The synthesis and properties of tris(diisopropylphosphanylmethyl)phenylborate ([TP(iPr)] − ) beryllium complexes [TP(iPr)]BeL with L = Cl, Br, I, CN, SCN, OCN, N 3 , and CF 3 SO 3 are described. In these compounds, the 1 J PBe NMR coupling constant can be used as a sensitive probe for the basicity and electron-donating properties of the L − anions in solution.