Izak M. Potgieter

The kinetics and mechanism of the substitution reactions oftrans-tetracyanodioxotungstate(IV) ions with monodentate ligands

SummaryThe kinetics of the substitution reactions of the protonated forms oftrans-tetracyanodioxotungstate(IV) ions with pyridine and thiocyanate ions were studied. The kinetic results were compared with those of the reactions with N3− and F− ions and a linear free energy relationship was obtained which was interpreted as additional evidence for a dissociative mechanism. Infrared data for this type of complex are reported and discussed in terms of thetrans influence of various monodentate ligands.

Observedtrans influence of donor atoms in monocharged bidentate ligands: Crystal structure of the acetone solvate of 2-carboxyquinolinatocarbonyltriphenylphosphinerhodium(I)

Summary2-Carboxyquinolinatocarbonyltriphenylphosphinerhodium(I), [Rh(Quin)(CO)(PPh3)], was prepared by replacement of CO by PPh3 in the corresponding dicarbonyl. The compound crystallizes in the triclinic space group

Crystal structure of tetraphenylarsonium aquatetracyanonitridorhenate(V), (AsPh4)2 [ReN(H2O)(CN)4]·5H2O

P\bar 1

Kinetic study of the reaction betweentrans-tetracyanodioxomolybdate(IV) and fluoride ions

Åb=17.168(6) Å,c=9.254(5) Å, α=101.49(5)°, β=95.74(4)°, γ=98.41(4)°, dcxp=1.45g cm−3 and Z=2. The crystal structure was dermined from 3496 observed reflections. The final R value was 0.061. This structure determination indicates that the nitrogen atom of the chelate ring has the largesttrans influence since the carbonyl grouptrans to this atom was substituted by the PPh3 ligand. The effects of different donor atoms in bidentate ligands, as well as the ring size of the chelate ring, on the relativetrans influence of the donor atoms are discussed.

Kinetic study of the reaction between trans-dioxotetracyanomolybdate(IV) ions and 1,10-phenanthroline

SummaryThe structure of (AsPh4)2[WO(CN)3(Pic)] · 2H2O has been determined from three dimensional x-ray data. The cell dimensions are:a=17.699(8),b=13.546(6),c= 13.590(6) Å, α=117.39(8), β = 71.54(7) and γ = 115.04(8)°, space group P¯1, Z = 2, The structure was solved from 5279 observed reflections. The anisotropic refinement converged to R = 0.060.The [WO(CN)3(Pic)]2−-ion is a distorted octahedron. The structure indicates that the aqua group in [WO(CN)4(H2O)]2− was displaced by an oxygen atom of the carboxylate of 2-picolinate, while a cyanide ligand was substituted by the pyridine nitrogen atom. Themer-arrangement of the three cyanide ligands has two normaltrans W-Cav = 2.17(2) Å bond distances and a significant shorter W-C = 2.042(18) Å bond trans to the W-N [2.188(18) Å] bond. The W=O and W-O bond lengths are 1.676(9)Å and 2.171 Å, respectively.

A kinetic study of the oxidation of formaldehyde by the octacyanomolybdate(V) ion in aqueous alkaline medium

SummaryThe crystal structure of (AsPh4)2[ReN(H2O)(CN)4]·5H2O has been determined from three-dimensional X-ray diffraction data. The yellow crystals are monoclinic, space group P21/n with cell dimensionsa=15.482(1),b=19.950(2),c=16.999(1)Å and β=101.69(6)o,Z=4,Dexpt=1.48(1)g cm−3 andDcalc=1.52g cm−3. The anisotropic refinement of 7858 observed reflections converged toR=0.055. The [ReN(H2O)(CN)4]2− ion has a distorted octahedral geometry. Bond distances: Re≡N=1.639(8), Re−OH2=2.496(7) and Re−C(av)=2.11(1) Å. The rhenium atom is displaced by 0.35 Å out of the plane formed by the four carbon atoms of the cyano ligands towards the terminal nitrido ligand.

The oxidation of acetaldehyde by the octacyanomolybdate(V) ion in an aqueous alkaline medium

The crystal structure of (Me4N)3[WO(CN)4(NCS)]·NaNCS was determined from three-dimensional x-ray diffraction data. The dark blue crystals are monoclinic, space group C2/m, with cell dimensions a=13.105(4), b=12.688(2), c=18.871(3) Å, β=100.4(8)°, z=4 and D=1.46 g cm−3. Anisotropic refinement of 1333 observed reflections converged to R=0.068. The [WO(CN)4(NCS)]3− ion is a distorted octahedron with the tungsten atom displaced by 0.35 Å out of the plane formed by the four cyano ligands, towards the oxo ligand. The coordinated thiocyanate ligand is bonded to the tungsten atomvia the nitrogen atomtrans to the oxo ligand. Bond distances found: W−CNav=2.14(3), W−O=1.61(2) and W−NCS=2.23(2) Å. The compound crystallizes as an adduct with an additional thiocyanate anion, ionically bonded to a severely disordered sodium cation. The results correlate with available data from similar complexes.

A kinetic study of the reduction of the octacyanomolybdate(V) ion by the hydroxide ion

SummaryThe kinetics of the reaction between [MoO2(CN)4]4− and F− have been studied in the pH range 8 to 11. The results indicated that the diprotonated form, [MoO(OH2)(CN)4]2−, is the only reactive species and that the aqua-ligand is substituted by the F− ion according to the following reaction. The k1 and k−1 values are 8.8(2) M−1 s−1 and 0.6(1)s−1, respectively, at 15°C. A dissociative substitution process is proposed.