Self-Assembly of Homochiral Double Helix and Side-by-Side Helix Conformers of Double-Stranded Disilver(I)- and Digold(I)-Tetra(tertiary phosphine) Helicates.
Self-Assembly of Homochiral Double Helix and Side-by-Side Helix Conformers of Double-Stranded Disilver(I)- and Digold(I)-Tetra(tertiary phosphine) Helicates.
复制标题
双链 Disilver(I)- 和 Digold(I)-四（叔膦）螺旋的同手性双螺旋和并排螺旋构象的自组装。
作者：
Anthea L. Airey;G. Swiegers;A. Willis;S. Wild
螯合C(2)-四(叔膦)(R，R)-(+/-)-1，1，4，7，10，10-hexaphenyl-1，4，7，10-tetraphosphadecane，(R，R)-(+/-)/(R，S)-1的(R，R)-(+/-)非对映异构体的对映体与适当的银(I)和金(I)盐反应，自发地自组装成[M(2)(四氮杂环)(2)]X(2)型的同手性双链双银(I)和二价(I)螺旋。相应的铜(I)络合物是单核的。报道了Delta-(-)-[Cu{(R，R)-1}]Pf(6).EtOH，Lambda-(-)-[Ag(2){(R，R)-1}(2)](Pf(6))(2)和Lambda-(-)-[Au(2){(R，R)-1}(2)](Pf(6))(2).ch(2).银和金配合物的结构测定是首次对手性配体的双金属螺旋对映体进行结构测定。双核银络合物在每个晶胞中阳离子和相关阴离子的左手(Lambda)D(2)-双螺旋和C(2)-并排螺旋构象各有一个分子结晶，而类似的金络合物晶体只包含并排螺旋和相关阴离子。每个配合物中的金属立体中心(S)的绝对构型(S)为S，在乙腈中的电导测量表明，在类似的条件下，单核铜配合物发生了较大的重排，形成了双核螺旋酸络合物，而银和金的配合物则以二价盐的形式进行。用Spartan 3.0程序对二银络合物阳离子的结构进行了能量最小化计算，得到了相当准确的预测结果，特别是预测了络合物中手性中心十元环的构象，以及该环的螺旋度与双螺旋和并排螺旋结构立体选择性形成的关系。(R，R)-(+/-)-1的拆分是首次在四(叔膦)上实现的。用四氢呋喃选择性萃取(R，R)-(+/-)形式从难溶的(R，S)形式中分离出易溶的(R，R)-(+/-)形式，然后用易于制备的同手性配合物(+)-di(&mgr；-chloro)bis[(R)-1-[1-(dimethylamino)ethyl]-2-phenyl-C(2)，N]二钯(II)-1-二氯甲烷，(R)-2.CH(2)Cl(2)进行金属络合拆分。通过从非对映异构体络合物(R(C)，(R(P)，R(P))-和(R(C))，(S(P)，S(P))-3(X=PF(6))中释放得到膦对映体，并通过丙酮-乙醇结晶提纯，得到熔点88℃和[α](21)(D)+20.5(c1.0，CH(2)Cl(2))(S，S对映体)和[α](21)(D)-20.5(c1.0，CH(2)Cl(2))(R，R对映体)。测定了(R(C))，(R(P)，R(P))-3(X=PF(6))的晶体和分子结构。四(叔膦)的每个对映体的完全光学纯度在每种情况下都通过定量重新制备从其上解出的非对映异构体钯配合物来确认。
The enantiomers of the (R,R)-(+/-) diastereomer of the chelating C(2)-tetra(tertiary phosphine) (R,R)-(+/-)-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane, (R,R)-(+/-)/(R,S)-1, spontaneously self-assemble into homochiral double-stranded disilver(I) and digold(I) helicates of the type [M(2)(tetraphos)(2)]X(2) upon reaction with appropriate silver(I) and gold(I) salts. The corresponding copper(I) complex is mononuclear. Crystal and molecular structures of Delta-(-)-[Cu{(R,R)-1}]PF(6).EtOH, Lambda-(-)-[Ag(2){(R,R)-1}(2)](PF(6))(2), and Lambda-(-)-[Au(2){(R,R)-1}(2)](PF(6))(2).CH(2)Cl(2) are reported. The structure determinations on the silver and gold complexes are the first to be performed on enantiomerically pure dimetal helicates with chiral ligands. The dinuclear silver complex crystallizes with one molecule each of the left-handed (Lambda) D(2)-double helix and C(2)-side-by-side helix conformers of the cation and associated anions in each unit cell, whereas crystals of the analogous gold complex contain only the side-by-side helix and associated anions. The absolute configuration(s) of the metal stereocenter(s) in each complex is S. Conductance measurements in acetonitrile indicated considerable rearrangement of the mononuclear copper complex into the dinuclear helicate complex, whereas the silver and gold complexes conducted as di-univalent salts under similar conditions. Energy minimization calculations of the structures of the disilver complex cation with use of the program SPARTAN 3.0 predicted the structures observed with considerable accuracy, especially the conformations of the chiral central ten-membered ring in the complex and the relationship of the helicity of this ring to the stereoselective formation of the double helix and side-by-side helix structures. The resolution of (R,R)-(+/-)-1 is the first on a tetra(tertiary phosphine). The more-soluble (R,R)-(+/-) form of the ligand was separated in high yield from the less-soluble (R,S) form by selective extraction with tetrahydrofuran, whereupon it was resolved by the method of metal complexation with the readily prepared homochiral complex (+)-di(&mgr;-chloro)bis[(R)-1-[1-(dimethylamino)ethyl]-2-phenyl-C(2),N]dipalladium(II)-1-dichloromethane, (R)-2.CH(2)Cl(2). The enantiomers of the phosphine were obtained by liberation from the diastereomeric complexes (R(C)),(R(P),R(P))- and (R(C)),(S(P),S(P))-3 (X = PF(6)) and brought to optical purity by crystallization from acetone-ethanol, giving colorless needles having mp 88 degrees C and [alpha](21)(D) +20.5 (c 1.0, CH(2)Cl(2)) (S,S enantiomer) and [alpha](21)(D) -20.5 (c 1.0, CH(2)Cl(2)) (R,R enantiomer). The crystal and molecular structures of (R(C)),(R(P),R(P))-3 (X = PF(6)) have been determined. The complete optical purity of each enantiomer of the tetra(tertiary phosphine) was confirmed in each case by the quantitative repreparation of the diastereomeric palladium complex from which it was liberated.