Reactions of diazo-compounds with the electron-rich germylene Ge[N(SiMe3)2]2. Characterisation and some addition reactions of [(Me3Si)2N]2GeNNC(COOMe)2: crystal and molecular structure of [(Me3Si)2N]2Ge[NHNC(COOMe)2][C(N2)COPh]
Two forms of the stable germyleneazine [(Me3Si)2N]2GeNNC(COOMe)2, formed by addition of the diazo-compound N2C(COOMe)2 to the electron-rich germylene Ge[N(SiMe3)2]2 have been characterised in solution by 1H and 13C n.m.r. spectroscopy. MNDO calculations on the simpler analogue [(H3Si)2N]2GeNNC(COOMe)2 indicate that the two forms have planar transoid and cisoid GeNNC groups respectively, with the cisoid isomer as the more stable: the calculations also indicate that charge-controlled additions of electrophiles will occur at N1, adjacent to germanium, while all nucleophilic addition will occur at Ge. Some adducts of [(Me3Si)2N]2GeNNC(COOMe)2 with weak acids HX are described; in all cases 1,2-addition of HX occurs across the Ge–N1 bond to yield [(Me3Si)2N]2Ge(X)[NHNC(COOMe)2]. Crystals of one such adduct [(Me3Si)2N]2Ge[NHNC(COOMe)2][C(N2)COPh] are triclinic, space group P, with a= 9.627(2), b= 12.672(19), c= 15.702(3)Å, α= 101.66(4), β= 85.02(2), γ= 77.65(5)°, and Z= 2. The structure was refined from diffractometer data (5 173 observed reflections) to an R value of 0.046. The structure determination confirms the 1,2-addition of HC(N2)COPh across the Ge–N1 bond of [(Me3Si)2N]2-GeNNC(COOMe)2 and reveals a free diazo-group, sterically unconstrained. Reaction of tosyl azide with Ge[N(SiMe3)2] follows a different course from the reactions involving diazo-compounds; nitrogen is lost and the product is a polygermazane {[(Me3Si)2N]2GeNSO2C6H4Me-p}n, which is insoluble in aqueous media and all common organic solvents, wholly resistant to hot 50% aqueous alkali, but readily hydrolysed by concentrated hydrochloric acid.