Synthesis, characterisation, reactivity and stereochemical studies of heterobimetallic complexes containing an orthometallated cyclopentadienylphosphine bridge

Abstract

The heterobimetallic diastereoisomer complexes [X(η ⁵ -C ₅ H ₅ )Mo{(η ⁵ -C ₅ H ₄ )PPh(o-C ₆ H ₄ )}M(CO) ₅ ] (X = Cl 1 and 1′ or I 2 and 2′; M = Cr a, Mo b or W c) containing an orthometallated cyclopentadienylphosphine bridge have been prepared and characterised. They were obtained by reaction of Li[M(CO) ₅ (PPh ₂ )] and the corresponding metallocene dichloride in tetrahydrofuran. The crystal structures of 1a and 2c showed that the η ⁵ -C ₅ H ₄ PPh[M(CO) ₅ ]C ₆ H ₄ fragment chelates the Mo. Similarly, methylated complexes 3 were prepared when [Mo(η ⁵ -C ₅ H ₄ Me) ₂ Cl ₂ ] was used as metallocene dichloride; the 1,3 regioselectivity of these reactions has been assigned on the basis of ¹ H and ³¹ P NMR data. Compound 1c reacted with LiAlH ₄ to give a dihydride molybdenocene complex [H(η ⁵ -C ₅ H ₅ )Mo(η ⁵ -C ₅ H ₄ PPh ₂ )HW(CO) ₄ ]. Alkylated diastereoisomers [R(η ⁵ -C ₅ H ₅ )Mo{(η ⁵ -C ₅ H ₄ )PPh(o-C ₆ H ₄ )}M(CO) ₅ ] (R = Me or Et) were obtained by reaction of 1c with a Grignard reagent; cleavage of the Mo–Me bond with hydrochloric acid has been found to occur with retention of configuration.