Solid-state isomerisation reactions of (η5-C5H4R)M(CO)2(PR3′)I (M=W, Mo; R=tBu, Me; R′=Ph, OiPr3)

The cis and trans monosubstituted cyclopentadienyl tungsten and molybdenum complexes (η5-C5H4R)M(CO)2(L)I (1) (M=W, R=Me, tBu, L=P(OiPr)3, PPh3; M=Mo, R=Me, L=PPh3) have been synthesised and fully characterised by elemental analysis and IR and NMR spectroscopy. It was found that 1 underwent a thermal solid-state ligand isomerisation reaction and that the favoured direction of the isomerisation reaction is related to the melting points of the cis and trans isomers, i.e., with intermolecular forces in the solid state. No obvious relationship between the melting point and the metal, the ring-substituent or the ligand was observed. Crystal structure determinations of the cis and trans isomers of (η5-C5H4Me)W(CO)2(PPh3)I reveal that a limited amount of isomer conversion can be accommodated in the unit cell of the trans isomer, prior to crystal fragmentation. The rearrangement of the molecules within the unit cell, during isomerisation, also leads to disorder in the crystal.