Butadiene complexes Particular studies

Studies of rc-complexcs containing ligands other than the Cp family of ligands have also appeared in the literature in 20 08.23 25 Of particular note is the synthesis of Mg and Ca complexes of the tetrakis(trimethylsilyl)cyclo-butadiene dianion, [Mg(thf)3][(Me3Si)4C4] (19) and [Ca(thf)J[(Me3Si)4C4] (20), via the reduction of tetrakis(trimethylsilyl)cyclobutadiene [(Me3Si)4C4] with metallic Mg or Ca. The structure of the half-sandwich 19 shows the presence of an -bonded [(Me3Si)4C4]2 671-dianion to the Mg centre.23... 

In reality, the second possibility occurred (57), and the same was true for the adducts containing other olefins. Finally, we verified the presence of hydroxyl in structure (IV) through reaction with phenyl isocyanate. Thus, the convincing experiments of Hoffmann, Middleton, and R. Adams were confirmed by our decisive evidence, so that 7T-structures were condemned to fade from the scene for these compounds. However, to emphasize the behavioristic similarity with the 77-complcxes, I suggested the term quasicomplex for the compounds which are formed from metallic salts and olefins or acetylenes through addition to the 7T-bond. A number of such quasi-complex compounds were obtained and studied by us. In particular, we showed that butadiene or its homologs, contrary to the earlier opinion of Sand, also formed the quasi-complex adducts in water, e.g.,... 

A theoretical study of the Diels-Alder reactions between 1,3-butadiene and, respectively, cyclopentadiene and 2H-phosphole, has revealed a remarkable similarity between the two reactions. Further studies of photocycloaddition reactions of phosphole moieties have also been reported. Transition metal complexes of phospholide anions continue to attract attention, and in particular the chemistry of phosphaferrocene systems remains a major interest . The past year has also seen significant activity in the chemistry of di- and tri-phospholes, related polyphospholide anions, and also heterodiphosphole systems. Routes have been developed to the diphosphonio-l,2-diphospholes 356,... 

The TT-allyl complexes of Pd , e.g. [Pd( j -C3Hs)X]2 (X = Cl, Br, I), are very stable and more numerous than for any other metal, and neither Ni nor Pt form as many of these complexes. Indeed, the contrast between Pd and Pt is such that in reactions with alkenes, where a particular compound of Pt is likely to form an alkene complex, the corresponding compound of Pd is more likely to form a rr-allyl complex. The role of the Pd and Ni complexes as intermediates in the oligomerization of conjugated dienes (of which 1,3-butadiene, C4H6, is the most familiar) have been extensively studied, particularly by... 

Apart from a patent (J) which appeared in 1947 no further work was published on this particular reaction until Hallam and Pauson (4) extended the study in 1958. These latter workers investigated further the product obtained from butadiene and Fe(CO)s. The diene complex was found to resist hydrogenation and not to undergo Diels-Alder-type reactions. Ozonolysis... 

Actinide diene complexes (Smith et al. 1986) can be prepared from Cp MCl (M = U, Th) and the appropriate Grignard reagent. The X-ray structure of the Cp2Th(r)" -C4H6) compound shows a bent sandwich CpJTh moiety coordinated to the butadiene ligand in s-cis conformation with an tj" bonding mode. Thermochemical studies of the thorium-butadiene bond disruption enthalpy do not indicate particular Th-butadiene stabilization, it is comparable to that for Th to carbon o-bonds. The compound adopts the familiar bent sandwich structure. 

---