Novel neutral hexacoordinate silicon(iv) complexes with two bidentate monoanionic benzamidinato ligands

Abstract

The novel neutral hexacoordinate bis(benzamidinato)silicon(iv) complexes 1-10 (SiN(4)X(2) skeletons; X = F, Cl, Br, C, N, S, Se) were synthesised and characterised by elemental analyses, single-crystal X-ray diffraction (except for 2) and NMR spectroscopy in the solid state and in solution. The dynamic behavior of 1 (SiN(4)Cl(2) skeleton) and 3 (SiN(4)F(2)) was additionally studied by variable-temperature NMR experiments. Compounds 1 and 2 (SiN(4)Br(2)) were obtained by reaction of SiCl(4) and SiBr(4), respectively, with two molar equivalents of the corresponding lithium amidinate. Compound 1 served as the starting material in the syntheses of 3-10, in which the two chloro ligands of 1 were substituted by two (pseudo)halogeno or one bidentate dianionic S,S, S,Se or Se,Se ligand. Compound 4 contains an SiN(4)C(2) skeleton and 5-7 contain an SiN(6) skeleton. With the preparation of 8 (SiN(4)S(2) skeleton), 9 (SiN(4)SSe) and 10 (SiN(4)Se(2)) it could be demonstrated that syntheses of hexacoordinate silicon(iv) complexes with soft chalcogeno ligand atoms are indeed feasible. Compounds 9 and 10 are the first hexacoordinate silicon(iv) complexes with Si-Se bonds.

The Donor‐Stabilized Silylene Bis[N,N′‐diisopropylbenzamidinato(−)]silicon(II): Synthesis, Electronic Structure, and Reactivity

“…The SiSe bond lengths of 10 (2.4470(10) and 2.4309(11) Å) are similar to those observed for the related compound 15 (2.3989(8) and 2.4142(7) Å),7c and the SiF distance of 11 is almost identical with the SiF bond lengths of 16 7c. The SiC distance of 11 is 2.0042(16) Å.…”

“…The structural features of compounds 10 , 11 , and 13 are very similar to what has been found for other six‐coordinate silicon( IV ) complexes with two bidentate amidinato ligands and two monodentate ligands 5. 7c As observed for the silicon( II ) complex 1 ,5 one bidentate and one monodentate amidinato ligand are bound to each of the two silicon coordination centers of the five‐coordinate silicon( IV ) complex 12 . The different coordination modes of the amidinato ligands in 10 – 13 (bidentate and/or monodentate) are reflected by different degrees of electron delocalization in the NC(Ph)N moieties as can be seen from the different NC bond lengths in these units (Table 1).…”

A Silacyclopropene with a Six‐Coordinate Silicon Atom and an SiN4C2 Skeleton: Synthesis and Structural Characterization

“…The 15 N NMR spectrum shows four resonance signals ( δ 29 Si = –205.6 to –188.7 ppm), and the 29 Si NMR spectrum displays one resonance signal ( δ 29 Si = –207.2 ppm), the isotropic chemical shift of which clearly reflects the presence of a six‐coordinate silicon atom. The 29 Si chemical shift is similar to those of the related six‐coordinate bis(amidinato)silicon(IV) complexes 11 ( δ 29 Si = –216.6 ppm), 12 ( δ 29 Si = –206 ppm), 13 ( δ 29 Si = –195.7 ppm), and 14 ( δ 29 Si = –193.2 ppm) (Scheme ) …”

Disilicon Complexes with Two Hexacoordinate Si Atoms: Paddlewheel‐Shaped Isomers with (ClN4)SiSi(S4Cl) and (ClN2S2)SiSi(S2N2Cl) Skeletons

“…The use of chelating ligands or buttressing ligands has proved successful in forcing “unusual” donor atoms into the Si coordination sphere (Scheme ) 4a. u, ac, 5h In addition, methimazolide (mt − ) as a buttressing ligand has been proved capable of stabilizing the SiSi bond between two hexacoordinate (distorted octahedrally coordinated) Si atoms ( F ; Scheme ) 3a. In our mt‐stabilized Si complexes (i.e., E and F ),3a, 5a,b,d we noticed that the buttressing four N,S‐heterobidentate mt ligands furnished paddlewheel‐shaped complexes of the so‐called (4,0) isomer (Scheme ), that is, with four donor atoms of the same type attached to the same central atom.…”