SYNTHESIS AND X-RAY STRUCTURES OF MONO-ACETONITRILE AND BIS-ACETONITRILE DERIVATIVES OF THE CATIONIC RHENIUM ALLYL COMPLEX [(ETA(5)-C5ME5)RE(CO)2(ETA(3)-C3H5)][BF4]

Replacement of CO ligands in the eta3-allyl complex [Cp*Re(CO)2(eta3-C3H5)][BF4] (1) has been accomplished by reacting 1 in acetonitrile with PhIO or Me3NO to yield endo isomers of [Cp*Re(CO)(NCMe)(eta3-C3H5)][BF4](2) and [Cp*Re(NCMe)2(eta3-C3H5)][BF4] (3) respectively. The assignment of the allyl proton resonances and the isomeric forms of 2 and 3 have been deduced with the aid of H-1 nuclear magnetic resonance nuclear Overhauser enhancement experiments. The X-ray crystal structures of 2 and 3 confirm that these are endo isomers. Poor quality crystals of 2 (with 0.5 toluene solvate) are monoclinic, of space group P2(1)/c, with Z = 4, a = 8.381(2) angstrom, b = 15.389(2) angstrom, c = 17.161(3) angstrom, beta = 91.71(2)degrees and V = 2212.4 angstrom. The structure refined to R(F) = 0.060 for 1950 data (I(o) greater-than-or-equal-to 2.5sigma(I(o))). Crystals of 3 are orthorhombic, of space group P2(1)2(1)2(1), with Z = 4, a = 11.296(2) angstrom, b = 12.012(2) angstrom, c = 14.760(2) angstrom and V = 2002.7 angstrom3. The structure refined to R(F) = 0.027 for 1815 data (I(o) greater-than-or-equal-to 2.5sigma(I(o))). The rhenium atom is bonded to the allyl group in 3 with an Re-C(7) distance of 2.124(11) angstrom to the central carbon atom and an Re-C(6) distance of 2.177(12) angstrom and an Re-C(8) distance of 2.201(12) angstrom to the terminal carbon atoms. The acetonitrile groups are bound with an Re-N(1) distance of 2.089(7) angstrom and an Re-N(2) distance of 2.086(10) angstrom, and N=C with an N(l)-C(9) distance of 1.125(11) angstrom and an N(2)-C(11) distance of 1.134(14) angstrom.