Comparing Nucleophilicity of Heavier Heteroleptic Amidinato‐Amido Tetrelylenes: An Experimental and Theoretical Study

Abstract

In our previous communication we have reported the isolation and reactivity of heteroleptic three coordinated silylene, LSi(2,6‐iPr2C6H3NPPh2) [L= PhC(NtBu)2] (2). Here we report the isolation of analogous germylene and stannylene, LGe(2,6‐iPr2C6H3NPPh2) (6) and LSn(2,6‐iPr2C6H3NPPh2) (7) from the reaction of 2,6‐iPr2C6H3N(Li)PPh2 (1) with LGeCl (4) and LSnCl (5), respectively. Both compounds are characterized by multinuclear NMR spectroscopy, EI‐mass spectrometry, and single crystal X‐ray diffraction studies. The comparison of the molecular orbitals and the molecular electrostatic potential (ESP) maps on the van der Waal's surface of the atoms in silylene (2), germylene (6), and stannylene (7) indicate that nucleophilicity of the group‐14 atom reduces from silylene to stannylene. The Si‐center is more nucleophilic than P‐center in 2, whereas Ge and P‐ centers have similar nucleophilicity in 6 and Sn‐center is much less nucleophilic than P‐center in 7. The global minimum of the ESP of 2 is in the direction of the lone pair on Si, whereas the global minimum of the ESP of 6 and 7 is located above 2,6‐iPr2‐C6H3 ring on the N‐atom and in the opposite direction of the P‐center. This is supported by the observation that silylene 2 forms complex with AuCl by coordinating with Si‐center, whereas germylene 6 and stannylene 7 do not form the analogous adducts.