SINGLE-CRYSTAL NEUTRON-DIFFRACTION STUDY OF (MU-ETA-1,ETA-1-C2H4)OS2(CO)8, A MODEL FOR ONE TYPE OF CHEMISORBED ETHYLENE

The molecular structure of (mu-eta-1, eta-1-C2H4)Os2(CO)8 (1) has been determined by single-crystal neutron diffraction in order to establish the hybridization at the carbon atoms of the bridging ethylene. The final values for the lattice constants are a = 7.308 (2) angstrom, b = 13.448 (3) angstrom, c = 13.482 (4) angstrom, beta = 101.25 (2)-degrees, and V = 1299.5 (3) angstrom 3; the space group (P2(1)/c) and value of Z (4) are known from an earlier X-ray study. 1 The results show that the ethylene carbons have almost completely rehybridized to sp 3. The C-C bond length in 1 (1.5225 (26) angstrom) is comparable to that in ethane and that of ethylene chemisorbed on Pt(111)-suggesting that the ethylene ligand in 1 is a good structural model for ethylene chemisorbed on Pt(111). The Os2C2 ring of 1 is distorted further away from planarity than the Os4 ring of Os4(CO)16 or the C4 ring of cyclobutane.