Functionalised phosphorus-based ligands in early transition metal chemistry

When the transition metal halides (Cp2ZrCl2)-Zr-x, (CpZrCl3)-Zr-x, (CpMoCl2)-Mo-x(Cp-x = C5H5, C5H4Me, C5Me4Et), or (CpMCl4)-M-x (Cp-x = C5H5, C5H4Me, C5Me4Et, C5Me5; M = Nb, Ta, or Mo) are treated with functionalised phosphorus-based ligands (functional group = P-H; P-SiMe3 or P-H for (Cp2ZrCl2)-Zr-x), reduction of the transition metal or substitution of chloro by phosphorus ligands occurs. With primary phosphines or lithium phosphanides, various phosphorus ligands are formed, depending on the steric bulk of the ligands on M and P, the reaction conditions, and solvent. Thus, complexes exhibiting phosphine, phosphanido, phosphinidene, triphospha-1,3-diyl, diphosphene, or diphosphanyl ligands are formed. The reactions of these early transition metal complexes include substitution of the P-based ligand by polar or protic reagents, insertion of multiply bonded inorganic or organic systems (CS2, diazoalkanes, diaryl- or dialkylcarbodiimide, phenylacetylene, isonitriles, isothiocyanates, nitriles, ketones etc.) into the metal-phosphorus bead, as well as insertion followed by elimination of PHR or PR fragments.