Simple two-coordinate acyclic silylenes, SiR(2), have hitherto been identified only as transient intermediates or thermally labile species. By making use of the strong σ-donor properties and high steric loading of the B(NDippCH)(2) substituent (Dipp = 2,6-(i)Pr(2)C(6)H(3)), an isolable monomeric species, Si{B(NDippCH)(2)}{N(SiMe(3))Dipp}, can be synthesized which is stable in the solid state up to 130 °C. This silylene species undergoes facile oxidative addition reactions with dihydrogen (at sub-ambient temperatures) and with alkyl C-H bonds, consistent with a low singlet-triplet gap (103.9 kJ mol(-1)), thus demonstrating fundamental modes of reactivity more characteristic of transition metal systems.

The alkali metal halide supported alkali metal materials, ca. 5% w/w Na/NaCl and 5% w/w K/KI, are prepared without specialist equipment by rapidly stirring molten alkali metal with finely ground alkali metal halide powder. Scanning electron microscopy reveals the particles of 5% w/w Na/NaCl to lie largely in the 10–100 μM size range. The freely flowing powders are easily dispersible in organic solvents and are used as reducing agents for the facile syntheses of three magnesium­(I) compounds, [{HC­(MeCNAr)2}­Mg]2, Ar = mesityl (Mes), 2,6-diethylphenyl (Dep), or 2,6-diisopropylphenyl (Dip), which can be obtained in yields of up to 12 g. The potential advantages Na/NaCl and K/KI powders offer to synthetic inorganic/organometallic chemists, relative to currently available alkali metal reducing agents, are discussed.

The chemistry of the Group 13 metals is dominated by the +1 and +3 oxidation states, and simple monomeric M(II) species are typically short-lived, highly reactive species. Here we report the first thermally robust monomeric MX2 radicals of gallium, indium and thallium. By making use of sterically demanding boryl substituents, compounds of the type M(II)(boryl)2 (M = Ga, In, Tl) can be synthesized. These decompose above 130 °C and are amenable to structural characterization in the solid state by X-ray crystallography. Electron paramagnetic resonance and computational studies reveal a dominant metal-centred character for all three radicals (>70% spin density at the metal). M(II) species have been invoked as key short-lived intermediates in well-known electron-transfer processes; consistently, the chemical behaviour of these novel isolated species reveals facile one-electron shuttling processes at the metal centre.

Making Ns meet: Triphenylphosphinazine N2(PPh3)2 is a donor–acceptor complex between nitrogen in the highly excited 1Γg state and two anti‐periplanar coordinated phosphine ligands (see structure). Although the dissociation into N2+2 PPh3 is calculated to be exergonic by 75 kcal mol−1, the compound is kinetically very stable as a result of the very large Lewis acidity of N2 in the excited 1Γg state.

The first examples of an amido-distibene, L(†)Sb[double bond, length as m-dash]SbL(†) (L(†) = -N(Ar(†))(SiPr(i)3), Ar(†) = C6H2{C(H)Ph2}2Pr(i)-2,6,4), and a boryl dibismuthene, {(DAB)B}Bi[double bond, length as m-dash]Bi{B(DAB)} (DAB = {(C6H3Pr(i)2-2,6)NCH}2, have been prepared by reaction of a lithium boryl complex, (THF)2LiB(DAB), with extremely bulky amido-group 15 dihalide precursor compounds. In these reactions, the lithium boryl acts as a boryl transfer reagent and/or a strong reducing agent.

Reactions of the extremely bulky amido alkali metal complexes, [KL'(η(6)-toluene)], or in situ generated [LiL'] or [LiL″] {L'/ L″ = N(Ar*)(SiR(3)), where Ar* = C(6)H(2){C(H)Ph(2)}(2)Me-2,6,4 and R = Me (L') or Ph (L″)} with group 13 metal(I) halides have yielded a series of monomeric metal(I) amide complexes, [ML'] (M = Ga, In, or Tl) and [ML″] (M = Ga or Tl), all but one of which have been crystallographically characterized. The results of the crystallographic studies, in combination with computational analyses, reveal that the metal centers in these compounds are one coordinate and do not exhibit any significant intra- or intermolecular interactions, other than their N-M linkages. One of the complexes, [InL'], represents the first example of a one-coordinate indium(I) amide. Attempts to extend this study to the preparation of the analogous aluminum(I) amide, [AlL'], were not successful. Despite this, a range of novel and potentially synthetically useful aluminum(III) halide and hydride complexes were prepared en route to [AlL'], the majority of which were crystallographically characterized. These include the alkali metal aluminate complexes, [L'AlH(2)(μ-H)Li(OEt(2))(2)(THF)] and [{L'Al(μ-H)(3)K}(2)], the neutral amido-aluminum hydride complex, [{L'AlH(μ-H)}(2)], and the aluminum halide complexes, [L'AlBr(2)(THF)] and [L'AlI(2)]. Reaction of the latter two systems with a variety of reducing agents led only to intractable product mixtures.

The very strong reducing capabilities of the boryllithium nucleophile (THF)2Li{B(NDippCH)2} (1, Dipp = 2,6-iPr2C6H3) render impractical its use for the direct introduction of the {B(NDippCH)2} ligand via metathesis chemistry into the immediate coordination sphere of transition metals (d(n), with n ≠ 0 or 10). Instead, 1 typically reacts with metal halide, amide and hydrocarbyl electrophiles either via electron transfer or halide abstraction. Evidence for the formation of M-B bonds is obtained only in the case of the d(5) system [{(HCDippN)2B}Mn(THF)(μ-Br)]2. Lower oxidation state metal carbonyl complexes such as Fe(CO)5 and Cr(CO)6 react with 1 via nucleophilic attack at the carbonyl carbon atom to give boryl-functionalized Fischer carbene complexes Fe(CO)4{C(OLi(THF)3)B(NDippCH)2} and Cr(CO)5{C(OLi(THF)2)B(NDippCH)2}. Although C-to-M boryl transfer does not occur for these formally anionic systems, more labile charge neutral bora-acyl derivatives of the type LnM{C(O)B(NDippCH)2} [LnM = Mn(CO)5, Re(CO)5, CpFe(CO)2] can be synthesized, which cleanly lose CO to generate M-B bonds. From a mechanistic standpoint, an archetypal organometallic mode of reactivity, carbonyl extrusion, has thus been shown to be applicable to the boryl ligand class, with (13)C isotopic labeling studies confirming a dissociation/migration pathway. These proof-of-methodology synthetic studies can be extended beyond boryl complexes of the group 7 and 8 metals (for which a number of versatile synthetic routes already exist) to provide access to complexes of cobalt, which have hitherto proven only sporadically accessible.

Synthetic routes to the first boryl complexes of cadmium and mercury are reported via transmetallation from boryllithium; the syntheses of related group 14 systems highlight the additional factors associated with extension to more redox-active post-transition elements.