Dihapto acyl complex

In view of the fact that early transition metal alkyls insert CO under very mild conditions (2, 5.) we chose to examine the reactions of electron-rich metal hydrides ( ) with the resultant dihapto acyl complexes. Such acyls obviously benefit from reduction of the CO bond order from three (in OO) to two. More significantly, the dihapto binding mode will significantly enhance the electrophilic character of the acyl carbon. 

Recently, Ford et al. explored laser flash photolysis of the Mn(CH3CO)(CO)5 to give acyl intermediates relevant to carbonylation of MnCH3(CO)5 [21]. The time resolved infrared (TRIR) and time resolved optical (TRO) spectra of the long-lived acyl intermediate indicated that a dihapto acyl complex Mn(rj -... 

Experimental evidence pointing to intermolecular methanolysis, or at least, not excluding this termination path has been reported as well. An in situ NMR investigation showed in fact that the Pd" acyl complexes [Pd(C(0)Me)(NCMe)(dppf)]OTs and [Pd(C(0)Me)(dppomf)]OTs, containing dihapto and trihapto ligands, respectively, undergo fast methanolysis at room temperature (dppomf = l,T-bis(diphe-... 

Several complexes with acetyl ligands bonded in a dihapto fashion have now been reported 120-122). It cannot be decided whether the chiral intermediates C5H5Mn(NO)(COCgH8) contain monohapto or dihapto acyl ligands, because they cannot be observed spectroscopically. However, dihapto bonding would not change the stereochemical outcome of all the results described. 

Theoretical studies [59] indicate that the lowest unoccupied molecular orbital (LUMO) of such molecules is localized primarily on the acyl carbon atom, similarly to the situation in Fischer complexes. An example of such a compound is shown in Fig. 23.9, where the shortness of the Th-O distance (2.37(2) A) relative to Th-Cg (2.44(2) A) is unprecedented for a dihapto-acyl. A second example of an actinide dihapto-acyl is shown in Fig. 23.10. It should be noted that the orientation of the C-O vector is in the opposite direction from that in Fig. 23.9. The relative magnitudes of the Th-O and Th-C distances appear to reflect both the orientation of the C-O vector and conjugation with the arene n system. The intricate chemistry exhibited by actinide dihapto-acyls is summarized in Fig. 23.11. Important reactions include C-C coupling to form monomeric (10) or dimeric enediolates [57,58,60,61], isomerization to yield enolates (//) [60,62], catalytic hydrogenation to yield alkoxides (/2) [63], CO tetramerization to form dionediolates (13) [62, 64], coupling with ketenes 14), coupling with CO and phosphines 15) [62, 64], and addition to isocyanides to yield ketenimines [62, 64] 16). 

Re(Tp)(CO)( BuNC)(2,3-ri2-5-R-furan)] (R = H, Me), obtained as a mixture of coordination diastereomers, reacts with aldehydes RC(=0)H (R = Me, Ph, 3-furyl) in the presence of BF3 OEt2 to yield dihydrofuran complexes. Dihapto-coordinated trans-2-alkyl-3-acyl-2,3-dihydrofuran, tr[Pg.131]

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