Stereoselective insertion of GeCl2 into tungsten-chlorine bonds of aminomethylene and aminocarbyne complexes

Treatment of Cp*(CO)(2)W equivalent to CNEt2 (1) (Cp* = eta (5)-pentamethyl cyclopentadienyl) with HCl affords the aminomethylene complex cis-Cp*(Cl)(C O)(2)W=C(K)NEt2 (2). Complex 2 inserts stereoselectively GeCl2 into the tun gsten-chlorine bond to afford cis-Cp*(GeCl3)(CO)(2)W=C(H)NEt2 (3). Complex 3 can also be obtained directly from 1 and GeCl2(diox) (diox = 1,4-dioxane) in CH2Cl2. Similarly, treatment of Cp**(CO)(2)W equivalent to CNEt2 (1a) ( Cp**=eta (5)-ethyltetramethylcyclopentadienyl) with GeCl2(diox) in toluene affords cis-Cp**(GeCl3)(CO)(2)W=C(H)NEt2 (3a). An isomerization equilibrium is established between 3 and trans-Cp*(GeCl3)(CO)(2)W=C(H)NEt2 (4) in the melt (208 degreesC), which favors the trans isomer (3:4 ratio = 1.6). The a minocarbyne complex cis-Cp*(Cl)(2)(CO)W equivalent to CNEt2 (5) reacts with GeCl2(diox) to yield stereoselectively spy-5-14-Cp*(Cl)(GeCl3)(CO)W equiva lent to CNEt2 (6). Complexes 2-6 were fully characterized and the crystal s tructures of the complexes 2, 3, 4 and 6 are presented. (C) 2001 Elsevier S cience B.V. All rights reserved.