Abstract
M. Sc.
This study comprises the preparation and characterisation of new cyclopentadienylmolybdenum carbonyl complexes. In addition, an unique isomeric equilibrium as well as the new packing pattern of the known compound of cyclopentadienyltricarbonylmolybdenum bromide is also described. The cyclopentadienylmolybdenum carbonyl complexes have been prepared from precursors of the type [CpMo(C0)3X] which reacts with alkyllithium reagent to -afford [CpMo(CO)3R] compounds. [CpMo(C0)3I] reacts with phenylacetylide lithium to form [Cp(C0) 3MoC-CP11] (1). The X-ray crystal structure of compound 1 has been determined and reveals that the length of the triple bond is somewhat
shorter than any of the other known acetylide complexes. Treatment of 1 with the electrophiles CF3SO3CH3 or (CH3)2SO4 gives the cationic complex [Cp(C0)3Mo=C=C(CH3)(Ph)r CF 3S03" (4). [CpMo(C0)3I] reacts with 1,3-dithianyllithium to form [Cp(C0)3Moe(H)SCH2CH2C1121 (2) which can easily be deprotonated on the coordinated carbon. [CpMo(C0) 3I] also reacts with methyllithium to form [CpMo(CO)3CH3] (3) which is a known compound. The reaction of CS2 with 1 which occurs by a (2 + 2) cycloaddition affords [Cp(CO)3MoC=C(Ph)C(=S)S] (5). As we could not alkylate this CS 2 adduct, additional studies with molybdenum compounds in which a CO ligand has been substituted with PPh 3 and PMe3 have been carried out. [CpMo(C0)3I] reacts with PPh3 to form [CpMo(CO)2(PPh3)I] (6), a stable compound, known and well characterised. The compound 6 also reacts with phenylethynyllithium to form [Cp(C0)2(PPh3)MoCE---CPh] (7). Treatment of 7 with CS2 leads to [Cp(C0)2(PPh3)MoC=C(Ph)C(=S)] (8). [CpMo(C0)3I] reacts with PMe3 to yield two isomers [CpMo(CO)2(PMe3)I] (cis-9) and (trans-9). These two isomers were isolated and we observed that in solution the cis isomer was slowly transformed into the trans isomer which indicated the existence of an isomeric equilibrium. Cis-9 react: with phenylethynyllithium to form [Cp(C0)2(PMe3)MoCCP11] (11). Finally, during unsuccessful attempts to react the dimeric compound [CpMo(CO)3]2 with alkyl and aryllithium, the known compounds [11 5-CpMo(C0)3C1] and [re-CpMo(C0)3Br] (12) were produced in crystalline form. The X-ray crystal structure of the neutral complex 12 has been determined and the molecular structure has bond distances and angles very similar to the literature values of the same compound. However, the compound 12 exhibits a different packing pattern in the unit cell.