SYNTHESIS, CHARACTERIZATION, AND HOMOPOLYMERIZATION AND COPOLYMERIZATION BEHAVIOR OF THE SILICON-BRIDGED [1]CHROMARENOPHANE CR(ETA-C6H5)(2)SIME(2)

The silicon-bridged [1]chromarenophane Cr(eta-C6H5)(2)SiMe(2) (7) was synthesized by the reaction of [Cr(eta-C6H5Li)(2)]. TMEDA (TMEDA, N,N, N,N-tetramethyl-1,2-ethylenediamine) with Me(2)SiCl(2) in hexanes. The molecular structure of 7 was determined by single-crystal X-ray diffr action and was shown to be strained, with an angle between the planes of the arene rings of 16.6(3)degrees. In addition, significant distort ion from planarity was detected in 7 for the arene carbon atom bonded to the bridging silane moiety, with angles between the planes of the a rene ligands and the C(arene)-Si bonds of 37.9(4)degrees and 38.2(4)de grees. Compound 7 does not undergo thermal ring-opening polymerization at temperatures approaching 180 degrees C, but instead decomposes to yield chromium metal and Ph(2)SiMe(2). This behavior contrasts with th at of silicon-bridged [1]ferrocenophanes such as Fe(eta-C5H4)(2)SiMe(2 ) (1), which readily thermally polymerize to yield poly(ferrocenylsila nes) at 130 degrees C and above. However, thermal treatment of equimol ar mixtures of 7 and 1 at 140 degrees C for 72 h resulted in the forma tion of the air-sensitive, heterobimetallic copolymer r(eta-C6H5)(2)Si Me(2)](x)[Fe(eta-C5H4)(2)SiMe(2)]y (9a), which was identified by H-1, C-13, and Si-29 NMR. Treatment of equimolar mixtures of 7 and 1 in THF with anionic initiators such as BuLi/hexanes resulted in the formatio n of an analogous copolymer 9b. H-1 NMR integration and, after selecti ve cleavage of the silicon-arene bonds in the copolymers by treatment with methanol, analysis of the residual ferrocenylsilane segments by G PC allowed an estimate of the molecular weights of 9a and 9b. These re sults indicated that the minimum value of M(w) for 9a was ca. 2.4 x 10 (3) and that for 9b was ca. 1.2 x 10(4).