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A series of neutral pyrithionato (OPTO) organosilicon compounds, R3Si(OPTO) [R = Me (1), Ph (2)], cis-R2Si(OPTO)2 [R = Me (3), Et (4), iPr (5), tBu (6), mesityl (10), allyl (11), p-tolyl (13); R2 = (CH2)3 (7), (CH2)4 (8), (CH2)5 (9), Me, allyl (12)], and cis-R2Si(OPTO)Cl [R = Me (14), iPr (15), allyl (16), p-tolyl (17), mesityl (18), Ph (19)], have been prepared and characterized by 1H, 13C, and 29Si NMR spectroscopy. X-ray crystallographic analysis reveals four-coordinate silicon atoms in 1, 2, 6, and 10, five-coordinate in 3, 9, 11, 12, and 14–19, six-coordinate in 7 and 8, and primarily six-coordinate with co-crystallized five-coordinate forms in 13. Collectively, a wide range of chelate strengths of the OPTO ligand is observed in these complexes characterized by the Si–S bond length and S–Si–O bite angle in the solid state, which correlates well with the solution-state 13C NMR C═S chemical shift. In TBP five-coordinate silicon complexes, the ambidentate potential of the OPTO ligand and π-electron delocalization (π-ED) that occurs within the ligand generally allows the chelate effect to be enhanced with sulfur occupying an equatorial vs axial position. For 8, 9, and 18, reversible chelation equilibria involving Si ← S bond formation and concurrent π-ED have been characterized by variable-temperature 13C and 29Si NMR spectroscopy. Solvents of varying dielectric constants were found to have pronounced effects on the 13C NMR chemical shifts of 1, 15, and pyrithione.



"This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Organometallics, copyright © American Chemical Society after peer review. To access the final edited and published work, see

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