Piro Nicholas A, Cummins Christopher C
Department of Chemistry, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 6-435, Cambridge, Massachusetts 02139, USA.
J Am Chem Soc. 2008 Jul 23;130(29):9524-35. doi: 10.1021/ja802080m. Epub 2008 Jun 28.
The diphosphaazide complex (MesNPP)Nb(N[Np]Ar)3 (Mes = 2,4,6-tri-tert-butylphenyl, Np = neopentyl, Ar = 3,5-Me2C6H3), 1, has previously been reported to lose the P2 unit upon gentle heating, to form (MesN)Nb(N[Np]Ar)3, 2. The first-order activation parameters for this process have been estimated here using an Eyring analysis to have the values Delta H(double dagger) = 19.6(2) kcal/mol and Delta S(double dagger) = -14.2(5) eu. The eliminated P2 unit can be transferred to the terminal phosphide complexes P[triple bond]M(N[(i)Pr]Ar)3, 3-M (M = Mo, W), and P[triple bond]Nb(N[Np]Ar)3, 3-Nb, to give the cyclo-P3 complexes (P3)M(N[(i)Pr]Ar)3 and (P3)Nb(N[Np]Ar)3. These reactions represent the formal addition of a P[triple bond]P triple bond across a M[triple bond]P triple bond and are the first efficient transfers of the P2 unit to substrates present in stoichiometric quantities. The related complex (OC)5W(MesNPP)Nb(N[Np]Ar)3, 1-W(CO)5, was used to transfer the (P2)W(CO)5 unit in an analogous manner to the substrates 3-M (M = Mo, W, Nb) as well as to (OC)5WP[triple bond]Nb(N[Np]Ar)3. The rate constants for the fragmentation of 1 and 1-W(CO)5 were unchanged in the presence of the terminal phosphide 3-Mo, supporting the hypothesis that molecular P2 and (P2)W(CO)5, respectively, are reactive intermediates. In a reaction related to the combination of P[triple bond]P and M[triple bond]P triple bonds, the phosphaalkyne AdC[triple bond]P (Ad = 1-adamantyl) was observed to react with 3-Mo to generate the cyclo-CP2 complex (AdCP2)Mo(N[(i)Pr]Ar)3. Reactions of the electrophiles Ph3SnCl, MesNPCl, and AdC(O)Cl with the anionic, nucleophilic complexes (OC)5W(P3)Nb(N[Np]Ar)3 and {(OC)5W}2(P3)Nb(N[Np]Ar)3 yielded coordinated eta(2)-triphosphirene ligands. The MesNPW(CO)5 group of one such product engages in a fluxional ring-migration process, according to NMR spectroscopic data. The structures of (OC)5W(P3)W(N[(i)Pr]Ar)3, [(Et2O)Na][{(OC)5W}2(P3)Nb(N[Np]Ar)3], (AdCP2)Mo(N[(i)Pr]Ar)3, (OC)5W(Ph3SnP3)Nb(N[Np]Ar)3, Mes*NP(W(CO)5)P3Nb(N[Np]Ar)3, and {(OC)5W}2AdC(O)P3Nb(N[Np]Ar)3, as determined by X-ray crystallography, are discussed in detail.
二磷叠氮配合物（MesNPP）Nb（N[Np]Ar）3（Mes = 2,4,6 - 三叔丁基苯基，Np = 新戊基，Ar = 3,5 - 二甲基苯基），即1，先前已有报道称其在温和加热时会失去P2单元，形成（MesN）Nb（N[Np]Ar）3，即2。在此利用艾林分析估算了该过程的一级活化参数，其值为ΔH‡ = 19.6(2) kcal/mol和ΔS‡ = -14.2(5) eu。消除的P2单元可转移至末端磷化物配合物P≡M（N[(i)Pr]Ar）3，3 - M（M = Mo，W）以及[P≡Nb（N[Np]Ar）3]−，3 - Nb，生成环 - P3配合物（P3）M（N[(i)Pr]Ar）3和[（P3）Nb（N[Np]Ar）3]−。这些反应代表了P≡P三键正式加成到M≡P三键上，并且是P2单元首次有效地转移到化学计量量存在的底物上。相关配合物（OC）5W（MesNPP）Nb（N[Np]Ar）3，1 - W（CO）5，以类似方式将（P2）W（CO）5单元转移至底物3 - M（M = Mo，W，Nb）以及[（OC）5WP≡Nb（N[Np]Ar）3]−。在末端磷化物3 - Mo存在下，1和1 - W（CO）5的碎片化速率常数未变，这支持了分子P2和（P2）W（CO）5分别是反应中间体的假设。在与P≡P和M≡P三键结合相关的反应中，观察到磷炔AdC≡P（Ad = 1 - 金刚烷基）与3 - Mo反应生成环 - CP2配合物（AdCP2）Mo（N[(i)Pr]Ar）3。亲电试剂Ph3SnCl、MesNPCl和AdC（O）Cl与阴离子亲核配合物[（OC）5W（P3）Nb（N[Np]Ar）3]−和[{（OC）5W}2（P3）Nb（N[Np]Ar）3]−反应生成配位的η2 - 三磷烯配体。根据核磁共振光谱数据，一种此类产物的MesNPW（CO）5基团参与了一个动态的环迁移过程。通过X射线晶体学确定的（OC）5W（P3）W（N[(i)Pr]Ar）3、[（Et2O）Na][{（OC）5W}2（P3）Nb（N[Np]Ar）3]、（AdCP2）Mo（N[(i)Pr]Ar）3、（OC）5W（Ph3SnP3）Nb（N[Np]Ar）3、Mes*NP（W（CO）5）P3Nb（N[Np]Ar）3和{（OC）5W}2AdC（O）P3Nb（N[Np]Ar）3的结构将详细讨论。
