Samarium versus aluminium Lewis acidity in a mixed alkyl carboxylate complex related to alkylaluminium activation in diene polymerization catalysis

Abstract

[(C5Me5)2Sm(mu-O2CPh)]2 reacts with iBu3Al to form a mixed bridge samarium aluminium complex [(C5Me5)2Sm(mu-O2CPh)(mu-iBu)Al(iBu)2], that displays two different carboxylate orientations toward the metals in a single crystal.

Reactivity of Yttrium Carboxylates Toward Alkylaluminum Hydrides

“…Both complexes feature a bridging hydrido and a μ 2 ‐bridging carboxylato moiety that connect the yttrium and aluminum metal centers, thereby forming an overall six‐membered ring. The CO bond lengths in both complexes are similar, and compare well to those reported for [Cp* 2 Sm(μ‐O 2 CPh)(μ‐ i Bu)Al i Bu 2 ] (1.251(3)/1.266(3) Å) 8a. The yttriumoxygen distances are shorter than those in the starting material ( 1 ), but lie well within the range found in other carboxylate‐bridged yttrium complexes24 and the aluminumoxygen distances also compare well to those found in other alkylaluminum‐carboxylate complexes, for example, [{Me 2 Al(μ‐O 2 C(C 6 H 2 i Pr 3 ‐2,4,6)} 2 ]4a (1.810(1)/1.840(1) Å) 8a.…”

“…The CO bond lengths in both complexes are similar, and compare well to those reported for [Cp* 2 Sm(μ‐O 2 CPh)(μ‐ i Bu)Al i Bu 2 ] (1.251(3)/1.266(3) Å) 8a. The yttriumoxygen distances are shorter than those in the starting material ( 1 ), but lie well within the range found in other carboxylate‐bridged yttrium complexes24 and the aluminumoxygen distances also compare well to those found in other alkylaluminum‐carboxylate complexes, for example, [{Me 2 Al(μ‐O 2 C(C 6 H 2 i Pr 3 ‐2,4,6)} 2 ]4a (1.810(1)/1.840(1) Å) 8a. 25 A closer look at the yttrium and aluminumhydrido distances showed that, in both complexes, the hydrido ligand was more closely associated with the aluminum atoms ( 2 : AlH1 1.68(2), YH1 2.20(2) Å; 3 : AlH1 1.64(2), YH1 2.19(2) Å), whilst the MH (M=Y,20, 26 Al27) distances were well within the range of those reported in the literature.…”

“…From the in situ NMR studies of the dimethylaluminum hydride reaction, we were not able to identify any of the compounds, but we were able to obtain crystals from the reaction mixture and characterize a carboxylate‐free yttrium‐aluminum‐hydride adduct complex (Scheme and Figure 4). Note that carboxylato displacement was also observed in the reaction of [{Cp* 2 Sm(μ‐O 2 CPh)} 2 ] with four equivalents of triisobutylaluminum, thereby affording the corresponding tetraalkylaluminate complex, [Cp* 2 Sm(Al i Bu 4 )] 8a. The most‐striking feature of complex 4 is the two sets of two methylaluminum hydride moieties that bridge between two yttrium metal centers, thereby forming an overall 12‐membered ring structure.…”

1,2 Enriched polymerization of isoprene by cobalt complex carrying aminophosphory fused (PN3) ligand

“…The mechanism for the catalytic result is proposed in Scheme and can be explained in the light of some of the more relevant studies presented in the literatures . Activated by Mg n‐ Bu 2 , a heterobimetallic intermediate M1 stabilized by F and butyl bridges well known for Ziegler‐Natta system could be formed, whose analogues were also reviewed for transition metals catalyzed organic transformation reactions . The monomer is then activated on the cobalt center probably via η 4 ‐1,4 coordination and then inserted to Co‐C( n‐ Bu), forming anionic allylic polymer end.…”

Structure and characterization for conterminously linked polymer of short‐chain epoxy resin with triallyl isocyanurate and bismaleimide

“…Considering the well‐known bridging ability of the borohydride ligand in lanthanide chemistry,33 the 1,4‐trans stereospecificity can be tentatively correlated to the formation of sterically hindered borohydrido‐bridged bimetallic Nd/Mg species 34, 35. The addition of Al( i Bu) 3 to rare earth complexes can lead to the isolation of well‐defined Ln‐Al bimetallic complexes with bridging isobutyl groups 36–39. The addition of 9 equiv Al( i Bu) 3 to a 2b /1 equiv BEM system may thus afford a polymetallic Mg/La/Al compound in which the [Al] core plays the role of an additional ligand, hence increasing the steric environnement around the lanthanum metal, in a subtle manner that it just allows the coordination of the incoming monomer to give rise to trans‐selectivity, without however shifting to 3,4 selectivity.…”