Monomeric Group 13 Metal(I) Amides: Enforcing One-Coordination Through Extreme Ligand Steric Bulk

Reactions of the extremely bulky amido alkali metal complexes, [KL′(η⁶-toluene)], or in situ generated [LiL′] or [LiL″] {L′/ L″ = N­(Ar*)­(SiR₃), where Ar* = C₆H₂­{C­(H)­Ph₂}₂­Me-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′AlH₂­(μ-H)­Li­(OEt₂)₂­(THF)] and [{L′Al­(μ-H)₃K}₂], the neutral amido-aluminum hydride complex, [{L′AlH­(μ-H)}₂], and the aluminum halide complexes, [L′AlBr₂(THF)] and [L′AlI₂]. Reaction of the latter two systems with a variety of reducing agents led only to intractable product mixtures

Monomeric Group 13 Metal(I) Amides: Enforcing One-Coordination Through Extreme Ligand Steric Bulk

Reactions of the extremely bulky amido alkali metal complexes, [KL′(η⁶-toluene)], or in situ generated [LiL′] or [LiL″] {L′/ L″ = N­(Ar*)­(SiR₃), where Ar* = C₆H₂­{C­(H)­Ph₂}₂­Me-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′AlH₂­(μ-H)­Li­(OEt₂)₂­(THF)] and [{L′Al­(μ-H)₃K}₂], the neutral amido-aluminum hydride complex, [{L′AlH­(μ-H)}₂], and the aluminum halide complexes, [L′AlBr₂(THF)] and [L′AlI₂]. Reaction of the latter two systems with a variety of reducing agents led only to intractable product mixtures

Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

Oxidative Bond Formation and Reductive Bond Cleavage at Main Group Metal Centers: Reactivity of Five-Valence-Electron MX₂ Radicals

Monomeric five-valence-electron bis­(boryl) complexes of gallium, indium, and thallium undergo oxidative M–C bond formation with 2,3-dimethylbutadiene, in a manner consistent with both the redox properties expected for M^II species and with metal-centered radical character. The weaker nature of the M–C bond for the heavier two elements leads to the observation of reversibility in M–C bond formation (for indium) and to the isolation of products resulting from subsequent B–C reductive elimination (for both indium and thallium)

A Stable Two-Coordinate Acyclic Silylene

Simple two-coordinate acyclic silylenes, SiR₂, 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>i</i>Pr₂C₆H₃), an isolable monomeric species, Si­{B­(NDippCH)₂}­{N­(SiMe₃)­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

A Stable Two-Coordinate Acyclic Silylene

Simple two-coordinate acyclic silylenes, SiR₂, 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>i</i>Pr₂C₆H₃), an isolable monomeric species, Si­{B­(NDippCH)₂}­{N­(SiMe₃)­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