Cycloaddition of carbonyl compounds and alkynes to (di)silenes and (di)germenes: reactivity and mechanism.

The chemistry of silenes, germenes, disilenes and digermenes has been extensively studied over the last 35 years; however, not much is known about the mechanisms of many of the fundamental reactions of this class of compounds, including cycloadditions. This review describes the current understanding of the reaction pathways for the cycloaddition of carbonyl compounds and alkynes to (di)tetrelenes. The question of whether or not the cycloaddition reactions of (di)tetrelenes follow the Woodward-Hoffman rules, established for alkenes and alkynes, is addressed.

Magnetic Hydrogels from Alkyne/Cobalt Carbonyl-Functionalized ABA Triblock Copolymers.

A series of alkyne-functionalized poly(4-(phenylethynyl)styrene)-block-poly(ethylene oxide)-block-poly(4-(phenylethynyl)styrene) (PPES-b-PEO-b-PPES) ABA triblock copolymers was synthesized by reversible addition-fragmentation chain transfer (RAFT) polymerization. PESn[Co2(CO)6]x-EO800-PESn[Co2(CO)6]x ABA triblock copolymer/cobalt adducts (10-67 wt % PEO) were subsequently prepared by reaction of the alkyne-functionalized PPES block with Co2(CO)8 and their phase behavior was studied by TEM. Heating triblock copolymer/cobalt carbonyl adducts at 120 °C led to cross-linking of the PPES/Co domains and the formation of magnetic cobalt nanoparticles within the PPES/Co domains. Magnetic hydrogels could be prepared by swelling the PEO domains of the cross-linked materials with water. Swelling tests, rheological studies and actuation tests demonstrated that the water capacity and modulus of the hydrogels were dependent upon the composition of the block copolymer precursors.

Control of the average spacing between aligned gold nanoparticles by varying the FIB dose.

This work presents a new method to align gold nanoparticles (Au NPs), based on three well-known techniques: self-assembled monolayer (SAM) formation, focused ion beam (FIB) lithography, and organo-metallic chemical vapour deposition (OMCVD). Silicon substrates are coated with CH(3)-terminated silane SAMs as resists. A fine beam of Ga(+) ions, applying different doses, damages/removes these SAMs to correspondingly form a pattern containing sets of lines. Atomic force microscopy (AFM) and time-of-flight secondary ion mass spectroscopy (ToF-SIMS) are used to study the SAM removal process. The FIB nano-lithographically patterned SAMs are re-filled with an SH-terminated silane SAM. An OMCVD process is carried out to grow Au NPs onto the SH-groups in the lines. The average spacing between the Au NPs is demonstrated to be controlled by varying the FIB dose. Scanning electron microscopy (SEM) image analysis indicates that the average spacing decreases exponentially with increasing the dose, up to a predefined threshold. In addition, the formation of OMCVD Au NPs spacing and its dose-dependence in the absence of the SH-terminated SAMs is studied.

Addition polymerization of 1,1-dimesitylneopentylgermene: synthesis of a polygermene.

A new polymer with an alternating germanium-carbon backbone has been synthesized from 1,1-dimesitylneopentylgermene via addition polymerization using an anionic initiator.

Addition of alkynes to digermynes: experimental insight into the reaction pathway.

The addition of an alkynyl cyclopropyl mechanistic probe to a digermyne did not lead to any ring-opened rearrangement products indicating that the reaction pathway does not involve any vinylic radicals or cations and providing experimental insight into the addition of alkynes to digermynes.

Facile synthesis of luminescent benzo-1,2-dihydrophosphinines from a phosphaalkene.

The addition of 4-trifluoromethyl-1-ethynylbenzene, phenylacetylene, or 4-ethynylanisole to P-mesityldiphenylmethylenephosphine, 1, produced photoluminescent 1,2-dihydrophosphinines 4a-c, respectively, in quantitative yield via a [4 + 2] cycloaddition. Limited reactivity was observed between 1 and non-aromatic alkynes. P-[Bis(trimethylsilyl)amino][(trimethylsilyl)methylene]phosphine, 2, and P-mesityl[(t-butyl)(trimethylsiloxy)methylene]phosphine, 3, showed extremely limited reactivity with all alkynes examined. The reactivity of phosphaalkenes toward terminal alkynes is compared to that of alkenes as well as silenes and germenes.

The addition of amides to group 14 (di)-metallenes.

The addition of a series of primary and secondary amides to the group 14 (di)metallenes Mes(2)Si=SiMes(2), Mes(2)Ge=GeMes(2) and (Me(3)Si)(2)Si=C(OSiMe(3))R, where R = t-Bu or R = 1-Ad, was examined. In general, the addition of primary and N-methyl amides gave amide adducts whereas the addition of N-phenyl amides gave imidate adducts. The regiochemistry of the additions was highly dependent upon the substituent bonded to the amide nitrogen. We propose that the formation of the adducts proceeds by way of a zwitterionic intermediate. The reactivity of tetramesityldigermene towards amides is used to predict the structure of the amide adducts formed on the Ge(100)-2 × 1 surface.

Binary Mixtures of SH- and CH3-Terminated Self-Assembled Monolayers to Control the Average Spacing Between Aligned Gold Nanoparticles.

This paper presents a method to control the average spacing between organometallic chemical vapor deposition (OMCVD) grown gold nanoparticles (Au NPs) in a line. Focused ion beam patterned CH3-terminated self-assembled monolayers are refilled systematically with different mixtures of SH- and CH3-terminated silanes. The average spacing between OMCVD Au NPs is demonstrated systematically to decrease by increasing the v/v% ratio of the thiols in the binary silane mixtures with SH- and CH3-terminated groups.