This collection of papers highlights the resurgence of main group chemistry in the last 30 years and its relevance to chemistry in Australia and the world.

Current boron-containing therapeutics and recent advances in the medicinal chemistry of boronic acid derivatives, 1,2-azaborines, and icosahedral carboranes are highlighted and illustrated with selected examples. The future potential of these boron-based structural motifs for medicinal chemistry is described.

Complexes containing mono-, di-, and mixed mono-/di-valent metal centres supported by [hpp]^– are reported, including heterobimetallic mixed lithium–magnesium and lithium–zinc heterometallic examples (hppH = 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine).

Reaction of Sn(OTf)₂ (OTf^– = OSO₂CF₃^–) with one and two equivalents of 1,3-bis(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) yielded the complexes [Sn(IPr)(OTf)₂] (1) and [Sn(IPr)(aIPr)(OTf)][OTf] (2), respectively. Both compounds display an NHC ligand bonded to tin(ii) via the C2 carbon in a ‘classical’ mode, while 2 also contains an ‘abnormal’ C4/C5-bonded carbene.

Three new zinc 8-quinaldinolate (MQ) complexes have been obtained from rearrangement reactions at elevated temperatures including the first homoleptic zinc 8-quinaldinolate complex, [Zn₃(MQ)₆], and two tetranuclear, heteroleptic MQ/Cl complexes [Zn₄Cl₄(MQ)₄] and [Zn₄Cl₂(MQ)₆].

A series of extremely bulky amido and amidinato ligands have been synthesised and used in the preparation of boron(iii) and aluminium(iii) halide complexes. Efforts to reduce these complexes to monomeric group 13 element(i) species are described.

The cyclo-phosphanes (t-BuP)_n (n = 3, 4) were used in the syntheses of cyclo-phosphanylphosphonium ions by introducing Ph₂P⁺ or chloronium. The dependency of such reactions on the presence of GaCl₃ or Me₃SiOTf as a chloride abstracting agent is discussed. In addition, a Me₃SiOTf-mediated ring expansion reaction of (t-BuP)₃ to (t-BuP)₄ is unveiled.

Facile entry to novel N-heterocyclic silylene (NHSi) group 9 metal complexes of the type [L(Cl)Si:→M(Cl)cod] (L = [HC(CMeNAr)₂], Ar = 2,6-ⁱPr₂C₆H₃, M = Rh and Ir, cod = 1,5-cyclooctadiene) is reported. Their ability to catalytically reduce amides is also presented, along with their contrasting reactivity patterns to nucleophiles.

π-Conjugated organophosphorus compounds can generally exhibit quite unique photophysical and electronic properties. This contribution reports on the synthesis and characterisation of a series of new luminescent P-benzyl dithienophospholes, as well as their modification at the scaffold and the P-centre. Density functional theory calculations that support the experimental findings are also included.

A combined theoretical and synthetic study on the classic bis-pyridine iodine cation reveals that the N–I bond can be considered as a dative bond, and hence the cation can be thought of as a coordination complex. This is in contrast to the bonding in the lighter halide derivatives, where the N–X bond is best considered as a standard covalent bond.

A variety of aliphatic ligands containing multiple Lewis donor atoms have been studied in reactions with the lithium aluminate bases LiAl(TMP)ⁱBu₃ and LiAl(TMP)₂ ⁱBu₂ (TMP = 2,2,6,6-tetramethylpiperidide). With the former alkyl rich base, only Lewis acid–Lewis base interactions between the bimetallic base and the ligand are observed, whereas the stronger bis-amido base can bring about aluminodeprotonation of the attached polydentate donor molecule.

The novel germanium(i) halides GeBr and GeCl were studied by ³⁵Cl, ⁷⁹Br, and ⁷³Ge solid-state NMR spectroscopy. The data, combined with the results of DFT calculations in Gaussian 09 and plane wave pseudopotential calculations in CASTEP, were used to suggest a possible structure for these amorphous compounds. The monohalides are proposed to be linear head-to-tail oligomers of GeX units, terminated by an inverted GeX unit giving rise to a Ge–Ge bond.

Cationic half-sandwich ruthenium complexes of the type [Cp*Ru(L)(κ²-H₂BNR₂)][BAr^f₄] (L = PCy₃, PPh₃, 1,3-bis-(2,4,6-trimethylphenyl)-imidazol-2-ylidene; R = ⁱPr, Cy) can readily be accessed from 16-electron precursors via chloride abstraction in the presence of H₂BNR_2. The κ²-binding mode of the aminoborane ligand in three cases was determined in the solid state by X-ray crystallography.

Rare metal-carbon bonded complexes such as methandiide complexes are of fundamental importance in molecular organometallic and inorganic chemistry. The synthesis and characterisation of sterically demanding methandiide aluminium complexes are described. Derivatisation chemistry on aluminium and different coordination modes for a methandiide ligand to two aluminium centres are reported.

Oxidation of the title compound >0.4 V v. Fc^+/0 produces the persistent radical Dipp₃As^+• which was unambiguously characterised by fluid and frozen solution EPR spectroscopy. Consideration of the A and B hyperfine parameters confirms that the ground state geometry is slightly pyramidal with ∑∠{CAsC} ≈ 351°.

Various complexes between N-heterocyclic carbene donors and element halides of Group 12 and 14 (Zn, Cd, Ge, Sn, and Pb) are reported along with their reactivity with various hydride sources.

The heterotopic As,S,P ligands 1-AsPh₂-2-S^tBu-3-PPh₂-C₆H₃ and 1-AsPh₂-2-SH-3-PPh₂-C₆H₃ and dinucleating As,S,As ligand 1,3-(AsPh₂)₂-2-S^tBu-C₆H₃ have been synthesized and characterized. The structural motif of these compounds suggests great potential for their use as monodentate, bidentate chelating, bidentate bridging, and tridentate ligands.

Reactions of bis(pentafluorophenyl)mercury with piperidine, sodium iso-propoxide, or sodium tert-butoxide have yielded the corresponding 4-substituted tetrafluorophenylmercurials, [Hg(C₆F₄X-4)₂] (X = cyclo-C₅H₁₀N (1), OCH(CH₃)₂ (2), OC(CH₃)₃ (3)), in reasonable yields but the bulkier nucleophiles, cis-2,6-dimethylpiperidine and 2,6-di-iso-propylphenolate (from sodium 2,6-di-iso-propylphenolate), decomposed the mercurial into pentafluorobenzene.

Ethene elimination in the metallation of 1,2-bis(diphenylarsino)ethane in 1,4-dioxane gave only a poor yield of [KAsPh₂]•2(1,4-dioxane) which was characterised structurally.

Calcium-mediated addition reactions of diphenylphosphane oxide to organic isocyanates and -thioisocyanates yield the corresponding N-organyl-diphenylphosphorylformamidinates as well as -thioformamidinates. These compounds form dimers by N–H···O–P hydrogen bridges (broken lines; C grey, N blue, O red, P green).

Thin films of indium oxide have been grown using a solution-based chemical vapour deposition (CVD) technique, aerosol-assisted CVD. The use of methanol as the solvent has been shown to influence the microstructure of the resulting film in comparison with using toluene as the solvent.

The complexes (o-(ⁱPr₂P)C₆H₄)₃PnM₃(μ₂-Cl)₃ (1, Pn = Sb, M = Cu; 2, Pn = Sb, M = Ag; 3, Pn = Bi, M = Cu; 4, Pn = Bi, M = Ag) have been synthesised by simple mixing of the group 11 chlorides with the (o-(ⁱPr₂P)C₆H₄)₃Pn ligands. The structures of 1–4 show that the heavy pnictogen atom (Pn) caps the M₃(μ₂-Cl)₃ unit, leading to a four-centre two-electron Pn→M₃ interaction.

Calcium and magnesium complexes with N,N-dialkyl-N′-2,3,5,6-tetrafluorophenylethane-1,2-diaminate, p-HC₆F₄N(CH₂)₂NR₂(1–) (L^RH; R = Me or Et), ligands were prepared, characterised, and shown to exhibit Ae–F(C) bonding. Prolonged heating of the complexes in C₆D₆ at 80°C showed no evidence of C–F activation.

Eleven homo- and heteroleptic bismuth(iii) thiobenzoates of form Ph_3–nBiL_n (n = 0–3) have been synthesised and evaluated alongside their parent thiocarboxylic acids for inhibitory activity against the Leishmania parasite. The tris-thiocarboxylate complexes (BiL₃) proved to be significantly less active (100 µM) than the monophenyl analogues (PhBiL₂), which were active in the range 0.39–4.69 μM.

Tris(2-pyridylseleno)methane, [Tpsem]H, has been employed to synthesize a variety of zinc complexes, namely [κ³-Tpsem]ZnN(SiMe₃)₂, [κ⁴-Tpsem]ZnNCO, [κ³-Tpsem]ZnSH, {[κ³-Tpsem]Zn}₂(μ-S), [κ²-Tpsem]₂Zn, and [κ⁴-Tpsem]Zn(κ²-SeC₆H₄N), thereby demonstrating that the [Tpsem] ligand can exhibit κ²-, κ³-, and κ⁴-coordination modes.

Reactions of a disilenide, a disila analogue of vinyl lithiums, with two α,β-unsaturated carboxylic acid chlorides yields the first examples of compounds with a bicyclo[1.1.1]pentane scaffold that feature one carbon and one silicon atom at bridgehead positions.