Here we studied the coordination mode of optically pure N-benzyl-N-phosphino-tert-butylsulfinamide (1a) toward Ir(I), Cu(I), Pd(II), and Pt(II). Ligand 1a can work as a hemilabile bidentate P,O or P,S or monodentate P ligand depending on the nature of the metal and its electronic and steric environment. X-ray analysis confirmed that soft metals, such as Ir or Pt, favor the P,S coordination mode, while harder ones, such as Cu(I), favor the formation of P,O five-membered-ring chelates. Finally, analysis of the resonances of the methylene and t-Bu groups in coordinated 1a allowed us to predict a P,S coordination mode for the corresponding (1a)PdCl2 complex 7.