Silvano F. Colmanet

Preparation and structure of bis(tetraphenylarsonium) trans-aquatetracyanonitridotechnetate(V) pentahydrate. ESR studies of the [TcN(CN)4(OH2)]2-/[TcNCl4]-system

Abstract The reaction of (AsPh4)[TcNCl4] with KCN and added AsPh4Cl in CH3CN/H2O yields crystals of (AsPh4)2[TcN(CN)4(OH2)]·5H2O (1). The complex crystallises in the monoclinic space group P21/n with a=17.107(5), b=19.965(7), c=15.473(5)A, β= 101.70(2)° and Z=4. Refinement with 3212 data measured with Cu Kα radiation converged at R= 0.065. The geometry of the anion is distorted octahedral with a water molecule coordinated trans to the nitrido ligand (TcOH2, 2.56(1) A). The TcN distance is 1.60(1) A. ESR studies have established the presence of two paramagnetic intermediates in the conversion of [TcN(CN)4(OH2)]2− to [TcNCl]4− in HCl solutions.

Preparation and crystal structures of [AsPh4]4[Tc4N4O2(ox)6] and [AsPh4]2[TcO(ox)2(Hox)]·3H2O: technetium complexes containing quadridentate or unidentate oxalato ligands

The reaction of oxalic acid (H2ox) with [AsPh4][TcNCl4] and [NBu4][TcOCl4] in aqueous acetone yields crystals of [AsPh4]4[Tc4N4O2(ox)6](1) and, after precipitation with AsPh4Cl, [AsPh4]2[TcO(ox)2(Hox)]·3H2O (2) respectively. Complex (1) crystallises in the monoclinic space group P21/n with cell parameters a= 14.433(1), b= 13.229(1), c= 27.020(1)A, β= 92.90(1)°, and Z= 4. Refinement with data measured with Cu-Kα radiation converged at R= 0.069 for 3 076 observed reflections. The anion in (1) is a cyclic tetranuclear complex, [Tc4N4O2(ox)6]4–, with Ci point symmetry. Each technetium(VI) atom is co-ordinated by five oxygen atoms and one nitrogen atom to give a distorted octahedron. In each half of the anion, a quadridentate oxalato ligand forms a bridge between the two octahedra, each of which is also linked to an adjacent octahedron by the corner sharing of an oxo ligand. Two oxygen atoms of a bidentate oxalato ligand and a nitrido nitrogen complete the octahedral co-ordination in each polyhedron. The Tc ⋯ Tc spacings of 3.586(2) and 5.756(3)A preclude any Tc–Tc bonding. The monoclinic crystals of complex (2) belong to the space group P21/c with a= 16.495(3), b= 14.802(2), c= 21.805(4)A, β= 98.76(1)°, and Z= 4. Refinement with 5 099 observed data measured with Mo-Kα radiation converged at R= 0.059. The technetium(V) atom is co-ordinated by six oxygen atoms to give a distorted octahedron. The structure of the anion is unusual in that it contains a protonated unidentate oxalato ligand and that there is no appreciable lengthening of the Tc–O bond trans to the oxo ligand.

Preparation of the technetium(VI) aquanitrido complexes (NEt4)[TcNX4(OH2)] (X= Cl or Br). Crystal structures of (NEt4)[TcNBr4(OH2)] and Cs2[TcNCl5]

Addition of NEt 4 X to a conc. HX solution of [TcNX 4 (OH 2 )] − (X= Cl or Br) yields crystals of (NEt 4 )[TcNX 4 (OH 2 )] (X=Cl ( 1 ) or Br ( 2 )). Complex 2 crystallises in the orthorhombic space group Pnma with a = 11.366(1), b = 12.930(2), c = 11.540(1) A and Z = 4. Refinement with 1434 data measured with Cu K α radiation converged with R = 0.047. The complex anion has distorted octahedral geometry with a water molecule trans to the nitrido ligand (TcN 1.599(9) and TcOH 2 2.443(7) A). Crystals of Cs 2 [TcNCl 5 ] ( 3 ) belong to the cubic space group Fm m with a = 10.211(1) A and Z = 4. The ligands of the complex anion are statistically disordered over six octahedral sites as required by the cubic space group. Refinement based on 78 data measured with Cu Kα radiation, and with a fixed TcN distance of 1.6 A, converged with R = 0.034. In this model Tc is displaced 0.401(3) A from the plane of the cis ligands towards the nitrido ligand with TcCl cis = 2.373(5), TcCl tras = 2.740(5) A.

Crystal structures of (AsPh4)[TcO(SCOCOS)2] and (AsPh4)2[TcN(SCOCOS)2]. A comparison of the TcVO3+ and TcVN2+ cores in the same coordination environment

Abstract The reaction of potassium dithiooxalate in acetone with (AsPh4)[TcNCl4] in acetonitrile yields crystals of (AsPh4)2[TcN(SCOCOS)2] (1). We now report the X-ray structures of 1 and the oxo analogue (AsPh4)[TcO(SCOCOS)2] (2), both of which contain the technetium atom in the +5 oxidation state and in the same coordination environment. Crystals of 1 and 2 belong to the triclinic space group P 1 with Z=2. Unit cell parameters are: 1, a=14.225(5), b=17.778(2), c=10.993(3) A, α=101.52(2), β= 111.74(2), γ=100.68(2)° and 2, a=12.294(2), b=12.531(2), c=13.071(2) A, α=115.10(1), β= 114.22(1), γ=101.93(1)°. Refinement with data measured with Cu Kα radiation converged at R= 0.055 for 7569 observed data 1 and at R=0.041 for 4739 observed data 2. The technetium atoms in the complex anions are five-coordinate with the four sulphur atoms in the basal position and either the oxygen or nitrogen in the apical position, to give a distorted square-pyramidal environment about each technetium. The TcO and TcN bond lengths are 1.646(4) and 1.613(4) A in 1 and 2 respectively.

TECHNETIUM(VII) NITRIDOPEROXO COMPLEXES

Preparation of a series of technetium(VII) nitridoperoxo complexes and evidence for [TcN(O 2 )-(OH) 2 ] in solution.

Synthesis and structure of di-µ-oxo nitridotechnetium(VI) dimers and a monomeric nitridotechnetium(V) mixed-ligand complex

The di-µ-oxo technetium(VI) complexes [{TcN(S2CNEt2)}2(µ-O)2]1, [{TcN(S2CNC4H8)}2(µ-O)2]2, [AsPh4]2[{TcN(CN)2}2(µ-O)2]4 and [AsPh4]2[{TcN(edt)}2(µ-O)2]5(H2edt = ethane-1,2-dithiol) have been prepared either by reaction of [{TcN(OH2)3}2(µ-O)2]2+ or Cs2[TcNCl5] in Na4P2O7 solution with the appropriate ligand. The ESR spectra of solutions of 1 and 2 in SOCl2 and of 4 in MeCN with added AsPh4Cl·HCl showed that cleavage of the dimer occurs to give the nitridotechnetium(VI) monomers [TcNCl2(S2CNR2)](R = Et or R2= C4H8) or [TcNCl2(CN)2]–. Reaction of [TcVINCl2(S2CNEt2)] with K2[SCOCOS] gave the mixed-ligand complex [AsPh4][TcVN(S2CNEt2)(SCOCOS)]3. Single-crystal X-ray structures (Cu-Kα radiation) were determined for 1, 2 and 3. Complexes 1 and 2 are dimeric and are best described as two edge-sharing square pyramids, with TcN and Tc–Tc distances of 1.623(4), 1.624(4), 2.543(1), and 1.65(2), 1.59(2) and, 2.542(2)A for 1 and 2 respectively. Complex 3 is monomeric with the technetium atom having a square pyramidal geometry, and a TcN distance of 1.54(2)A.

Evidence for the technetium(VI) aquanitrido cation [{TcN(OH2)3}2(µ-O)2]2+ in solution: preparation and structure of [{TcN(S2CNEt2)}2(µ-O)2]

Electrophoretic and spectroscopic data together with the isolation and structural characterisation of [{TcN(S2CNEt2)}2(µ-O)2] provide evidence for the formation of the TcVI aquanitrido dimer [{TcN(OH2)3}2(µ-O)2]2+ in solutions of weakly co-ordinating acids.

Crystal structure of [AsPh4]2[{TcN(O2)2}2(ox)]·2Me2CO: an oxalate-bridged technetium(VII) nitridoperoxo dimer

Recrystallisation of [AsPh4]2[{TcN(O2)2}2(ox)]1(ox = oxalate (2–)] from acetone gives [AsPh4]2-[{TcN(O2)2}2(ox)]·2Me2CO 2. Complex 2 crystallises in the monoclinic space group C2/c with cell parameters a= 34.49(1), b= 14.684(3), c= 22.776(6)A, β= 107.18(3)° and Z= 8. The structure refined to a final R= 0.092 and R′= 0.100 based on 2156 observed data. The structure is dimeric and consists of two TcN(O2)2 units bridged by a quadridentate sideways-bound oxalate. The geometry about each technetium atom is distorted pentagonal-bipyramidal with the nitrido ligand in an apical position.

Preparation and structure of [Cs(18-crown-6)][TcNCl4]–an ‘infinite sandwich’ Cs+–crown ether complex containing polymeric [TcNCl4]– anions

The compound [Cs(18-crown-6)][TcNCl4] is prepared and is shown to consist of an ‘infinite sandwich’ Cs+ cation/crown ether configuration and two types of polymeric [TcNCl4]– anions, with distinct TcN distances of 1.56(3) and 1.693(5)A, and TcN ⋯ Tc separations of 4.275(4)A.

Preparation and crystal structures of bis(tetraphenylarsonium) tris(oxalato)technetate(IV), and tetraphenylarsonium tris(benzene-1,2-dithiolato)technetate(V): octahedral versus trigonal-prismatic geometry for tris-bidentate complexes of technetium

The addition of [NH4]2[TcBr6] to an aqueous solution of oxalic acid yields the complex [AsPh4]2[Tc(ox)3](1), and the reaction of benzene-1,2-dithiol (H2bdt) with [AsPh4][TcNCl4] in acetone yields crystals of [AsPh4][Tc(bdt)3](2). The syntheses and crystal structures of the two compounds are reported. [AsPh4]2[Tc(ox)3] crystallises in the monoclinic space group C2/c with cell parameters a= 23.164(2), b= 13.507(2), c= 16.047(1)A, and β= 104.90(5)°, with Z= 4. Refinement on 3 223 non-zero data measured with Cu-Kα radiation converged to R= 0.054. The co-ordination geometry of the technetium(IV) atom and the six co-ordinated oxygen atoms is distorted octahedral and of pseudo-D3 symmetry. Crystals of (2) are monoclinic, space group P21/n with a= 12.966(1), b= 12.746(1), c= 23.233(1), and β= 92.27(8)° with Z= 4. Refinement on 5 395 non-zero data measured with Cu-Kα radiation converged to R= 0.048. The technetium(V) atom is co-ordinated to six sulphur atoms in close to ideal trigonal-prismatic geometry. The complex is distorted from ideal D3h symmetry by the bending of SC6H4S ligand planes from the relevant TcS2 planes by 4.1, 1.7, and 1.1°. Factors affecting octahedral versus trigonal-prismatic geometries in these two tris-bidentate complexes are discussed.