Novel germanium(II) binaphthoxide complexes: synthesis and crystal structure of (R,R)-[Ge{OC20H10(OSiMe3)-2′-(SiMe3)2-3,3′}2] and (R)-[Ge{O2C20H10(SiMe2Ph)2-3,3′}{NH3}]; catalytic function of Ge[N(SiMe3)2]2 for the mono-silylation of 3,3′-disubstituted-1,1′-bi-2,2′-naphthols