Group 14 Metal Terminal Phosphides: Correlating Structure with |<i>J</i><sub>MP</sub>|

A series of heavier group 14 element, terminal phosphide complexes, M­(BDI)­(PR<sub>2</sub>) (M = Ge, Sn, Pb; BDI = CH­{(CH<sub>3</sub>)­CN-2,6-<i>i</i>Pr<sub>2</sub>C<sub>6</sub>H<sub>3</sub>}<sub>2</sub>; R = Ph, Cy, SiMe<sub>3</sub>) have been synthesized. Two different conformations (<i>endo</i> and <i>exo</i>) are observed in the solid-state; the complexes with an <i>endo</i> conformation have a planar coordination geometry at phosphorus (M = Ge, Sn; R = SiMe<sub>3</sub>) whereas the complexes possessing an <i>exo</i> conformation have a pyramidal geometry at phosphorus. Solution-state NMR studies reveal through-space scalar coupling between the tin and the isopropyl groups on the <i>N</i>-aryl moiety of the BDI ligand, with <i>endo</i> and <i>exo</i> exhibiting different <i>J</i><sub>SnC</sub> values. The magnitudes of the tin–phosphorus and lead–phosphorus coupling constants, |<i>J</i><sub>SnP</sub>| and |<i>J</i><sub>PbP</sub>|, differ significantly depending upon the hybridization of the phosphorus atom. For Sn­(BDI)­(P­{SiMe<sub>3</sub>}<sub>2</sub>), |<i>J</i><sub>SnP</sub>| is the largest reported in the literature, surpassing values attributed to compounds with tin–phosphorus multiple-bonds. Low temperature NMR studies of Pb­(BDI)­(P­{SiMe<sub>3</sub>}<sub>2</sub>) show two species with vastly different |<i>J</i><sub>PbP</sub>| values, interpreted as belonging to the <i>endo</i> and <i>exo</i> conformations, with sp<sup>2</sup>- and sp<sup>3</sup>-hybridized phosphorus, respectively.