Bifunctional W/NH Cuboidal Aminophosphino W₃S₄ Cluster Hydrides: The Puzzling Behaviour behind the Hydridic‐Protonic Interplay

Abstract

This work is dedicated to Professor Rinaldo Poli on the occasion of his 65 th birthday.The novel [W 3 S 4 H 3 (edpp) 3 ] + (edpp = (2-aminoethyl) diphenylphosphine) (1 + ) cluster hydride with an acidic À NH 2 functionality has been synthetized and studied. Its crystal structure shows the characteristic incomplete W 3 S 4 cubane core with the outer positions occupied by the P and N atoms of the edpp ligands. Although no signal due to the hydride ligands is observed in the 1 H NMR spectrum, hydride assignment is supported by 1 H-15 N HSQC techniques, the changes in the 31 P { 1 H} NMR chemical shift, and FT-IR spectra in the WÀ H region of the deuterated [W 3 S 4 D 2 H(edpp) 3 ] + (1 + -d 2 ) samples. Moreover, all NMR evidences suggest that one of the hydrogen atoms of the NH 2 group in 1 + is rapidly exchanging with the hydride. The reaction of 1 + with acids (HCl, HBr and DCl) features complex polyphasic kinetics with zero-order dependence with respect to the acid concentration, being also independent of the solvent nature. This behavior differs from that of their diphosphino analogues, suggesting a different mechanism.