THIAPENTADIENYL IRIDIUM PHOSPHINE CHEMISTRY - SYNTHESIS OF SULFUR-CONTAINING IRIDACYCLES VIA C-H BOND ACTIVATION

Treatment of (Cl)Ir(PR3)3 (R = Me, Et) with potassium thiapentadienide produces ((1,2,5-eta)-5-thiapentadienyl)Ir(PR3)3 (1, R = Me; 2, R = Et). While 1 is stable indefinitely in solution, 2 undergoes intramolecular activation of thiapentadienyl C-H bonds, producing a mixture of mer-(Ir-CH=CH-CH=CH-CH-S)(PEt3)3(H) (3) and mer-(Ir-C(=CH2)-CH=CH-S)(PEt3)3(H) (4). Over time, all of the six-membered thiairidacycle 3 converts to the thermodynamically favored five-membered-ring compound 4.