Themed collection Frontiers in Molecular Main Group Chemistry

The diversity of Main Group inorganic and organometallic chemistry is encapsulated in this web themed issue.

Ligand-stabilized early main group metal hydride clusters.

Polyimido sulfur anions and ylides provide a rich scope of different coordination modes to various metals due to their different charges and donor sites.

This review highlights new classes of main group tris-2-pyridyl ligands of the type [Y(2-py)₃]ⁿ⁻ containing metallic or semi-metallic bridgehead atoms (Y) and explores the way in which they can be used to form heterometallic complexes in a targeted way.

In this feature article we describe the activation of phosphorus using compounds with low valent group 14 elements.

Soluble [K([2.2.2]crypt)]⁺ salts of pseudo-homoatomic Pb–Bi Zintl anions readily react with ZnPh₂ or Ni(cod)₂ to yield ternary intermetalloid Ni–Pb–Bi or Zn–Pb–Bi clusters in a highly efficient way.

Four-membered AlPC₂ heterocycles react as “masked Frustrated Lewis Pairs” by ring opening and activation of small molecules such as acetonitrile.

Carbaborane-substituted 1,2-diphosphetane reacts with lithium and hydrogen chloride to give a secondary bis(phosphino)carbaborane, which is a suitable precursor for carbaborane-substituted 1-aza-3,6-diphosphepanes.

Dimeric tetrahedral Zintl clusters [(η²-E₄)Zn(η²-E₄)]⁶⁻ (E = Si/Ge) were obtained from ammonia solutions of the ternary Zintl phase K₁₂Si_17−xGe_x (x = 5).

A novel d–π electron system: 1,2-bis(ferrocenyl)diphosphene.

A silanedithiolate silanolate assembles spontaneously forming an inorganic rugby ball shaped 32 vertex polyhedral cluster stabilized by organic substituents and LiCl.

Silicon analogue of the formyl chloride, silaformyl chloride IPr·SiH(Cl)O·B(C₆F₅)₃ (IPr = 1,3-bis(2,6-diisopropyl-phenyl)imidazol-2-ylidene) was stabilized by Lewis donor–acceptor ligands.

The reactions of Me₂NH·BH₃ with cationic Rh(III) and Ir(III) complexes have been shown to generate an 18-electron aminoborane adduct and a 14-electron aminoboryl complex.

Prototypical Me₃P complexes of SnCl₃⁺ and SnCl₂²⁺, and of SnCl₄ illustrate fundamental bonding environments for tin.

Cp*Si⁺ acts as a stoichiometric source of silicon in the reaction with a disilenide.

Two synthetic routes to cationic ruthenium germylene complexes are described, and a hydrogen-substituted germylene complex was found to undergo rapid additions of the Ge–H bond to unsaturated substrates.

Amazingly, the di-substituted deltahedral Zintl ions [Ge₉R₂]²⁻ are stable in the presence of water, and this has been exploited in a Schiff-base reaction producing water as a byproduct.

Addition of E₂O (E = Me₃Si or H) to [(pyridyl)BX₂][AlX₄] (X = Cl or Br) and subsequent heating produced the unprecedented trications [(2,6-lutidine)₄B₅O₆]³⁺ and [(pyridine)₄B₃O₃]³⁺.

Prototypical phosphinophosphonium cations are synthesized from phosphines and halophosphines, illustrating the versatility of the Menschutkin reaction for E–E bond formation.

Reactions of Cp* substituted pentelidene complexes with the primary phosphine Cp*PH₂ yield novel polycyclic phosphorus/arsenic and carbon containing cage compounds via cascade-like reactions.

A straightforward substitution of silicon-bonded methoxy groups by a lithium amide is presented, providing mixed N,O-precursors for chemoselective transformations.

Active species, product distributions and a suggested catalytic cycle are reported for the dehydrocoupling of the phosphine–borane H₃B·P^tBu₂H to give HP^tBu₂BH₂P^tBu₂BH₃ using the [Rh(COD)₂][BAr^F₄] pre-catalyst.

Calcium-mediated hydroamination of diphenylbutadiyne succeeds once even with rather weak nucleophiles such as diphenylamine employing heterobimetallic K₂Ca(NR₂)₄.

The uncommon tin–tellurium cluster [{(Me₃Si)₃SiTe}₄Te₂Sn₄] as well as other Sn–Te and Pb–Te compounds are described.

Tris(2-pyridyl)borates are introduced as a new robust and tunable ligand family that combines the desirable complexation behavior of “scorpionate” ligands with the high stability of weakly coordinating arylborate anions.

The preparation and structures of the first alkynyl-functionalised and catenated Sn₂Si₃ bicyclo[1.1.1]pentanes are reported, together with NMR spectroscopic and computational studies of their properties.

The first magnesium, copper and zinc disilenides were prepared via transmetallation reactions of a lithium disilenide and structurally characterised. The copper and zinc derivatives show red-shifted UV/vis absorptions due to admixture of metal d-orbitals to the highest occupied molecular orbital.

The synthesis and chiroptical properties of chiral rhenium complexes bearing mono- or di-topic phosphole ligands are described.

The 15-membered rings [(^tBuN)P(μ-N^tBu)₂P(N^tBu)(μ-E–E)]₃ (E = Se, S) are comprised of planar P₆E₆ motifs stabilised by perpendicular P₂N₂ rings.

We report a convenient synthesis of 1,2,3-tripnictolide anions and their subsequent reactivity towards a transition metal organometallic reagent.

The first comparative study on reactions of the title reactive intermediates with a conjugated π-system reveals a significantly increased selectivity of the Li–Cl phosphinidenoid complex; DFT calculations provide a first explanation based on a lithium cation template in a stepwise formal [4+1] cycloaddition reaction.

1 reacts with 2-mercaptoimidazole (Hmt^iPr) to afford the [4.3.3]propellane 5. The EI mass spectra of 1 and 5 are dominated by fragments corresponding to [anthracene]⁺˙ and [B₂R₂]⁺˙ (R = NMe₂, mt^iPr).

We report varied reduction reactions of a sterically demanding diaminobromoborane which are mediated by the nature of the alkali metal reductant.

Frozen early stages of oxidative additions and B–H–metal interactions are two schemes in complexes of a specific doubly-base-stabilised diborane(4).

Facile syntheses of monoalkylsilylenes LSitBu (2) and LSi[C(SiMe₃)₃] (3) by metathesis reaction of LitBu and KC(SiMe₃)₃ with LSiCl (1) (L = PhC(NtBu)₂).

The heteroleptic magnesium alkyl complex [CH{C(Me)NAr}₂MgⁿBu] (Ar = 2,6-ⁱPr₂C₆H₃) is reported as a highly efficient pre-catalyst for the hydroboration of aldehydes and ketones with pinacolborane.

Phosphine-boronates R₂P(o-C₆H₄)B(OR′)₂ have been evaluated as bifunctional organocatalysts for Michael addition reactions. Isolation of a key β-phosphonium enolate intermediate has substantiated the role of the Lewis acidic moiety.

Reductions of group 14 metal(II) chloride complexes with a magnesium(I) dimer have led to significantly different outcomes, including the formation of the first β-diketiminato tin(I) dimer (see picture).

Two new ligand-dependent lithium-zincate methodologies (via two-fold deprotonation or C–H alkylation) are disclosed for the selective functionalisation of pyrazine.

An efficient synthesis of the stable Si(II) dihydride complex IPr·SiH₂·BH₃ (IPr = [(HCNDipp)₂C:]; Dipp = 2,6-ⁱPr₂C₆H₃) is reported.