A hexaphosphorus chain as part of a dimeric P,P′-containing ligand; 1,3-phosphozirconation of white phosphorus; X-ray structure of [Zr(η-C5H5)2P(PR2)PP(PR2)P](R = SiMe3) - Simon Bott (J. Chem. Soc., Chem. Commun., 1987)