Bis(trimethylsilyl)phosphido complexes. Part 3. Syntheses, structures and reactions of [bis(trimethylsilyl)phosphido]-zirconocene(IV) complexes and the X-ray structure of {AlMe2[µ-P(SiMe3)2]}2

Abstract

The complexes [Zr(cp)₂(PR₂)X](cp =η-C₅H₅; R = SiMe₃; X = Cl, 2; PR₂, 3; or Me, 6) and [Zr(η-C₅H₄R)₂(PR₂)Y](Y = Cl, 4; or PR₂, 5) were obtained from [{Li(µ-PR₂)(thf)₂}₂]1(thf = tetrahydrofuran) and [Zr(cp)₂Cl₂] or [Zr(η-C₅H₄R)₂Cl₂], respectively. Each of 2, 3, and 6 was treated with a variety of reagents causing scission of the Zr–P bond. Two types of reactions were observed: (i) substitution or (ii) insertion. Examples of (i) are the reaction of (a) complex 3 with Mel to afford [Zr(cp)₂I(PR₂)]7, (b)2 with LiOR′(R′= C₆H₂Bu^t₂-2,6-Me-4), SiMe₃(N₃), Mel or EtOH yielding [Zr(cp)₂Cl(Z)](Z = OR′, 8; N₃, 9; or I, 10) or [{Zr(cp)₂Cl}₂(µ-O)]11, respectively and (c)2 with (AlMe₃)₂ to furnish [AlMe₂(µ-PR₂)]₂12. The X-ray structure of 12 shows a planar nearly square Al₂P₂ ring [Al–P 2.460(2) and 2.453(2)Å, P–Al–P′89.4(1), Al–P–Al′ 90.60(5)°], a configuration which is retained in hydrocarbon solution (¹H and ²⁹Si NMR spectroscopy). Type (ii) reactions were those between (a)2 and a diazoalkane N₂CR′R″ yielding [[graphic omitted](PR₂)}](R′= R″= Ph, 13; or R′= H, R″= CO₂Et, 14), (b)2 or 6 with CS₂, affording [Zr(cp)₂{S₂C(PR₂)}X](X = Cl, 15; or Me, 16), and (c)3 with white phosphorus to give [[graphic omitted]]17. Each of the complexes 3 and 6 reacted with sulphur to furnish [{Zr(cp)₂(µ-S)}₂], which was also obtained by thermolysis of 15. The thermolysis of 2, 4 or 6 led to elimination of SiMe₃X (X = Cl or Me).