimethylformamide produces fac(S)-[Rh(aet)(baete)]2+ ([1]2+, baete = (NH2CH2CH2SCH2)2), in which two of the three thiolato S atoms in fac(S)-[Rh(aet)3] are linked by an ethylene group. When methyl iodide is used as an alkylating reagent, two of the three thiolato S atoms are methylated to give fac(S)-[Rh(aet)(mtea)2]2+ ([2]2+, mtea = NH2CH2CH2SCH3). Complexes [1]2+ and [2]2+ nwere optically resolved into the two enantiomers by SP-Sephadex C-25 column chromatography. The synthesis of a trimethylated complex, fac(S)-[Rh(mtea)3]3+ ([3]3+), has been achieved by treatment of an aqueous solution of [2]2+ with dimethyl sulfate. Reactions of [1]2+ or [2]2+ with Ag+ in a 2 ∶ 1 molar ratio in water produce S-bridged RhIIIAgIRhIII trinuclear complexes, [Ag{Rh(aet)(baete)}2]5+ ([4]5+) and [Ag{Rh(aet)(mtea)2}2]5+ ([5]5+), nindicating that [1]2+ and [2]2+ act as an S-donating monodentate complex-ligand. These complexes have been characterized by UV-VIS absorption, CD and NMR spectroscopic methods, together with single-crystal X-ray analyses for [1]2+ and [3]3+.