Zirconium dialkyls with carbon

Bercaw and coworkers have studied the reaction of bis(penta-methylcyclopentadienyl)zirconium dialkyls with carbon monoxide (47,48). As in the case of the aforementioned biscyclopentadi-enyls, reversible monoinsertion is observed (equation (7)) yielding a bihaptoacyl (vqq 1537 cm"1). Interestingly, when car-... 

Reaction of dialkyl derivatives of zirconium(IV) of formula Zr(j -C5Me5)2R2 with carbon monoxide gives a mononuclear ene-diolato compound resulting from carbon-carbon coupling of the product of monoinsertion into both zirconium-carbon bonds ... 

Carbon monoxide rapidly inserts into the carbon—zirconium bond of alkyl- and alkenyl-zirconocene chlorides at low temperature with retention of configuration at carbon to give acylzirconocene chlorides 17 (Scheme 3.5). Acylzirconocene chlorides have found utility in synthesis, as described elsewhere in this volume [17]. Lewis acid catalyzed additions to enones, aldehydes, and imines, yielding a-keto allylic alcohols, a-hydroxy ketones, and a-amino ketones, respectively [18], and palladium-catalyzed addition to alkyl/aryl halides and a,[5-ynones [19] are examples. The acyl complex 18 formed by the insertion of carbon monoxide into dialkyl, alkylaryl, or diaryl zirconocenes may rearrange to a r 2-ketone complex 19 either thermally (particularly when R1 = R2 = Ph) or on addition of a Lewis acid [5,20,21]. The rearrangement proceeds through the less stable... 

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