Bonaccorsi Cristina, de Biani Fabrizia Fabrizi, Leoni Piero, Marchetti Fabio, Marchetti Lorella, Zanello Piero
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento, 35, 56126 Pisa, Italy.
Chemistry. 2008;14(3):847-56. doi: 10.1002/chem.200700765.
The previously reported hexanuclear cluster Pt(6)(mu-PtBu(2))(4)(CO)(6)Y (1-Y(2): Y=CF(3)SO(3) (-)) contains a central Pt(4) tetrahedron bridged at each of the opposite edges by another platinum atom; in turn, four phosphido ligands bridge the four Pt-Pt bonds not involved in the tetrahedron, and, finally, one carbonyl ligand is terminally bonded to each metal centre. Interestingly, the two outer carbonyls are more easily substituted or attacked by nucleophiles than the inner four, which are bonded to the tetrahedron vertices. In fact, the reaction of 1-Y(2) with 1 equiv of [nBu(4)N]Cl or with an excess of halide salts gives the monochloride Pt(6)(mu-PtBu(2))(4)(CO)(5)Cl[Y], 2-Y, or the neutral dihalide derivatives [Pt(6)(mu-PtBu(2))(4)(CO)(4)X(2)] (3: X=Cl; 4: X=Br; 5: X=I). Moreover, the useful unsymmetrically substituted [Pt(6)(mu-PtBu(2))(4)(CO)(4)ICl] (6) was obtained by reacting equimolar amounts of 2 and [nBu(4)N]I, and the dicationic derivatives Pt(6)(mu-PtBu(2))(4)(CO)(4)L(2)Y (7-Y(2): L=(13)CO; 8-Y(2): L=CNtBu; 9-Y(2): L=PMe(3)) were obtained by reaction of an excess of the ligand L with 1-Y(2). Weaker nitrogen ligands were introduced by dissolving the dichloride 3 in acetonitrile or pyridyne in the presence of TlPF(6) to afford Pt(6)(mu-PtBu(2))(4) (CO)(4)L(2)Z (Z=PF(6) (-), 10-Z(2): L=MeCN; 11-Z(2): L=Py). The "apical" carbonyls in 1-Y(2) are also prone to nucleophilic addition (Nu(-): H(-), MeO(-)) affording the acyl derivatives [Pt(6)(mu-PtBu(2))(4)(CO)(4)(CONu)(2)] (12: Nu=H; 13: Nu=OMe). Complex 12 is slowly converted into the dihydride [Pt(6)(mu-PtBu(2))(4)(CO)(4)H(2)] (14), which was more cleanly prepared by reacting 3 with NaBH(4). In a unique case we observed a reaction involving also the inner carbonyls of complex 1, that is, in the reaction with a large excess of the isocyanides R-NC, which form the corresponding persubstituted derivatives Pt(6)(mu-tPBu(2))(4)(CN-R)(6)Y, (15-Y(2): R=tBu; 16-Y(2) (2-): R=-C(6)H(4)-4-C triple bond CH). All complexes were characterized by microanalysis, IR and multinuclear NMR spectroscopy. The crystal and molecular structures of complexes 3, 5, 6 and 9-Y(2) are also reported. From the redox viewpoint, all complexes display two reversible one-electron reduction steps, the location of which depends both upon the electronic effects of the substituents, and the overall charge of the original complex.
先前报道的六核簇合物Pt(6)(μ-PtBu(2))(4)(CO)(6)Y（1-Y(2)：Y = CF(3)SO(3) (-)）包含一个中心Pt(4)四面体，在相对的每条边上各由另一个铂原子桥连；进而，四个磷化物配体桥连四面体中未涉及的四个Pt-Pt键，最后，一个羰基配体端基键合到每个金属中心。有趣的是，两个外层羰基比与四面体顶点键合的内层四个羰基更容易被亲核试剂取代或进攻。实际上，1-Y(2)与1当量的[nBu(4)N]Cl或过量的卤化物盐反应得到一氯化物Pt(6)(μ-PtBu(2))(4)(CO)(5)Cl[Y]，即2-Y，或中性二卤化物衍生物[Pt(6)(μ-PtBu(2))(4)(CO)(4)X(2)]（3：X = Cl；4：X = Br；5：X = I）。此外，通过使等摩尔量的2与[nBu(4)N]I反应得到有用的不对称取代物[Pt(6)(μ-PtBu(2))(4)(CO)(4)ICl]（6），通过使过量的配体L与1-Y(2)反应得到二阳离子衍生物Pt(6)(μ-PtBu(2))(4)(CO)(4)L(2)Y（7-Y(2)：L = (13)CO；8-Y(2)：L = CNtBu；9-Y(2)：L = PMe(3)）。通过在TlPF(6)存在下将二氯化物3溶解于乙腈或吡啶中引入较弱的氮配体，得到Pt(6)(μ-PtBu(2))(4) (CO)(4)L(2)Z（Z = PF(6) (-)，10-Z(2)：L = MeCN；11-Z(2)：L = Py）。1-Y(2)中的“顶端”羰基也易于发生亲核加成（Nu(-)：H(-)，MeO(-)），得到酰基衍生物[Pt(6)(μ-PtBu(2))(4)(CO)(4)(CONu)(2)]（12：Nu = H；13：Nu = OMe）。配合物12缓慢转化为二氢化物[Pt(6)(μ-PtBu(2))(4)(CO)(4)H(2)]（14），通过使3与NaBH(4)反应能更纯净地制备该二氢化物。在一个独特的例子中，我们观察到一个反应还涉及配合物1的内层羰基，即，在与大量过量的异腈R-NC反应时，形成相应的全取代衍生物Pt(6)(μ-tPBu(2))(4)(CN-R)(6)Y，（15-Y(2)：R = tBu；16-Y(2) (2-)：R = -C(6)H(4)-4-C≡CH）。所有配合物均通过微量分析、红外光谱和多核核磁共振光谱进行表征。还报道了配合物3、5、6和9-Y(2)的晶体和分子结构。从氧化还原角度看，所有配合物均显示两个可逆的单电子还原步骤，其位置既取决于取代基的电子效应，也取决于原始配合物的总电荷。
