Search

An efficient synthetic strategy that includes protection–modification–deprotection consequence was successfully developed to obtain novel water-soluble, amphiphilic, surface-active maltodextrin-based glycosilicones.

A family of the C,N-cyclometalated species [Pt(ppy)Cl(PPh3)], [Pt(ppy)Cl(CNCy)], [Pt(ppy)(CNCy)(PPh3)](OTf), and [Pt(ppy)(CNCy)2](BF4) (ppy = 2-phenylpyridinato-C2,N; Cy = cyclohexyl) was generated...

C,N-Chelate deprotonated diaminocarbene platinum(II) complexes were synthesized by coupling coordinated isocyanides and azinyl-substituted ureas. The complexes act as catalysts of α,ω-divinylpolydimethylsiloxane and poly(dimethylsiloxane-co-methylhydrosiloxane) hydrosilylation cross-linking. Silicone rubbers obtained with (aminoisoquinoline)-containing complex 3d exhibit temperature-responsive luminescence. Their emission changes irreversibly when heated from 80–100 °C (green radiation) to 120 °C or more (blue radiation).

4-Substituted O-benzyl benzamide oximes reacted with 2-iodobenzonitrile in the presence of 0.1 mol % of [Pd2(dba)3], 0.2 mol % of XantPhos, and 1.5 equiv of Cs2CO3 in dioxane under argon to give 2-arylquinazolin-4-amines. The described reaction is a new type of cascade processes, which affords 4-amino-quinazoline derivatives without using highly reactive chlorinating agents.

Acetylacetonate and 4-arylimino-2-pentanonate carbonyl complexes of rhodium(I) [Rh(RC(O)C(R')C(O)R“)(CO)2] (1: R = Me, R' = H, R'' = Me; 2: R = Me, R' = Cl, R'' = Me; 3: R = Me, R' = H, R'' = CO2Me; 4: R = Ph, R' = H, R'' = Me; 5: R = Ph, R' = H, R'' = Ph) and [Rh(MeC(NR''')CHC(O)Me)(CO)2] (6: R''' = Ph; 7: R''' = 2,6-Me2C6H3) were examined as hydrosilylation cross-linking catalysts at RT for the reaction of poly(dimethylsiloxane-co-ethylhydrosiloxane) copolymer with vinyl terminated poly(dimethylsiloxane) or vinyl terminated poly(dimethylsiloxane-co-styrene) copolymer. All complexes allow cross-linking of vinyl- and hydride-containing polysiloxanes and copolymers at RT without inhibitor addition. Complexes 1–7 possess catalytic activity comparable to the industrially used complex of Pt0 and divinyltetramethyldisiloxane (Karstedt’s catalyst). 1 is the most active among the studied rhodium complexes at 1.0 × 10−4 mol⋅L−1 and 1.0 × 10−5 mol⋅L−1. Silicone rubbers obtained with the rhodium catalysts compared to Karstedt’s catalyst possess no visible defects (bubbles or cracks), and differed by improved elastic properties (the elongation at break increased from 160 to 255%) The activity and improved silicone rubber properties using 1 renders it one of the suitable alternatives to Karstedt’s catalyst.

The platinum-catalyzed self-cross-linking of polymethylhydrosiloxane at RT in air was performed for the first time and proved by 1H, 13C, and 29Si SSNMR and swelling measurements. Quantum chemical modeling of possible structures was investigated. Platinum (0) and (ii) complexes were used as catalysts between the Si-H groups of polymethylhydrosiloxane. Karstedt's catalyst leads to Si-O-Si and Si-Si bond formation, but cis-[PtCl2(BnCN)2] generates predominantly Si-O-Si cross-links. cis-[PtCl2(BnCN)2] allows creating high-quality silicone rubbers without visible mechanical defects. This cross-linking approach can be used to obtain new Si-H-containing silicone materials.

Cyclic organosilicon triperoxides were found to be vinyl-selective free-radical initiators for thermal curing at 100–180 °C of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated polymethylhydrosiloxane producing homogeneous transparent silicone rubbers with antibacterial properties. The usage of the cyclic organosilicon triperoxides as the curing agents does not require free radical inhibitors in comparison with diacyl- and dialkyl peroxides. Among the tested compounds, the peroxide with the Me–Si–Me fragment and two cyclohexane rings is a much more active curing agent (180 °C, c = 0.22 M, τcuring = 45 min) than other organosilicon peroxides. Cured silicone samples from mixtures with vinyl-terminated polysiloxane and silicone hydride have improved mechanical properties: peroxides provide more than 200% elongation, and compression sets of the samples are less than 1%. The prepared silicone rubbers showed pronounced antibacterial activity.

Hydrosilylation catalyzed by the rhodium(I) complex [Rh(acac)(CO)2] or platinum(0)-based Karstedt's catalyst was employed to combine hydrophilic propargylated hydroxyethyl cellulose and hydrophobic hydride-terminated polydimethylsiloxane to give polymer hybrid structures. The final polymers were characterized by FTIR, solid state 1H, 13C and 29Si NMR, contact angle, microcalorimetry and thermogravimetry measurements. The grafting degree was controlled by the catalyst choice and by the reagent load variations; an increase of the polysiloxane load and a change from Karstedt's to the rhodium catalyst led to a higher (from 2 to 7%) silicon content in the glycosilicones. The glycosilicones were insoluble in water, but swelled in organic solvents (DMSO, DMF, and chloroform). The hydrophilicity of the glycosilicones decreased with incrementing silicon content: the contact angles increased from 30 (cellulose) to 103-131° in the hybrids. The glycosilicones obtained via the hydrosilylation are less toxic toward algae Chlorella vulgaris and infusoria Paramecium caudatum than those obtained with CuAAC.

The reaction of 3,4-diaryl-1H-pyrrol-2,5-diimines with cis-dichlorobis(isonitrile)platinum(II) affords the C,N-chelated diaminocarbene platinum(II) complexes, which have been fully characterized including molecular spectroscopy, single crystal X-ray diffraction and DFT calculations. The obtained platinum(II) complexes are effective catalysts for the hydrosilylation of alkynes and alkenes. Thus, the reaction of phenylacetylene with triethoxysilane leads to the formation of α- and β-(E)-vinylsilanes, generating TON's in the range of 103 to 104 and TOF's in the range of 102 to 103 h−1. Also, the cross-linked silicones, possessing the luminescence properties, were obtained by the hydrosilylation reaction of vinyl- and hydride-containing polysiloxanes. Additionally, the efficiency of diaminocarbene platinum(II) complexes against CH1/PA-1, SW480, and A549 cancer cell lines has been demonstrated by in vitro cytotoxicity studies.

The effect of the binary catalytic systems [the Karstedt catalyst–platinum(II) isocyanide complex] of the cure of vinyl-containing polydimethylsiloxane and hydride-containing siloxane oligomer via the hydrosilylation reaction has been studied.

The nitrile complexes trans-[PtCl2 (RCN)2 ] (R=Et (NC1), tBu (NC2), Ph (NC3), p-BrC6 H4 (NC4)) and cis-[PtCl2 (RCN)2 ] (R=Et (NC5), tBu (NC6), Ph (NC7)) react with 1 equiv of the hydroxyguanidine OC4 H8 NC(=NOH)NH2 (HG) furnishing the mono-addition products trans- and cis-[PtCl2 (RCN){NH=C(R)ON=C(NH2 )NC4 H8 O}] (1-4 and 9-11; 7 examples; 54-74 % yield). Treatment of any of the nitrile complexes NC1-NC7 with HG in a 1:2 molar ratio generated the bis-addition products trans- and cis-[PtCl2 {NH=C(R)ON=C(NH2 )NC4 H8 O}2 ] (5-8 and 12-14; 7 examples; 69-89 % yield). The PtII -mediated coupling between nitrile ligands and HG proceeds substantially faster than the corresponding reactions involving amid- and ketoximes and gives redox stable products under normal conditions. Complexes 1, 6⋅4 CH2 Cl2 , 7⋅4 CH2 Cl2 , 8⋅2 CH2 Cl2 , and NC4 were studied by X-ray crystallography. Platinum(II) species 1-3, 10, 11, and especially 9, efficiently catalyze the hydrosilylation cross-linking of vinyl-terminated poly(dimethylsiloxane) and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) giving high-quality thermally stable silicon resins with no structural defects. The usage of these platinum species as the catalysts does not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl-terminated polysiloxanes are shelf-stable in air.

Cyclometallated iridium(III) complexes with 2-phenylpyridine [Ir(ppy)2(CNR)Cl] (ppy = (2-phenylpyridinato-C2,N), R = Xyl, Mes), [Ir(ppy)2(CNR)2](OTf) (R = Xyl, Mes), and fac-[Ir(ppy)3] catalyse the cross-linking of polysiloxanes exclusively at temperatures above 100 °C leading to luminescent rubbers.

cis- and trans-Isomers of the platinum(II) nitrile complexes [PtCl2(NCR)2] (R = NMe2, N(C₅H10), Ph, CH2Ph) were examined as catalysts for hydrosilylation cross-linking of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) producing high quality silicone rubbers. Among the tested platinum species the cis-complexes are much more active catalysts than their trans-congeners and for all studied platinum complexes cis-[PtCl2(NCCH2Ph)2] exhibits the best catalytic activity (room temperature, c = 1.0 × 10(-4) mol/L, τpot-life 60 min, τcuring 6 h). Although cis-[PtCl₂(NCCH2Ph)2] is less active than the widely used Karstedt's catalyst, its application for the cross-linking can be performed not only at room temperature (c = 1.0 × 10(-4) mol/L), but also, more efficiently, at 80 °C (c = 1.0 × 10(-4)-1.0 × 10(-5) mol/L) and it prevents adherence of the formed silicone rubbers to equipment. The usage of the cis- and trans-[PtCl2(NCR)2] complexes as the hydrosilylation catalysts do not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl terminated polysiloxanes are shelf-stable in air. Tested catalysts do not form colloid platinum particles after the cross-linking.