Ligands forming metal-carbon multiple bonds

Table IR-10.3 Names for ligands forming metal—carbon multiple bonds...

Attack by a metal nucleophile at a metal-carbon multiple bond, instead of an unsaturated metal-metal bond, can be used to form clusters containing two- or three-electron carbon ligands. The reaction of Pt(cyclooctadiene)2 with carbene complexes (OC)5MC(OMe)Ph gives the corresponding (OC)5M[/i2-C(OMe)Ph]Pt(cod), where M = Cr or W . Performing this reaction in the presence of PR3 gives a more stable a product ... 

If a ligand forms one or more metal-carbon single bonds as well as metal-carbon multiple bonds, the order of endings is yl , ylidene , ylidyne . Method (b) should then be used to give the lowest possible set of locants for the free valencies. If a choice remains, lower numbers are selected for the yl positions before the ylidene positions and then for any side chains or substituents. 

Typical ligands forming a metal-carbon double or triple bond are listed in Table IR-10.3, and this is followed by examples illustrating the naming of compounds containing one or more metal-carbon multiple bonds. The r term in Example 5 is explained in Section IR-10.2.5.1. 

As a result of the multiple orbitals available for metal-ligand bonding, alkynes readily coordinate with multiple metal centres [12]. Where two metals coordinate to a single alkyne (or acetylide) moiety, a number of different arrangements have been characterised (Fig. 2). An acetylide moiety may coordinate in an end-on fashion via two metal-carbon o-bonds (structure A) with the C = C axis perpendicular to the metal-metal axis (p—r r ). The alkyne can also coordinate parallel to the metal-metal axis (structure B), with each alkyne carbon forming a o-bond to a different... 

Equation (65) is an example of a process that may be readily promoted by a cluster but not necessarily with a mononuclear complex. Scheme 8 shows how the multiple-coordination capabilities of a trinuclear cluster could reduce the N—C bond and eventually cleave it. To date, examples of the NCO ligand bridging more than two metals in either a mono- or polyhapto fashion are unknown. The reverse process represents a unique method for forming carbon-nitrogen bonds. Although the above chemis-... 

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