Aqueous chemistry of the five-coordinate zirconocene dichloride PhP(CH2CH2–η5-C5H4)2ZrCl2: X-ray structure of the sulfato complex PhP(CH2CH2–η5-C5H4)2Zr(η2-SO4)

ES-MS of dilute solutions of (bcep)ZrCl2 (1) (bcep = PhP(CH2CH2–η5-C5H4)2) in acetonitrile–water indicates the presence of three species in solution: [(bcep)Zr(H2O)2]2+ (2), [{(bcep)Zr(μ-OH)}2]2+ (3), and the singly deprotonated form of dimer 3, [{(bcep)Zr}2(μ-O)(μ-OH)]+ (4). In aqueous solutions, reactivity studies investigated largely by 31P NMR spectroscopy support the presence of 2, 3 and 4. One equivalent of fluoride was found to react immediately with 2, but slowly with 3 and 4, to give the monofluoro complex [(bcep)ZrF]+ which was isolated as the BPh4- salt. Addition of aqueous sodium sulphate gave insoluble crystals of the sulfato complex (bcep)Zr(SO4) which was characterised by X-ray crystallography. Addition of acids HX (X = Br, NO3, HSO4, HCO3) to aqueous solutions of 1 gave species observed by ES-MS corresponding to [(bcep)ZrX]+.

The novel five-coordinate zirconocene(IV) dichloride complex PhP(CH2CH2–η5-C5H4)2ZrCl2 contains an unusual tridentate cyclopentadienyl-phosphine ligand which stabilises the complex in aqueous solutions. Its aqueous solution chemistry has been investigated using largely 31P NMR spectroscopy and ES-MS.Figure optionsDownload as PowerPoint slide