Synthesis of strontium and barium bis{tris[ (trimethylsilyl)methyl]zincates} via the transmetalation of bis[(trimethylsilyl)methyl] zinc

The transmetalation of bis[(trimethylsilyl)methyl] zinc in THF with distill ed strontium and barium yielded bis(tetrahydrofuran)strontium and tetrakis( tetrahydrofuran)barium bis{tris [(trimethylsilyl)methyl]zincates} (1 and 2 , respectively). The reaction of barium with Zn(CH2SiMe3)(2) in toluene gav e bis(eta (6)-toluene)barium bis{tris[(trimethylsilyl)methyl]zincate} (3) w ith rather short Ba-C bond lengths of 3.028(5) and 3 055(5) Angstrom. All o f these trialkylzincate anions coordinate as bidentate ligands with M-C-Zn three-center two-electron bonds. When carried out in the nondonor solvent h eptane, the transmetalation reaction yielded barium bis{tris[(trimethylsily l)methyl]zincate} (4), which reacts with THF to give the complex 2 and a sm all amount of [(THF)(3)Ba](2)O-(mu (4)-O)(2)[(Me3SiCH2ZnC2)(2)SiMe2](2) (5) . The central moiety is a centrosymmetric Ba2O2 cycle with Ba-O distances o f 2.514(2) and 2.570(3) Angstrom. The oxygen dianion is surrounded, distort ed tetrahedrally by two barium and two zinc atoms.