Synthesis, characterisation and coordination chemistry of novel chiral N,N-dialkyl-N ′-menthyloxycarbonylthioureas. Crystal and molecular structures of N,N-diethyl-N ′-(−)-(3R)-menthyloxycarbonylthiourea and cis-(S,S)-[Pt(L)Cl(DMSO)] [where HL = N-(+)-(3R)-menthyloxycarbonyl-N′-morpholinothiourea or N-benzoyl-N′,N′-diethylthiourea]
作者:Cheryl Sacht、Michael S. Datt、Stefanus Otto、Andreas Roodt
DOI:10.1039/b007589m
日期:——
The novel ligands N,N-diethyl-Nâ²-(â)-(3R)-menthyloxycarbonylthiourea (HL3), N,N-diethyl-Nâ²-(+)-(3R)-menthyloxycarbonylthiourea (HL4), N-(â)-(3R)-menthyloxycarbonyl-Nâ²-morpholinothiourea (HL5) and N-(+)-(3R)-menthyloxycarbonyl-Nâ²-morpholinothiourea (HL6) have been prepared and characterised. The molecular structure of HL3 has been confirmed by X-ray crystallography. The reaction of these N,N-disubstituted-Nâ²-menthyloxycarbonylthiourea ligands with cis-[PtCl2(DMSO)2] in the presence of sodium acetate yields geometric isomers of the resultant [Pt(L)Cl(DMSO)] complexes, that is the DMSO is sulfur bonded to the platinum in either a cis-(S,S) or trans-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. This is in contrast to the complexation reaction of cis-[PtCl2(DMSO)2] with N-benzoyl-Nâ²,Nâ²-diethylthiourea (HL1) or N-benzoyl-Nâ²-morpholinothiourea (HL2) which yields only one [Pt(L)Cl(DMSO)] complex in which the DMSO is in a cis-(S,S) arrangement with respect to the sulfur donor atom of the chelated ligand. The molecular structures of cis-(S,S)-[Pt(L)Cl(DMSO)], where LÂ =Â (L1)â or (L6)â, have been determined by X-ray crystallography. The difference in the coordination chemistry of the acylthiourea and alkoxycarbonylthiourea ligands has been examined further by treating the [Pt(L)Cl(DMSO)] complexes with PPh3 to give the corresponding mono- and bis-(phosphine) complexes, [Pt(L)Cl(PPh3)] and [Pt(L)(PPh3)2]+. The 31P NMR studies of these complexes reveal that the alkoxycarbonylthiourea ligands bind less strongly than the acylthiourea ligands, which is consistent with the crystallographic studies. The weaker binding properties of the alkoxycarbonylthiourea ligands might be a possible explanation for the observed geometric isomerisation of the complexes and that the mechanism could involve a chelate ring opening step.
新型的N,N-二乙基-N’-(–)-(3R)-萜品氧羰基硫脲(HL3)、N,N-二乙基-N’-(+)-(3R)-萜品氧羰基硫脲(HL4)、N-(–)-(3R)-萜品氧羰基-N’-吗啉基硫脲(HL5)和N-(+)-(3R)-萜品氧羰基-N’-吗啉基硫脲(HL6)已经制备并进行了表征。HL3的分子结构已经通过X射线单晶衍射分析确定。在乙酸钠存在下,这些N,N-二取代-N’-萜品氧羰基硫脲配体与二氯二DMSO合铂(II)反应,生成了相应的[Pt(L)Cl(DMSO)]配合物几何异构体。在这些配合物中,DMSO采取的是(S,S)-顺式或(S,S)-反式方式以硫原子与铂配位,这与螯合配体硫供体原子的配位方式有关。这与二氯二DMSO合铂(II)与N-苯甲酰基-N’,N’-二乙基硫脲(HL1)或N-苯甲酰基-N’-吗啉基硫脲(HL2)的配位反应不同,后者反应只能生成一种[Pt(L)Cl(DMSO)]配合物,其中DMSO采取的是(S,S)-顺式方式与铂配位。通过X射线单晶衍射分析测定了(S,S)-顺式-[Pt(L)Cl(DMSO)]的分子结构,其中L= (L1)– 或 (L6)–。H1和H6的分子结构已经通过X射线单晶衍射分析确定。我们还进一步研究了酰基硫脲配体和烷氧基羰基硫脲配体的配位化学性质,方法是使[Pt(L)Cl(DMSO)]配合物与PPh3反应生成相应的单膦配合物和双膦配合物[Pt(L)Cl(PPh3)]和[Pt(L)(PPh3)2]+。这些配合物的31P NMR研究结果表明,烷氧基羰基硫脲配体的配位能力弱于酰基硫脲配体,这和晶体学研究结果相一致。烷氧基羰基硫脲配体的较弱配位能力也许可以解释观测到的配合物几何异构化现象,反应机理也许涉及螯合环的开环步骤。