. Can. J. Chem. 53,1622Chem. 53, (1975. The crystal and molecular structure of bis(n-cyc1opentadienyl)titanium dichloride, (C5H5)?-TiCI,, has been determined from three dimensional X-ray data. The crystals are triclin~c with a = 7.882(5), b = 19.478(10), c = 12.156(9) A, a = 90.46(2), a = 102.58(2), y = 143.49(2)". Intensity data (3742 reflections above background) were collected by the 8-20 scan method using an automated counter diffractometer. The structure was refined in space group PI by block-diagonal least squares methods to a conventional R of 0.032. Since Z = 4, there are two symmetry independent molecules per unit cell. However, these two molecules are almost identical structurally. The coordination about the titanium atom formed by the two chlorine atoms and the centroids of the cyclopentadiene rings is that of a distorted tetrahedron. The average Ti-Cl bond distance is 2.364(3) A and Ti-Cp-(centroid) 2.058 A. The C--C distances vary from 1.339(11) to 1.419(9) A. The structural results are compared to those for similar type molecules.ABRAHAM CLEARFIELD, DAVID KEITH WARNER, CARLOS HERMAN SALDARRIAGA-MOLINA, RAMANATHAN ROPAL et IVAN BERNAL. Can. J. Chem. 53,1622 (1975.On a determine la structure cristalline et molkulaire du dichlorure de bis (n-cyclopentadiknyl)
Introduction
Bis(n-cyclopentadienyl)titanium(IV)dichloride, hereafter referred to as either titanocene dichloride or Cp2TiC12, was prepared in 1954 by Wilkinson and Birmingham (I), who suggested from infrared studies that the molecule contains n-bonds between the Ti and the two cyclopentadienyl moieties. In 1957, Natta et al.(2) isolated the adduct of titanocene dichloride with diethyl aluminum as part of their studies 'Portions of this paper are based on the M.S. Thesis of D. K. Warner, presented to the Chemistry Department, Ohio University, Athens, Ohio, March, 1969. of the mechanism of Ziegler catalysis in the polymerization of ethylene. The isolation of this compound was an important achievement since Natta and his associates were attempting then to show that the Ziegler catalysts for the polymerization of ethylene are, in general, bimetallic compounds containing organometallic bonds.In 1966, an electron diffraction study was reported (3) in which Cp2TiC12 was described as a prismatic sandwich in which the Cp rings are inclined towards each other at an angle of 58.5". The Ti-Cl and Cl-Ti-Cl parameters were listed as 2.24 A and 100°, respectively.
1623These results are significantly different from those obtained in single crystal, X-ray (4), and neutron (5) diffraction studies of closely related substances.In the solid state, titanocene dichloride has been studied twice by single crystal X-ray diffraction methods (6, 7). In the first report (6) no positional parameters were given. The second one (7) gives positional parameters but the results are not very accurate. For example, the C-C distances range from 1.32(4) to 1.50(4) A.Thus, for the purposes of more accurate comparisons (4, 5, 8-10) these results are not very useful. Since, at th...
