Rob Prins

Synthesis, spectroscopic, and electrochemical properties of bis(2,2′-bipyridyl)-ruthenium compounds of some pyridyl-1,2,4-triazoles

A series of bis(2,2′-bipyridyl)ruthenium compounds with pyridin-2-yl-1,2,4-triazoles has been prepared and characterised by their 1H and 13C n.m.r. spectra and their electronic and electrochemical properties. The 1H n.m.r. spectra have been used to ascertain the co-ordination mode of the ligands. The ligands bind in a bidentate fashion and they have π-acceptor properties that are weaker than 2,2′-bipyridyl (bipy). The excited-state properties of the complexes are similar to those of [Ru(bipy)3]2+ but important variations in the energies of the absorption and the emission maxima are observed.

Trinuclear copper(II) coordination compounds with the new ligand 1,9-bis-(3-amino-4H-1,2,4-triazol-5-yl)-3,7-dithianonane; X-ray structures and magnetochemistry

Abstract The syntheses of three new trinuclear copper(II) complexes with the ligand 1,9-bis-(3-amino-4 H -triazol-5-yl)-3,7-dithianonane (attn) are described. The X-ray structures of two of them, [Cu 3 (attn) 2 (H 2 O) 2 Cl 2 ]Cl 4 (H 2 O) 4 ( 1 ) and [Cu 3 (attn) 2 (ZnCl 4 ) 2 Cl 2 ] (H 2 O) 4 ( 2 ), have been solved. The magnetic properties of these and those of the third related complex, [Cu 3 (attn) 2 (H 2 O) 2 Br 2 ]Br 4 (H 2 O) 4 ( 3 ), have been studied. Crystallographic data: 1 : Cu 3 Cl 6 C 22 H 52 N 16 O 6 S 4 , P i , a = 8.003(3), b = 11.330(4), c = 13.072(6) A , α = 112.36(3), β = 90.62(3), γ = 96.64(3)°, Z = 1, V = 1087(1) A 3 , least-squares refinement based on 8956 significant reflections converged to R ( R w ) = 0.028 (0.037); 2 : Cu 3 Zn 2 Cl 10 C 22 H 48 N 16 O 4 S 4 , P2 1 /c, a = 8.248(5), b = 28.203(3), c = 10.405(4) A , β = 93.07(2)°, Z = 2, V = 2417(2) A 3 , refinement based on 1510 significant reflections converged to R ( R w ) = 0.043(0.049); 3 is isomorphous to 1 . The structures consist of linear trinuclear units of three copper(II) ions bridged by two triazole N1N2 bridges and one chloride. The central copper ion lies on a centre of symmetry, coordinated by 4 N and 2 Cl. The coordination distances in A are: 1 : CuN = 2.040(1) and 1.985(1), CuCl(bridging) = 2.7390(3); 2 : CuN = 2.04(1) and 1.98(1), and CuCl(bridging) = 2.878(3). The terminal copper ions are coodinated by N 2 S 2 Cl 1 O 1 ( 1 ) and N 2 S 2 Cl 2 ( 2 ), respectively. The distances in A are for 1 : CuN = 2.003(1) and 2.023(1), CuS = 2.3854(3) and 2.3637(3), CuCl(bridging) = 2.5505(3), CuO (water) = 2.659(1); for 2 : CuN = 1.99(1) and 1.98(1), CuS = 2.369(4) and 2.390(4), CuCl(bridging) = 2.713(4), CuClZnCl 3 = 2.979(5). The shortest CuCu distances within one cluster are 3.5426(1) and 3.620(3) A for 1 and 2 , respectively. The magnetic susceptibility data have been interpreted on the basis of Heisenberg intracluster interactions ( J = −75.1, −70.9, −72.3 cm −1 for compounds 1,2,3 , respectively); a small intercluster exchange ( zj ′ = + 1.47, +0.81, + 2.03 cm −1 for 1,2 and 3 , respectively) has been taken into account in the mean field approximation.

Acid–base chemistry of polypyridyl ruthenium compounds of (pyridin-2′-yl)-1,2,4-triazoles. X-Ray crystal structure of bis(2,2′-bipyridine)[3-methyl-5-(pyridin-2′-yl)-1,2,4-triazolato-N1]ruthenium hexafluorophosphate tetrahydrate

The acid–base chemistry of the two co-ordination isomers of the complex of bis(2,2′-bipyridyl)-ruthenium(II)[Ru(bipy)2]2+ with 3-(pyridin-2′-yl)-1,2,4-triazole (HL1) and of the analogous compound with 3-methyl-5-(pyridin-2′-yl)-1,2,4-triazole (HL2) has been investigated. As expected the ligands act as stronger acids after binding to the Ru(bipy)2 moiety. The two co-ordination isomers of the HL1 compound show distinctly different pKa values of 4.07 ± 0.05 and 5.95 ± 0.05. Luminescence titrations and lifetime measurements indicate that both ligands are stronger acids in the excited state than in the ground state. This suggests that they act as spectator ligands and are not directly involved in the photophysical processes. The crystal structure of [Ru(bipy)2L2]PF6·4H2O has been determined by single-crystal X-ray diffraction. Crystal data: trigonal, space group P31 with a=b= 1 3.760(6), c= 30.503(9)A, α=β= 90.00, γ= 120.00°, and Z= 6. The refinement based on 4 288 unique reflections [I > 2σ(I)] yielded a R(R′) value of 0.036(0.049). The pyridyltriazole ligand is co-ordinated to ruthenium via the N1 atom of the triazolato ring. The Ru–N distances are between 2.050(5) and 2.086(4)A. Four water molecules have been located near the pyridyltriazole ligand, giving rise to an extended hydrogen-bridged, structure.

Mononuclear rhodium(I) complexes of 4-Amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole. Crystal structure of [Rh(CO)2(NH2bpt)]ClO4

Abstract Reaction of 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole (NH2bpt) or its potassium salt (KNHbpt) with several rhodium(I) compounds, produces new neutral and cationic complexes of Rh(I). One of the complexes [Rh(CO)2(NH2bpt)]ClO4 has been characterized by single-crystal X-ray diffraction. The crystals are monoclinic, space group P21/n, with a = 17.6130(6), b = 11.3072(2), c = 9.0013(2) A, β = 101.536(2)° and Z = 4. The structure has been refined to R = 0.049.

Structures and properties of bis(thiocyanato-N)bis(6-methyl[1,2,4]triazolo[1,a]pyrimidine-N3)copper(II), a distorted tetrahedral copper(II) thiocyanate compound, and bis(thiocyanato-N)bis(5-methyl[1,2,4]triazolo[1,5-a]pyrimidine-N3)copper(II), a polynuclear pseudo-layered system

The molecular structures and spectroscopic properties of the compounds [Cu(NCS)2(L)2] (L = 6-methyl[1,2,4]triazolo[1,5-a]pyrimidine, C6N4H6, abbreviated 6mtp, and L = 5-methyl[1,2,4]triazolo[1,5-a]pyridimine, C6N4H6, abbreviated 5mtp) are described. The structures of [Cu(NCS)2(6mtp)2] (1) and [Cu(NCS)2(5mtp)2] (2) have been determined by single-crystal X-ray diffraction. Compound 1 is monoclinic, space group C2/c, with a = 12.096(9), b = 8.466(6), c = 18.327(7) A, β = 101.95(9)°, Z = 4. Compound 2 is monoclinic, space group P21/c, with a = 12.451(7), b = 8.952(5), c = 8.061(5) A, β = 106.53(2)°, Z = 2. Both structures have been solved from diffractometer data by Patterson and difference Fourier methods, and refined by full-matrix least-squares to R = 0.0365 for 1400 observed reflections (1) and to R = 0.0370 for 1195 independent observed reflections (2). In 1 mononuclear complexes are present, in which each copper atom is surrounded by four donor nitrogen atoms: two N-atoms of two N(3)-coordinating 6mtp ligands, and two N-atoms of the non-bridging NCS-ions in a distorted tetrahedral arrangement (CuN = 1.931(3)–1.975(2) A, NCuN = 93.5(1)–143.5(1)°). In 2 four donor nitrogen atoms, from two N(3)-coordinating 5mtp ligands and two monodentate NCS-ions, give square-planar copper in a trans configuration (CuN = 1.921(4)–2.020(4) A, NCuN = 91.2(1)-88.8(2)°). Two N(1)-atoms of the 5mtp ligands of neighbouring complexes, at a rather long distance of 2.677 A, complete the elongated octahedral coordination of the metal and join the complexes in layers.

A novel type of tetranuclear copper(II) cluster, containing deprotonated 3-(pyridin-2-yl)-5-(pyrazin-2-yl)-1,2,4-triazole (Hppt) as a diatomic bridging ligand. Preparation, magnetism, and X-ray crystal structure of [Cu(µ-ppt)(H2O)]4(NO3)4(H2O)12

The title compound, characterized by means of an X-ray structure analysis, represents the first example of a tetranuclear co-ordination compound with only diatomic bridges.

Synthesis, characterisation, reactivity, and X-ray structure of cis-carbonylchlorobis[1-methyl-3-(pyridin-2-yl)-1,2,4-triazole-N4N′]ruthenium hexafluorophosphate

The compound [Ru(L–L′)2(CO)Cl]PF6[L–L′= 1-methyl-3-(pyridin-2-yl)-1,2,4-triazole] has been obtained in high yield from ruthenium trichloride and the pyridyltriazole ligand in dimethylformamide, as a mixture of co-ordination isomers. One of these isomers was obtained using crystallisation techniques and crystallises in the monoclinic space group P21/n with unit-cell parameters a= 11.085(1), b= 13.120(2), c= 16.108(2)A, β= 97.17(1)°, and Z= 4. The metal cation has a cis geometry for CO and Cl, and the triazole ring is bound to the ruthenium centre via its N4 nitrogen atom. The CO and Cl groups are trans to the triazole rings of the pyridyltriazole ligand. The average ruthenium nitrogen distance is 2.09 A. From this compound the species [Ru(L–L′)(CO)L]+ have been obtained, where L = NCS– or H–. All the compounds have been characterised by spectroscopic, electrochemical, and high-performance liquid chromatographic methods. The results, and in particular the high yield in which the title compound is obtained, strongly suggest that the pyridyltriazole ligand is a weaker π acceptor than 2,2′-bipyridyl.