Stabilization of a two-coordinate, acyclic diaminosilylene (ADASi): completion of the series of isolable diaminotetrylenes, :E(NR₂)₂(E = group 14 element)

Abstract

An extremely bulky boryl-amide ligand, [N(SiMe3){B(DAB)}](-) (TBoN; DAB = (DipNCH)2, Dip = C6H3Pr(i)2-2,6), has been utilised in the preparation of the first isolable, two-coordinate acyclic diaminosilylene (ADASi), viz. :Si(TBoN)2. This is shown to have a frontier orbital energy separation, and presumed level of reactivity, intermediate between those of the two classes of previously reported isolable two-coordinate, acyclic silylenes.

Synthesis and Reactivity Studies of Amido‐Substituted Germanium(I)/Tin(I) Dimers and Clusters

“…To access germanium(I) compounds bearing amide ligands, monomeric amido-germanium(II) halide precursor complexes 4-6 (Scheme 1) were prepared in good yields by standard salt metathesis reactions. The X-ray crystal structures of the new complexes 5 and 6 (see Supporting Information) revealed them to be monomeric and to have very similar structures to the previously reported complex 4 [18] and other closely related amido-germanium chloride systems, for example, L † GeCl. [11] Comparable to the syntheseso f1 and 2,t oluenes olutionso f compounds 4-6 were reduced with 0.5 equivalents of the magnesium(I) dimer {( Mes Nacnac)Mg} 2 ( Mes Nacnac = [(MesNC- Scheme1.Synthesis of compounds 7-9.…”

“…The three amide ligands chosen fort his study are depicted in Figure2.T he two boryl/silyl amides ( TBo L [18] and PhBo L [19] )h ave been previously reportedb yu s. Althougha tf irst glance they possess somewhat similar steric bulk to the amide ligands in the ditetrelynes, 1-3,t hey have the potential to act as weaker N p-donors towards coordinated tetrel centers, considering the possibility of competing N!B p-donation within the ligand itself. The third ligand used in the currentw ork is the alkyl/aryl amide, DBu L, [20] whichi sc onsiderably less bulky than the amides utilized in 1-3.H owever,g iven the smaller covalent radius of C versus Si, it should provide more steric protection to coordinated tetrel centers than that given by the well-established amide, -N(SiMe 3 )(Dip), which has been widely used for the kinetic stabilization of low-valent Group 14 compounds andclusters.…”

“…In summary,t hree amide ligandso fv arying steric bulk and electronic properties were utilized to prepareaseries of amido-germanium(II)/tin(II) halide compounds. Reductions of these with am agnesium(I) dimer afforded av ariety of amido- (3),G e(1)ÀN(1) 1.8325 (14), Ge(1)ÀC(35) 1.9852 (18), Ge(1)ÀC(33) 2.0015 (18), Ge(2)ÀN(2) 1.8343 (14), Ge(2)ÀC(34) 1.9840 (18),G e(2)ÀC(36) 2.0035 (18), C(33)ÀC(34) 1.551(3), C(35)ÀC(36) 1.551(3), N(1)ÀGe(1)ÀGe(2) 153.76 (5), N(2)ÀGe(2)ÀGe(1) 152.34 (5). Selectedbond lengths ()a nd angles (8)for 16:Ge(1)ÀN(1) 1.854(9), Ge(1)ÀC(39) 2.005 (14), Ge(1)ÀC(33) 2.064 (16), Ge(1)ÀGe(2) 2.4390 (19), Ge(2)ÀN(2)1.857(10), Ge(2)ÀC(40) 2.034 (16), Ge(2)ÀC(36) 2.163 (18), N(1)ÀGe(1)ÀGe(2) 140.0(3),N(2)ÀGe(2)ÀGe(1) 137.5(3).…”

“…The reaction of the germanium(I) cluster 9 towards dihydrogen was then explored. At room temperature, no reaction was observed, but upon heating C 6 D 6 solutions of the compound to 80 8Cu nder an atmosphere of H 2 for 12 hours, an almost (8): Ge(1)ÀGe(1)' 2.5353(5), Ge(1)ÀH(1) 1.419(10), Ge(1)ÀN(1) 1.8556 (18), N(1)À B(1) 1.446 (3), Si(1)ÀN(1) 1.7407 (19), N(1)ÀGe(1)ÀGe(1)' 107.05 (6), N(1)ÀGe(1)À H(1) 115.0(19), Ge(1)'ÀGe(1)ÀH(1) 122.7 (19). Symmetryoperation: Àx + 1, Ày + 1, Àz + 1.…”

Cyclic Amino(Ylide) Silylene: A Stable Heterocyclic Silylene with Strongly Electron‐Donating Character

“…[4] However,c ompared to the very large family of stable carbenes,t he structural diversity of stable silylenes is still limited, [5] and most of known stable cyclic and acyclicsilylenes are only symmetrically substituted (A-F). [6][7][8][9][10] Only af ew exceptions with an unsymmetrical pattern have recently been reported, namely the acyclica mino(silyl) and amino(boryl) silylenes (G [11] and H [12] ), which are stabilized by p-a nd s-donating substituents.B oth compounds clearly show an ambiphilic reactivity that allows the activation of small molecules such as H 2 .T ot he best of our knowledge, as table silylene featuring two different p-donating groups remains elusive.Out of all the possibilities,wewere interested in an amino/ylide substitution pattern for the stabilization of heterocyclic silylenes (I). In contrast to amino substituents, which behave not only as excellent p donors but also as strong s acceptors toward the silylene center, an effect that is directly related to the electronegativity difference between nitrogen and silicon (3.0 vs.1.9), less-electronegative carbonbased p-donating substituents such as ap hosphonium ylides are strong p donors and poorer s acceptors.T herefore,w e assumed that the combination of these two types of substituents should enhance the nucleophilic character of the corresponding silylenes.Indeed, Driess et al reported that the symmetrical bis-ylide-stabilized silylene D shows an extraordinarily basic character and reacts even with ethereal solvents such as THF or DME.…”