Neutral and Cationic Bis-Chelate Monoorganosilicon(IV) Complexes of 1-Hydroxy-2-pyridinone

Abstract

A series of spirocyclic monoorganosilicon compounds of the form RSi(OPO) 2 Cl [R = phenyl (1 1); p-tolyl (2 2); benzyl (3 3); Me (4 4); t Bu (5 5); thexyl (6 6)] (OPO = 1-oxo-2-pyridinone) was synthesized and characterized by 1 H , 13 C, and 29 Si NMR spectroscopy, X-ray crystallography, and elemental analysis. In the solid state, complexes 1 1, 2 2, and 3 3 are neutral and possess cis-OPO ligands in an octahedral arrangement, and complexes 4 4, 5 5, and 6 6 are cationic and possess effectively trans-OPO ligands in nearly ideal square pyramidal geometries along the Berry-pseudorotation coordinate. In 4-6 4-6, chloride dissociation is attributed to the additive effect of multiple intermolecular C-H•••Cl interactions in their crystals. In DMSO-d 6 solution, compounds 1 1-6 6 form cationic hexacoordinate DMSO adducts with trans-OPO ligands, all of which undergo dynamic isomerization with energy barriers of ~18-19 kcal/mol. Compounds with better leaving groups, (p-tolyl)Si(OPO) 2 X [X = I (7 7); X = triflate (8 8)], exhibit identical solution NMR spectra as 2 2, supporting anion dissociation in each. The fluoride derivatives RSi(OPO) 2 F [R = benzyl (9 9); Me (10 10)] exhibit hexacoordinate geometries with cis-OPO ligands in the solid state and exhibit dynamic isomerization in solution. Overall, these studies indicate, in both the solid and solution states, that the trans-OPO ligand arrangement is favored when anions are dissociated and a cis-OPO ligand arrangement when anions are coordinated.

Synthesis, Biological Activity and QSAR Studies of Organotin(IV) and Organosilicon(IV) Complexes

“…The 29 Si and 119 Sn NMR spectrum exhibited a sharp singlet in all the complexes signifying the formation of single species. In the 29 Si NMR spectra, sharp peaks were observed at δ −13.37 to δ −20.2 ppm . Similarly in the 119 Sn NMR spectra, chemical shift values were obtained in the range δ −143.97 to δ −156.21 ppm, which clearly showed penta‐ coordinated environment around the silicon and tin atoms (Figure ).…”

Synthesis and crystal structures of bis[1-oxopyridin-2-olato(1−)]bis(pentafluorophenyl)silicon(IV)–tetrahydrofuran–pentane (2/1/1), bis[1-oxopyridin-2-olato(1−)]bis(p-tolyl)silicon(IV), and dimesitylbis[1-oxopyridin-2-olato(1−)]silicon(IV)

“…There are five entries of hexacoordinate R 2 Si(OPO) 2 [R = Me, Et, iPr, Ph; R 2 = (CH 2 ) 3 ] complexes containing two bidentate OPO ligands (CSD refcodes NITSAM, NITSEQ, NITSOA, NISMIN, NITSUG, respectively; Kraft & Brennessel, 2014). Also reported with two bidentate OPO ligands are monoorgano neutral hexacoordinate complexes, RSi(OPO) 2 X (X = Cl, F; CSD refcodes ODEFIP, ODEFOV, ODEFUB, ODEHAJ, and ODEHEN), and cationic pentacoordinate complexes, [RSi(OPO) 2 ] + X À (X = Cl, trifluoromethanesulfonate; CSD refcodes ODEGAI, ODEGIQ, ODEGOW, and ODEGUC; Koch et al, 2017) CN and [O(CH 2 ) 3 ]Si(OPO) 2 (CSD refcodes UBUWET and UBUWIX, respectively; Tacke, Burschka et al, 2001). Monodentate OPO ligand complexes of any metal are limited to three organosilicon complexes: Me 3 Si(OPO), tBu 2 Si(� 1 -OPO)(� 2 -OPO), and Ph 3 Si(OPO)•Ph 3 Si(OH)•0.5C 5 H 12 (CSD refcodes NITROZ, NITSOA, and NITRIT, respectively; Kraft & Brennessel, 2014).…”