data reports IUCrData (2017). 2, x170042 https://doi.org/10.1107/S2414314617000426 1 of 3 trans-Acetyldicarbonyl(g 5 -cyclopentadienyl)- [tris(3,5-dimethylphenyl)phosphane-jP]- molybdenum(II) Matthew T. Whited, a * Eli J. Ruffer, a Jia Zhang, a Dominique J. Rabaey b and Daron E. Janzen b a Department of Chemistry, Carleton College, 1 N. College St., Northfield, MN 55057, USA, and b Department of Chemistry and Biochemistry, St Catherine University, 2004 Randolph Ave., St Paul, MN 55105, USA. *Correspondence e-mail: mwhited@carleton.edu The title compound, [Mo(C 5 H 5 )(C 2 H 3 O)(C 24 H 27 P)(CO) 2 ], was prepared by reaction of [Mo(C 5 H 5 )(CO) 3 (CH 3 )] with tris(3,5-dimethylphenyl)phosphane. The complex exhibits a four-legged piano-stool geometry with trans-disposed acetyl and phosphane ligands. The molecular geometry is nearly identical to that of the triphenylphosphane derivative, but introduction of methyl groups on the aromatic phosphane substituents significantly impacts supramolecular organiza- tion. In the crystal, non-classical C—HO interactions involving the acetyl carbonyl group lead to a chain motif along [010], and another set of C—HO close contacts join inversion-related molecules. Structure description The synthesis of the title complex, [Mo(C 5 H 5 )(C 2 H 3 O)(C 24 H 27 P)(CO) 2 ], (1), has not been reported previously, though several analogous complexes are known. The most closely related complex for which structural information is available contains a tri- phenylphosphane ligand (Churchill & Fennessey, 1968). Complex (1) exhibits a four-legged ‘piano-stool’ geometry, common for cyclopenta- dienyl (Cp) complexes of molybdenum (Fig. 1, Table 1). The acetyl and phosphane ligands are trans-disposed and the acetyl ligand is oriented with the O atom syn to the Cp ring, which is consistent with the majority of related crystal structures, the only exception being the recently reported tri(2-furyl)phosphane derivative (Whited et al., 2013). The Mo—Cp centroid distance is 2.016 (1) A ˚ . The Mo1—P1 bond length [2.4708 (7) A ˚ ] is nearly identical within error to that of the triphenylphosphane derivative and only Received 30 December 2016 Accepted 9 January 2017 Edited by S. Parkin, University of Kentucky, USA Keywords: crystal structure; phosphine; piano- stool complex; cyclopentadienyl; divalent molybdenum. CCDC reference: 1526390 Structural data: full structural data are available from iucrdata.iucr.org ISSN 2414-3146