Reactivity of Iridium PCP Pincer Complexes toward CO and CO2. Crystal Structures of IrH(κ2-O2COH){C6H3-2,6-(CH2PBut2)2} and IrH(C(O)OH){C6H3-2,6-(CH2PBut2)2}·H2O

The reactivity of a series of PCP pincer complexes with carbon monoxide and carbon dioxide has been studied. The reactions of CO 2 with PCP pincer iridium complexes provide the 16-electron complex Ir(η 2 -CO 2 ){C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 2 ). Analogously, reactions with CO yield the 16-electron monocarbonyl compound Ir(CO){C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 4 ). When IrH(OH){C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 1b ) is reacted with CO 2, the hydrido bicarbonate complex IrH(κ 2 -O 2 COH){C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 3 ) is obtained. Analogously, when IrH 2 {C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 1a ) is reacted first with CO 2 and then with H 2 O, the reaction affords the same species ( 3 ). Thus, compound 3 can be obtained irrespective of the order of addition of the substrates CO 2 and H 2 O to 1a . Similarly, the reaction of 1b with CO affords the insertion product IrH(C(O)OH){C 6 H 3 -2,6-(CH 2 PBu t 2 ) 2 } ( 5 ). The identities of 3 and 5 have been confirmed by single-crystal X-ray structure determinations.