Contrastive Study on Substitution of the Bulky Phosphanide [P(SiPr)] toward Heavier Tetrylenes.

The super bulky sodium phosphanide, NaP(SiPr), was reacted with amidinatotetrylenes LECl (L = PhC(NBu), E = Si, Ge), resulting in the formation of phosphasilene LSi(SiPr) = PSiPr () and phosphanido germylene LGeP(SiPr) (), respectively. Investigation on the reactivity of and toward elemental sulfur was carried out, where a stepwise reaction yielding the silanethione LSi(=S)SiPr () and the silicon thioester analogue LSi(=S)SSiPr () was observed in the case of , while the treatment of with sulfur exclusively afforded the germanium thioester analogue. In addition, the reactions of with Fe(CO) and GeCl·1,4-dioxane led to the germylene-coordinated iron carbonyl and the asymmetric Ge-Ge-bonded complex, respectively, exhibiting the reactivity of the lone pair as well as a weak Ge-P bond. Further investigations into the stability and bonding characteristics of the Si-P and Ge-P bonds in and , employing DFT, NBO, QTAIM, and EDA-NOCV analyses, suggest their polarized nature, with electron density accumulation on the phosphorus atoms supported by electrostatic potential maps. EDA-NOCV results indicate that the Si-P bond is primarily stabilized by covalent interactions, whereas the Ge-P bond exhibits a dative character arising from interactions between ionic fragments [(SiPr)P(S) + LGe(S)], further confirming its polarization.