Kitto Heather J, Rae A David, Webster Richard D, Willis Anthony C, Wild S Bruce
Research School of Chemistry, Australian National University, Canberra, Australian Capital Territory 0200, Australia.
Inorg Chem. 2007 Sep 17;46(19):8059-70. doi: 10.1021/ic700912q. Epub 2007 Aug 15.
The ligand (S,S)-1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane, (S,S)-tetraphos, reacts with hexa(aqua)nickel(II) chloride in the presence of trimethylsilyl triflate (TMSOTf) in dichloromethane to give the yellow square-planar complex Ni{(R,R)-tetraphos}2, which has been crystallographically characterized as the square-pyramidal, acetonitrile adduct [Ni(NCMe){(R,R)-tetraphos}]OTf. Cyclic voltammograms of the nickel(II) complex in dichloromethane and acetonitrile at 20 degrees C showed two reduction processes at negative potentials with oxidative (E(p)(ox)) and reductive (E(p)(red)) peak separations similar to those observed for ferrocene/ferrocenium under identical conditions, suggesting two one-electron steps. The cyclic voltammetric data for the divalent nickel complex in acetonitrile at temperatures below -20 degrees C were interpreted according to reversible coordination of acetonitrile to the nickel(I) and nickel(0) complexes. The divalent palladium and platinum complexes M{(R,R)-tetraphos}2 and M2{(R,R)-tetraphos}24 have been prepared. The reduction potentials for the complexes M{(R,R)-tetraphos}2 increase in the order nickel(II) < palladium(II) < platinum(II). The reaction of (S,S)-tetraphos with bis(cycloocta-1,5-diene)nickel(0) in benzene affords orange [Ni{(R,R)-tetraphos}], which slowly rearranges into the thermodynamically more stable, yellow, double-stranded helicate [Ni2{(R,R)-tetraphos}2]; the crystal structures of both complexes have been determined. The reactions of (S,S)-tetraphos with [M(PPh3)4] in toluene (M = Pd) or benzene (M = Pt) furnish the double-stranded helicates [M2{(R,R)-tetraphos}2]; the palladium complex crystallizes from hot benzene as the 2-benzene solvate and was structurally characterized by X-ray crystallography. In each of the three zerovalent complexes, the coordinated (R,R)-tetraphos stereospecifically generates tetrahedral M(PP)2 stereocenters of M configuration.
配体（S,S）-1,1,4,7,10,10-六苯基-1,4,7,10-四磷癸烷，即（S,S）-四磷，在二氯甲烷中与三甲基甲硅烷基三氟甲磺酸酯（TMSOTf）存在下与六水合氯化镍（II）反应，生成黄色平面正方形配合物Ni{(R,R)-四磷}2，其晶体结构已被表征为正方锥型乙腈加合物[Ni(NCMe){(R,R)-四磷}]OTf。20℃下在二氯甲烷和乙腈中镍（II）配合物的循环伏安图显示在负电位下有两个还原过程，氧化（E(p)(ox)）和还原（E(p)(red)）峰间距与相同条件下二茂铁/二茂铁鎓的类似，表明有两个单电子步骤。在温度低于-20℃时乙腈中+2价镍配合物的循环伏安数据根据乙腈与镍（I）和镍（0）配合物的可逆配位进行了解释。已制备出二价钯和铂配合物M{(R,R)-四磷}2和M2{(R,R)-四磷}24。配合物M{(R,R)-四磷}2的还原电位按镍（II）<钯（II）<铂（II）的顺序升高。（S,S）-四磷与双（环辛-1,5-二烯）镍（0）在苯中反应得到橙色的[Ni{(R,R)-四磷}]，其缓慢重排为热力学上更稳定的黄色双链螺旋体[Ni2{(R,R)-四磷}2]；已测定了这两种配合物的晶体结构。（S,S）-四磷与[M(PPh3)4]在甲苯（M = Pd）或苯（M = Pt）中的反应生成双链螺旋体[M2{(R,R)-四磷}2]；钯配合物从热苯中结晶为2-苯溶剂化物，并通过X射线晶体学进行了结构表征。在这三种零价配合物的每一种中，配位的（R,R）-四磷立体定向地生成M构型的四面体M(PP)2立体中心。
