Copper(I) complexes of isobutyl- (i-BuL) and isopropyl-substituted (i-PrL) proazaphosphatranes have been synthesized. Structural and computational studies of a series of monomeric complexes i-BuLCuX (X = Cl, Br, I) and dimeric [i-PrLCuCl]2 provide insight into the transannulation within and steric properties of the proazaphosphatrane ligand. These halide complexes are competent precatalysts in a model borylation reaction, and the silylamido complex i-BuLCuN(TMS)2 catalyzes hydrosilylation of benzaldehyde under mild conditions.