Ytterbium complexes divalent compounds

In order to study a bis[8]annulene compound with a divalent central metal atom we have synthesized and characterized the divalent ytterbium complex K2[Yb(CgHg)2]F K2[Yb(CgHg)2]r and its calcium analogue, K2[Ca(CgHg)2].51 These compounds were prepared by a reaction which utilizes the solubility of ytterbium and calcium metals in liquid ammonia. Reaction of cyclooctatetraene, potassium and either ytterbium or calcium, in liquid ammonia solution, gives the desired potassium salt of the complex dianion. 

The divalent state of the metal in complexes is confirmed by the diamagnetism of ytterbium derivative and the EPR spectrum of Eu compound, which is characteristic of Eu(II) complexes. The presence or absence of coordinately linked NH3 does not essentially influence the spectrum. It testifies to the ionic character of complex. Both compounds are pyrophoric on air and quickly hydrolysed in water. They interact with Lewis bases to form the coordination complexes. It results in a change of the compound colour. Heating in vacuum (200°C/10 mm Hg) gives back unsolvated compound. Complexes of ytterbium with the substituted ligand t-BuCgH7 has been synthesized by the same method [21]. 

While ytterbium(II) benzamidinate complexes have been known for many years/ the synthesis of the first divalent samarium bis(amidinate) required the use of a sterically hindered amidinate ligand, [HC(NDipp)2l (Dipp = C6H3Pr2-2,6)/ As illustrated in Scheme 54, the dark green compound Sm(DippForm)2(THF)2 (DippForm = [HC(NDipp)2] ) can be prepared by three different synthetic routes. Structural data indicated that hexacoordinated... 

Divalent lanthanide chemistry has been dominated by the most readily accessible divalent lanthanide metals samarium(II), europium(II), and ytterbium(II) (classical ) for decades, and a large number of divalent lanthanide compounds have been prepared [92], There are three routes to generate divalent organolanthanide complexes oxidative reaction of lanthanide metal, metathesis reaction of a divalent lanthanide halide, and reductive reaction of a trivalent lanthanide complex. 

Recently, aminotroponiminate complexes of divalent lanthanides were prepared for the first time [129], With regard to catalytic applications, amido complexes of europium and ytterbium were synthesized. The preparation of compounds 169 and 170 was undertaken in a one-pot reaction of KL31, anhydrous lanthanide diiodides and KN(SiMe3)2 in THF at room temperature (Scheme 64). 

Similar divalent metallocene complexes of ytterbium, i.e., (Cp),Yb(base/ligand) y, were also shown to act as mild, one-electron reducing agoits toward transition metal carbonyl compounds such as Co2(CO)g (Tilley and Andarsen, 1981), CpCo(CO)2 (Boncella and Andersen, 1984) and other organometallic derivatives of cobalt. 

Bimetallic complexes of Ln(II) are also formed in the interaction of ytterbium solution in liquid ammonia with K2(t-BuCgH7) [38] and Sml2 with two equivalents of K2(CgHg) [25]. Analogous compounds of ytterbium have been prepared in the reaction of cyclo-octatetraene with a solution of ytterbium and potassium in liquid ammonia [37]. [(CgHg)2Yb]K is formed at the equimolar ratio of potassium and ytterbium but at the ratio 2 1 the reaction leads to the complex with divalent ytterbium [(CgHg)2Yb]K2. 

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