Themed collection Philip Power at 65: an icon of organometallic chemistry

We are delighted to present this collection of articles to celebrate the work of Philip Power on the occasion of his 65th birthday.

This review presents and discusses the use of multidentate silanide ligands in transition metal chemistry depending on their ligand architecture.

This Perspective discusses the synthesis and reactivity of low valent germanium and tin hydrides. The use of hindered terphenyl ligands has led to the isolation of a number of unusual structure types (each predicted by theory), and has culminated in their use as precursors to new cluster archetypes.

Although rare, O_yl–U–O_yl bending in the uranyl (UO₂²⁺) ion can be effected by either steric perturbation or electronic perturbation.

As one of the simplest examples of functionalized Si(II) species, the SiCl₂/[SiCl₃]⁻ system is not only fundamentally interesting, but also an important starting point for the assembly of oligosilane chains, rings, and clusters.

Current work on the synthesis, characterization and bonding in the heavier group 14 element (Si–Pb) analogues of alkynes is described and discussed.

The synthesis and diverse structures, reactivity (small molecule activation and catalysis) and magnetic properties of Ni(I) complexes are summarized.

Expanding the scope of N-heterocyclic carbene stabilized silyliumylidene ions: isolation of the first silyl-substituted Si(II) cations.

Anionic tetraphosphido complexes are accessible by reacting white phosphorus with low-valent cyclopentadienyliron species prepared by alkali metal reduction (Ar = C₆H₄-4-Et, 18-c-6 = [18]crown-6).

Unusual arene⋯Ge/Sn interactions stabilise the rare diarsatetrylenes 8Ge/Sn by up to 181 kJ mol⁻¹.

Reduction of [(PN)₂MCl₂] (M = Zr (1), and Hf (2)) both readily prepared by transmetallation of 2 LiPN with [MCl₄(THF)₂], with a slight excess of KC₈, resulted in the isolation of the trivalent complexes [(PN)₂MCl] (M = Zr (3), and Hf (4)).

Alkali metal carbazolido complexes are precatalysts for the dehydrogenation of Me₂NH·BH₃, where the cation plays a vital role in the reaction outcome.

The first β-diketiminate ligated chlorosilylene has been synthesised and isolated from the corresponding β-diketiminato dichlorohydrosilane through dehydrochlorination with an N-heterocyclic carbene.

Zirconium compounds appear to promote the liberation of silylene fragments via an N–Si coupling event.

A new cyclopentadienyl-containing dialane is prepared and found to undergo dialumination reactions with unsaturated species.

Two stable triarylarsine radical cation salts have been synthesized and fully characterized by X-ray crystallography and EPR spectroscopy.

The novel binary P₄ analogue (Ge₂P₂)²⁻ proved to be a suitable precursor for heteroatomic cluster synthesis. Upon reaction with CdPh₂, an unprecedented cluster anion is formed, [Cd₃(Ge₃P)₃]⁻.

Cooperativity between the Li and Al centres is implicated in catalytic hydroboration reactions of aldehydes and ketones with pinacolborane via heteroleptic lithium diamidodihydridoaluminates.

Bismuth(III) TEMPOxide complexes are active catalysts for oxidative coupling reactions to generate TEMPO silylethers.

The reaction of the P_n ligand complex [Cp*Fe(η⁵-P₅)] (1: Cp* = η⁵-C₅Me₅) with CuCl in the presence of 4,4′-bipyridine or 1,2-di(4-pyridyl)ethylene leads to the formation of three unprecedented neutral 2D organometallic–organic hybrid networks.

A series of highly electrophilic [(NHC)Ag]⁺ complexes (NHC = N-heterocyclic carbene) have been prepared which approach the limit of monocoordination for silver(I).

Stable digermynes with sterically demanding Bbt (Bbt = 2,6-[CH(SiMe₃)₂]₂-4-[C(SiMe₃)₃]-C₆H₂) or Tbb (Tbb = 4-tBu-2,6-[CH(SiMe₃)₂]₂-C₆H₂) groups underwent reversible [2+2] cycloadditions with terminal alkenes to give the corresponding 1,2-digermacyclobutenes.

A rare terminal cadmium hydride complex has been synthesised. Reduction to the cadmium(I) dimer complex was achieved upon treatment with carbodiimides.

Cp*Al reacts with diphenylacetylene to form a Cp*-substituted 1,4-dialuminacyclohexene, which mediates the coupling of isonitriles to form a new zwitterionic diamide ligand with a carbocationic backbone.

1,3,2-Diazaborole-derived carbene complexes of boron were synthesized via 1,2-hydrogen migration.

We describe the synthesis of an ambiphilic phosphine/H-bond donor ligand featuring a trifluoroacetamide functionality, its coordination to gold(I) chloride, and its application as a self-activating catalyst for the cyclization of propargylamides.

An NHC promotes intramolecular C–H activation in bis(pentalene)dititanium; this process is reversed by the addition of hydrogen, forming a dihydride.

New hybrid 1,4-thiazine-1,2,3-dithiazolylium salts were prepared via Smiles rearrangement. The cations can be readily reduced to the corresponding stable neutral radicals with delocalised spin densities.

Facile access to heavier silaacylium ions stabilized by two NHCs and their chalcogen transfer and exchange reactivity are reported.

The addition of phenyl lithium (PhLi) to an aromatic 1,3,2,5-diazadiborinine (1) afforded isolable ionic species 2, which can be deemed as an inorganic analogue of a Janovsky complex.

The combination of electron-rich diaminoalkynes and ditopic Lewis acids diboranes(4) leads to unusual diboration reactions involving internal Lewis adduct and zwitterion formation and C–C bond formation.

A highly fluorinated pyrazolate complex of zinc has been isolated and utilized as a competent catalyst for olefin aziridination.

Scandium and yttrium congeneric complexes, supported by a monoanionic PNP ligand, were studied as catalysts for alkene hydrogenation and hydrosilation and alkyne semihydrogenation and semihydrosilation.

The reaction of the metalloid tin cluster [Sn₁₀(Hyp)₄]²⁻ with (Ph₃P)Au-SHyp (Hyp = Si(SiMe₃)₃) gave an intermetalloid cluster [Au₃Sn₁₈(Hyp)₈]⁻1, which is the longest intermetalloid chain compound of tin to date.

Synthesis, structure, EPR and theoretical calculations of cyclic (alkyl)(amino)carbene stabilized mononuclear neutral radicals of aluminum containing mono- and di-organo groups.

A metalloid Ge clusters receives reactive substituents.

Mixtures of E and Z isomers of alkenylboranes are isomerized upon treatment with stoichiometric or catalytic amounts of tBu₂PH or other donors.

{Ar^Me₆Sn(μ-OMe)}₂ (1, Ar^Me₆ = C₆H₃-2,6-(C₆H₂-2,4,6-Me₃)₂) and {Ar^iPr₄Sn(μ-OMe)}₂ (2, Ar^iPr₄ = C₆H₃-2,6-(C₆H₃-2,6-iPr₂)₂) facilitate the dehydrocoupling of ammonia, 1° and 2° amines with HBpin. 2 catalyzes the reactions faster than 1 but is limited to 1° amines. Synthesis and characterization of a tin(II) amide and amide-hydride give insight into the catalytic mechanism.

The reactions of Ar′GaGaAr′ with alkenes revealed the addition of two olefins per Ar′GaGaAr′ under ambient conditions with ethylene, propene, 1-hexene or styrene but no addition for more hindered or cyclic olefins.

The first linearly coordinated heteroleptic cobalt(II) species Ar′CoN(SiMe₃)₂ shows an unexpectedly large effective magnetic moment.

The iron(II) diaryl FeAr′₂ (1) reacts cleanly with O₂ or CO to afford the monomeric, two-coordinate bis(aryloxide) Fe(OAr′)₂ (2) or the acyl–carbonyl complex (η²-Ar′CO)₂Fe(CO)₂ (3) via oxygen atom or CO insertion into the Fe–C bonds. Complex 2 has a strictly linear geometry and shows remarkable resistance to O₂ oxidation.

The reaction of Ar′CrCrAr′ with N₂O or N₃(1-Ad) under mild conditions leads to complete cleavage of the Cr–Cr quintuple interaction.

H₂ reacts with a series of distannynes at ca. 25 °C and 1 atmosphere pressure to give Sn₂H₂Ar₂ products whose structures depend on the type of terphenyl ligand employed.

Unlike their Cr(I) counterpart, the arene complexes of the univalent MAr moieties (M = Mn or Fe, Ar = terphenyl) are stable under ambient conditions.

Two complementary routes to an unusual pentagonal bipyramidal cluster, Sn₅(SnAr′)₂ (Ar′ = terphenyl ligand), are reported.

The reactions of the digermanium and ditin alkyne analogues Ar′MMAr′ (M = Ge or Sn) with R₂NO, (R₂NO = Me₂C(CH₂)₃CMe₂NO or N₂O), result in complete MM bond cleavage to afford the germylene :Ge(Ar′)ONR₂ or the germanium(II) or tin(II) hydroxides {M(Ar′)(μ–OH)}₂.

The reduction of Ar*GeCl with one equivalent of potassium affords a germanium analogue of an alkyne Ar*GeGeAr* which reacts with dimethyl-1,3-butadiene to yield the structurally characterized compound [Ar*Ge{CH₂C(Me)C(Me)CH₂}CH₂C(Me)]₂2, illustrated opposite.

Computations on the heavier group 14 dimetallenes [E{CH(SiMe₃)₂}₂]₂ and [E{N(SiMe₃)₂}₂]₂ (E = Ge, Sn, or Pb) and their respective monomers indicated that empirically observed dimerization is principally driven by attractive dispersion forces.

The magnetic properties of two-coordinate complexes of iron(II) were analyzed to explore their utility as single-molecule magnets.

The synthesis and characterization of a series of digermynes and distannynes stabilized by terphenyl ligands are described. The findings are in agreement with calculations that show that there is little energy difference between the multiple and singly bonded forms of distannynes.

The synthesis of cobalt substituted germanes of the composition GeCl_x[Co(CO)₃PR₃]_4−x (x = 0–3; R = ⁿPr, ⁿBu) is presented. Reductive coupling with different reducing agents leads amongst others to the pseudo-cubic cluster compound Ge₇Co(CO)₃[Co(CO)₃PⁿBu₃]₇.

A variety of isolable, 2 : 1 and 1 : 1 copper(I)–alkyne complexes of containing pyrazolate ligand supports are presented as well as the copper pyrazolate mediated acetylenic C–H and alkyne CC bond functionalizations.

Halide ions provide a promising tool to stabilize – through bridging interactions – copper carbonyl clusters of fluorinated pyrazolates.

A neutral heterobimetallic triple-decker stannole complex was prepared by the reaction of an anionic ruthenocene bearing a stannole dianionic ligand with [Rh(cod)Cl]₂ (cod = 1,5-cyclooctadiene), and the resulting Ru–Rh complex exhibits an electronic property different from those of the corresponding Ru–Ru and Rh–Rh complexes.

A series of Sn(II) pyrrolide complexes have been synthesised, characterised and their thermal properties assessed for their potential application in the MOCVD and ALD of SnO thin films.

Calculations show that dispersion forces in four-coordinate (Me₂IPr)Fe(NAd)(1-nor)₂ (2b) contribute to greater D(FeR) and subtly slow its migratory insertion relative to the neopentyl analogue.

The reaction of cyclic disilylated germylene phosphane adducts with alkynes gives spirocyclic germanes via the intermediate formation of cyclic divinylgermylenes.

The new zinc complexes 2,6-(ArNCH)₂C₆H₃ZnBu (6) and 2,6-(ArNCH)₂C₆H₃ZnCl₂Li(THF)₃ (7), supported by a bis(imino)phenyl NCN pincer ligand, were prepared (Ar = 2,6-ⁱPr₂C₆H₃).

Calix[4]phyrin (1,1,1,1) proves to be a versatile ligand for boron with both mono- and di-boron complexes exhibiting unusual regio- and stereoisomerism.

Me₄Pb and Ph₄Pb readily transfer methyl or phenyl groups to an equivalent molar ratio of tin(IV) chlorides in the order SnCl₄ > MeSnCl₃ > Me₂SnCl₂ > Me₃SnCl, often in a selective manner.

Applications of the bifunctional Lewis acid 1,1′-fc{B(C₆F₅)₂}₂ in FLP chemistry are described, including reactions towards H₂O, NH₃, CO₂ and cyclohexylisocyanate.

The reactions of 1-bora-7a-azaindenide anions, prepared in moderate to excellent yields by reduction of the appropriate 1-bora-7a-azaindenyl chlorides with KC₈ in THF, with alkyl halides and carbon dioxide were studied.

New T- and Y-shaped Ni(I) complexes are reported and analysed by DFT and EPR.

The coordination chemistry of intramolecular stannylene phosphorus Lewis pairs incorporated into four or three membered ring molecules is presented.

Deprotonation of a secondary diaminophosphane-borane yields lithium and potassium diaminophosphanide-boranes which undergo transmetalation to yield isolable Cu(I) and Zn(II) complexes.

Homoleptic thorium(IV), uranium(IV), and lanthanum(III) dithiocarboxylate complexes were prepared and studied electrochemically; the lanthanum complex was found to bind toluene.

Monomeric group 13 metal(I) complexes of gallium, indium and thallium stabilised by a sterically demanding bis(iminophosphoranyl)methanide ligand have been prepared and characterised.

The synthesis of a zwitterionic triphosphenium molecule which acts as a multidentate donor with various zero-velent transition metal complexes is presented. These mono- and bimetallic complexes can either be bound through the P(I) center or through the cyclopentadienyl moiety on the backbone of the molecule.