Pi-Chang Kong

Study of the aqueous reactions of K[Pt(Ph2SO)Cl3] with nitrile ligands and crystal structures of N(C4H9)4[Pt(Ph2SO)Cl3], N(C2H5)4[Pt(Ph2SO)Br3] and cis-Pt(Ph2SO)(C3H5CN)Cl2

Abstract The aqeuous reactions of K[Pt(Ph2So)Cl1] with nitriles were studied in different conditions of pH, mainly by 195Pt and 1H NMR. At normal pH (≈ 2.4), the ligands RCN have produced the neutral complexes Pt(Ph2SO)(RCN)Cl2. For acetonitrile, only the cis isomer was obtained, while for other nitriles a mixture of the two isomers was formed. The 195Pt NMR spectra of the compounds were measured. The signals of the cis isomers were observed around −3040 ppm, while those of the trans isomers were found around − 3180 ppm. The study has shown that the first product formed is the trans isomer, which then isomerizes partially to the cis compounds. The 195Pt NMR spectra of the products obtained in neutral medium (pH adjusted to ∼ 7 with NaOH) have shown several signals depending on the nitrile. Dimeric species of the type Pt(Ph2SO)Cl(μ-NHC(R)O2Pt(Ph2SO)Cl are suggested to exist in solution. Head-to-head and head-to-tail isomers are probably formed. The crystal structures of N(C4H9)4[Pt(Ph2SO)Cl3] (I), N(C2H5)4[Pt(Ph2SO)Br3] (II) and cis-Pt(Ph2SO)(C3H5CN)Cl2 (III) were determined. The chloro ionic complex is triclinic, P-1, with a = 10.674(2), b = 11.424(2), c = 13.731(2) A , α = 89.54(1), β = 83.27(1), γ = 80.48(1)°, Z = 2 rmand R = 0.042, while the bromo complex is monoclinic, P21/n, with a = 11.258(3), b = 19.425(4), c = 11.590(2) A , β = 102.62(2)°, Z = 4 and R = 0.053 . Crystal III is orthorhombic, space group P2 1 2 1 2 1 , a = 9.532(3), b = 11.787(2), c = 15.464(4) A , Z = 4 and R = 0.031 . The compound is the cis isomer. For crystal I, the PtCl bond in trans position to the sulfoxide is 2.312(2) A, while the cis bonds are 2.282(2) and 2.299(2) A. For the bromo compound (II), the PtBr bonds vary between 2.397(3) and 2.421(3) A. In crystal III, the PtCl bond located in trans position to the nitrile is considerably shorter (2.269(3) A) than the PtCl bond in trans position to the sulfoxide ligand (2.311(3) A). The PtS bond distances vary between 2.201(2) and 2.228(3) A.

Reactions between nucleosides and platinum dimethylsulfoxide complexes.

Nucleosides (Nuc) react with cis-[Pt(DMSO)2Cl2] in dimethysulfoxide (DMSO) solution, to produce trans-[Pt(DMSO)(Nuc)Cl2], which then isomerize to cis-[Pt(DMSO)(Nuc)Cl2]. They also displace chlorine from K[Pt(DMSO)Cl3] in water to form trans-[Pt(DMSO)(Nuc)Cl2]. K[Pt(inosine)Cl3] and DMSO give in water cis-[Pt(DMSO)(Inosine)Cl2]. The configuration assignment of the compounds was based on chemical reactions, NMR techniques, analytical results, conductivity measurements and comparison with pyridine analogues. Chemical shifts in NMR and coupling constants of the aromatic protons of the nucleosides with 195Pt were used for the assignment of the binding sites of the nucleosides.

Rearrangement of tetramethylthiourea to dimethyldithiocarbamate and crystal structures of [Tc(O)(C5H12N2S)2((CH3)2NCSS)](PF6)2 and [Tc(DPPE)2((CH3)2NCSS)](PF6)

Abstract The reaction of [Tc v (O)(tetramethylthiourea) 4 ](PF 6 ) 3 with bis(diphenylphosphino)ethane (DPPE) in DMF solution produced at least two compounds, which were identified by X-ray diffraction methods as [Tc v (O)(tetramethylthiourea) 2 ((CH 3 ) 2 NCSS)](PF 6 ) 2 and [Tc II (DPPE) 2 ((CH 3 ) 2 NCSS)](PF 6 ). The bidentate dithiocarbamate ligand was produced from the reaction of bonded tetramethylthiourea in the reaction medium. The crystals of the Tc(V) compound, [Tc(O)(tetramethylthiourea) 2 ((CH 3 ) 2 NCSS)](PF 6 ) 2 are monoclinic with P 2 1 / c space group, a =9.388(4), b =26.745(20), c =11.990(3) A, β=101.62(3)° and Z =4. The structure was refined to R =0.059 and R w =0.069. The geometry around the Tc atom is square pyramidal. The TcO bond distance is 1.661(6) A while the TcS bond lengths are 2.328(2) and 2.343(2) A for tetramethylthiourea and 2.349(2) and 2.353(2) A for dimethyldithiocarbamate. The crystals of [Tc(DPPE) 2 ((CH 3 ) 2 NCSS)](PF 6 ) are monoclinic, P 2 1 space group with a =11.693(8), b =19.282(7), c =12.148(6) A, β=104.78(5)° and Z =2. The structure was refined to R =0.074 and R w =0.063. The Tc(II) complex has a distorted octahedral geometry. The TcP bond distances vary from 2.413(6) to 2.473(6) A while the TcS distances are 2.439(6) and 2.448(7) A. The bidentate dimethyldithiocarbamate ligand is planar. A mechanism for the formation of the ligand is suggested.

Synthesis and crystal structures of oxo pyridinemethanolate technetium(V) complexes

Abstract Oxo Tc(V) complexes with 2-(hydroxymethyl)pyridine and 2,6-di(hydroxymethyl)pyridine were synthesized from the reaction of n-Bu4[Tc(O)X4] (X = Cl or Br) with the ligand in methanol or ethanol. The three compounds Tc(O)(OCH2PyCH2OH)2Cl (1). Tc(O) (OCH2PyCH2OH)2Br (2) and Tc(O) (OCH2Py)2Cl (3) (Py = pyridine) were studied by crystallographic methods. Crystal 1 is triclinic, P 1 , a = 7.479(2), b = 8.043(2), c = 14.940(4) A , α = 93.66(2), β = 102.16(2), γ = 117.18(2)°, Z = 2 and R = 0.050 . The bromo analogue 2 is also triclinic, P 1 , a = 7.416(4), b = 8.115(4), c = 15.151(10) A , α = 94.36(5), β = 102.09(5), γ = 116.77(4)°, Z = 2 and R = 0.060 . Compound 3 crystallizes in the monoclinic P21/c space group with a = 12.861(4), b = 7.111(2), c = 14.623(6) A , β = 92.86(3)°, Z = 4 and R = 0.043 . The geometry around the Tc atom is a very distorted octahedron with the oxo and halide ligands in cis position to each other. Crystal 3 is disordered on two positions. The two organic ligands are deprotonated and the disubstituted molecule 2,6-di(hydroxymethyl)pyridine in 1 and 2 is bidentate with one free -CH2OH group.

Synthesis and crystal structures of nitrido diphosphinoethane technetium(V) complexes

Abstract The reaction of [Tc(N)(tu) 4 Cl]Cl with bis(dimethylphosphino)ethane(dmpe) or bis(diphenylphosphino)ethane (dppe) in ethanol solution produced yellow compounds, which were characterized by X-ray diffraction methods. The geometry around the technetium atom in [Tc(N)(dmpe) 2 Cl]CF 3 SO 3 ·0.5(NH 2 CSNH 2 ) is octahedral with the chloro ligand located in the position trans to the nitrido ligand. The Tc-N bond distance is 1.613(9) A, Tc-Cl = 2.643(3) A and the Tc-P bonds vary from 2.450(3) to 2.459(3) A. The anions are in the mirror planes and the compound crystallized with a molecule of thiourea, which is also located in the mirror. The compound with dppe crystallized with a molecule of methanol. The geometry around the technetium atom in [Tc(N)(dppe) 2 Cl]Cl·CH 3 OH is octahedral with the chloro ligand located in the position trans to the nitrido ligand. The technetium atom is located on an inversion centre and the Cl − and nitrido ligands are disordered on each side of the TcP 4 plane. The Tc-N [1.794(7) A] and Tc-Cl [2.412(2) A] bond distances are probably not precise, caused by the refinement of the disordered atoms. The Tc-P bonds are 2.491(1) and 2.473(1) A. The anions are also located on an inversion centre. The methanol molecules are disordered on two positions.

Synthesis of new mixed-ligands Tc complexes containing monodentate phosphine and isothiocyanato ligands: Crystal structures of complexes Tc(P(C3H7)3)2(NCS)4, Tc(P(CH3)2Ph)4(NCS)2 and Tc(P(OCH3)Ph2)4(NCS)2·1/2CH2Cl2

Abstract Three mixed-ligand neutral technetium complexes containing monodentate phosphine and isothiocyanato ligands have been synthesized and studied by crystallographic methods. In the Tc(IV) compound trans-Tc(P(C3H7)3)2(NCS)4, the Tc atom is located on an inversion centre. The TcP bond distances are 2.519(3) A while the TcN bonds are 1.991(6) and 2.003(6) A. Two Tc(II) compounds containing tetrasubstituted phosphine ligands were also characterized by X-ray diffraction methods. In trans-Tc(P(CH3)2Ph)4(NCS)2 (II), the Tc atom is located on a twofold axis. The TcP bond distances are 2.429(2) and 2.482(2) A while the TcN bonds are 2.052(6) A. In trans-Tc(P(OCH3)Ph2)4(NCS)2·1/2CH2Cl2, the TcP bond distances vary between 2.423(1) and 2.442(1) A, while the TcN bonds are 2.039(1) and 2.037(1) A. All the complexes have octahedral geometry around the Tc atom, with N-bonded isothiocyanato ligands. Important distortions of the octahedron was observed in compound II, due to the bulkiness of the four dimethylphenylphosphine ligands located in the same coordination plane. An important tetrahedral deformation of the plane containing the Tc and the four P atoms was observed.

Mononucleoside platinum complexes

New platinum complexes with mononucleosides have been prepared by a new method which is also applicable to pyridine and amine analogues.

Synthesis and crystal structure of mixed-ligand Tc(I) complexes, with dimethylphenylphosphine and t-butylisonitrile

The reaction of mer-Tc(PMe2Ph)3Cl3 with t-butylisonitrile (TBI) in ethanol solution produced, depending on the experimental conditions, two compounds which were identified as trans-[Tc(PMe2Ph)2(TBI)4]+ and [Tc(PMe2Ph)(TBI)5]+. The proton NMR spectra of the two compounds showed that the complexes are quite pure. The two compounds were studied by X-ray diffraction methods. Trans-[Tc(PMe2Ph)2(TBI)4]PF6 (I) is monoclinic, space group C2/c with a = 17.933(9), b = 9.878(6), c = 25.675(18) A and β = 105.29(5)°. The Tc atom is located on a center of inversion, while P (of PF6−) is located on a two-fold axis. [Tc(PMe2Ph)(TBI)5]PF6 (II) belongs to the tetragonal P4/n space group with a = 29.561(11), c = 10.614(5) A. The geometry around the Tc atom is octahedral with TcC bonds from 2.036(15) to 2.045(13) A for I and from 1.996(19) to 2.064(18) A for II. The TcP bond distances are quite short for I (2.389(3) A) and slightly longer in crystal II (2.403(6) A). The short TcP bonds are caused by the presence of multiple bonding which increases as the oxidation state of Tc decreases, while the slightly longer TcP bond distance observed for crystal II is ascribed to a large trans influence of the isonitrile ligands, greater than the one of phosphines.