Sen-ichi Aizawa

Complexation equilibria and structures of dimethyltin (IV) complexes with N-methyliminodiacetate, pyridine-2,6-dicarboxylate, ethylenediamine-N,N′-diacetate and ethylenediamine-N,N,N′,N′-tetraacetate

Abstract The complexation equilibria of the dimethyltin (IV) ion with N -methyliminodiacetate (mida), pyridine-2,6-diacarboxylate (pdc), ethylenediamine- N , N ′-diacetate (edda) and ethylenediamine- N , N , N ′, N ′-tetraacetate (edta) have been investigated in aqueous solution at 25.0 °C and I = 0.1 mol dm −3 ((H, Na)NO 3 ) by potentiometric measurements. The overall stability constants B pqr for [(SnMe 2 ) p H q L r ] (2 p + q − nr ) + ( n = 2 for L = mida, pdc, edda; n = 4 for L = edta) defined as [[(SnMe 2 ) p H q L r ] 2 p + q − nr ) + ] [SnMe 2 2+ ] − p [H + ] − q [L n − ] −1 are evaluated as follows: log β 1−11 = 2.53(3), log β 101 = 9.625(4) and log β 112 = 20.73(4) for L = mida; log β 101 = 10.533(6), log β 111 = 12.65(5) and log β 112 = 17.69(3) for L = pdc; log β 101 = 12.412(8), log β 111 = 15.75(3), log β 112 = 24.12(4) and log β 122 = 30.87(4) for L = edda; log β 2−21 = 4.75(1), log β 2−11 = 10.44(2) and log β 201 = 15.41(2) for L = edta. The crystal structures of [SnMe 2 (mida)(H 2 O)] · H 2 O, [SnMe 2 (pdc)(H 2 O)] · H 2 O, [SnMe 2 (edda)] and [(SnMe 2 ) 2 (edta) (H 2 O) 2 ] · H 2 O have been determined by X-ray crystal structure analyses. The mida and pdc complexes have a dimeric structure which consists of distorted pentagonal-bipyramidal tin units with two methyl groups in the axial position. The edda complex has a distorted octahedral monomer structure with two methyl groups in the cis position. The edta complex consists of a polymer structure with spanning edta ligands in which each tin unit has a geometry quite analogous to those of the mida and pdc complexes. The preference in geometry of the dimethyltin(IV) complexes is discussed in terms of the effects of the bound ligands. The dimethyltin(IV) complexes formed in aqueous solution have been characterized on the basis of the molecular structures in the crystals and the values of the stability constants and p K a .

Complexation equilibria of oxy-acid–2-amino-2-deoxy-d-gluconic acid–metal(II) ion ternary systems in aqueous solution as studied by potentiometry. Binding characteristics of borate and germanate

Abstract The complexation equilibria for the boric acid– d -glucosaminic acid and d -glucosaminic acid–metal(II) ion binary systems, the boric acid– d -glucosaminic acid–metal(II) ion ternary system, and the corresponding binary and ternary systems with germanic acid instead of boric acid involving nickel(II), zinc(II), cadmium(II) and lead(II) as the metal(II) ion have been investigated in aqueous solution at 25°C and I =0.1 mol dm −3 (NaClO 4 ) by potentiometric measurements ( d -glucosaminic acid is 2-amino-2-deoxy- d -gluconic acid). The complexes have been characterized in aqueous solution by 13 C NMR spectra and the p K a values. The 1:2 ester of borate and d -glucosaminate shows a selectivity for metal(II) ions different from the free d -glucosaminate ligand. It has been demonstrated that the coordination site of the 1:2 ester can distinguish the difference in metal ion size. Such selectivity for metal(II) ions in the boric acid system is discussed by comparison with the germanic acid system.

Hydrolysis, polymerisation, and structure of dimethyltin (IV) in aqueous solution. Molecular structure of the polymer [(SnMe2)2(OH)3]ClO4

The hydrolysis and polymerisation equilibria of dimethyltin(IV) ion have been investigated by potentiometric measurements at 25 °C and I= 0.10 mol dm–3(NaNO3). Tetramer formation has been observed at high concentrations of dimethyltin(IV) ion up to 6 × 10–2 mol dm–3. The polymer structure of [(SnMe2)2(OH)3]ClO4 has been determined by crystal structure analysis: triclinic, space group P, a= 8.533(1), b= 9.474(1), c= 9.479(2)A, α= 88.27(1), β= 68.97(1). γ= 74.44(1)°, Z= 2. The final R value is 0.029. The polymer consists of five-co-ordinate tin(IV) units with di- and mono-hydroxo bridging. The co-ordination geometry of the tin unit is a distorted trigonal bipyramid with two methyl groups and one µ-hydroxo group in equatorial positions and the other two µ-hydroxo groups in axial positions. The species formed by hydrolysis have been characterised on the basis of the molecular structure in the crystals and are discussed together with their pKavalues.