NDLI: Prototropic rearrangements in cycloheptatrienyl PCP pincer iridium complexes

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Kaska, William C. Mack, Hans-georg Winter, Angelika M. Eichele, Klaus Mayer, Hermann A.
Description	Author Affiliation: Winter AM ( Institut für Anorganische Chemie, Universität Tübingen, Auf der Morgenstelle 18, 72076 Tübingen, Germany.)
Abstract	When the cycloheptatriene iridium(III) pincer complex (PCP)Ir(CO)(H)(Cl) (3) (PCP = $2,7-(CH_{2}P^{t}Bu_{2})_{2}C_{7}H_{5})$ is treated with the bases NaH, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and lithium 2,2,6,6-tetramethylpiperidide (LiTMP) under various conditions different products are obtained. At elevated temperatures and with DBU or LiTMP as a base the transdihydride $(PCP′)Ir(CO)(H)_{2}$ (PCP′ = $2-(CHP^{t}Bu_{2})-7-(CH_{2}P^{t}Bu_{2})C_{7}H_{4})$ (5) is formed where the π-system extends into one of the phosphine bridges. This compound loses $H_{2}$ to give the square-planar iridium(I) carbonyl complex 7 (PCP′IrCO). The dihydride 5 can also rearrange to the new isomeric iridium(I) carbonyl 6 (PCP″IrCO, PCP″ = $2,7-(CH_{2}P^{t}Bu_{2})_{2}C_{7}H_{5}).$ Thus the two hydrides have moved into the ligand backbone creating a methylene group in the 3-position of the cycloheptatriene ring. Alternatively, 6 is formed by a rearrangement from 6a which differs from 6 by having the methylene group in the 4-position of the cycloheptatriene ring. The iridium(I) carbonyl 6a in turn is made from 3 by treatment with DBU at room temperature. Interestingly, when compound 3 is heated to reflux in THF the hydrogen bound at the metal carbon is shifted to a carbon atom in the cycloheptatriene ring generating a ring methylene group (3a). From this complex HCl is eliminated upon chromatography forming 6 as the final product. Quantum chemical calculations at various levels of theory illustrate the relative energetic stabilities of all iridium complexes.
ISSN	14779226
Journal	Dalton Trans.
Issue Number	4
e-ISSN	13645447
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2008-01-28
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Chemistry
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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