Molecular structure of two dicyclopentadienylmolybdenum derivatives containing a four-membered ring [Mo(η 5-C 5H 5) 2(2-NHNC 5H 4)][PF 6] and [Mo(η 5C 5H 5) 2(2-ONC 5H 4)][PF 6

Abstract

The structure of the new compound [Mo(η 5-C 5H 5) 2(2-NHNC 5H 4)][PF 6] ( 1) has been determined. The crystals are orthorhombic, space group Pca2 1 with a 20.807(1), b 8.0030(8), c 10.056(3) Å, V 1674.5 Å 3, Z = 4. The structure of [Mo(η 5-C 5H 5) 2(2-ONC 5H 4)][PF 6] ( 2) has also been determined. The crystals are orthorhombic, space group Pnma with a 12.727(3), b 10.174(2), c 12.918(1) Å, V 1672.8 Å 3, Z = 4. The structures were solved by Patterson and difference electron density syntheses and refined by least-squares to R of 0.028 for 1287 reflections for 1 and 0.059 for 1178 reflections for 2. Although not isostructural the two cationic complexes have equivalent geometries with the normal bent bismetallocene structure. For 1 the MoN bond lengths are 2.160(8) and 2.142(9) Å, with a NMoN bond angle of 59.8(3)°, whereas for 2 MoO is 2.142(10), MoN is 2.138(11) Å, the NMoO angle is 61.2(4)°. These parameters are discussed and compared with the corresponding data for similar biscyclopentadienyl complexes of molybdenum(IV). Extended Hückel molecular orbital calculations have been carried out to throw light on the nature of the bonding between the metal and the bidentate ligand.