STEREOCHEMICALLY NONRIGID ORGANOMETALLIC MOLECULES .21. CRYSTAL AND MOLECULAR STRUCTURES OF TRIS(CYCLOPENTADIENYL)NITROSYLMOLYBDENUM

The crystal and molecular structures of tris(cyclopentadienyl)nitrosylmolybdenum, (C5H5)3MoNO, have been determined from 2288 independent, nonzero reflections collected with a counter diffractometer. The compound crystallizes in the monoclinic space group B21/a with eight molecules in a unit cell of dimensions a = 15.425 ± 0.006 Å, b = 7.423 ± 0.004 Å, c = 24.050 ± 0.007 A, and β = 103° 40ʹ ± 3ʹ (pobsd = 1.60 g cm-3; pcaud = 1.59 g cm-3). The structure, including hydrogen atoms, was solved from Patterson and electron density maps and refined by least-squares methods to a conventional unweighted R factor of 3.5%. The principal features of the structure are the following. (1) There is an essentially linear (179.2°) Mo-N-O group, with Mo-N = 1.751 (3) Å and N-0 = 1.207 (4) Å. The short Mo-N and relatively long N-O distances indicate very strong metal- ligand π bonding. (2) One of the C5H5 rings is an exemplary ó or monohapto cyclopentadienyl ring. The Mo-C distance is 2.291 (3) Å and the C-C distances (in Å) listed in order from the bound carbon atom around the ring are 1.468 (5), 1.349 (5), 1.442 (6), 1.344 (5), 1.468 (5). (3) The other two rings have almost identical relationships to the metal atom. No simple distinction (such as pentahapto vs. trihapto) can be made between them. Around each one, the Mo-C distances go in the following order, where pairs of corresponding bonds to the two rings are listed together: 2.599 (4), 2.682 (5); 2.588 (5), 2.609 (5); 2.343 (5), 2.347 (4); 2.338 (5), 2.324 (3); 2.422 (5), 2.444 (4). These two rings have very different orientations relative to the h1-C5H5 ring, however, and this is most important in considering how to interpret the low-temperature pmr spectrum which has been reported for this fluxional molecule. © 1969, American Chemical Society. All rights reserved.