Organophosphorous partners bearing P-H bonds with a wide range of acidities (pKa 9.0 to 22.4) can be activated with transition metal catalyts. For secondary phosphines, coordination followed by deprotonation results in a metal-phosphido complex, with high nucleophilicity, and recent studies have revealed impressive versatility of catalytically generated Cu-phosphido complexes. 9e,9g-h, Glueck elucidated mechanistic and structural details, 15d,e while both Glueck and Yin demonstrated catalytic transformations using Cu-phosphidos (Figure ). 9g,h Previous strategies using cyclopropenes to forge C-P bonds focused on Pd catalysis.