Synthesis and reactivity of mononuclear molybdenum phosphido complexes, [Mo(CO)2{P(Cl)R}(η-C5H5)][R = CH(SiMe3)2 or NCMe2CH2CH2CH2CMe2]. X-Ray crystal structures of [Mo(CO)2{P(X)(NCMe2CH2CH2CH2CMe2)}(η-C5H5)](X = Cl or NMe2) and [Mo2(CO)4{µ-P2[CH(SiMe3)2]2}(η-C5H5)2]

Abstract

Reaction of K[Mo(CO)₃(η-C₅H₅)] with PCl₂R affords the mono-chlorophosphido species, [Mo(CO)₂{P(Cl)R}(η-C₅H₅)][R = 2,2,6,6-tetramethyl-1-piperidyl (tmp), (1), or CH(SiMe₃)₂, (3)]. Both (1) and (3) contain a three-electron donor phosphido ligand featuring Mo–P multiple bonding and a trigonal-planar configuration at phosphorus. Compound (1) has been characterised by X-ray diffraction. The reaction of (1) with Li[NMe₂] affords [Mo(CO)₂{P(NMe₂)(tmp)}(η-C₅H₅)](7), which has also been characterised by X-ray crystallography. The synthesis of (7) demonstrates the reactivity of the P–Cl functionality but (7) may also be prepared by direct reaction between K[Mo(CO)₃(η-C₅H₅)] and PCl(NMe₂)(tmp). Reduction of (3) with sodium dihydronaphthylide leads to a coupling reaction via P–P bond formation resulting in the cis-diphosphene complex [Mo₂(CO)₄{µ-P₂[CH(SiMe₃)₂]₂}(η-C₅H₅)₂](8), which was characterised by X-ray diffraction. Spectroscopic evidence is also presented for a dimolybdenum diphosphinidene complex, isomeric with (8).