A preliminary investigation into the feasibility of using organozirconium reagents to functionalize the methyl groups of polydimethylsiloxanes is made. Hexamethyldisiloxane is deprotonated and then bound to Zr to give CpaZrtCHaSiMeaOSiMesla (1) and Cp*ZrCl2(CH2-SiMe2OSiMe3) (3). These represent the first well-characterized compounds possessing methylsiloxane coordinated to zirconium. X-ray crystallography of 1 and 3 reveals a monodentate and a bidentate coordination mode, respectively, with 3 possessing an unexpected and very weak bond to the siloxane oxygen [Zr-0 = 2.427 (3) Á]. This is among the longest Zr-0 bonds known. Data for 1: cell constants a = 8.330
The reactions of the triply-bonded monoisocyanide complexes Re2Xg(#-dppm)2(CNR ) (X = C1 or Br; dppm = Ph2PCH2PPh2; R=t-Bu or xylyl) with the alkyne ligands HCCH and n-PrCCH in the presence of T103SCF 3 afford the complexes [Re2X3(#-dppm)2-(CNR)(fl2-HCCR)]OaSCF3 (R=H or n-C3HT). The structure of this set of complexes has been established by an X-ray structure determination on a single crystal of composition [Re2C13(#-dppm)2(CN-t-Bu)(r/2-HCCH)] -OaSCF3"CHaC(O)OC2H 5 (2a). The structure of the dirhenium(II) cation, F(t-BuNC)C12Re(#-dppm)2ReC1-(r/E-HCCH)] +, involves different coordination numbers for the two Re centres and an anti arrangement of the tBuNC and q2-HCCH ligands. The Re--Re bond length of 2.3171(5)A accords with the retention of a Re--Re bond.
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