Isocarbonyl complexes

A similar reaction (see equation 27) has been reported for hexacarbonylvanadium(O). By these reactions, the tetracarbonylcobaltate(-I) and the hexacarbonylvanadate(-I) anions are generated. The crystal and molecular structure of the product of the disproportionation reaction of V(CO)6 with tetrahydrofuran of formula [V(THF)4][V(CO)6]2 has been shown to consist of vanadium(II) octahedrally surrounded by four thf s in the equatorial positions and by two axial carbonyl oxygens from two hexacarbonylvanadate anions resulting in a linear V-O-C-V sequence see Isocarbonyl Complexes). 

In related work, an unusual ytterbium(IIl) complex, [(i7-C5Me5)2-Yb]2[Fe3(CO)7(ja-CO)4], was shown by Tilley and Andersen to contain four isocarbonyl ligands (30). The iron portion of this complex acts formally as a l,3,5-trimetalla-/3-diketonato ligand coordinated to the two Yb(III) ions. 

V(py) ][V(CO)6]2 precipitated by adding solid [V(CO)6] to a toluene solution containing an excess of pyridine. By dissolving it in CH2C12, an isocarbonyl-bridged complex... 

Organolanthanide complexes are coordinately unsaturated and as a result take part in forming mixed complexes with transition metal complexes containing nitrosyl or carbonyl groups. As a result, mixed complexes containing metal-metal bonds or lanthanide-isocarbonyl or isonitrosyl interactions have been characterized. Some typical complexes are given below. 

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]. 

The reason for isocarbonyl bridging rather than for Al-tm bonding in these complexes can be found in the interaction of the small and therefore hard group 13 metal A1 with the CO group. The A1 is better suited to the harder basic site in the tm compound, and this is the carbonyl oxygen rather than the metal center. 

The samarium and ytterbium" species have been characterized crystallographically and were found to contain discrete anions and cations, whereas in the closely related unfunctionalized ytterbium complex Cp 2Yb(OC)Co(CO)3(THF) an Yb-OC-Co interaction (i.e., an isocarbonyl bridge) is observed. This reflects nicely the coordinative saturation effected by the intramolecular coordination in the ether-functionalized complexes. Both cations adopt Cz symmetry (approximate for Sm. crystallographically exact for Yb) and contain two chelating ether groups [Sm-0 249.6(10) and 249.9(10) pm. O-Sm-0 150.5-... 

ITie reaction of some dicyclopentadienyl lanthanide chlorides and some bis(meth-ylcyclopentadienyl) lanthanide chlorides with Na[WCp(CO)3] results in some complexes, stable up to 220°C, which are soluble in tetrahydrofuran and dimethylsulfo-xide. Other anionic metal carbonyl or metal nitrosyl compounds gave no satisfying results, mainly because of side reactions. Infrared spectra indicate polymeric structures containing isocarbonyl bridges (Crease and Legzdins, 1973b) ... 

Scheme 3.1 Erroneously proposed Yb-Co bonded complex (top) that was shown to be ather ionic or isocarbonyl-bridged, depending on solvation (bottom).

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],... 

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