Synthesis, structure and reactivity of a donor-stabilised silylene with a bulky bidentate benzamidinato ligand

Abstract

The novel donor-stabilised silylene was prepared in a four-step synthesis, starting from bis(2,6-diisopropylphenyl)carbodiimide (Dipp-N[double bond, length as m-dash]C[double bond, length as m-dash]N-Dipp), and its reactivity was studied in a series of oxidative addition reactions and a nucleophilic substitution reaction. The three-coordinate silicon(ii) complex contains the bulky bidentate amidinato ligand Dipp-NC(Ph)N-Dipp(-) and a dimethylamido ligand. Treatment of with N2O afforded the dinuclear five-coordinate silicon(iv) complex (SiO2N3 skeletons), and the reaction with S8 yielded the dinuclear four-coordinate silicon(iv) complex (SiS2N2 skeletons). Treatment of with Se and Te afforded the respective four-coordinate silicon(iv) complexes (SiSeN3 skeleton) and (SiTeN3 skeleton), which contain an Si[double bond, length as m-dash]Se and Si[double bond, length as m-dash]Te double bond, respectively. The reaction of with the silyl azide Me3SiN3 yielded the four-coordinate silicon(iv) complex (SiN4 skeleton) with an Si[double bond, length as m-dash]N double bond, whereas the reaction with the alkyl azide PhSCH2N3 gave the four-coordinate silicon(iv) complex (SiSN3 skeleton), the first silicon(iv) complex with an unsubstituted methyleneamido ligand. The reaction of with [Fe(CO)5] afforded the four-coordinate silicon(ii) complex (SiFeN3 skeleton) with an Si-Fe bond. Compounds (and the precursors and (five-coordinate silicon(iv) complexes with an SiCl3N2 and SiCl2N3 skeleton, respectively) in the synthesis of ) were characterised by elemental analyses, crystal structure analyses and multinuclear NMR spectroscopic studies in the solid state and in solution.

Reactivity of the Donor‐Stabilized Guanidinatosilylene [ArNC(NMe2)­NAr]Si[N(SiMe3)2] (Ar = 2,6‐Diiso­propylphenyl)

“…The Si–N distances of the guanidinato ligands of 9 , 10 , 12 , 13 , and 16 are quite similar [1.8153(14)–1.876(5) Å] and significantly longer than those of the amido ligands [ 9 , 10 , and 16 only: 1.7145(14)–1.734(2) Å] and much longer than the Si=N double bonds [ 9 , 10 , 12 , and 13 only: 1.589(5)–1.6139(5) Å]. The Si=N bond lengths of 9 , 10 , 12 , and 13 compare well with those of a series of structurally related amidinato‐ or guanidinato‐stabilized silaimines [1.5728(12)–1.5936(14) Å; see ref 3l. and literature cited therein].…”

Isoelectronic Aluminium Analogues of Carbonyl and Dioxirane Moieties

“…Ther esulting colourless crystals were remarkably thermally stable,w ith no visible change or melting behaviour noted up to 260 8 8C(limit of the apparatus). [25] Thea nion consists of ap lanar,t hree-coordinate aluminium centre chelated by the NON Ar ligand and aterminal selenium atom (Figure 3). [21b,c] This chemical shifts falls outside of the range previously reported for transition-metal compounds containing the [Se] 2À ligand (700-2400 ppm), [24] but is within the range observed for the isoelectronic (neutral) Si = Se group (À567 ppm to À302 ppm).…”

“…[21b,c] This chemical shifts falls outside of the range previously reported for transition-metal compounds containing the [Se] 2À ligand (700-2400 ppm), [24] but is within the range observed for the isoelectronic (neutral) Si = Se group (À567 ppm to À302 ppm). [25] Thea nion consists of ap lanar,t hree-coordinate aluminium centre chelated by the NON Ar ligand and aterminal selenium atom (Figure 3). TheAl ÀSe bond length of 2.2032(6) is the shortest recorded (%Dd AlSe = 6.6 %), confirming that the Se···K interactions in 1 cause am inor elongation of the bond.…”

Reactivity of the Donor‐Stabilized Silylenes [iPrNC(Ph)NiPr]2Si and [iPrNC(NiPr2)NiPr]2Si: Activation of CO2 and CS2

“…Thus, based on Gibbs free energies, dimer 5 is now favored by 31.9 kcal mol À1 with respectt ot wo monomers 3,a nd dimer 6 is favored by 75.9 kcal mol À1 and 30.7 kcal mol À1 with respect to two monomers 7 and two monomers 7',r espectively.T hese resultss how that the potential equilibriad epicted in Scheme 3a re strongly governed by the intact dimers 5 and 6.T hus, it is an open question whether the monomers 3, 7,a nd 7' (and the respective equilibria 2 3Ð5,2 7Ð6,a nd 2 7'Ð6)p lay ar ole in the transformation of 5 and 6 into the six-coordinate carbonatosilicon(IV)c omplexes 4 and 8,r espectively.H owever,i nt his context it is interesting to note that we have quite recently established experimentally an analogous dynamic equilibrium between monomer 14 (a silicon(IV)c omplex with an Si=Sd ouble bond) and the corresponding dimer 15 (Scheme 6). [16] The computed structures of 3, 5, 6, 7,a nd 7' are shown in Figures 4-8. Selected geometric parametersa re given in the respective figure legends.…”