Synthesis of star-shaped poly(lactide)s, poly(valerolactone)s and poly(caprolactone)s via ROP catalyzed by N-donor tin(ii) cations and comparison of their wetting properties with linear analogues.

In this study, we report the use of N-coordinated tin(ii) cations [L1→Sn(H2O)][OTf]2·THF (1) and [L1→SnCl][SnCl3] (2) (L1 = 1,2-(C5H4N-2-CH = N)2CH2CH2) as efficient ROP catalysts, which, in combination with benzyl alcohol, afford well-defined linear poly(ε-caprolactone) (PCL) and poly(δ-valerolactones) (PVL) via an activated monomer mechanism (AMM). Thanks to the versatility of complexes 1 and 2 as catalysts, star-shaped PCL, PVL and PLA were also prepared using three-, four-, five- and six-functional alcohols. The number of arms was determined by SEC-MALS-Visco analysis. Spin-coated thin layers of linear and selected six-armed polymers were further studied in terms of their wettability to water. Attention was focused on the influence of the composition and structure of the polymers. Finally, to increase the hydrophobic properties of the studied polymers, stannaboroxines L2(Ph)Sn[(OB-(C6H4-4-CF3))2O] and L2(Ph)Sn[(OB-(C6H4-3,5-CF3)2)2O] (L2 = C6H3-2,6-(Me2NCH2)2) were applied.

Tin(II) cations stabilized by non-symmetric N,N',O-chelating ligands: synthesis and stability.

A series of novel non-symmetric neutral N,N',O-chelating ligands derived from the α-iminopyridine 2-(C(R1)N(C6H3-2,6-iPr2))-6-(R2R3PO)C5H3N (L1: R1 = H, R2 = R3 = Ph; L2: R1 = Me, R2 = R3 = Ph; L3: R1 = H; R2 = Ph, R3 = EtO; L4: R1 = Me, R2 = Ph, R3 = EtO; L5: R1 = H, R2 = R3 = iPrO; L6: R1 = Me, R2 = R3 = iPrO) were synthesized. Ligands L1-6 were reacted with SnCl2 and Sn(OTf)2 with the aim of studying the influence of different R2R3PO functional groups on the Lewis base mediated ionization of SnCl2 and Sn(OTf)2. While all ligands L1-6 provided the corresponding ionic tin(II) complexes [L1-6 → SnCl]+[SnCl3]- (1-6), only ligands L1, L4 and L6 were able to stabilize tin(II) dications [L1,4,6 → Sn(H2O)][OTf]2 (7-9). The auto-ionized compounds [L3-6 → SnCl]+[SnCl3]- possessing ethylphenyl phosphinate and diisopropylphosphite substituents undergo elimination of EtCl and iPrCl, respectively, yielding compounds 10-13. These can either be interpreted as neutral tin(II)phosphinate chloride (10, 11) and tin(II)phosphonate chloride (12, 13), respectively, containing Sn-O and Sn-Cl bonds, and a PO → SnCl2 interaction, or as zwitterionic compounds, where the positive charge of the central tin atom is compensated by an [OSnCl2]- anion. Finally, DFT studies were performed to better understand the steric and electronic properties of the ligands L1-6 as well as the nature of the bonds in the resulting products, with a particular focus on complexes 10-13.

Synthesis and optical properties of N→Ga coordinated gallium boroxines.

Reactions of the N,C,N-chelated organogallium amide LGa(NEt2)2 (1), where L is {2,6-(Me2NCH2)2C6H3}-, with organoboronic acids RB(OH)2 yielded molecular gallium boroxines LGa(O3B2R2) (2: R = OH, 3: R = Ph, 4: R = 4-MeO-C6H4, 5: R = 4-CHO-C6H4, 6: R = Fc), neutral analogues of gallaborates. The molecular structures revealed the presence of a six-membered central GaB2O3 ring. The film forming properties of 5 allowed the deposition of transparent thin films by a spin coating method. The thicknesses, refractive index, energy of the optical gap (Eoptg), activation energy of surface electrical conductivity (Esa) and pre-exponential factor (σ0) of the thin layers of 5 were measured and they are close to those found for related oxygen glass. Finally, GBO 5 was also used as an additive to printing ink and a thin film of 5 was prepared by the gravure printing technique.

N-Donor stabilized tin(II) cations as efficient ROP catalysts for the synthesis of linear and star-shaped PLAs via the activated monomer mechanism.

α-Iminopyridine ligands L1 (2-(CHN(C6H2-2,4,6-Ph3))C5H4N), L2 (2-(CHN(C6H2-2,4,6-tBu3))C5H4N) and L3 (1,2-(C5H4N-2-CHN)2CH2CH2) differing by the steric demand of the substituent on the imine CHN group and by the number of donating nitrogen atoms were utilized to initiate a Lewis base mediated ionization of SnCl2 in an effort to prepare ionic tin(II) species [L1-3 → SnCl][SnCl3]. The reaction of L1 and L2 with SnCl2 led to the formation of neutral adducts [L1 → SnCl2] (2) and [L2 → SnCl2] (3). The preparation of the desired ionic compounds was achieved by subsequent reactions of 2 and 3 with an equivalent of SnCl2 or GaCl3. In contrast, ligand L3 containing four donor nitrogen atoms showed the ability to ionize SnCl2 and also Sn(OTf)2, yielding [L3 → SnCl][SnCl3] (7) and [L3 → Sn(H2O)][OTf]2 (8). The study thus revealed that the reaction is dependent on the type of the ligand. The prepared complexes 4-8 together with the previously reported [{2-((CH3)CN(C6H3-2,6-iPr2))-6-CH3O-C5H3N}SnCl][SnCl3] (1) were tested as catalysts for the ROP of L-lactide, which could operate via an activated monomer mechanism. Finally, a DFT computational study was performed to evaluate the steric and electronic properties of the ionic tin(II) species 1 and 4-8 together with their ability to interact with the L-lactide monomer.

Synthesis and Application of Monomeric Chalcogenolates of 13†Group Elements.

Utilization of the N,C,N-chelating ligand L (L={2,6-(Me2 NCH2 )2 C6 H3 }- ) in the chemistry of 13 group elements provided either N→In coordinated monomeric chalcogenides LIn(µ-E4 ) (E=S, Se) with unprecedented InE4 inorganic ring or monomeric chalcogenolates LM(EPh)2 (M=Ga, In). Complex LGa(SePh)2 was selected as the most suitable single source precursor (SSP) for the deposition of amorphous semiconducting GaSe thin films using spin coating method.