Main Group Chemistry

The persistent phosphinyl radical •P[CH(SiMe $_{3})_{2}$ ] $_{2}$ reacts readily with elemental sulfur, selenium or tellurium to afford the chalcogen-bridged derivatives of formula R $_{2}$ P-X-PR $_{2}$ [R= (Me $_{3}$ Si) $_{2}$ CH; X= S, Se, Te], each of which was characterized by single-crystal X-ray diffraction.

An unprecedented class of multichromic single crystals has been investigated after their initial discovery almost 15~years ago in industry. Single crystals have been prepared that are crystallographically identical, yet may be grown colorless, yellow, or green from crystal to crystal, or surprisingly, multicolored within the same crystal at all viewing angles, where one would expect that only a single color would exist. The system examined consisted of Me $_{2}$ GaCl complexed with 1,4-bis(2,6-diisopropylphenyl)-1,4-diazabutadiene in varying ratios. The work described is primarily geared towards understanding the factors leading to the multichromic nature of the complexes. Our results indicate that the most plausible explanation for the yellow/green mixed crystals is that the yellow crystals are contaminated with small amounts of an intensely-colored blue byproduct. In crystal regions where both the yellow and blue compounds are found, the crystals appear dark green. Identification of the blue byproduct was confirmed by X-ray diffraction.

Reactions of lithium salts of the bulky guanidinate ligands, [ArNC(NR $_{2}$ )NAr] $^{-}$ (R=C $_{6}$ H $_{11}$ (Giso $^{-}$ ) or Pr $^{i}$ (Priso $^{-}$ )) with BBr $_{3}$ have given the neutral complexes [Br $_{2}$ B(Giso)] and [Br $_{2}$ B(Priso)]. The reaction of [Br $_{2}$ B(Giso)] with GaBr $_{3}$ led to bromide abstraction and the formation of the ion separate salt, [BrB(Giso)][GaBr $_{4}$ ]. All compounds have been spectroscopically and crystallographically characterized.

The group 13 monoalkoxometallanes [Me $_{2}$ Ga(OC(CH $_{3})_{2}$ CH $_{2}$ OMe)] $_{2}$ (1) and [Me $_{2}$ In(OCH(CH $_{3}$ )CH $_{2}$ OMe)] $_{2}$ (2), incorporating donor functionalised alkoxides, were synthesised from the reaction of GaMe $_{3}$ or InMe $_{3}$ with ROH (R=C(CH $_{3})_{2}$ CH $_{2}$ OMe (1); R=CH(CH $_{3}$ )CH $_{2}$ OMe (2)) in toluene. X-ray crystallography showed that both compounds adopt dimeric structures with a planar M $_{2}$ O $_{2}$ ring, and each group 13 atom is coordinated in a distorted trigonal bipyramidal geometry. The AACVD reaction of GaMe $_{3}$ and ROH (R =C(CH $_{3})_{2}$ CH $_{2}$ OMe, CH $_{2}$ CH $_{2}$ OMe, CH $_{2}$ CH $_{2}$ NMe $_{2}$ ) resulted in the formation of thin films of Ga $_{2}$ O $_{3}$ on glass substrates at 450°C. The gallium oxide films were analyzed by scanning electron microscopy, X-ray powder diffraction, energy dispersive analysis of X-rays, wavelength dispersive analysis of X-rays and X-ray photoelectron spectroscopy. This CVD technique offers a rapid, convenient route to Ga $_{2}$ O $_{3}$ , which involves the in situ formation of dimethylgallium alkoxides, of the type [Me $_{2}$ Ga(μ-OR)] $_{2}$ similar to compound 1.

Reaction of diethylacetylene dicarboxylate (EtO $_{2}$ CC≡CCO $_{2}$ Et) with trans-(N $_{3})_{2}$ Ru(PMe $_{3}$ ) $_{4}$ in THF at 25°C gave the bis-triazolato complex (PMe $_{3}$ ) $_{3}$ Ru[N $_{3}$ C $_{2}$ -(CO $_{2}$ Et) $_{2}$ ] $_{2}$ (1) in 41% yield. Reaction of trans-(N $_{3}$ ) $_{2}$ Ru(PMe $_{3}$ ) $_{4}$ with phenylacetylene in toluene at 110 $^{\circ}$ C gave the mixed azide acetylide complex cis-(PMe $_{3}$ ) $_{4}$ Ru(N $_{3})$ (C≡CC $_{6}$ H $_{5})$ (2) (51%. The analogous alkynyl acetylide cis-(PMe $_{3}$ ) $_{4}$ Ru(N $_{3})$ (C≡CC $_{6}$ H $_{4}$ C≡ CH) (3) is formed from 1,4-diethynylbenzene in 72% yield. Reaction of trans-(N $_{3}$ ) $_{2}$ Ru(PMe $_{3}$ ) $_{4}$ with HC≡CSiMe $_{3}$ in CH $_{2}$ Cl $_{2}$ at 41°C gave trans-(PMe $_{3}$ ) $_{4}$ Ru[C≡ C(SiMe $_{3})$ ] $_{2}$ (4) (37%. A similar reaction in toluene at 110°C gave the dinuclear azide [(PMe $_{3}$ ) $_{3}$ (N $_{3})$ Ru] $_{2}$ (μ $_{1,3}-$ N $_{3}$ ) $_{2}$ (5) (30% 3,5-bis(trifluoromethyl)pyrazole (PzH) with trans-(N $_{3}$ ) $_{2}$ Ru(PMe $_{3}$ ) $_{4}$ in refluxing toluene gave [(PMe $_{3}$ ) $_{3}$ Ru] $_{2}$ (μ $_{1}$ -N $_{3}$ ) $_{3}$ ][Pz· 2PzH (6). Complexes 1–6 have been characterized spectroscopically as well as by single crystal X-ray diffraction studies.

The syntheses and first structural characterization of terminal (diisopropylamino)borylene complexes are reported. The $^{11}$ B NMR chemical shifts for these novel systems (δ $ _{B}$ 93.8 and 90.2 for [Cp'Fe(CO) $_{2}$ (BN $^{i}$ Pr $_{2}$ )][BAr $^{f}_{4}$ ], 3, and [CpRu(CO) $_{2}$ (BN $^{i}$ Pr $_{2}$ )][BAr $^{f}_{4}$ ], 4, respectively) are ca. 40 ppm downfield of those measured for the boryl precursor complexes, consistent with observations for related trimethylsilyl and cyclohexylamino substituted compounds. Structurally, the linearity of the M – B – N fragment in each case and the marked shortening of the M – B bonds (cf. the single bonds found in boryl complexes CpFe(CO) $_{2}$ (BN $^{i}$ Pr $_{2}$ )Cl, 1b, and CpRu(CO) $_{2}$ (BN $^{i}$ Pr $_{2}$ )Cl, 2) reflect the fact that the M – B bond order in borylene systems 3 and 4 is between one and two.

The bulky m-terphenyl benzyl alcohols ArCH $_{2}$ OH (Ar=2,4,6-triphenylphenyl) 1 and Ar*CH $_{2}$ OH (Ar*= C $_{6}$ H $_{3}$ -2,6-Mes $_{2}$ , Mes=2,4,6-trimethylphenyl) 2 were synthesized via treatment of the corresponding aryllithium salt with DMF followed by NaBH $_{4}$ reduction. A zinc complex of 1 was prepared and contains a rather uncommon trigonal planar geometry for a zinc organometallic compound. All compounds were characterized spectroscopically and were studied by single crystal X-ray diffraction techniques.

Reaction of 4-(lithiophenyl)dimesitylborane with xanthone followed by reaction of the resulting alcohol with HBF $_{4}$ affords the cation 1-dimesitylboron-4-(9-xanthylium)-phenylene [1] $^{+}$ as a tetrafluoroborate salt. This salt has been fully characterized and its crystal structure determined. Cation [1] $^{+}$ can be reduced to produce a persistent radical that has been studied by EPR and whose reaction with dioxygen affords a peroxo derivative.

In this micro-review, the "click" synthesis and functions of organo-silicon dendrimers are summarized. Hydrosilylation of polyallyl dendrimer cores using chlomethyldimethylsilane followed by substitution of chloride by azide and "click" reactions with terminal alkynes provided ferrocenyl and olefin terminated dendrimers. Coordination of the triazolyl dendrimers by metal ions followed by reduction gives access to organo-silicon dendrimer-stabilized palladium and gold nanoparticles.

According to cyclic voltammetry, the stable 1,3-diborata-2,4-diphosphonio-cyclobutane-1,3-diyl 1 can be readily oxidized. The oxidation is irreversible, preventing the characterization of the corresponding radical cation, whose structure has been investigated by DFT calculations. Diradicaloid 1 is oxidized by silver salts AgX (X=Cl, OTf), to give silver mirror along with the bis(chloride) and bis(trifluoromethane sulfonate) adducts 2 and 3.

The synthesis of the low valent In-In bonded indium amide dimer [(In{N(Dipp)SiMe $_{3}$ }) $_{2}$ (μ $ _{2}$ -η $ ^{1}$ :η $ ^{1}$ C $_{5}$ H $_{5}$ )(μ $ _{2}$ -η $^{1}$ : η $ ^{2 }$ C $_{5}$ H $_{5}$ )] (Dipp=2,6 diisopropylphenyl) (1) is reported. The complex was synthesized by the addition of [LiN(Dipp) (SiMe $_{3})$ ] $_{2}$ to In(η $ ^{5}$ >-C $_{5}$ H $_{5}$ ), which led to (1) apparently via a disproportionation reaction. The structure of (1) features a unique bridging of the In-In bond via two cyclopentadienyl ligands and has a short metal-metal distance of 2.7146(3)Å. Complex (1) is a unique example of a low valent indium amido species stabilized by monodentate amide ligands.

The conjugate acids of benzo-2,1,3-selena- and benzo-2,1,3-telluradiazole are the simplest members of the family of N-substituted chalcogenadiazolium cations. Four crystalline phases that in principle contain such molecular ions were isolated and structurally characterized: C $_{6}$ H $_{4}$ (NH) $_{2}$ TeCl $_{2}$ , [C $_{6}$ H $_{5}$ (NH)] $_{3}$ [C $_{6}$ H $_{4}$ (NH) $_{2}$ TeCl $_{4}$ ]Cl, C $_{6}$ H $_{4}$ N(NH)SeCl and C $_{6}$ H $_{4}$ N(NH)SeCl · 1/2 [H $_{5}$ O $_{2}$ ]Cl. The stepwise protonation of benzo-2,1,3-teluradiazole in DMSO solution was monitored by $^{1}$ H NMR, providing an estimate of the basicity of this molecule relative to pyridine. While most of the structures are consistent with the chalcogen in oxidation state II, the molecular geometry of C $_{6}$ H $_{4}$ (NH) $_{2}$ TeCl $_{4}$ is suggestive of oxidation state IV. The relationship between the two structural types was examined with DFT calculations.

Phenylenediamines are shown to form benzodiazaborolanes upon reaction with borazine, essentially extracting the B-H bonds. This surrogate for partially dehydrogenated ammonia borane provides useful insight into potential regeneration strategies for ammonia borane spent fuel.

The treatment of the soluble indium(I) salt [In([18]crown-6)][O $_{3}$ SCF $_{3}$ ] with several potassium salts of the form [K][A] results in the release of the indium(I) cation from the crown ether and the production of salts of [K([18]crown-6)] $^{+}$ and uncomplexed [In] $^{+}$ .

An account of recent research on the syntheses, structures, properties, and catalytic applications of the nanoparticles/composites formed between nanostructured and supported polyhedral carborane cages and metals is given. The development of other nanomaterials, such as dendrimers is also briefly discussed.

A variety of Schiff base ligands have been synthesized in an effort to study the coordination chemistry of these ligands when reacted with various metal salts. By varying the structural features of the ligand as well as the synthetic route used to make the corresponding metal complexes, a number of different structural motifs have been observed. Schiff base ligands were chosen due to their ease of synthesis as well as their ability to bind a variety of metal salts. These complexes serve as model systems for and precursors to monomers for the preparation of conducting metallopolymers. Further functionalization of the Schiff base ligand with bithiophene end groups has resulted in electropolymerizable monomers. When polymerized these monomers give conducting metallopolymers which can then be used for a variety of applications. The products were characterized by multinuclear NMR, UV-Vis, and IR spectroscopy, and mass spectrometry. Solid-state structures were determined by single crystal X-ray diffraction studies. Electropolymerization yielded novel conducting polymers with embedded metals.

Mixtures of boric anhydride (B $_{2}$ O $_{3}$ ) or orthoboric acid (B(OH) $_{3}$ ) with MgO in 1:1, 1:10 and 1:100 ratios were heated in alumina crucibles from 400°C to 1000°C. The resulting crystalline compounds were identified by powder X-ray diffraction. Solid state $^{11}$ B NMR and FT-IR were used to identify the boron bonding environment. Three- and four-coordinate boron species were found in the mixtures at the various temperatures. Temperature had the greatest effect on which compounds could be identified, with no effect observed below 800°C. It was found that mixtures of boron oxide and magnesium oxide produced a magnesium hexaborate (MgB $_{6}$ O $_{10}$ ·7H $_{2}$ O) and suanite (Mg $_2$ B $_{2}$ O $_{5}$ ), whereas mixtures of boric acid and magnesium oxide produced kotoite (Mg $_{3}$ (BO $_{3}$ ) $_{2}$ ) and suanite. Thus, the type of boron starting material in the solid mixture determined what compounds formed at higher temperatures. The implication is that, at low levels, the boron reagents combine with magnesium oxide differently during heating and with boric acid, before dehydration occurs.