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In 1963 Shriver reported a metal-boron dative bond in a complex formulated as [(η5-C5H5) 2WH2 (BF3)]. 33 However, these findings were refuted around 30 years later when differing products of the reaction of [(η5-C5H5) 2WH2] with alkylboranes were reported in a series of papers from this laboratory. 34–36

At this time, the concept of transition metal basicity was a young one; as Shriver noted,“[transition metal] basicity toward acids other than the proton has never been demonstrated”. His program of screening transition metal complexes for reactivity with boranes was nevertheless a prescient one, and it led to the development of metal basicity as a synthetic concept by the groups of Vaska, Werner, and others. 37 Shortly after the findings of Shriver, Parshall reported a number of transition metal complexes of BH3 prepared by the action of borane-ether adducts on anionic transition metal carbonyls. 38