Photoinduced isomerisation of cis-[M(L-S,O)2] (M = Ptiiand Pdii) complexes of N,N-diethyl-N′-3,4,5-trimethoxybenzoylthiourea: key to preparation of the trans isomer

Photoactive PtII and PdII complexes of N,N-diethyl-N′-3,4,5-trimethoxybenzoylthiourea: synthesis, crystal structures, DFT and cytotoxicity studies

New trans-Pd^II/Pt^II acylthiourea complexes prepared by photo-induced isomerism are found to be more cytotoxic than cis-Pd^II/Pt^II against human prostate cancer and normal embryonic kidney cell lines.

Reversible photo-isomerization of cis-[Pd(L-κS,O)2] (HL = N,N-diethyl-N'-1-naphthoylthiourea) to trans-[Pd(L-κS,O)2] and the unprecedented formation of trans-[Pd(L-κS,N)2] in solution

Upon ex situ UV-visible light irradiation, complex cis-bis(N,N-diethyl-N'-naphthoylthioureato)-palladium(ii), cis-[Pd(L-κS,O)2], undergoes isomerization in acetonitrile-d3 and chloroform-d to yield trans-[Pd(L-κS,O)2] which then rearranges thermally to novel trans-[Pd(L-κS,N)2] prior to reverting thermally to the cis isomer in the absence of light. The thermal isomerization rate is highly solvent dependent and harnessed to enable each of these three geometric isomers to be isolated and characterized by 1H NMR spectroscopy, X-ray crystallography, melting point and thermal analysis. The formation of the trans-[Pd(L-κS,N)2] isomer as part of this isomerization has only been observed with the sterically demanding cis-bis(N,N-diethyl-N'-(naphthoylthioureato)palladium(ii) precursor based on our knowledge to date. In situ irradiation with monochromatic laser light (λ = 355 nm) coupled to 1H NMR spectroscopy of solutions of cis-[Pd(L-κS,O)2] in acetonitrile-d3 supports the ex situ photo-induced isomerization experiments.

Rare, hypodentate L-κS coordination mode of N,N-dialkyl-N′-aroylthioureas leads to unprecedented mixed-ligand [Pt(phen)(L-κS)2] complexes

Unprecedented [Pt(phen)(L¹-κS)₂] complexes with two N,N-dibutyl-N′-1-naphthoyl-thioureato molecules coordinated in a rare, hypodentate (L-κS)⁻ mode, stabilised by intra-molecular π–cation type stacking have been isolated. In contrast N,N-diethyl-N′-pivaloyl-thiourea, binds in a bidentate (L-κS,O) mode to give the [Pt(phen)(L³-κS,O)]⁺ species, the [Pt(phen)(L³-κS)₂] complex being unstable.

Rhenium and Technetium Complexes with N,N-Dialkyl-N‘-benzoylthioureas

N,N-Dialkyl-N'-benzoylthioureas, HR(1)R(2)btu, react under single deprotonation and form air-stable chelate complexes with common rhenium or technetium complexes such as (NBu(4))[MOCl(4)] (M = Re, Tc) or [ReOCl(3)(PPh(3))(2)]. Compositions and molecular structures of the products are strongly dependent on the precursors used and the reaction conditions applied. Reactions with [ReOCl(3)(PPh(3))(2)] in CH(2)Cl(2) give complexes of the general formula [ReOCl(2)(R(1)R(2)btu)(PPh(3))] (3), with the benzoyl oxygen atom of the chelating benzoylthiourea being trans to the oxo ligand, and/or Re(III) complexes of the composition [ReCl(2)(R(1)R(2)btu)(PPh(3))(2)] (4) with the PPh(3) ligands in trans positions to each other. In polar solvents such as MeOH, EtOH or acetone, corresponding reactions without addition of a supporting base only result in intractable brown solutions, from which no crystalline complexes could be isolated. The addition of NEt(3), however, allows the isolation of the bis-chelates [ReOCl(R(1)R(2)btu)(2)] (1) in good yields. In this type of complex, one of the chelating R(1)R(2)btu- ligands coordinates equatorially, while the second occupies the position trans to the oxo ligand with its oxygen atom. The latter compounds can also be prepared from (NBu(4))[ReOCl(4)] in MeOH when no base is added, while the addition of NEt(3) results in the formation of [ReO(OMe)(R(1)R(2)btu)(2)] (5) complexes with the methoxo ligand trans to O(2-). Compounds of the type 5 can alternatively be prepared by heating 1 in MeOH with addition of NEt(3). A reversible conversion of 5 into oxo-bridged dimers of the composition [{ReO(R(1)R(1)btu)(2)}(2)O] (6) is observed in water-containing solvents. Starting from (NBu(4))[TcOCl(4)], a series of technetium complexes of the type [TcOCl(R(1)R(2)btu)(2)] (2) could be prepared. The structures of such compounds are similar to those of the rhenium analogues 1. Reduction of 2 with PPh(3) in CH(2)Cl(2) gives Tc(III) complexes of the composition [TcCl(R(1)R(2)btu)(2)(PPh(3))] (7) having the chloro and PPh(3) ligands in cis positions. When this reaction is performed in the presence of excess chelating ligand, the Tc(III) tris-chelates [Tc(R(1)R(2)btu)(3)] (8) are formed.

Proton-Induced Cis−Trans Conversion of a Platinum(II) Center Coordinated by l-Cysteinatocobalt(III) Metalloligands

Treatment of LambdaL-[Co(L-cys-N,S)(en)2]+ (l-H2cys = L-cysteine) with [PtCl4]2- in water, followed by the addition of acid, gave an S-bridged CoIII2PtII trinuclear complex ([1]4+), which was reversibly converted to its deprotonated complex ([2]2+) in an aqueous solution. While [1]4+ formed only a trans isomer, [2]2+ existed as a mixture of trans and cis isomers. The selective formation of a cis isomer was achieved by treatment of [1]4+ or [2]2+ with phthalic acid in water, which afforded a unique CoIII4PtII2 hexanuclear complex ([3]4+). Complex [3]4+ was reverted back to [1]4+ by treatment with aqueous HCl, accompanied by the complete cis-to-trans conversion.

Reactions of halogens with Pt(ii) complexes of N-alkyl- and N,N-dialkyl-N′-benzoylthioureas: oxidative addition and formation of an I2 inclusion compound

The treatment of cis-[Pt(II)(L(1a/b)-S,O)2] complexes of N,N-diethyl- (HL(1a)) and N,N-di(n-butyl)-N'-benzoylthiourea (HL(1b)) with I2 or Br2 in chloroform, leads to rapid oxidative addition to yield several geometric isomers of [Pt(IV)(L-S,O)(2)X(2)](X = I, Br); the reactions can be monitored by (195)Pt NMR and UV-visible spectrophotometry. The products cis-[Pt(IV)(L(1a)-S,O)2I2] and cis-[Pt(IV)(L(1a)-S,O)2Br2], which have been isolated and structurally characterized, are the first-reported crystal structures of complexes of Pt(iv) with this class of ligand. Molecules of 6 pack such that the I-Pt-I axes are essentially aligned, with unusually close nearest-neighbour iodide contacts (3.553(1)A). These short II intermolecular interactions lead to infinite chains of weakly connected molecules in crystals of the compound. No such interactions are evident in the corresponding crystals of . Reaction of the Pt(II) complex of N-propyl-N'-benzoylthiourea (H2L(2a))cis-/trans-[Pt(II)(H2L(2a)-S)2Br2] with Br2 also results in oxidative addition, to yield trans-Pt(IV)(H2L(2a)-S)2Br4. By contrast, treatment of cis-/trans-[Pt(II)(H2L(2a)-S)2I2] with I2 does not lead to an oxidative addition product, yielding instead an interesting iodine inclusion compound of Pt(II), trans-[Pt(II)(H2L(2a)-S)2I2.I2. In 8, short intermolecular II distances of 3.453(1)A between I2 and coordinated iodide ions in trans-[Pt(II)(H(2)L(2a)-S)(2)I(2)] molecules, result in infinite chains of weakly linked trans-[Pt(II)(H2L(2a)-S)2I2]...I2 groups in the lattice. However, the empirically estimated bond order of 0.75 for the included I2 molecules does not support the possible existence of discrete tetraiodide ions (I4(2-)) in the lattice of compound 8.