Synthesis and structures of germanium(II) calixarenes and clusters

Abstract

The purpose of this work was to examine the structures of novel germanium containing compounds. This was accomplished by characterizing the products of the reaction between the germanium(II) amide, Ge[N(SiMe 3 ) 2 ] 2 , and para-tert-butylcalix[8]arene with subsequent reaction with Fe 2 (CO) 9 . The phenols, HOC 6 H 3 Bu t -2-Me-6, HOC 6 H 4 Bu t -4 and HOC 6 H 3 Bu t -2-Me-4, were selected due to their relative steric bulkiness and were also reacted with Ge[N(SiMe 3 ) 2 ] 2 and the products of the reactions were characterized. Products were characterized by NMR and IR spectroscopy, GC/MS spectrometry and X-ray crystallography. The reaction between para-tert-butylcalix[8]arene and Ge[N(SiMe 3 ) 2 ] 2 yielded the germylene complex {p-Bu t 8 calix[8]arene}Ge 4 and contains two Ge 2 O 2 rhombi located on opposite sides of the molecule. The two rhombi are planar where the Ge - O(terminal) bonds are shorter than the Ge - O(bridging) bonds. Each germanium is in the divalent oxidation state. In the subsequent reaction with Fe 2 (CO) 9 , the Fe - Fe bond was cleaved with addition of Fe(CO) 4 to two of the four germanium atoms with concomitant loss of Fe(CO) 5 . The reaction of Ge[N(SiMe 3 ) 2 ] 2 yielded the monomeric complex Ge(OC 6 H 3 Bu t -2-Me-6) 2 . The reaction with HOC 6 H 4 Bu t -4 yielded the hexagermanium cluster Ge 6 (μ 3 -O) 4 (μ 2 -OC 6 H 4 Bu t -4) 4 that is held together by four μ3-bridging oxo atoms and four μ2-p-Bu t aryloxide ligands. The reaction with HOC 6 H 3 Bu t -2-Me-4 resulted in the formation of two clusters that were structurally characterized. One is the octagermanium cluster Ge8(μ 3 -O) 6 (OC 6 H 3 -Bu t -2-CH 3 -4)4 that is connected together by six μ 3 -oxo atoms with four terminal aryloxide groups. The second structure that was determined was the dimer [Ge 4 (μ-O) 2 (OC 6 H 3 -Bu t -2-CH 3 -4) 4 ·NH 3 ] 2 that contains two Ge 4 O 2 rings that are connected by two Ge - Ge single bonds. The dimer appears to be an intermediate in the formation of the larger octagermanium cluster. All of the germanium atoms are present in the divalent oxidation state.