Zhao Guangyu, Basuli Falguni, Kilgore Uriah J, Fan Hongjun, Aneetha Halikhedkar, Huffman John C, Wu Gang, Mindiola Daniel J
Department of Chemistry and Molecular Structure Center, Indiana University, Bloomington, IN 47405, USA.
J Am Chem Soc. 2006 Oct 18;128(41):13575-85. doi: 10.1021/ja064853o.
Alpha-hydrogen abstraction and alpha-hydrogen migration reactions yield novel titanium(IV) complexes bearing terminal phosphinidene ligands. Via an alpha-H migration reaction, the phosphinidene ((tBu)nacnac)Ti=PTrip ((tBu)nacnac(-) = [Ar]NC((t)Bu)CHC((t)Bu)N[Ar], Ar = 2,6-(CHMe2)(2C6H3, Trip = 2,4,6-(i)Pr3C6H2) was prepared by the addition of the primary phosphide LiPH[Trip] to the nucleophilic alkylidene triflato complex ((tBu)nacnac)Ti=CH(t)Bu(OTf), while alpha-H abstraction was promoted by the addition of LiPH[Trip] to the dimethyl triflato precursor ((tBu)nacnac)Ti(CH)(2)(OTf) to afford ((tBu)nacnac)Ti=PTrip. Treatment of ((tBu)nacnac)Ti=PTrip with B(C6F5)(3) induces methide abstraction concurrent with formation of the first titanium(IV) phosphinidene zwitterion complex ((tBu)nacnac)Ti=P[Trip]{CH3B(C6F5)(3)}. Complex ((tBu)nacnac)Ti=P[Trip]{CH3B(C6F5)(3)} [2 + 2] cycloadds readily PhCCPh to afford the phosphametallacyclobutene [((tBu)nacnac)Ti(P[Trip]PhCCPh)][CH3B(C6F5)(3)]. These titanium(IV) phosphinidene complexes possess the shortest Ti=P bonds reported, have linear phosphinidene groups, and reveal significantly upfielded solution 31P NMR spectroscopic resonances for the phosphinidene phosphorus. Solid state 31P NMR spectroscopic data also corroborate with all three complexes possessing considerably shielded chemical shifts for the linear and terminal phosphinidene functionality. In addition, high-level DFT studies on the phosphinidenes suggest the terminal phosphinidene linkage to be stabilized via a pseudo Ti[triple bond]P bond. Linearity about the Ti-P-C(ipso) linkage is highly dependent on the sterically encumbering substituents protecting the phosphinidene. Complex ((tBu)nacnac)Ti=P[Trip]{CH3B(C6F5))(3)} can catalyze the hydrophosphination of PhCCPh with H(2)PPh to produce the secondary vinylphosphine HP[Ph]PhC=CHPh. In addition, we demonstrate that this zwitterion is a powerful phospha-Staudinger reagent and can therefore act as a carboamination precatalyst of diphenylacetylene with aldimines.
α-氢抽象和α-氢迁移反应生成了带有末端磷烯配体的新型钛（IV）配合物。通过α-H迁移反应，磷烯（（tBu）nacnac）Ti=PTrip （（tBu）nacnac(-) = [Ar]NC((t)Bu)CHC((t)Bu)N[Ar]，Ar = 2,6-(CHMe2)(2C6H3, Trip = 2,4,6-(i)Pr3C6H2）是通过将伯膦化物LiPH[Trip]添加到亲核亚烷基三氟甲磺酸酯配合物（（tBu）nacnac）Ti=CH(t)Bu(OTf)中制备的，而通过将LiPH[Trip]添加到二甲基三氟甲磺酸酯前体（（tBu）nacnac）Ti(CH)(2)(OTf)中促进α-H抽象，得到（（tBu）nacnac）Ti=PTrip。用B(C6F5)(3)处理（（tBu）nacnac）Ti=PTrip会引发甲基抽象，同时形成第一个钛（IV）磷烯两性离子配合物（（tBu）nacnac）Ti=P[Trip]{CH3B(C6F5)(3)}。配合物（（tBu）nacnac）Ti=P[Trip]{CH3B(C6F5)(3)} [2 + 2]容易与PhCCPh发生环加成反应，生成磷金属环丁烯[((tBu)nacnac)Ti(P[Trip]PhCCPh)][CH3B(C6F5)(3)]。这些钛（IV）磷烯配合物具有报道中最短的Ti=P键，具有线性磷烯基团，并且磷烯磷的溶液31P NMR光谱共振明显向高场移动。固态31P NMR光谱数据也证实了所有三种配合物对于线性和末端磷烯官能团都具有相当大的屏蔽化学位移。此外，对磷烯的高水平DFT研究表明，末端磷烯键通过伪Ti[三键]P键得以稳定。Ti-P-C（ipso）键的线性高度依赖于保护磷烯的空间位阻取代基。配合物（（tBu）nacnac）Ti=P[Trip]{CH3B(C6F5))(3)}可以催化PhCCPh与H(2)PPh的氢膦化反应，生成仲乙烯基膦HP[Ph]PhC=CHPh。此外，我们证明这种两性离子是一种强大的磷杂施陶丁格试剂，因此可以作为二苯乙炔与醛亚胺的碳胺化预催化剂。
