Synthesis and structure of cyclotrigermenium salts of tetrakis{3,5-bis(trifluoromethyl)phenyl}borate, tetrakis(pentafluorophenyl)borate and tetrakis{4-[tert-butyl(dimethyl)silyl]-2,3,5,6-tetrafluorophenyl}borate: A stable free germyl cation in the condensed phase

The reaction of tetrakis(tri-tert-butylsilyl)cyclotrigermene (1a) with Ph3C +[3,5-(CF3)(2)C6H3](4)B- [TFPB-], Ph3C+(C6F5)(4)B-(TPFPB-), and Ph3C+[4-(tB uMe(2)Si)C6F4](4)B- (TSFPB-) in benzene produced the stable free tris(tri-t ert-butylsilyl) cyclotrigermenium ion (2a(+)) with the corresponding tetraa rylborate as the counterion. The crystal structures of 2a(+)TFPB(-) and 2a( +)TSFPB(-) reveal a free germyl cation with a two n-electron system. The th ree-membered ring of germanium atoms constitutes an almost equilateral tria ngle. The cyclotrigermenium tetraarylborates, 2a(+)TFPB(-), 2a(+)TPFPB(-), and 2a(+)TSFPB(-), are stable in solution. The spectroscopic data show that 2a(+) is a free germyl cation, does not coordinate to either the solvent m olecules (dichloromethane, chloroform, toluene, or diethyl ether) or the co unter anions (TFPB-, TPFPB-, or TSFPB-). The tris (tri-tert-butylgermyl)cyc lotrigermenium ion (2b(+)) was also characterized.