Ge–Cu-Complexes Ph(pyO)Ge(μ 2 -pyO) 2 CuCl and PhGe(μ 2 -pyO) 4 CuCl—Representatives of Cu(I)→Ge(IV) and Cu(II)→Ge(IV) Dative Bond Systems

Phenylgermaniumpyridine-2-olate PhGe(pyO) 3 (compound 1Ge ) and CuCl react with the formation of the heteronuclear complex Ph(pyO)Ge(μ 2 -pyO) 2 CuCl ( 2Ge’ ) rather than forming the expected compound PhGe(μ 2 -pyO) 3 CuCl ( 2Ge ). Single-point calculations (at the B2T-PLYP level) of the optimized molecular structures confirmed the relative stability of isomer 2Ge’ over 2Ge and, for the related silicon congeners, the relative stability of 2Si over 2Si’ . Decomposition of a solution of 2Ge’ upon access to air provided access to some crystals of the copper(II) compound PhGe(μ 2 -pyO) 4 CuCl ( 3Ge ). Compounds 2Ge’ and 3Ge were characterized by single-crystal X-ray diffraction analyses, and the Ge–Cu bonds in these compounds were analyzed with the aid of quantum chemical calculations, e.g., Natural Bond Orbital analyses (NBO), Non-Covalent Interactions descriptor (NCI), and topology of the electron density at bond critical point using Quantum Theory of Atoms-In-Molecules (QTAIM) in conjunction with the related silicon compounds PhSi(μ 2 -pyO) 3 CuCl ( 2Si ), PhSi(μ 2 -pyO) 4 CuCl ( 3Si ), as well as the potential isomers Ph(pyO)Si(μ 2 -pyO) 2 CuCl ( 2Si’ ) and PhGe(μ 2 -pyO) 3 CuCl ( 2Ge ). Pronounced Cu→Ge (over Cu→Si) lone pair donation was found for the Cu(I) compounds, whereas in Cu(II) compounds 3Si and 3Ge, this σ-donation is less pronounced and only marginally enhanced in 3Ge over 3Si .