Synthesis of Group 4 transition-metal complexes bearing a secondary phosphine pendant cyclopentadienyl ligand

Reactions of some chlorides of the Group 4 transition metals were examined with secondary phosphine pendant cyclopentadienyl derivatives, XC5H4CH2CH2PHR (X=Li, SiMe3, Sn(n-Bu)3; R=2,4,6-trimethylphenyl (Mes), 2,4,6-tri-i-propylphenyl (Tip), 2,4,6-tri-t-buthylphenyl (Mes*)). Although reactions of MCl4 (M=Zr, Hf) did not yield (C5H4CH2CH2PHR)MCl3, reactions of MCl4(SR′′2)2 (SR′′2=SMe2, tetrahydrothiophene) gave (C5H4CH2CH2PHR)MCl3(SR′′2)n (n=1, 2). The steric bulkiness of the substituent (R) on the secondary phosphine affects the coordination mode of the phosphine moiety in solution. When R is Mes, the phosphine-coordinated species is stable, when R is Tip, the phosphine-coordinated and -dissociated species are in equilibrium, and when R is Mes*, only the phosphine-dissociated species is observed.