Ketenido complexes

Terminal and bridging ketenido complexes are prepared by deprotonation of acyl complexes or by insertion of CO into a vinyl-, carbene-or methylene-metal bond. 

Hydrogenation of ketenido complexes 79 (Section IV.D in Chapter 5 ) affords 80, which in turn reacts with Mel to give [Zr(7 -Cp )2(I) Z-OCH=CHBu-t ]. This complex isomerizes to [Zr( -Cp )2l(ii-OCH=CHBu-f)] after heating". ... 

In Section IV.D we describe the synthesis of complexes containing the dianionic enolato -C,0-ketenido ligand, which usually are not prepared from ketenes. In this section we will show how ketenes are useful reagents to prepare other enolato complexes. In most cases a ketene RR C=C=0 inserts into a M—C bond of a [M]—R" complex to give... 

When a ketene is coordinated to a metal through both C and O atoms, two extreme resonance forms can be considered that containing the ketene as a neutral ligand (358) and that with a ketenide dianion (359). The contribution of the enolato form 359 can be estimated by the C—O bond distance (d) and the O—C—C angle (a). In some complexes, a ketenido ligand can bridge two metal centers, as in 360. 

Treatment of [Ru3(CO)io (PPh2)2CH2 ] with CH2N2 affords a mixmre containing complex 371, which has the simplest ketenido as a /z3-bridging ligand . The tantalum-lithium complex 372 reacts with CO to afford 373 . ... 

Insertion of a terminal carbonyl hgand [M]CO into a metal carbene [M ]=CRR bond can generate a complex containing a bridging ketenido ligand (374) . 

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