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Article citation: Hadrien Heuclin, Dalton Trans., 2010, DOI: 10.1039/b915468j
Phosphorus stabilized carbene complexes: bisphosphonate dianion synthesis, reactivity and DFT studies of O
CO zirconium(IV) complexesHadrien Heuclin, Dan Grünstein, Xavier-Frederic Le Goff, Pascal Le Floch and Nicolas Mézailles
The reactivity of the geminal dianion of tetraisopropyl methylenediphosphonate, 3, with [ZrCl4(THF)2] affords a trinuclear structure 5 in which an unprecedented triscarbene–Zr dianionic fragment is found. The overall trinuclear arrangement is assembled by PO bridging moieties. The X-ray crystal structure of 5 is presented. The reaction of complex 5 with stoichiometric amounts of pyridine affords a dinuclear complex 6 whose formulation was ascertained by an X-ray crystal structure. Complexes 5 and 6 cleanly react with aldehydes (R1)(H)C
O to afford the corresponding olefin of general formula [((OiPr)2PO)2CC(R1)(H)]. DFT calculations which were carried out on the model complex of 5t and a hypothetical monometallic Zr complex [Zr( 3)Cl2(OMe2)2] 8t indicate that the Zr–C bond only features a weak 
-interaction between the carbon atom and a vacant orbital at the metal. The polarization of the orbital towards the carbon center is consistent with the observed nucleophilic character of the carbene complexes described here.
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