Synthesis, Structure, Spectroscopy, and Reactivity of a Neutral Iridathiabenzene1
journal contributionposted on 16.08.2004, 00:00 by John R. Bleeke, Paul V. Hinkle, Monica Shokeen, Nigam P. Rath
Treatment of the cationic iridathiabenzene (3) with sodium tert-butylthiolate leads to the production of a stable neutral iridathiabenzene, (4). Compound 4 exists in solution as an equilibrating mixture of two square pyramidal isomers, “cis” 4a and “trans” 4b. When 4 is cooled to −30 °C in acetonitrile, it precipitates as an acetonitrile adduct, (6), featuring an iridathiacyclohexa-1,3-diene ring system. Compound 6 reverts back to 4 upon redissolving and warming to room temperature. Treatment of 4 (or 6) with excess PMe3 results in addition of PMe3 to the iridium center and replacement of the bulky PEt3 ligands with PMe3's, producing (7) as a mixture of equilibrating isomers, “cis” 7a and “trans” 7b. Compound 7, like 6, includes a nonaromatic iridathiacyclohexa-1,3-diene ring. When 4 in acetonitrile solvent (or 6) is reacted with trifluoromethanesulfonic acid, protonation occurs at the thiolate sulfur, causing loss of thiol. The resulting cationic fragment dimerizes to produce (8), in which the two iridium centers are bridged by the two ring sulfurs. Finally, treatment of 4 (or 6) with [(η5-C5Me5)Ru(NCMe)3]+O3SCF3- results in production of the sandwich compound (9), which exists in solution as an equilibrating mixture of isomers, “cis” 9a and “trans” 9b. Compounds 4a, 7a, 8, and 9a have been structurally characterized by X-ray diffraction.