Cerium complexes bridging

Two other dimeric complexes which are related in structure to [Yb-(C5H4(CH3))2C1]2 are [Ce(C8H8)Cl 2THF]2 and [Sc(C5H5)2Cl]a. The cerium complex was discussed earlier. The structure of the scandium complex 118) is the same as that in Fig. 11. For the planar unit with symmetrical bridges, changing... 

Two ring-bridged dicyclopentadienyl rare earth phenylacetylides have been synthesized according to eq. (52) by John and Tsutsui (1980, 1981). The lanthanum complex shows two singlets in the proton NMR spectrum at 6 = 7.57 and 7.74 ppm with equal intensity, which are assigned to the cyclopentadienyl protons, and broad peaks at 4.24 and 4.54 ppm for the methylene protons. The phenyl proton signal appears at 6 = 8.92 ppm. The cerium complex shows a singlet at 6 = 9.16 ppm for Ph and a multiplet between 7.29 and 7.59 ppm for the cyclopentadienyl protons. 

The reactions of LnCls with only one equivalent of K2C8H8, carried out in THF, afford complexes of the type [C8H8LnCl(THF)2]2 (105,111, 112). The investigation of the structure of the cerium complex proves the dimeric nature and shows the two cerium atoms bridged asymmetrically by the two chlorine atoms,and, in each case, coordinated by one cyclooctatetraenyl ring and two THF molecules (113). The complexes loose THF upon heating to 60 C in vacuo. The lutetium compound reacts with alkyl-lithium compounds with formation of the first cyclooctatetraenyl(organ-yl)lutetium compounds (11 ) ... 

Alkynyl complexes Cp2LnC R are associated even in donating solvents [148, 154, 169, 170]. In most cases association degree is equal 2 except the lanthanum and cerium complexes obtained by Tsutsui and coworkers [151, 152], in which Cp-rings are bonded by the trimethylene bridge... 

Use of less basic triphenylsiloxide ligands also allowed the isolation of mononuclear complexes (Table 1) [46,47]. In addition to the silylamide route, anhydrous nitrates and isopropoxides were employed as synthetic precursors (Eqs. 1,2). The siloxide bridges in the solvent-free dimeric systems Ln2(OSiPh3)6 are readily disrupted by donor solvents like THF, OP Bu3 or DME. The m s-THF adducts of lanthanum, cerium (Fig. 5) and yttrium adopt an approximately /ac-octahedral geometry. 

Two binuclear complexes containing 2,2 -bipyridyl (bipy) have been reported in which the imido ligand appears to function in a bridging role. These are [0s2(NH)Cl2(bipy)4](C104)2, made from [Os(bipy)2(NH3)Cl]+ and cerium(TV), and Os2(NH2)(bipy)4, made from Os(bipy)2Cl2 and ammonia.173 The IR spectrum of the first complex has been recorded.294 The oxidation states seem too low for these to be true imido complexes and further investigation would certainly be of interest. 

The reduction of Ce(0-i-C3H7)if with triethylaluminium in the presence of cyclooctatetraene yields a yellow colored cerium(lll) complex with two alkoxy-bridges between Ce and A1 (l62) ... 

This bimetallic complex was characterized by elemental analysis, infrared spectrum and mass spectrum. The infrared indicates that the eight-membered ring is present as [8]annulene. It was suggested from the mass spectrum and iH-NMR studies that this complex exists with the isopropoxide ligands bridging between the cerium and aluminum ions (Figure 11). The bimetallic [8]annulene complex has also been made as its acetonitrile adduct. 7... 

---