Zirconium Complexes Involving 2-Phosphorus-Substituted Indenyl Fragments

A series of 2-R2P-substituted indenes, where R2P = Ph2P, Cy2P, iPr2P, and tBu(H)P, were
obtained via Pd-catalyzed reactions of 2-bromo-1H-indene (or 1H-inden-2-yl trifluoromethane
sulfonate) with R2PH/Et3N. Analogous indenes bearing Me2P, tBu(Cl)P, and tBu2P substituents at position 2 were obtained through the reaction of 1H-inden-2-ylphosphonous
dichloride with MeLi, tBuMgCl, and tBuMgCl/tBuLi−CuCN, respectively. Diethyl 1H-inden-2-ylphosphonate, prepared via the Ni-catalyzed Arbuzov reaction of 2-bromo-1H-indene with
P(OEt)3, was found to be a convenient starting material for the synthesis of 2-H2P-substituted
indene. 1H-Inden-2-yl(phenyl)phosphine, prepared via the Pd-catalyzed arylation of 2-H2P-substituted indene by PhI, turned out to react with 2-bromo-1H-indene in the presence of
Pd(PPh3)4 and Et3N to form di(1H-inden-2-yl)(phenyl)phosphine in almost quantitative yield.
Analogously, di(1H-inden-2-yl)(tert-butyl)phosphine was prepared via catalytic reaction of
tBuPH2 with 2 equiv of 2-bromo-1H-indene. Triethylamine-promoted condensation of indenes
bearing P(H)tBu and P(Cl)tBu fragments gave a mixture of cis- and trans-bis-indenyldiphosphines. Zirconium complexes (2-R2P-indenyl)2ZrCl2 (R2P = Ph2P, Me2P, Cy2P, iPr2P, tBu2P),
as well as ansa-zirconocenes RP(2-indenyl)2ZrCl2 (R = Ph, tBu), were obtained in good yields
from ZrCl4(THF)2 and lithium salts of the respective 2-P-substituted indenes. Ansa-zirconocene (tBuP)2(2-indenyl)2ZrCl2 including a P2R2 bridge was synthesized in a similar
manner and isolated as the pure rac-isomer.