Complexes of a dianionic bis(diphosphinomethanide) with lithium, sodium, potassium and zirconium. Effect of substitution on the Schlenk dimerisation of vinylidene phosphines

摘要

The vinylidene phosphine ((Pr2P)-P-n)(2)C=CH2 (1) undergoes Schlenk dimerisation on treatment with an excess of any of the alkali metals Li, Na or K to give the butane-1,4-diide complexes [(L)M{((Pr2P)-P-n)(2)CCH2}](2) [(L)M = (THF)(2)Li (6), (THF)(3)Na (7b), (DME)(2)K (8b)], after recrystallisation. Whereas the reaction between the analogous phenyl derivative (Ph2P)(2)C = CH2 and K results in cleavage of a P-C bond, 1 reacts smoothly with K to give 8, with no evidence for P C cleavage. Compound 6 is an excellent ligand transfer reagent: metathesis reactions between either 6 or its phenyl analogue [(THF)(2)Li {(Ph2P)(2)CCH2}](2) (2) and two equivalents of Cp2ZrCl2 in THF give the corresponding dinuclear zirconocene derivatives [Cp2Zr(Cl){(R2P)(2)CCH2}](2) in good yields [R = Ph (11), Pr-n (12)]. Compounds 6, 7b, 8b, 11 and 12 have been characterised by multi-element NMR spectroscopy and, where possible, by elemental analysis; compounds 6, 7b, 11 and 12 have additionally been characterised by X-ray crystallography.