Telfer Shane G, Sato Tomohiro, Kuroda Reiko, Lefebvre Julie, Leznoff Daniel B
JST ERATO Kuroda Chiromorphology Project, Park Building, 4-7-6 Komaba, Meguro-ku, Tokyo 153-0041, Japan.
Inorg Chem. 2004 Jan 26;43(2):421-9. doi: 10.1021/ic034585k.
The synthesis and coordination chemistry of two chiral tetradentate pyridylimine Schiff base ligands are reported. The ligands were prepared by the nucleophilic displacement of both bromides of 1,3-bis(bromomethyl)benzene (2) or 3,5-bis(bromomethyl)toluene (3) by the anion of (S)-valinol, followed by capping of both amine groups with pyridine-2-carboxaldehyde. Both ligands react with CoCl(2) and NiCl(2) to give M(2)L(2)Cl(2) complexes. Remarkably, neither fluoride nor bromide ions can act as bridging ligands. The formation of Co(2)((S)-3)(2)Cl(2) is highly diastereoselective, and X-ray crystallography shows that both metal centers in the Co(2)((S)-3)(2)Cl(2) complex adopt the lambda configuration (crystal data: Co(2)(C(31)H(40)N(4)O(2))(2)Cl(2).(CH(3)CN)(3), monoclinic, P2(1), a = 11.595(2) A, b = 22.246(4) A, c = 15.350(2) A, V = 3705(1) A(3), beta = 110.643(3) degrees, Z = 2). Structurally, the dinuclear complex can be viewed as a helicate with the helical axis running perpendicular to the [Co(2)Cl(2)] plane. The reaction of racemic 2 with CoCl(2) was shown by (1)H NMR spectroscopy to yield a racemic mixture of Lambda,Lambda-Co(2)((S)-2)(2)Cl(2) and delta,delta-Co(2)((R)-2)(2)Cl(2) complexes; that is, a homochiral recognition process takes place. Spectrophotometric titrations were performed by titrating (S)-3 with Co(ClO(4))(2) followed by Bu(4)NCl, and the global stability constants of Co((S)-3) (log beta(110) = 5.7), Co((S)-3)(2) (log beta(120) = 11.6), and Co(2)((S)-3)(2)Cl(2) (log beta(110) = 23.8) were calculated. The results revealed a strong positive cooperativity in the formation of Co(2)((S)-3)(2)Cl(2). Variable-temperature magnetic susceptibility curves for Co(2)((S)-2)(2)Cl(2)(2) and Co(2)((S)-3)(2)Cl(2)(2) are very similar and indicate that there are no significant magnetic interactions between the cobalt(II) centers.
报道了两种手性四齿吡啶基亚胺席夫碱配体的合成及配位化学。通过（S）-缬氨醇的阴离子对1,3-双（溴甲基）苯（2）或3,5-双（溴甲基）甲苯（3）的两个溴化物进行亲核取代，随后用吡啶-2-甲醛封端两个胺基来制备配体。两种配体均与CoCl₂和NiCl₂反应生成[M₂L₂Cl₂]²⁺配合物。值得注意的是，氟离子和溴离子均不能作为桥连配体。[Co₂((S)-3)₂Cl₂]²⁺的形成具有高度非对映选择性，X射线晶体学表明Co₂((S)-3)₂Cl₂配合物中的两个金属中心均采用λ构型（晶体数据：Co₂(C₃₁H₄₀N₄O₂)₂Cl₂·(CH₃CN)₃，单斜晶系，P2₁，a = 11.595(2) Å，b =
