No abstract

The reaction [Pt3(M3-CO)(ji-dppm)3]2+, 1, with RNC (R = f-Bu, cyclohexyl or o-xylyl) gives an intermediate characterized as [Pt3(ji-CO)(CNR)(/i-dppm)3]2+, 2, which then isomerizes to the stable complex [Pt3(/x3-CO)-(CNR)(ju-dppm)3]2+, 3. When R = o-xylyl, reaction of 3 with more RNC gives an intermediate [Pt3(/i-CO)-(CNR)2(M-dppm)3]2+, 4, which then loses CO to give [Pt3(CNR)2(/i-dppm)3]2+, 5, the first example of a Pt3 cluster complex having no bridging atom. The cluster 5 has been characterized by an X-ray structure determination. [The solvated salt crystallizes in the monoclinic space group P2t, cell dimensions a = 17.639(2) A, b = 19.704(3) A, c = 14.5444(12) A, and /3 = 101.99(2)°w ith Z = 2. Full matrix least-squares refinement on F2 of 558 variables converged at a conventional R factor of 0.0393 for 6334 data with I > 2a(l).] The two xylyl isocyanide ligands are trani-bonded to Pt(l), and as a result the Pt(2)-Pt(3) distance of 2.548(1) A is significantly shorter than the mean of the two distances to Pt(l), 2.649(1) A. Complexes 3 and 5 are fluxional; the RNC ligands can migrate easily around the face of the Pt3 triangle. The diisocyanides 1,4-C^NC6R4N^C, R = H or Me, react with 1 to give polymeric complexes j[Pt3(/u-l,4-C=NC6R4N=C)(/i-dppm)3][PF6]2}?!, 7, in which the diisocyanide bridges between Pt3 cluster units. The local stereochemistry at platinum is similar to that in 5, and the fluxionality appears even easier in 7 than in 5. Evidence is presented for diisocyanide complexes analogous to 2 and 3, namely [Pt3(^t-CO)(CNC6H4NC)(M-dppm)3]2+ and [{Pt3(>i3-CO)(/Li-dppm)3j2(/u-CNC6H4NC)]4+, 8. Calculations of the EHMO type on model complexes give insight into the factors which influence the preferred binding mode (terminal or triply bridging) of the isocyanide at the Pt3 triangle.

Nano-delivery systems for the active ingredients of pesticides can improve the utilization rates of pesticides and prolong their control effects. This is due to the nanocarrier envelope and controlled release function. However, particles containing active ingredients in controlled release pesticide formulations are generally large and have wide size distributions. There have been limited studies about the effect of particle size on the controlled release properties and biological activities of pesticide delivery systems. In the current study, avermectin (Av) nano-delivery systems were constructed with different particle sizes and their performances were evaluated. The Av release rate in the nano-delivery system could be effectively controlled by changing the particle size. The biological activity increased with decreasing particle size. These results suggest that Av nano-delivery systems can significantly improve the controllable release, photostability, and biological activity, which will improve efficiency and reduce pesticide residues.

The real time FT‐IR (RT/FT‐IR) technique has been recognized as a very vital tool to quantitatively study the curing parameters such as the effects of initiator (or catalyst) type and concentration, accelerator, stabilizer, irradiation wavelength, temperature, and curing environments. Herein, our results in studies of photoinduced polymerizations for adhesive and coating applications are reported. The photoinduced polymerizations studied included anionic and hydrosilation (a polyaddition polymerization) reactions. In photoinduced anionic polymerization our studies for ethyl cyanoacrylate polymerization are described. The effect of the concentration of photoinitiator and inhibitor on the ethyl cyanoacrylate polymerization kinetic rate will be discussed. In photoinduced catalytic hydrosilation reaction studies, the effects of the catalyst concentration and staging irradiation are disclosed. The hydrosilation reaction was monitored using a SiH silicone hydride stretching band located at 2169 cm−1. The cyanoacrylate polymerization was monitored using the CC stretching band occurring at 1617 cm−1. The hydrosilation conversion was completed with an appropriate formulation. For monofunctional cyanoacrylate monomer, the photoinduced conversion to straight chain polymer was approximately 85% for a 60 s period. The intrinsic rates of the reactions were calculated for kinetic comparisons. For very fast cyanoacrylate polymerization studies, new FT‐IR kinetic software was used to collect 204 spectra/min. Some detailed experimental techniques and polymerization reaction mechanisms are also discussed. © 1993 John Wiley & Sons, Inc.