The chemistry of silenes, germenes, disilenes and digermenes has been extensively studied over the last 35 years; however, not much is known about the mechanisms of many of the fundamental reactions of this class of compounds, including cycloadditions. This review describes the current understanding of the reaction pathways for the cycloaddition of carbonyl compounds and alkynes to (di)tetrelenes. The question of whether or not the cycloaddition reactions of (di)tetrelenes follow the Woodward-Hoffman rules, established for alkenes and alkynes, is addressed.

A series of alkyne-functionalized poly(4-(phenylethynyl)styrene)-block-poly(ethylene oxide)-block-poly(4-(phenylethynyl)styrene) (PPES-b-PEO-b-PPES) ABA triblock copolymers was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PESn[Co2(CO)6]x-EO800-PESn[Co2(CO)6]x ABA triblock copolymer/cobalt adducts (10-67 wt % PEO) were subsequently prepared by reaction of the alkyne-functionalized PPES block with Co2(CO)8 and their phase behavior was studied by TEM. Heating triblock copolymer/cobalt carbonyl adducts at 120 °C led to cross-linking of the PPES/Co domains and the formation of magnetic cobalt nanoparticles within the PPES/Co domains. Magnetic hydrogels could be prepared by swelling the PEO domains of the cross-linked materials with water. Swelling tests, rheological studies and actuation tests demonstrated that the water capacity and modulus of the hydrogels were dependent upon the composition of the block copolymer precursors.

A new polymer with an alternating germanium-carbon backbone has been synthesized from 1,1-dimesitylneopentylgermene via addition polymerization using an anionic initiator.Addition polymerization of vinylic monomers, a standard protocol for the preparation of organic polymers, has only recently been applied to the synthesis of inorganic polymers. The development of this important method for inorganicbased polymers was undoubtedly delayed by the lack of or difficulty in the synthesis of suitable monomers. In fact, much of the research on unsaturated inorganic, primarily main group, compounds over the last 30 years has focused on understanding how to prevent oligomerization reactions. One key strategy involves the use of bulky substituents to kinetically stabilize the doubly-bonded species; 1 it follows that such compounds would not be suitable as monomers for polymer synthesis. However, in a landmark series of papers, Gates et al. have shown that readily accessible stable phosphaalkenes (PQC) with relatively bulky substituents can indeed undergo addition polymerization using radical or anionic initiators to form poly(methylenephosphine)s, a new and interesting class of polymers. 2 Furthermore, the phosphaalkenes undergo living anionic polymerization at ambient temperatures using organolithium reagents as initiators. 3 This discovery has opened up numerous exciting possibilities for the synthesis of novel copolymers containing the functional poly(methylenephosphine) block. Block copolymers, in general, and particularly those with inorganic segments, have been the subject of intense research of late due to the spontaneous self assembly of the polymers into varied and interesting nanostructures. 4 We have long been interested in the chemistry of multiplybonded germanium derivatives and were intrigued by the possibility that germenes (GeQC) may also be able to undergo addition polymerization to provide an entry into a hitherto unknown [GeC] n polycarbogermane system. Given the extensive interest in poly(silylenemethylene) polymers, [SiC] n , 5 particularly in their pyrolysis chemistry to give silicon carbide, 6 and the relatively scarce information available on the pyrolysis of polycarbogermanes, 7 we have now investigated the addition polymerization of a solution stable germene as a new route to polymers with a [GeC] n backbone.A pale yellow pentane solution of 1,1-dimesitylneopentylgermene ( 1) was prepared from the addition of t-butyllithium (1 equiv.) to a solution of fluorovinylgermane 2. 8 Germene 1 was stable in solution for several hours; however, upon addition of t-butyllithium (0.1 equiv.) to the solution (Scheme 1), the colour of the solution changed from pale to bright yellow. After 30 min, the reaction was quenched with methanol and the bright yellow colour dissipated immediately. The solvents were removed and the residue was dissolved in CH 2 Cl 2 .A white solid precipitated from the CH 2 Cl 2 solution upon the addition of methanol; the solid was purified by re-precipitation. The air stable material (...

A variety of terminal alkynes were added to Mes 2 SidCHCH 2 t-Bu, 4, a naturally polarized silene. Three different modes of reactivity were observed: addition across the acetylenic C-H bond to give silylacetylenes 6a-i and 12, cycloaddition to give silacyclobutenes 7 and 9, and ene-addition to give vinylsilane 8. The reactivity of the naturally polarized silene 4 toward terminal alkynes is compared to that of nonpolar silenes.

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