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

Abstract

The novel [W3S4H3(edpp)3]+ (edpp=(2-aminoethyl)diphenylphosphine) (1+) cluster hydride with an acidic −NH2 functionality has been synthetized and studied. Its crystal structure shows the characteristic incomplete W3S4 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 1H NMR spectrum, hydride assignment is supported by 1H-15N HSQC techniques, the changes in the 31P{1H} NMR chemical shift, and FT-IR spectra in the W−H region of the deuterated [W3S4D2H(edpp)3]+ (1+-d2) samples. Moreover, all NMR evidences suggest that one of the hydrogen atoms of the NH2 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.