(Pentamethylcyclopentadienyl)molybdenum oxide

Reductive aggregation of [(eta-C5Me5)MoCl(O)] 2(mu2-O) or (eta-C5Me5)MoCl 2(O) with sodium amalgam, magnesium turnings or tributyltin hydride produced a new black cluster [(eta-C5Me5)Mo] 4O7, as well as the known dinuclear compounds [(eta-C 5Me5)Mo(O)(mu2-O)]2 and [(eta-C 5Me5)Mo(mu2-Cl)2]2 as coproducts according to equation (i). A reaction scheme was developed to account for the products of the reaction. 6h -C5Me5 MoClO 2m2-O +8Na → 2h -C5Me5 Mo4O7 +h-C 5Me5Mo Om2-O 2+ h-C5Me5 Mom2-Cl 22 +8 NaCl i .;The cluster [(eta-C5Me5)Mo]4O 7 was characterized by elemental analysis, mass, 1H NMR and infrared spectroscopies and X-ray diffraction. X-ray diffraction showed that the [(eta-C5Me5)Mo]4 unit was tetrahedral with an average Mo---Mo distance of 2.909 (3) A. The Mo4O 7 core geometry may be described as Mo4(mu2-O) 6(mu3-O) (Figure i). One triangular Mo3 face of the tetrahedron was bridged by a mu3-oxygen atom, and also edge-bridged by three mu2-oxygen atoms. The Mo3 triangular unit was then connected to the fourth molybdenum atom by three mu2 -oxygen atoms which bridged the edges of the Mo4 tetrahedron. The magnetic and 1H NMR data showed that [(eta-C5Me 5)Mo]4O7 was unusual in that it exhibits conformational equilibria, that is, it existed in two forms which were in equilibrium in solution. Form 1 had C3 symmetry, (Figure i) and was paramagnetic (S = 1); form 2 had C2v symmetry and was diamagnetic (S = 0) (Figure ii). Form 1 of the cluster [(eta-C5Me5)Mo]4O7 which was paramagnetic, had six cluster electrons and an effective magnetic moment of 1.26 muB at 300 K in the solid state. In chloroform solution, the cluster was also paramagnetic with an effective magnetic moment of 1.43 muB at 298 K. The 1H NMR spectrum showed a broad resonance at 16.3 ppm (Deltanu1/2 = 113 Hz), the shift and line width of which was temperature dependent.*.;*Please refer to dissertation for diagrams.