Alkyl-arene and -cyclo-octadiene complexes of molybdenum(II) containing tertiary phosphines

Abstract

Treatment of trichlorotris(tetrahydrofuran)molybdenum, MoCl₃(C₄H₈O)₃, with tertiary phosphines under certain conditions gives MoCl₃(PR₃)(C₄H₈O)₂(PR₃= PMe₃ or PMe₂Ph) which on alkylation with dimethylmagnesium in the presence of arenes yield the 18-electron methyl–arene complexes Mo(CH₃)₂(η⁶-Ar)(PR₃)₂(Ar = benzene, toluene, or o- and p-xylene). The reaction in tetrahydrofuran affords the known dimers Mo₂(CH₃)₄(PR₃)₄. Action of CO on the benzene complex at 1 atm gives Mo(CH₃)₂(η⁶-C₆H₆)(CO)(PR₃) which when set aside under N₂ yields Mo(η⁶-C₆H₆)(PMe₂Ph)₃ possibly via the acetone complex Mo(Me₂CO)(η⁶-C₆H₆)(PMe₂Ph). Reaction of MoCl₃(PR₃)(C₄H₈O)₂ with Me₂Mg and cyclo-octa-1,5-diene (cod) affords Mo(CH₃)₂(cod)(PR₃)₂ in low yields. The new compounds have been characterised by i.r. and ¹H, ¹³C, and ³¹P n.m.r. spectroscopy.