Metalated 1,3-Azaphospholes: Structure and Reactivity of 2-Lithio-1-methyl-1,3-benzazaphosphole, an Isolable −PC(Li)−NR Heterocycle

Abstract

The preparation, NMR data, a crystal structure, and the reactivity of isolable 2-lithio-1,3-benzazaphospholes are described. The compounds are or belong to the most stable PCLi species, although they lack steric congestion. Reactions with organoelement or organometal halides W(CO)6 as well as with CO2 or benzophenone allow access to various novel functionally substituted 1,3-benzazaphospholes (2-R = SnMe3, Fe(CO)2Cp, C[W(CO)5]OLi(THF)3, CPh2OH, PPh2, P(O)Ph2). The crystal structure of the tungsten-carbene derivative is described. Attempts to lithiate and functionalize a 1,3-benzazaphosphole P−W(CO)5 complex failed, but reactions of 1-methyl-2-stannyl- and 1-methyl-2-phosphino-1,3-benzazaphosphole with W(CO)5(THF) furnished examples for a 2-metalated benzazaphosphole P−W(CO)5 complex and the preferred complexation of the phosphino substituent, respectively. The considerable upfield shifts of the 31P NMR signals after complexation of the low-coordinated phosphorus atom by W(CO)5 attest that the ligands are stronger acceptors than donors.