Facile access to a stable divalent germanium compound with a terminal PH2 group and related PR2 derivatives

摘要

The first stable beta-diketiminate germanium(II) complexes LGcY [L = CH {(CMe)(2,6-(Pr2C6H3N)-Pr-i)}2] with terminal phosphanyl groups Y (Y = PH2, PHR, and PR2) are described. Thus, LGePH2 (2) is synthesized by salt metathesis reaction of LGeCl (1) with lithium phosphanide and can be isolated in the form of orange crystals in 83% yield. Its silylation with 1 molar equiv of Me3SiOTf (OTf = OSO2CF3) in the presence of triethylamine as auxiliary base leads solely to LGeP(H)SiMe3 (3). In contrast, reaction of 2 with 2 molar equiv of Me3SiOTf does not lead to the desired product LGeP(SiMe3)(2) (4), but LGeOTf (6) and HP(SiMe3)2 are formed. However, compound 4 is conveniently accessible from I and the corresponding lithium phosphanide LiP(SiMe3)(2), While attempts to metalate the PH2 group in 2 applying BuLi and Me2Zn, respectively, lead merely to Ge-P fission and undesired side products, its conversion with (Bu2Hg)-Bu-t occurs without Ge-P fission but P-P bond formation to give the novel P,P'-bis(phosphanylgermylene) LGeP(H)-P(H)GeL (5), elemental mercury, and isobutane. Compounds 2-6 have been fully characterized, including elemental analyses, NMR spectroscopy, and single-crystal X-ray diffraction analysis.