Martin's Phosphino-Triol Revisited: Unexpected P-C Bond Cleavage Reactions and Their Suppression via Complexation of Al³⁺ and Sc³

A revised synthesis of Martin's phosphino-triols (two derivatives) is reported. Once isolated, these thermally sensitive triols were shown to disassemble selectively via an unexpected P-C bond cleavage reaction. This degradation pathway was effectively suppressed via complexation of Al³⁺ and Sc³⁺. In the resulting half-cage complexes, the ligand scaffold is bound to each metal (Al³⁺ and Sc³⁺, respectively) via all four donor atoms. So far, this κ⁴-P,O,O',O″-coordination mode has not been observed for any other phosphino-triol.