Polymer/trimer/metal complex mixtures as precursors of gold nanoparticles: tuning the morphology in the solid-state

The pyrolysis of several physical mixtures of AuCl(PPh3) with polymeric [NP(O2C12H8)]n or cyclic N3P3(O2C12H8)3 phosphazenes, formed as solid powders or films with different molar ratios, have been studied under air and at 800 °C. The characterization of the products has shown that the particle size and morphology are strongly dependent on the nature of the phosphazene, the phosphazene/AuCl(PPh3) molar ratio and on the preparation methodology. Gold nanoparticles (NPs) with mean sizes as small as 3.5 nm were obtained from a [NP(O2C12H8)]n/AuCl(PPh3) 1:1 film. The particle morphology was also strongly dependent on the experimentally conditions of the pyrolysis. Powdered materials exhibit a 3-D irregular morphology in the mixture [NP(O2C12H8)]n/AuCl(PPh3) 3:1 film, and gold foams in the 1:1 ratio, both from the [NP(O2C12H8)]n/AuCl(PPh3) as well as N3P3(O2C12H8)3/AuCl(PPh3) mixtures. These results show for the first time the possibility of controlling morphology and size of gold particles obtained by solid-state reactions

Polyphosphazenes for the Stille reaction: A new type of recyclable stannyl reagents

Producción CientíficaThe random phosphazene copolymer {[N=P((CH2)7-Br)Ph]0,5[N=PMePh]0,5}n (2) and the block copolyphosphazene {[N=P((CH2)7-Br)Ph]25[N=PMePh]20}-b-[N=P(O2C12H8)]55 (5), having a branch with two randomly distributed units, have been synthesized and used as precursors for the stannyl derivatives {[N=P((CH2)7-SnBu2An)Ph]0,5[N=PMePh]0,5}n (3) and {[N=P((CH2)7-SnBu2An)Ph]25[N=PMePh]20}-b-[N=P(O2C12H8)]55 (6, An = p-MeOC6H4). Polymers 3 and 6 were tested as recyclable tin reagents in the Stille cross-coupling reaction with C6H5I, using various Pd catalysts and different experimental conditions. Polymer 6 can be recycled without significant release of tin, but its efficiency decreased after three consecutive cycles. This effect was explained by studying the self-assembly of the polymer under the same conditions used for the catalytic experiments, which evidenced the progressive coalescence of the polymeric vesicles (polymersomes) leading to stable and bigger core-shell aggregates by the attraction of the [N=P(O2C12H8)] rich membranes, thus decreasing the accessibility of the tin active centers.2017-12-15Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. VA302U13)Ministerio de Economía, Industria y Competitividad (CTQ2014-56345)Ministerio de Economía, Industria y Competitividad (CTQ2013-48406-P)Universidad de Oviedo (Project UNOV-13-EMERG-GIJON-08

Synthesis of the first phosphazene random copolymers containing thiophenoxy groups

The reaction of [NPCl2]n with substoichiometric amounts of the thiophenols HS—C6H4—R (R = H, Br) and Cs2CO3 in THF at room temperature, gave solutions of {[NPCl2]1-x[NP(S—C6H4—R)2]x}n [R = H (1a), Br (1b)]. The reaction of the derivative with R = Br and x = 0.3 with HO—C6H4—Br gave the random copolymer {[NP(O—C6H4—Br)2]0.7 [NP(S—C6H4—Br)2]0.3}n (2); similarly, the reaction of 1 with the biphenol HO—C6H4—C6H4—OH gave the random copolymers {[NP(O2C12-H8)]0.75[NP(S—C6H4—R)2]0.25}n [R = H, (3a); R = Br, (3b)] as soluble and stable white solids.We thank the Spanish Dirección General de Investigación Científica y Técnica (DGYCYT), Project PB97-1276, for support.Peer reviewe

Dioxybiphenyl and chiral dioxybinaphthyl polyphosphazene random copolymers carrying carboxylic acids and their reactions with ∈-caprolactam to form nylon-6-branched phosphazene materials

The phosphazene polymers carrying phenoxycarboxylic acids {[NP(O-C 6H 4-CO 2H) 2] x[NP-(O 2C 12H 8)] 1-x} n [x = 0.2 (1a), 0.35 (1b), 0.5 (1c), 0.7 (1d), 0.85 (1e), x = 1(2)] and the chiral analogues {[NP(O-C 6H 4-CO 2H) 2] x[NP(O 2C 20H 12)] 1-x} n [x = 0.2 (3a), 0.45 (3b), 0.7 (3c)] (O 2C 12H 8 = 2,2'-dioxybiphenyl, O 2C 12H 12 = R-2,2′dioxy-1,1′-binaphthyl) have been synthesized by hydrolysis of the corresponding precursors with [NP(O-C 6H 4-CO 3Pr) 2] units. The new polymers have extensive H-bonding between the -COOH groups in the solid state, and those with x > 0.5 are very soluble in aqueous 0.5 M sodium carbonate. These polymers were used as initiators of the ring-opening polymerization of the ∈-caprolactam (∈-CL) at 230°C to give un-cross-linked polyphosphazenes, branched with short polyamide chains but having a fraction of the phosphazene units (from 20 to 35%) modified by secondary reactions. © 2005 American Chemical Society

Synthesis and thermal decarbonylation of W(CO)5 complexes supported by nitrile, pyridine or phosphine ligands to poly-spirophosphazene random copolymers carrying O-C6H5-CO2Pr groups

The phosphazene copolymers {[NP(O2C12H 8)]0.5[NP(O-C6H4-CO 2Prn)(O-C6H4-L)]0.5} n [L = CN (1), PPh2 (2)] and {[NP(O2C 12H8)]0.6[NP(O-C6H 4-CO2Prn)(O-C5H4N)] 0.4}n (3) have been synthesized by sequential substitution from [NPCl2]n. Their reactions with [W(MeOH)(CO) 5] gives the corresponding tungsten carbonyl complexes {[NP(O 2C12H8)]0.5[NP(O-C6H 4-CO2Prn)(O-C6H4-CN) (W(CO)5)0.4]0.5}n (4), {[NP(O 2C12H8)]0.5[NP(O-C6H 4-CO2Prn)(O-C6H4-PPh 2)(W(CO)5)0.7]0.5}n (5), {[NP(O2C12H8)]0.6[NP(O-C 6H4-CO2Prn)(O-C5H 4N-W(CO)5)]0.4}n (6a), and {[NP(O2C12H8)]0.6[NP(O-C 6H4-CO2Prn)(O-C5H 4N)(W(CO)5)0.4]0.4}n (6b), that have been fully characterized by IR and NMR spectroscopies. The thermal properties (TGA and DSC) of the polymeric complexes showed that they are high glass transition materials that undergo a complete decarbonylation below 300°C forming metal containing species that have a stabilizing effect on the polymeric matrices. The final residues up to 800°C are of the order of30-50%. © 2005 Els