Syntheses and structures of the first terminal phosphanylphosphido complex of hafnium [Cp2Hf(Cl){eta(1)-(Me3Si)P-P(NEt2)(2)}] and the first zirconocene-phosphanylphosphinidene dimer [Cp2Zr{mu(2)-P-P(NEt2)(2)}(2)ZrCp2]

Reactions of (Et2N)(2)P-P(SiMe3)Li with [Cp2MCl2] (M = Zr, Hf) in toluene or pentane yield the related terminal phosphanylphosphido complexes [Cp2M(Cl){eta(1)-(Me3Si)P-P(NEt2)(2)}]. The solid state structure of [Cp2Hf(Cl){eta(1)-(Me3Si)P-P(NEt2)(2)}] was established by single crystal X-ray diffraction. The reaction of (Et2N)(2)P-P(SiMe3)Li with [Cp2ZrCl2] in THF or DME solutions leads to the formation of deep red crystals of the first neutral diamagnetic zirconocene-phosphanylphosphinidene dimer [Cp2Zr{mu P2--P(NEt2)(2)}(2)ZrCp2]. The molecular structure of this compound was confirmed by X-ray diffraction. The reactions of (R2N)(2)P-P(SiMe3)Li with [CpZrCl3] yield the related tetraphosphetanes R2NP(mu(2)-PSiMe3)(2)PNR2, which apparently are formed as a result of a transfer of NR2 groups from a P atom to the Zr atom.