Bis(trimethylsilyl)phosphinodithioformates, the phosphorus analogues of dithiocarbamates; X-ray structure of [Zr(cp)2(Cl)(η2-S2CPR2)] and its thermolysis product [Zr(cp)2(µ-S)2](cp =η-C5H5, R = SiMe3) - Simon Bott (J. Chem. Soc., Chem. Commun., 1987)