Hexacoordinate Silicon(IV) Complexes Containing Thiocyanato‐N Ligands — Syntheses, Structural Characterization, and Computational Studies

Abstract

The hexacoordinate silicon(IV) complexes [NEt4]2[Si(NCS)6] (2), [K(18‐crown‐6)]2[Si(NCS)6]·2CH3CN (3·2CH3CN), and cis‐[(acac)2Si(NCS)2] (cis‐4; acac = acetylacetonato‐O, O) were synthesized, starting from Si(NCS)4 (1). Compounds 1, 2, 3·2CH3CN, and cis‐4 were structurally characterized in the solid state (13C, 15N (cis‐4 only), and 29Si MAS NMR; crystal structure analyses) and in solution (1H, 13C, and 29Si NMR; cis‐4 only). The experimental investigations were complemented by computational studies (RI‐MP2 geometry optimizations of 1, [Si(NCS)6]2—, cis‐4, and trans‐4; calculations of the 29Si NMR chemical shifts using the optimized structures).

Synthesis and Structural Characterization of Neutral Higher‐Coordinate Silicon(iv) Complexes with Tridentate Dianionic Chelate Ligands

“…The 1 H, 13 1 H transmitter pulse length, 3.6 ms; repetition time, 4 s). The precursors tetra(cyanato-N)silane and tetra(thiocyanato-N)silane were synthesized according to reference [21] (for the synthesis of tetra(thiocyanato-N)silane, toluene instead of benzene was used as the solvent [1] ). 4-[(2-Hydroxyphenyl)amino]pent-3-en-2-one was synthesized according to reference [5].…”

“…and N-C-X angles have also been reported for the Si-NCX moieties of 1-7. [1][2][3] To the best of our knowledge, compound 8 is the first pentacoordinate silicon compound with cyanato-N ligands Scheme 1. Syntheses of compounds 8, 9, and 10.…”

“…[ [1][2][3] These silicon(iv) complexes contain two monodentate NCX À (X = O, S) ligands each and two bidentate monoanionic chelate ligands (1)(2)(3)(4)(5)(6) or one tetradentate dianionic chelate ligand (7). We have now succeeded in synthesizing the pentacoordinate silicon compounds 8 and 9 and the hexacoordinate silicon compound 10·1/2 CH 3 CN, starting from Si(NCO) 4 or Si(NCS) 4 .…”

Selectively Tunable Domino Reaction of 1,3‐Diphenylpropane‐1,3‐dione on the Ethoxy‐Silicon Core

“…The two ethoxy groups are in cis position and their oxygen atoms are bonded with strong Si–O bonds [Si1–O5 1.6908(18) and Si1–O6 1.6855(16) Å]. The cis arrangement is common among the hexacoordinate silicon compounds containing two bidentate β‐diketonato ligands . In the six‐membered rings formed by the β‐diketonato ligand and the silicon the Si–O bonds are significantly elongated compared to the ethoxy Si–O bonds and differ somewhat from each other in the same ring [Si1–O1 1.8481(18) and Si1–O2 1.8040(16) for the first ring, and Si1–O3 1.7967(16) and Si1–O4 1.8565(16) for the second ring].…”

“…The cis arrangement is common among the hexacoordinate silicon compounds containing two bidentate -diketonato ligands. [19][20][21] In the six-membered rings formed by the -diketonato ligand and the silicon the Si-O bonds are significantly elongated compared to the ethoxy Si-O bonds and differ somewhat from each other in the same ring [Si1-O1 1.8481 (18) and Si1-O2 1.8040 (16) for the first ring, and Si1-O3 1.7967 (16) and Si1-O4 1.8565 (16) for the second ring]. Oxygens situated trans from the ethoxy groups (O1 and O4) exhibit larger Si-O distance (by about 0.04 Å) than those in cis position (O2 and O3).…”