The versatile reactivity of cyclo-(P(5)tBU(4))(-) with complexes of the nickel triad

摘要

Na[cyclo-(P(5)tBu(4))] (1) reacts with [NiCl2(PEt3)(2)] and [PdCl2-(PMe2Ph)(2)] with elimination of tBuCl and formation of the corresponding metal(0) cyclopentaphosphene complexes [Ni{cyclo-(P(5)tBu(3))}(PEt3)(2)] (2) and [Pd{cyclo-(P(5)tBu(3))}(PMe2Ph)(2)] (3). In contrast, complexes with the more labile triphenylphosphane ligand, such as [MCl2(PPh3)2] (M=Ni, Pd), react with 1 with formation of [NiCl-{cyclo-(P(5)tBu(4))}(PPh3)] (4) and [Pd-{cyclo-(P(5)tBu(4))}2] (5), respectively, in which the cyclo-(P(5)tBu(4)) ligand is intact. In the case of palladium, the cyclopentaphosphene complex [Pd-{cyclo-(P(5)tBu(3))}(PPh3)(2)] (6) in trace amounts is also formed. However, [Ni-{cyclo-(P(5)tBu(4))}(2)] (7) is easily obtained by reaction of two equivalents of 1 and one equivalent of [NiCl2(bipy)] at room temperature. Complex 7 rearranges on heating in n-hexane or toluene to the previously unknown [Ni-{cyclo-(P(5)tBu(4))PtBu}{cyclo-(P(4)tBu(3))}] (8), which presumably is formed via the intermediate [Ni{cyclo-(P(5)tBu(4))}-{cyclo-(P(4)tBu(3))PtBu}], which, after an unexpected and unprecedented phosphanediide migration, gives 8, but always as an inseparable mixture with 7. In the reaction of I with [PtCl,(PPh3)(2)], ring contraction and formation of [PtCl{cyclo-(P(4)tBu(3))PtBu}-(PMe2Ph)] (9) is observed. Complexes 3-5 and 7-9 were characterised by (PNMR)-P-31 spectroscopy, and X-ray structures were obtained for 5-9.