Tert-butylamidinate tin(ii) complexes: high activity, single-site initiators for the controlled production of polylactide

Abstract

The tin(ii) coordination chemistry of two monoanionic N,N'-bis(2,6-diisopropylphenyl)alkylamidinate ligands is described. Complexation studies with the acetamidinate, [MeC(NAr)(2)](-), (Ar = 2,6-(i)Pr(2)C(6)H(3)) are complicated by the side formation of the bis(amidinate) tin(ii) compound, [MeC(NAr)(2)](2)Sn. By contrast, the bulkier tert-butylamidinate, [(t)BuC(NAr)(2)](-), allows tin(ii) mono-halide, -alkoxide and -amide complexes to be isolated cleanly in high yields. Thus, the reaction of [(t)BuC(NAr)(2)]H with (n)BuLi and subsequent treatment with SnCl(2) generates [(t)BuC(NAr)(2)]SnCl, in ca. 70% yield. Reactions of with LiO(i)Pr, LiNMe(2) and LiNTMS(2) afford [(t)BuC(NAr)(2)]Sn(O(i)Pr), [(t)BuC(NAr)(2)]Sn(NMe(2)), and [(t)BuC(NAr)(2)]Sn(NTMS(2)), respectively. The molecular structures of complexes are reported. Complexes, and have been investigated as initiators for the ring-opening polymerisation of rac-lactide: and display characteristics of well-controlled polymerisation initiators, but high molecular weight polymer is observed with due to inefficient initiation, a consequence of the steric bulk of the NTMS(2) unit. Polymerisations with and are faster than for the corresponding beta-diketiminate tin(ii) complexes, consistent with the more open nature of the tin(ii) coordination sphere.

Oxidative Additions of Homoleptic Tin(II) Amidinate

“…9 Hz, 2H, ArH), 3.40 (br s, 2H, CyH), 3.23 (br s, 2H, CyH), 2.37 (t, 3 J = 7.2 Hz, 4H, α CH 2 ), 2.09−1.08 (br m, 48H, CyH, CyH+ β CH 2 + γ CH 2 ), 0.96 (t, 3 J = 7.1 Hz, 6H, CH 3 ). 13 3 Hz, 6H, CH 3 ). 13 (9).…”

η3‐Allyl Coordination at Tin(II)—Reactivity towards Alkynes and Benzonitrile

“…The central structural motif is a tricyclic structure, namely tricyclo[3.3.2.0 3,7 ]-1,5-distannadec-9-ene. The saturated carbon analogue was first described in 1979 and as one of the adamantane isomers, it is part of the "adamantaneland".…”

“…[4] Another negatively charged three-atom ligand system featuring four p-electrons is the amidinate ion, which, in contrast, coordinates at tin(II) centers exclusively in h 2 fashion. [7] Natural bonding orbital (NBO) analysis and a secondorder perturbation theory analysis of 1 support the description of the bonding interaction as a s-bonded allyl moiety with a donor-acceptor interaction (42 kcal mol À1 ) of the p-electrons of the allylic double bond into the empty p orbital at the Sn atom. Furthermore, a donor-acceptor interaction of 46 kcal mol À1 from the Sn À C s-bond orbital into the antibonding C = C orbital was determined, which is in line with the resonance stabilization expected for an h 3 -coordinated allyl moiety.…”

Improving the ring-opening polymerization of ε-caprolactone and l-lactide using stannous octanoate

“…However, the drawbacks include low polymerization activity and undesirable inter-and intramolecular transesterification reactions. Numerous researchers [22,[34][35][36][37][38][39][40] have attempted to synthesize Sn complexes to overcome these issues; however, they have encountered difficulties resulting from the sensitivity to air requiring that they be prepared under N 2 , making them difficult to manufacture or research without the glove box and vacuum lines.…”