Isocarbonyl linkage

Other compounds containing carbonyl groups are known, involving a transition metal. Most of these feature isocarbonyl linkages. Thus [Cp 2Yb] reacts with Co2(CO)s in THF solution to form [Cp 2Yb(THF)-0-C-Co(CO)3]. A few compounds actually contain metal-metal bonds involving a lanthanide, thus ... 

While the former was obtained directly by reaction of [Ybljfthf), ] with KlReCpj], the latter was synthesized via salt elimination from (Ybljfthf) ] and Na[RuCp(CO)2] followed by cracking of the isocarbonyl linkages in the primary polymeric product with 4-tert-butylpyridine (Scheme 3.3, top and middle) [13]. Using an iodo-bridged, NHC-stabilized dimer of neodymium and K[FeCp(CO)2], a complex with an unsupported Nd-Fe bond was obtained (Scheme 3.3, bottom) [14],... 

Another complex with a short Ln-M distance, Er[MoCp(CO)3]3(Et20H)(H20), unfortunately is characterized incompletely [57]. The Er-Mo distance has been found to be 3.143 A. In this case the direct Ln-M interaction is supported by the isocarbonyl linkage. 

Thus, one can conclude that most of the known up to the present carbonylmetalates of lanthanoids do not contain a direct Ln-M bond and have the ionic nature. The distinctive feature of the compounds appears to be the existence of isocarbonyl linkages Ln-O-C-M. At the same time the compounds with short distances (characteristic of a covalent bond) between the Ln and M atoms evidently also can be synthesized in some cases. The problem in the whole needs an additional theoretical study. 

The complexes show low CO stretching frequencies typical of isocarbonyl linkages between Mo or W and uranium. 

D. McIntosh, and G. A. Ozin, Synthesis of Binary Gold Carbonyls, Au(CO)n (n = 1 or 2). Spectroscopic Evidence for Isocarbonyl(carbonyl)gold, a Linkage Isomer of Bis (carbonyl)gold, Inorg. Chem. 16, 51-59 (1977). 

Isocarbonyl and isonitrosyl linkages to lanthanides are evident in the complexes noted above [256], confirmed by IR spectroscopy. In the Yb complex, an isocarbonyl bridge Yb-OC-Co has been confirmed while in the Iutetium complex Lu-Ru metal-metal bond is present [257]. 

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