The Reaction Of 7-phosphanorbornadiene Complexes With Borane Complexes And Boron Trihalides

The reaction of 7-phosphanorbornadiene complexes with borane complexes and boron trihalides were systematically studied.1. A method to prepare tungsten-stabilized disecondary diphosphines [RPH-PHR][W(CO)5]2 is developed based on the reaction of Ph3P-BH3 with 7-phosphanorbornadiene W(CO)5 complexes.Transient terminal phosphinidene complexes [RP-W(CO)5] are released from the corresponding precursors, 7-R-7-phosphanorbornadiene W(CO)5 complexes, in the presence of copper chloride at relatively low tempreture(60 ℃) in THF, and then dimerize to highly unstable diphosphene complexes,which are reduced in situ by triphenylphosphine-borane to form the disecondary diphosphine complexes [RPH-PHR][W(CO)5]2. Further reaction with 1,3-dibromopropane when R = Ph in the presence of aqueous K2CO3 gives a 1,2-diphospholane. The reaction with Et3N-BH3 results in the same products but lowers the yield. While the molybdenum counterpart [Ph P-Mo(CO)5] tends to insert into the B-H bond.2. The reported reaction of 7-phosphanorbornadiene complexes with Lewis acids is scarce. The results of their reaction with representative Lewis acids boron trihalides are unexpected.The reaction of 7-phosphanorbornadiene M(CO)5(M = Mo, W) complexes with BX3(X = Cl, Br) yields products containing C(O)P(X)M(CO)5 moiety. The results indicate that RP-M(CO)5 unit inserts into one of the carboxyl group of the phthalic derivative, the by-product of the collapse of the bridges. While other studies imply no involving of transient terminal phosphinidene complexes [RP-M(CO)5], for which the 7-phosphanorbornadiene complexes are normally used. When X = Br, the products further undergo cyclization to 6-membered P-containing heterocycles possessing a quasi-planar structure, which leading to 5-membered rings resulting from a ring contraction when allowed with an excess of BBr3.