Dipartimento di Chimica Inorganica, Chimica Analitica e Chimica Fisica, Universit di Messina, Salita Sperone, 31 Contrada Papardo, 98166 Messina Italy.
Inorg Chem. 2010 Oct 18;49(20):9236-46. doi: 10.1021/ic100715v.
The meso-dithioxamide H-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl)-H (H(2)-mesoDTO) bonds (η(6)-p-cymene)chlorido-ruthenium(II) or (η(3)-allyl)-palladium(II) fragment and provides the C(s) symmetrical complexes [(η(6)-p-cymene)ClRu(H-mesoDTO κ-S,S Ru)] (1) and [(η(3)-allyl)palladium(H-mesoDTO κ-S,S Pd)] (2). These complexes are pseudochiral, and each of them exists as a mixture of two symmetrical meso forms. The improper symmetry of [(η(3)-allyl)palladium(H-mesoDTO κ-S,S Pd)] has been broken in two different ways: (i) by changing the symmetrical allyl moiety with a η(3)-crotyl frame or (ii) by substituting the residual amidic hydrogen in the dithiooxamidate ligand with a M(PR(3))Cl(+) fragment (M = Pd or Pt and PR(3) = triorganophosphine). As a consequence, a chiral plane is added to the pseudochiral palladium center, and two pairs of enantiomers are formed in each case. Furthermore, (η(6)-p-cymene)chlorido-ruthenium(II) and (η(3)-allyl)-palladium(II) fragments have been joined by means of the binucleating meso-dithiooxamidate ligand in a κ-S,S Ru κ-N,N Pd coordination mode. The resulting C(s)-symmetrical complex [(η(6)-p-cymene)ClRu(μ-mesoDTO κ-S,S Ru κ-N,N Pd)Pd(η(3)-allyl)] (8) possesses two pseudochiral metal centers, and it is therefore a mixture of four isomeric meso forms. All of these isomers in a chloroform solution interconvert in that both palladium and ruthenium invert their configurations. A mechanism of epimerization for both palladium and ruthenium is proposed. The absolute configurations of pseudochiral palladium in [(η(3)-allyl)(c)-Pd(μ-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl) κ-N,N (c)-Pd κ-S,S (A,C)-Pd)(A,C)-Pd(tri(n)propyl-phosphine)Cl] (6) and of pseudochiral palladium and ruthenium in [(η(3)-allyl)(c)-Pd(μ-((R)-1-(1-phenyl)ethyl)-NSC-CSN-((S)-1-(1-phenyl)ethyl) κ-N,N (c)-Pd κ-S,S(s)-Ru)(s)-Ru(η(6)-isopropyltoluene)Cl] (8) are provided. A suitable stereochemical notation is proposed for bimetallic complexes containing pseudochiral centers in either a chiral or an achiral environment.
中-二硫代酰胺 H-((R)-1-(1-苯基)乙基)-NSC-CSN-((S)-1-(1-苯基)乙基)-H(H(2)-mesoDTO)键 [(η(6)-p-枯烯)氯代钌(II)] (+)或[(η(3)-烯丙基)-钯(II)] (+)片段，并提供 C(s)对称配合物 [(η(6)-p-枯烯)ClRu(H-mesoDTO κ-S,S Ru)] (1) 和 [(η(3)-烯丙基)钯(H-mesoDTO κ-S,S Pd)] (2)。这些配合物是假手性的，它们中的每一个都以两种对称的内消旋形式存在。[(η(3)-烯丙基)钯(H-mesoDTO κ-S,S Pd)]的不适当对称性已经以两种不同的方式被打破：(i) 通过改变对称的烯丙基部分为 η(3)-巴豆基框架，或 (ii) 通过用 M(PR(3))Cl(+)片段 (M = Pd 或 Pt 和 PR(3)=三有机膦)取代二硫代氧酰胺配体中的剩余酰胺氢。结果，手性平面被添加到假手性钯中心，并且在每种情况下都形成两对对映体。此外，[(η(6)-p-枯烯)氯代钌(II)] (+)和[(η(3)-烯丙基)-钯(II)] (+)片段通过双螯合的中-二硫代氧酰胺配体以 κ-S,S Ru κ-N,N Pd 配位模式连接。所得 C(s)对称配合物 [(η(6)-p-枯烯)ClRu(μ-mesoDTO κ-S,S Ru κ-N,N Pd)Pd(η(3)-烯丙基)] (8) 具有两个假手性金属中心，因此是四种内消旋形式的混合物。在氯仿溶液中，所有这些异构体都可以相互转化，因为钯和钌都反转了它们的构型。提出了钯和钌的消旋化机制。[(η(3)-烯丙基)(c)-Pd(μ-((R)-1-(1-苯基)乙基)-NSC-CSN-((S)-1-(1-苯基)乙基) κ-N,N (c)-Pd κ-S,S (A,C)-Pd)(A,C)-Pd(tri(n)propyl-phosphine)Cl] (6) 中假手性钯和 [(η(3)-烯丙基)(c)-Pd(μ-((R)-1-(1-苯基)乙基)-NSC-CSN-((S)-1-(1-苯基)乙基) κ-N,N (c)-Pd κ-S,S(s)-Ru)(s)-Ru(η(6)-异丙基甲苯)Cl] (8) 中假手性钯和钌的绝对构型被提供。为含有假手性中心的双金属配合物提出了一种合适的立体化学符号，这些配合物在手性或非手性环境中都含有假手性中心。
