Oxidative addition to M(II) (M = Ge, Sn) amidinate complexes: routes to group 14 chalcogenolates with hypervalent coordination environments

Oxidative addition of diphenyl dichalcogenides, PhE-EPh (E=S, Se) to Ge(II) and Sn(II) amidinate complexes is reported. In the case of the bis(alkylam idinato)Ge complexes, Ge(CyNC(R')NCy) (Cy=cyclohexyl; R'=Me, Bu-t), six coo rdinate Ge(IV) compounds were isolated and the structure of (PhS)(2)Ge(CyNC (Me)NCy) (10) was confirmed by single crystal X-ray diffraction analysis. M ixed amidinato-amido species, M(CyNC(R')NCy)[N(SiMe3)(2)] (M=Ge, Sn; R=Me, Bu-t), react in a similar manner to yield novel bis(phenylchalcogenolate) c omplexes of Sn and Ge. Spectroscopic features and, in the case of (PhSe)(2) Ge(CyNC(Me)NCy)[N(SiMe3)(2)] (13), a single crystal structural analysis ind icate that this ligand environment appears to favor Ge(IV) complexes with a strong disposition towards a tetrahedral geometry. In these cases, a five coordinate environment for the metal center is avoided by one of the amidin ate ligands exhibiting a monodentate coordination mode, which preserves the pseudo-tetrahedral metal coordination geometry. These observations contras t with the Sn(II/IV) analogues which exhibit no such tendency. For example the single crystal structure of (PhS)(2)Sn(CyNC(Me)NCy)[N(SiMe3)(2)] (14) d isplays a bidentate ligand and a five coordinate metal coordination geometr y. Complex 13 reacts with elemental Se to generate the terminal germanium s elenide and regenerate PhSeSePh. Concomitant with this reaction is a rearra ngement of the previously monodentate amidinate ligand to a bidentate coord ination mode.