Electro-oxidation of ethanol on PtSn/CeO2–C electrocatalyst

PtSn/CeO₂–C electrocatalyst was prepared in a single step by an alcohol-reduction process using ethylene glycol as solvent and reducing agent and CeO₂ (15 wt%) and Vulcan XC72 (85 wt%) as supports. The performance for ethanol oxidation was investigated by cyclic voltammetry and in situ FTIR spectroscopy. The electrocatalytic activity of the PtSn/CeO₂–C electrocatalyst was higher than that of the PtSn/C electrocatalyst. FTIR studies for ethanol oxidation on PtSn/C electrocatalyst showed that acetaldehyde and acetic acid were the principal products formed, while on PtSn/CeO₂–C electrocatalyst the principal products formed were CO₂ and acetic acid.     

Combustion synthesis of porous Ti-Co alloys for orthopedic applications

A mechanoactivation of Ti-Co mixtures was used to perform the SHS of Ti-Co alloys without preheating and heat-generating additives. The SHS of Ti-Co alloys from non-activated Ti + Co green mixtures containing an admixture of B₄C as a heat-generating agent without preliminary heating was carried out for the first time. The phase composition, structure, and mechanical properties of synthesized materials were explored upon variation in [B₄C] within the range 2–10 wt %. The desired structure/properties of combustion products were attained at [B₄C] = 2–4 wt %. The materials synthesized under the above optimal conditions exhibited a developed and uniformly distributed system of pores (largely open) with a size of 150–400 μm, at a wall thickness of 70–100 μm. By their properties (interconnected pores in the range 200–500 μm, compression strength 40–65 MPa), the synthesized materials can be recommended for use as metallic scaffolds intended for bone tissue ingrowths.      

Comparative studies on the fatty acid composition of moderately and extremely thermophilic bacteria

The fatty acids of three strains of extremely thermophilic bacteria and three strains of moderately thermophilic bacteria were examined by gas liquid chromatography. All the thermophiles contained straight, iso, and ante-iso branched fatty acids. Iso C_17∶0 acid was abundant in both the moderately thermophilic strains (10–33%) and the extremely thermophilic strains (50–61%). The pair of fatty acids iso C_15∶0 and iso C_17∶0 was the predominant pair in both the moderately (34–64%) and extremely (76–87%) thermophilic strains. The pair of fatty acids ante-iso C_15∶0 and ante-iso C_17∶0 was present in larger amount in moderately (25–34%) than in extremely (8.5–15%) thermophilic strains. No hydroxy cyclopropane, or unsaturated fatty acids were found. One extreme thermophile,Flavobacterium thermophilum HB-8 was grown at 6 different culture temperatures from 49–82 C, and the changes of its fatty acid composition were studied. The ratios of iso C_17∶0/iso C_15∶0 and ante-iso C_17∶0/ante-iso C_15∶0 were much greater at higher culture temperatures, indicating chain elongation.     

Methane and carbon dioxide emissions and nitrogen turnover during liquid manure storage

Animal slurry stored in-house and outside is a significant source of atmospheric methane (CH₄). The CH₄ source strength of stored slurry is greatly affected by temperature. To improve emission calculations on a global scale there is a need for knowledge about the relationship between production of CH₄ in slurry and temperature. In this study, the filling of slurry channels was reproduced in the laboratory by gradually filling 1 m-high PVC vessels during 9 days followed by incubation for 100–200 days. A preliminary test showed that little CH₄ was produced from animal slurry during 10 days of incubation at 20°C, if no inoculum (slurry incubated anaerobically at the test temperature for 1.5–2 months) was present. However, the addition of 7.6% inoculum supported an immediate production of CH₄. Vessels amended with inoculum and gradually filled with cattle or pig slurry were then incubated at 10, 15 and 20°C. Methane production from stored pig and cattle slurry was not significant at temperatures below 15°C, where CO₂ was the main product of decomposition processes. In contrast, the anaerobic production of CH₄ was high and significant relative to the production of CO₂ at 20°C. Peak emissions of CH₄ averaging 0.012 and 0.02 g C h⁻¹ kg⁻¹ volatile solids (VS) were reached within about 10 days at 10 and 15°C, respectively. At 20°C, the emission of CH₄ from pig slurry was about 0.01 g C h⁻¹ kg⁻¹ for 10 days, and thereafter emissions increased to about 0.10 g C h⁻¹ kg⁻¹ VS. For cattle slurry a peak emission of 0.08 g C h⁻¹ kg⁻¹ VS was measured after 180 days. Degradation of organic nitrogen (N) in cattle slurry was related to the reduction of organic material as reflected in CO₂ and CH₄ emission. The mineralization of organic N during storage represented 10–80% of organic N in cattle slurry, and 40–80% of the organic N in pig slurry.     

Catalytic process for decolorizing yellow plume

Yellow-colored exhaust gas streams from internal engines or gas turbines, frequently referred to as “yellow plume,” contain nitrogen dioxide (NO₂) at concentrations as low as 15 ppm. The process developed in this work for decolorizing the yellow plume is based on reduction of NO₂ to NO utilizing a combination of a Pt catalyst and a reducing agent. A stoichiometric excess of carbon monoxide, diesel oil, methanol or ethanol were used as reducing agents. Depending on the type of the reductant, the active temperature window of NO₂ reduction was varied with methanol and CO being active at lower temperatures and ethanol and diesel oil at higher temperatures. By changing the Pt loading of the catalysts the active temperature window of NO₂ reduction was also changed, higher loading Pt catalysts being active at lower temperatures. This scheme of NO₂ reduction process was verified in a pilot-scale test with the real exhaust gas from the gas turbine power plant, showing 96% of NO₂ reduction at the stack temperatures of 102–123 °C and at space velocities of 28,000–95,000 h⁻¹ with inherent CO in the exhaust gas as the reducing agent.     

Activated combustion of a silicon—carbon mixture in nitrogen and SHS of Si3N4—SiC composite ceramic powders and silicon carbide

It is established that Si₃N₄—SiC composites with a mass content of SiC 5–60% and a dominating content of the β-modification of silicon nitride can be produced by interaction of the components in the Si—C—N₂ system in the combustion regime. It is found that the fraction of α-Si₃N₄ can be increased by diluting the starting mixture with the end products, but this leads to the occurrence of a certain amount of unreacted silicon in the products. It is shown that the use of chemical activation allows one to perform a single-stage synthesis of Si₃N₄—SiC composites with any contents of the individual components (from 0 to 100%), including pure carbide silicon. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 5, pp. 56–62, September–October, 2006.     

The fatty acids ofEntomophthora coronata

The total lipids and fatty acid composition ofEntomophthora coronata were determined. The fungus was grown on a chemically defined medium and a chemically nondefined medium (Sabouraud dextrose yeast extract) for a period of 26 days. The organism contained from 16.2% to 44.6% total lipids depending upon the days of growth. The major fatty acids were 12∶0 (5.5–9.0%), 13∶0 (1.2–8.2%), 14∶0 (33.5–43.5%), 16∶0 (9.7–13.9%), 18∶1₉ (20.4–22.4%), and 18∶2_9,12 (3.5–10.5%). Lesser amounts of 15∶0, 16∶1, 16∶2, 17∶0, 18∶0, two other 18∶2 (both having conjugated double bonds), 18∶3_6,9,12, another 18∶3 (conjugated double bonds), 20∶3_8,11,14, 20∶4_5,8,11,14, another 20∶4 (conjugated double bonds), and 24∶1 acids were found. Trace amounts of 20∶0, 20∶1, 20∶2, 22∶0 and 24∶0 were also present. The relative percentage of most of the fatty acids did not vary appreciably with growth. However, 18∶2_9,12 and 20∶4_5,8,11,14 increased with age of the chemically defined culture. Peak E (18∶2, conjugated double bonds) increased and 13∶0 and 18∶3_6,9,12 decreased with age of the chemically nondefined culture. The fatty acids were predominately saturated (56.9–69.1%) and contained a high percentage of shorter chain fatty acids (C 12 to C 15). The fatty acids of the chemically defined culture were more unsaturated than the Sabouraud culture and the unsaturation increased with age of the culture.     

Composite WSi<Subscript>2</Subscript>–<Emphasis Type="Italic">Me</Emphasis><Superscript>V</Superscript>B<Subscript>2</Subscript> materials in W–Si–<Emphasis Type="Italic">Me</Emphasis><Superscript>V</Superscript>–B systems

Sections are constructed for WSi₂–Me ^VB₂ of the quaternary systems W–Si–(V, Nb, Ta)–B described by eutectic diagrams of state with T _eut (1940 ± 20), (1980 ± 20) and (2020 ± 30)°C and a boride content in the eutectics of 35, 20 and 15 mol.% respectively. Translated from Novye Ogneupory, No. 3, pp. 41 – 44, March 2009.     

Potential bile acid metabolites. 24. An efficient synthesis of carboxyl-linked glucosides and their chemical properties

A facile and efficient synthesis of the carboxyl-linked glucosides of bile acids is described. Direct esterification of unprotected bile acids with 2,3,4,6-tetra-O-benzyl-d-glucopyranose in pyridine in the presence of 2-chloro-1,3,5-trinitrobenzene as a coupling agent afforded a mixture of the α- and β-anomers (ca. 1∶3) of the 1-O-acyl-d-glucoside benzyl ethers of bile acids, which was separated effectively on a C₁₈ reversedphase chromatography column (isolated yields of α- and β-anomers are 4–9% and 12–19%, respectively). Subsequent hydrogenolysis of the α- and β-acyl glucoside benzyl ethers on a 10% Pd−C catalyst in acetic acid/methanol/EtOAc (1∶2∶2, by vol) at 35°C under atmospheric pressure gave the corresponding free esters in good yields (79–89%). Chemical specificities such as facile hydrolysis and transesterification of the acyl glucosides in various solvents were also discussed.     

Pd–Ru/C as the electrocatalyst for hydrogen peroxide reduction

Pd–Ru, Pd and Ru nanoparticles supported on Vulcan XC-72 carbon were prepared by chemical reduction of PdCl₂ and/or RuCl₃ in aqueous solution using NaBH₄ as the reducing agent. Transmission electron microscopy measurements showed that Pd–Ru particles were uniformly dispersed on carbon. The particle size of Pd–Ru is around 5–9 nm. X-ray diffraction analysis indicated that Ru formed alloy with Pd in Pd–Ru/C catalyst. The electroreduction of hydrogen peroxide on Pd–Ru/C, Pd/C and Ru/C in H₂SO₄ solution was examined by linear sweep voltammetry and chronoamperometry measurements. Results revealed that Pd–Ru/C catalyst exhibited higher electrocatalytic activity for hydrogen peroxide reduction than Pd/C and Ru/C. All the catalysts showed good stability for hydrogen peroxide electroreduction in H₂SO₄ electrolyte.     

Synthesis,characterization and catalytic properties of mesoporous Al-FSM-16 materials

Al-substituted mesoporous FSM-16 materials with different SiO₂/Al₂O₃ (28–452) ratios have been synthesized by intercalating kanemite using cetyltrimethylammonium bromide (CTMABr) as the intercalating agent and sodium aluminate as the aluminium source, and characterized by different physico-chemical characterization techniques. The XRD measurements revealed a slightly disordered hexagonal packing of channels in the Al-FSM-16 samples. The thermal stability of Al-FSM-16 samples was confirmed by DTA analysis, where no structural changes were observed in the temperature range of 600–900°C. No significant changes were observed in the morphology of kanemite and the Al-FSM-16 sample obtained from kanemite as revealed by the SEM analysis. This result clearly indicated that the Al-FSM-16 sample is formed via a folded sheet mechanism. Moreover, TEM measurements confirmed the presence of a slightly disordered hexagonal array of channels in Al-FSM-16 in agreement with the XRD results. The BET surface areas (638–788 m² g⁻¹) and pore volumes (0.57–0.87 cm³ g⁻¹) were indicative of the high porosity of the Al-FSM-16 samples. The Al-FSM-16 (SiO₂/Al₂O₃ = 49) sample exhibited excellent hydrothermal stability at 150°C. The Al-FSM-16 samples were found to catalyze the isomerization of m-xylene to p- and o-xylenes.     

Electrodeposition of zinc–iron alloy from an alkaline bath in the presence of sorbitol

The chronopotentiometric technique was used to analyze the electrodeposition of Fe–Zn film on a Pt electrode. Three different Fe³⁺/Zn²⁺ molar ratios, Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.%, were used in a solution containing sorbitol as the Fe³⁺-complexing agent, with a total concentration of the two cations of 0.20 M. Coloration of Fe–Zn films were light gray, dull dark gray and bright graphite, depending on the Fe³⁺/Zn²⁺ ratios in the deposition bath. The highest stripping to deposition charge density ratio was 47.5%, at 15 mA cm⁻² in the Fe26.8 wt.%–Zn73.2 wt.% bath. Energy dispersive spectroscopy indicated that the codeposition type of Fe and Zn in the Fe26.8 wt.%–Zn73.2 wt.% and Fe46 wt.%–Zn54 wt.% baths was normal at all j_d tested, while in the Fe66.6 wt.%–Zn33.4 wt.% bath there was a transitional current density from normal to equilibrium codeposition at 50 mA cm⁻². Scanning electron microscopy showed that Fe–Zn films of high quality were obtained from the Fe66.6 wt.%–Zn33.4 wt.% and Fe26.8 wt.%–Zn73.2 wt.% baths, since the films were smooth. X-ray analysis of the Zn–Fe films obtained at 15, 25 and 50 mA cm⁻², in the Fe26.8 wt.%–Zn73.2 wt.%, Fe46 wt.%–Zn54 wt.% and Fe66.6 wt.%–Zn33.4 wt.% plating baths, suggested the occurrence, in general, of a mixture of Fe₁₁Zn₄₀, Fe₄Zn₉, βFe, αFe, Fe₂O₃, Zn and PtZn alloys in the deposit.     

Study on synthesis of novel soluble aromatic polyamides with pendant cyano groups

A series of novel soluble aromatic polyamides with pendant cyano groups were synthesized by low temperature polycondensation of aromatic diamines with a new monomer 2,6-bis(4-chloroformylphenoxy)benzonitrile (ClPOBN) in the presence of N,N-dimethylacetamide (DMAC) as the solvent and tertiary amines as the absorbent of HCl. The properties and structures of obtained polymers were characterized by means of FTIR, TG, and elemental analysis. Structures of prepared polymers are as expected. TG studies show that the polymers had excellent thermal stability as measured by 5% weight loss temperatures in nitrogen (409–438 °C).They are soluble in aprotic polar organic solvents such as N-methyl pyrrolidone (NMP), dimethyl sulphoxide (DMSO) and N,N-dimethylformamides (DMF) and are swelled in common solvents, such as CHCl_3, ethylene dichloride (DCE), CH₂Cl₂, tetrahydrofuran (THF), etc. Their thin films which cast from DMF had tensile strength of 79–93 MPa, Young’s moduli of 1.7–2.6 GP, elongation at break of 9–15%, indicating they are strong in mechanical properties.     

Study of compaction of high-alumina ceramoconcretes. 4. The effect of firing temperature on the properties of a matrix system and on ceramoconcrete

The effect of firing temperature on variations of the linear sizes, open porosity, apparent density, and mechanical strength both of the matrix system and of industrially produced ceramoconcretes based on a high-concentrated ceramic binding suspension (HCBS) containing 90% bauxite and 10% quartz glass is investigated. Experimental materials based on HCBS of density 2.62–2.77 g/cm³ (C _V = 0.65–0.70) with the content of particles of size below 1 μm varying from 4 to 15% encompass the whole spectrum of quantitative parameters of initial suspensions that are prescribed or possible in industrial production. Samples based on a bauxite HCBS with 10% highly disperse quartz glass, as well as samples of ceramoconcrete consisting of the same HCBS (35%) and a bauxite-based refractory filler, were obtained by compaction, heat-treated and fired in the interval of 100–1420°C. Perceptible sintering accompanied by shrinkage and significant strengthening of the material is registered in the interval of 1000–1250°C. A certain expansion and loosening of the material is observed in the range of 1300–1400°C due to intense mullite formation. Significant sintering and strengthening is achieved by protracted firing at 1400–1420°C. Comparative analysis of the properties of the matrix system and ceramoconcrete has established that, other terms being equal, σ_comp of ceramoconcrete amounts to 40–50% σ_comp of the matrix system. __________ Translated from Novye Ogneupory, No. 10, pp. 29–37, October, 2006.     

Preparation of microporous silica membranes for gas separation

Microporous silica membranes for hydrogen separation were prepared on a γ-alumina coated α-alumina tube by sol-gel method. The reactants of sol-gel chemistry were tetraethoxysilane (TEOS) and methacryloxypropyl-trimethoxysilane (MOTMS). The silane coupling agent, MOTMS, was added as a template in order to control the pore structure to the silicon alkoxide, TEOS. In particular, the microporous membranes were prepared by changing the molar ratio of MOTMS with respect to other substances, and their pore characteristics were analyzed. Then, the effects of thermal treatment on the micropore structure of the resulting silica membranes were investigated. The pore size of the silica membrane prepared after calcination at 400–700 ‡C was in the range of 0.6–0.7 nm. In addition, permeation rates through the membranes were measured in the range of 100–300 dgC using H₂, CO₂, N₂, CH₄, C₂H₆, C₃H₆ and SF₆. The membrane calcined at 600 ‡C showed a H₂ permeance of 2×10^-7-7×10^-7 molm^-2s^-1Pa^-1 at permeation temperature 300 ‡C, and the separation factors for equimolar gas mixtures were 11 and 36 for a H₂/CO₂ mixture and 54 and 132 for a H₂/CH₄ mixture at permeation temperatures of 100 ‡C and 300 ‡C, respectively.     

Synthesis of ethylene and propylene on a SAPO-34 silica—alumina—phosphate catalyst

A process for the preparation of ethylene and propylene from methanol on a microporous silica—alumina—phosphate SAPO-34 catalyst is described. The influence of the temperature and the nature and concentration of the diluting agent on the catalyst activity, its selectivity with respect to C₂₌-C₄₌ olefins, and ability to be regenerated were studied. The SAPO-34 catalyst was shown to be highly effective in the selectivity of ethylene and propylene formation; the total yield of C₂₌-C₄₌ olefins at 350–450°C was 77–84% and methanol conversion was up to 96–99%. In the conversion of methanol under helium at 450°C, the yield of ethylene (∼36%) was higher than at 375°C (∼29%), while the yield of propylene (∼30%) was lower (∼38%). The use of water and helium vapors as a diluent increased the yield of ethylene to ∼36% at 375°C and to ∼50% at 450°C. In the conversion of methanol at 450°C in water vapors without helium, the yield of ethylene reached ∼44–49% and the yield of propylene was 24–29%. The C₃₌ to C₂₌ ratio in the process varied from ∼0.5 to 1.5. The high efficiency of the SAPO-34 catalyst is the consequence of the microporous structure of zeolite and the high content of acid centers of medium strength. In the course of methanol conversion, the catalyst was deactivated due to coking. After regeneration with air at 550°C, the catalyst activity was completely restored, while the crystal structure and the acid properties did not change. The activity of the catalyst in a cycle is prolonged if water vapors are used as a diluent and the catalyst is processed at a high temperature with vapors. The industrial processes for the production of ethylene and propylene from nonpetroleum materials are not used in Russia. The results of this study are comparable to the data obtained from the UOP/Norsk Hydro process on the SAPO-34 catalyst. The catalyst can be recommended for further trials on an FCC type pilot plant with a moving catalyst bed.     

Conversion of oils to monoglycerides by glycerolysis in supercritical carbon dioxide media

Glycerolysis of soybean oil was conducted in a supercritical carbon dioxide (SC-CO₂) atmosphere to produce monoglycerides (MG) in a stirred autoclave at 150–250°C, over a pressure range of 20.7–62.1 MPa, at glycerol/oil molar ratios between 15–25, and water concentrations of 0–8% (wt% of glycerol). MG, di-, triglyceride, and free fatty acid (FFA) composition of the reaction mixture as a function of time was analyzed by supercritical fluid chromatography. Glycerolysis did not occur at 150°C but proceeded to a limited extent at 200°C within 4 h reaction time; however, it did proceed rapidly at 250°C. At 250°C, MG formation decreased significantly (P<0.05) with pressure and increased with glycerol/oil ratio and water concentration. A maximum MG content of 49.2% was achieved at 250°C, 20.7 MPa, a glycerol/oil ratio of 25 and 4% water after 4 h. These conditions also resulted in the formation of 14% FFA. Conversions of other oils (peanut, corn, canola, and cottonseed) were also attempted. Soybean and cottonseed oil yielded the highest and lowest conversion to MG, respectively. Conducting this industrially important reaction in SC-CO₂ atmosphere offered numerous advantages, compared to conventional alkalicatalyzed glycerolysis, including elimination of the alkali catalyst, production of a lighter color and less odor, and ease of separation of the CO₂ from the reaction products.     

Thermophilic phospholipase A2 in the cytosolic fraction from the archaeon Pyrococcus horikoshii

Hyperthermophilic archaeon Pyrococcus horikoshii produced phospholipase A² in a cytosolic fraction. The enzyme displayed optimal activity at 90°C and pH 7 and preferentially hydrolyzed sn-2 fatty acids in the following order: linoleoyl> oleoyl>arachidoyl phosphatidylcholine. Phospholipase A₂ had similar activities toward l-α-1-palmitoyl-2-arachidoyl derivatives of phosphatidylcholine and phosphatidylethanolamine. Phospholipase A₂ activity was unaffected by the addition of 0.0001–1 mM calcium, but was inhibited slightly by the addition of 2–10 mM calcium. The activity was enhanced more than 5–18-fold in the presence of 3–20% (vol/vol) glycerol. The activity was unaffected by the addition of 1–5 mM EDTA or 0.01–20 mM dithiothreitol. A caldarchaetidic acid derivative having a molecular weight of 1544 disappeared upon incubation of the cytosolic fraction with total lipid. The phospholipase A₂ was difficult to purify by general chromatography because it existed as an aggregate. Electrophoresis was carried out using 10–15% polyacrylamide gels containing sodium dodecyl sulfate (SDS-PAGE). No activity of phospholipase A₂ activity was observed in the absence of proteins less than 19 kD in size, as fractionated by SDS-PAGE. Portions of this article were presented at the Biocatalysis Symposium at the 91st Annual Meeting and Expo of the American Oil Chemists’ Society in San Diego, CA, April, 2000.     

Synthesis and characterization of zeolite mazzite analogue in Na<Subscript>2</Subscript>O–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>–Piperazine–H<Subscript>2</Subscript>O

Zeolite Mazzite (MAZ) analogue was synthesized directly using piperazine as a structure directing agent. The reactive gel composition used was (5.0–7.0) piperazine:(6.0–7.0) Na₂O:Al₂O₃:20.0SiO₂:400H₂O. Using this composition, the reaction time was shortened greatly to 4 days and the crystallization time was reduced as well. The DTA data showed that piperazine, in as-synthesized zeolite omega decomposed easily. The decomposition of the piperazine occurred at 400–480°C. NH₃-TPD analysis proved that zeolite H-omega from piperazine had strong surface acidity with ammonia desorption temperature up to 590°C.     

Synthesis,Optical Properties,and Photoluminescence of Organometallic Acetylide Polymers of Platinum Functionalized with Si and Ge-Bridged Bis(3,6-Diethynyl-9-butylcarbazole)

A series of light-emitting group 14 element-containing organometallic platinum polyynes of the form trans-[–Pt(PBu₃)₂C≡ CArC≡ C(ER₂)C≡ CArC≡ C–] _n (Ar = 9-butylcarbazole-3,6-diyl, ER₂ = SiMe₂, SiPh₂, GeMe₂, GePh₂) were synthesized and spectroscopically characterized. The solution properties and regiochemical structures of this new structural class of organosilicon- and organogermanium-based metallopolyynes were studied by IR and NMR (¹H, ¹³C, ²⁹Si, and ³¹P) spectroscopies. The optical absorption and photoluminescence spectra of these metallopolymers were examined and compared with their well-defined dinuclear model complexes trans-[Pt(Ph)(PEt₃)₂C≡ CArC≡ C(ER₂)C≡ CArC≡ CPt(Ph)(PEt₃)₂]. The influence of the heavy platinum atom and the group 14 silyl or germyl structural unit possessing different side group substituents on the thermal and phosphorescence properties were investigated in detail. We have also established the goal for studying the evolution of the lowest singlet and triplet excited states with the nature of ER₂ unit in these metallopolymers. The present work indicates that the phosphorescence emission efficiency harnessed through the heavy-atom effect of platinum in the main chain changes significantly with the identity of ER₂ in the general orders GeR₂ > SiR₂ (R = Me, Ph) and EMe₂ > EPh₂ (E = Si, Ge). Dedicated to Professor Ian Manners in recognition of his outstanding contribution to inorganic and organometallic polymers.