Proton spongephosphines: electrospray-active ligands

Abstract

Attachment of a proton sponge to a phosphine ligand renders neutral complexes of the ligand highly amenable to analysis by electrospray ionisation mass spectrometry (ESI-MS). The ligand 1,8-bis(dimethylamino)naphthyldiphenylphosphine (3) is extremely efficient and highly selective in forming exclusively [M + H]⁺ ions, which may be detected at very low concentration. Ionisation efficiency of 3 in the presence of H⁺ approached 100%. The bis-substituted ligand bis{1,8-bis(dimethylamino)naphthyl}phenylphosphine (4) was also prepared and characterised, as were Fe(CO)₄- (5c), Mn(η⁵-C₅H₄Me)(CO)₂- (6) and W(CO)₅- (7) complexes of 3. Compounds 3, 3·HBr·EtOH, 4 and 5c were all structurally characterised.