This report deals with the first examples of butadienes bonded to a Zr-O matrix provided by a calix[4]arene skeleton and their reactivity. The reaction of [{p-Bu t -calix[4]-(OMe) 2 -(O) 2 }ZrCl 2 ], 2, with Mg(C 4 H 6 )(thf) 2 and Mg(Ph 2 C 4 H 44. The butadiene fragment exhibits a π 2 ,η 4 bonding mode, as shown by an X-ray analysis on both compounds. Extended Hu ¨ckel calculations confirmed the energetically preferred s-cis conformation and the π 2 ,η 4 bonding mode vs the σ 2 ,π,η 4 one. The parent compound 3 of this series behaves, however, both as a source of zirconium(II) in displacement reactions or as a dialkyl derivative of zirconium(IV) in insertion reactions. In the former class of transformations, the reaction of 3 with Ph 2 CO and PhCOCOPh led to the dioxo metallacycles6, respectively. Butadiene was also displaced by diphenylacetylene leading to [{p-Bu t -calix-[4]-(OMe) 2 (O) 2 }Zr(η 2 -Ph 2 C 2 )], 7, and by a phenylnitrene source [PhN 3 ] forming the dinuclear phenylimido-bridged complex [{p-Bu t -calix[4]-(OMe) 2 (O) 2 } 2 Zr 2 (µ-NPh) 2 ], 8. Unlike at room temperature, Ph 2 CO reacted with 3 at low temperature without displacing the butadiene, but leading, instead, to the stepwise insertion of the ketone to form [{p-Bu t -calix[4]-(OMe) 2 (O) 2 }Zr{CH 2 CHdCHCH 2 C(Ph) 2 O}], 10, and [{p-Bu t -calix[4]-(OMe) 2 (O) 2 }Zr{-OC(Ph) 2 -CH 2 CHdCHCH 2 C(Ph) 2 O-}], 11. Using 2 mol of acetone, [{p-Bu t -calix[4]-(OMe) 2 (O) 2 }Zr{-OC(Me) 2 CH 2 CHdCHCH 2 C(Me) 2 O-}], 12, was obtained. MeCN and EtCN inserted in a single Zr-C bond (of a formal σ 2 ,π,η 4 structure) yielding [{p-Bu t -calix[4]-(OMe) 2 (O) 2 }Zr{-CH 2 CHdCHCH 2 C(Me)dN-}], 13, and [{p-Bu t -calix[4]-(OMe) 2 (O) 2 }Zr{-CH 2 CHdCHCH 2 -C(Et)dN-}], 14. Bu t NC engaged 3 in a multistep insertion reaction leading to [{p-Bu tcalix[4]-(OMe) 2 (O) 2 }Zr{-(Bu t )NC(C 4 H 6 )C(CdNBu t )N(Bu t )-}], 15, via a pathway which has been observed in the reaction of Bu t NC with dialkylzirconium calix[4]arene derivatives. The σ 2 behavior of butadiene in 3 was further verified in the reaction with H 2 O to give [{p-Bu tcalix[4]-(OMe) 2 (O) 2 } 2 Zr 2 (µ-O) 2 ], 9, and butenes.