Coordination Site Selective <i>Janus Head</i> Ligands

The deprotonation of PhP(CH2Py)2 (Py = 2-pyridyl) (1) leads to a Janus head ligand, in which one coordination site is provided by the two carbanionic CH bridges, while the two ring nitrogen atoms and the phosphorus atom supply the second site. This coordination pattern is displayed in the metal complexes [(Et2O)3Li2{C(H)Py}2PPh]2 (2) and [{(SiMe3)2NSn}2{C(H)Py}2PPh] (3). In accordance with the different size of the metal moieties, 2 is a dimeric compound, while 3 forms a monomeric complex. The comparison of the solid-state structures of 2 and 3 displays a distinct response of the bonding of the deprotonated ligands toward the various metal atoms. Detailed NMR experiments show that the tin complex 3 has identical structures in both solution and the solid state.