M. Sakhawat Hussain

X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and electrical conductivity studies of copper phosphate glasses

Phosphate glasses containing CuO with composition (CuO)x(P2O5)1-x, where x = 0.1, 0.2, 0.3, 0.4 and 0.5, were studied by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR) and room temperature electrical conductivity, σ. The spin orbit components Cu 2p32 and Cu 2p12 show doublet structures which may be associated with Cu+ and Cu2+. The ratio C = Cu+Cutotal as a function of x was determined using the Cu 2p32 spectra. It is observed that the ratio, C, initially decreases with x, becomes minimum at x = 0.3 and then increases. Although the variation of σ with C was very small, it is close to the uncertainty in the measurement of its value; nevertheless it was maximum at C = 0.5, in agreement with the previous prediction. The FT-IR spectra indicated a maximum shift in the P = O absorption at 30% CuO contents in the glasses, which essentially follows the same pattern as the shift for the POP absorption. Further, the development of the high energy component peak in the O 1s (associated with POP oxygen) spectra follows a trend similar to the 760 cm−1 (also associated with POP) absorption band in the FT-IR spectra.

13C, 15N AND 31P NMR STUDY OF THE DISPROPORTIONATION OF CYANOGOLD(I) COMPLEXES : R3PAU13C15N

Abstract The disproportionation of cyanogold(I) complexes of general formula [R 3 PAu 13 C 15 N] forming [(R 3 P) 2 Au] + and [Au( 13 C 15 N) 2 ] − ions has been investigated using 13 C, 15 N and 31 P NMR spectroscopy for a series of phosphines with R=cyclohexyl, i -propyl, Et, Me, cyclohexyl/diphenyl, o -tolyl, p -tolyl, m -tolyl, p -tolyl/diphenyl, allyl/diphenyl, phenyl, tri(cyanoethyl) CEP, and 1-naphthyl. The 13 C NMR of the 13 C 15 N group in these complexes exhibited two distinct resonances, one due 13 C in the starting [R 3 PAu 13 C 15 N] complex and the second in the [Au( 13 C 15 N) 2 ] − anion. The 31 P NMR spectra revealed two 31 P resonances due to [R 3 PAu 13 C 15 N] complex, and the [(R 3 P) 2 Au] + cation. The 15 N NMR revealed only an averaged resonance due to [R 3 PAu 13 C 15 N] and [Au( 13 C 15 N) 2 ] − anion, except in the cases of [Me 3 PAu 13 C 15 N] and [Et 3 PAu 13 C 15 N] where two resonances were observed. The coupling constants, 1 J( 13 C– 15 N), 2 J( 31 P– 13 C) and 3 J( 31 P– 15 N) were obtained for all complexes and the free energies of activation for ligand disproportionation were determined using 31 P–{ 1 H} NMR band shape analysis.

Gold(I) complexes of N-alkyl substituted imidazolidine-2-thiones: synthesis, spectroscopic studies and X-ray structure

Abstract N-alkyl-substituted imidazolidine-2-thiones act as monodentate ligands coordinating through sulfur. The gold(I) complex, chloro(N-propyl-1,3-imidazolidine-2-thione)gold(I), [(PrImt)AuCl] crystallizes in the monoclinic space group C2/c with a=10.164(4), b=14.836(2), c=13.590(9)A, β=95.08(5)° and Z=8. The X-ray structure determined using intensity data collected on a CAD4 diffractometer and refined by full-matrix least-squares methods, converged to a conventional R factor value of 0.077 for 1153 observed reflections. Gold(I) has a linear coordination with an S-Au-Cl angle of 173.3° and Au-S and Au-Cl distances of 2.26(1) and 2.27(1)A. The 13C nmr spectra of the complexes indicated a high-field shift of about 8 ppm for the C-S carbon, suggesting identical coordination sites in the solid and solution states. This large shift in 13C resonance can be used as a diagnostic nmr observation for location of coordination sites in solution of these and other C-S bonded complexes.

X-ray photoelectron spectroscopy and Fourier transform-infrared studies of transition metal phosphate glasses

X-ray photoelectron spectroscopy and Fourier transform-infrared studies were carried out on phosphate glasses containing oxides of iron, cobalt, nickel, copper and zinc. The results suggest that the glasses containing iron and zinc may have structures in which both the phosphorus and the iron (or zinc) atoms are tetrahedrally coordinated by oxygen into three-dimensional structures which resemble the polymorphic forms of silica, whereas the glasses containing cobalt, nickel and copper may consist of polymeric chains of PO4 tetrahedra bonded to adjacent tetrahedra via bridging oxygens. These polyphosphate chains are linked together by the interaction between the metal cation and the oxygens of the network former. In addition, the core level 2p shake-up satellites of the 3d-transition metal ions in these glasses were studied. The results support a suggestion that the satellites in the glass are most likely due to the electron transfer from ligand to metal 3d orbitals.

Gold(I)-selenium bond: synthesis and x-ray structure of chloro(triphenylphosphine selenide)gold(I)

The crystal and molecular structures of chloro(triphenylphosphineselenide)gold(I), [(C6H5)3PSe]AuCl, have been determined from three-dimensional X-ray intensity data collected on a CAD4 diffractometer. The compound crystallizes in the triclinic space groupPl witha=9.322(3),b=10.639(5),c=9.252(3) A, α=104.74(4), β=99.52(3), γ=76.97(3)°, andZ=2. Atomic parameters were refined by full-matrix least-squares to anR value of 5.7% for 2591 observed reflections. This is one of the few known examples of linear gold(I) complexes having an Au-Se linkage. The Se-Au-Cl angle is 178.6(1)°, and the Au-Se and Au-Cl distances are 2.371(2) and 2.277(6) A, respectively. As expected, the Au-Se bond length is 0.10–0.18 A longer than the Au-S bond length observed in similar two-coordinate linear gold(I) complexes.

Synthesis, 13C NMR and IR spectroscopic studies of gold(I) complexes of imidazolidine-2-thione and its derivatives

Abstract The gold(I) complexes of imidazolidine-2-thione and its derivatives were synthesized and their 13C NMR and IR spectroscopic studies were carried out. When gold(III) was reacted with the ligands using a 1:4 metal to ligand ratio, gold(III) was reduced to gold(I), the bis complexes of the general formula AuLnX (where n = 2) were formed. However, when gold(III) was reduced to gold(I) by a reducing agent followed by an addition of the ligand to an aqueous or methanolic solution of gold(I), only mono complexes of the type AuLX were obtained. The structures of the reported complexes are proposed on the basis of their spectroscopic measurements.

COMPLEXATION OF IMIDAZOLIDINE-2-THIONE AND ITS DERIVATIVES WITH GOLD(I) CYANIDE

Abstract New 1:1 complexes of the type [LAu-CN] where L = imidazolidine-2-thione and its N-alkylated derivatives are obtained from reactions between the thione ligands and gold(I) cyanide. The complexes are characterized by elemental analyses, 13C NMR and IR spectroscopy.

Mixed-ligand complexes of copper(I) with heterocyclic thiones

SummaryNovel mixed-ligand copper(I) complexes of general formula [TPP−Cu−(L)Cl] or [TPPhos−Cu−(L)Cl], where TPP=triphenylphosphine, TPPhos=triphenylphosphate and L=imidazolidine-2-thione [Imt],N-propylimidazolidice-2-thione [PrImt],N-i-propylimidazolidine-2-thione [iPrImt], and 1,3-diazinine-2-thione [Diaz] and bis coniplexes of formula [(L)2CuCl] where L=[PrImt] and [iPrImt] have been prepared and characterized by electronic, vibrational and n.m.r. spectroscopy. The spectral data are consistent with S-donation of thiones. The magnitude of upfield shift in13Cn.m.r. of the thionreide carbon on complexation has been interpreted in terms of coordination geometry around the metal stoms. X-ray structure analysis agrees with the conclusions from the spectroscopic measurements. The structure of [(PrImt)2CuCl] revealed three-coordinated copper(I) with crystal data:a=14.106(4),b=14.380(2),c=19.024(3) A, β=108.8(2)°,z=8 and space group P2/c.

Bis(N-propyl-1,3-imidazolidine-2-thione)gold(I) chloride: Crystal and molecular structure

SummaryThe crystal and molecular structures of bis(N-propyl-1,3-imidazolidine-2-thione)gold(I) chloride, [(PrImt)2Au]Cl, has been determined from three-dimensional x-ray intensity data collected on a CAD4 diffractometer. The compound crystallizes in the monoclinic space group P21/n witha=7.195(7),b=15.283(3),c=15.899(6) Å, β=91.7(1) and Z = 4. Atomic parameters were refined by full-matrix least-squares methods to the R value of 6.2% for 2272 observed reflections. Gold(I) exhibits the usual linear coordination with S(1)-Au-S(10) angle of 177.7(1)°. The two [Prlmt] molecules are arranged intrans configuration which is attributed to the effects of intermolecular H-bonding between N-H and the halogen. The Au-S bond length is compared with the corresponding bond length in several known structures in order to evaluate thetrans influence of phosphorus, sulfur and chloride ligands on the Au-S bond.

Synthesis and spectroscopic characterization of (trialkll/triaryl)-phosphine gold(I) thiocyanate complexes

Abstract R 3 PAuS 13 C 15 N (where R 3 P = Me 3 P, Et 3 P, i -Pr 3 P, p -TolPh 2 P, Ph 3 P and cyanoethyl-phosphine CEP) complexes have been prepared. The AuNCS/AuSCN ratios for these complexes have been determined, using IR spectroscopy ( v CN integrated absorption intensity ratios). The observation that the AuNCS/AuSCN ratio increases as the trans influence of the phosphine ligand increases is completely in agreement with the trend predicted by the antisymbiotic trans influence theory. In the solid state only the S-bonded isomer of each complex is observed. The 13 C, 15 N and 31 P NMR chemical shifts of these complexes were also measured and are compared with R 3 PAu 13 C 15 N complexes. The results show that unlike R 3 PAu 13 C 15 N complexes, which undergo disproportion in solution, the R 3 PAuS 13 C 15 N complexes do not undergo disproportion.