1065614-63-2Relevant academic research and scientific papers
Cyclopentadienyl chromium β-diketiminate complexes: Initiators, ligand steric effects, and deactivation processes in the controlled radical polymerization of vinyl acetate
Champouret, Yohan,Cory MacLeod,Baisch, Ulrich,Patrick, Brian O.,Smith, Kevin M.,Poli, Rinaldo
, p. 167 - 176 (2010/03/04)
The new compounds CpCr(nacnacAr,Ar') with nacnac Ar,Ar' = Ar-N=C(Me)=CHC(Me)=N-Ar' (Ar = Ar' = C6H 2Me3-2,4,6 or mes, 2; C6H3Et 2-2,6 or dep, 3; Ar = C6H3Me2-2,6 or xyl and Ar' = C6H3iPr2-2,6 or dipp, 4) have been synthesized and used in polymerization experiments in addition to the previously known analogues with Ar = Ar' = xyl, 1, or dipp, 5. The compounds were used as moderators for the polymerization of vinyl acetate (VAc) initiated by V-70, according to an OMRP mechanism. The alkylchromium(III) thermal initiator CpCr(nacnacxyl,xyl)(CH2CMe3) (8) was synthesized from CpCr(nacnacxyl,xyl)(OTs) (7) and Mg(CH 2CMe3)2(dioxane), while 7 was obtained from CpCr(nacnacxyl,xyl)Cl (6) and AgOTs. The polymerizations carried out with (l-5)/V-70/VAc at elevated temperatures yielded rapid deactivation, suggestive of irreversible radical trapping. On the other hand, room-temperature polymerizations carried out with 6/VAc proceeded, albeit slowly, to greater conversions. A labilizing effect of the Ar/Ar' steric bulk is suggested by QM/MM calculations of Cr'-C BDE for models of the OMRP dormant species with 1,5, and the parent system where Ar = Ar' = Ph. Thermal deactivation of the nacnac xyl'xyl system has been evidenced, with formation of the acetate complex CpCr(nacnacxyl'xyl)(OAc), 9, as confirmed by an UV-vis study and by independent synthesis. This product is proposed to form by β-acetate transfer from the growing radical chain, triggered by a head-head monomer insertion. Compounds 2, 3, 6, 7, 8, and 9 have been structurally characterized by X-ray diffraction methods.
Chromium-catalyzed radical cyclization of bromo and chloro acetals
MacLeod, K. Cory,Patrick, Brian O.,Smith, Kevin M.
, p. 6639 - 6641 (2011/02/27)
Cyclopentadienyl chromium β-diketiminate catalysts are used for the radical cyclization of bromo and chloro acetals. Mn powder activated with PbBr2 or PbCl2 is the stoichiometric reductant, and γ-terpinene is the hydrogen atom donor.
