Addition of Water Across Si−Ir Bonds in Iridium Complexes with κ-<i>P</i>,<i>P</i>,<i>Si</i> (biPSi) Pincer Ligands

Electrophiles such as Me+, Ag+, or protons react with the five-coordinate Ir(III) complex [IrClH(biPSi)] (biPSi = κ-P,P,Si-Si(Me){(CH2)3PPh2}2) by abstracting its chloride ligand. The resulting species can be stabilized by a variety of L ligands to give the cationic complexes [IrH(biPSi)L2]+. The derivative [IrH(biPSi)(NCMe)2]+ has been subjected to a kinetic study regarding the facile dissociations of its acetonitrile ligands. The presence of water changes the course of the reaction producing dihydride complexes that contain the silanol ligand κ-O,P,P-HOSi(Me){(CH2)3PPh2}2 (biPSiOH). The water activation product [IrH2(biPSiOH)(NCMe)](CF3SO3) undergoes insertion reactions with ethylene and phenylacetylene. The use of hydrolyzable fluorinated counterions such as PF6− or BF4− further modifies the reaction by provoking the incorporation of fluoride at the silicon atom of the former biPSi ligand. The dihydride resulting after such a process, [IrH2(biPSiF)(NCMe)2]BF4 (biPSiF = κ-P2-FSi(Me){(CH2)3PPh2}2), displays a trans-chelating diphosphine ligand. When dehydrogenating the Ir center, spontaneously or using ethylene as hydrogen acceptor, the diphosphine backbone undergoes a Si−C bond cleavage leading to a new Ir(III) species with κ-P,Si and κ-C,P chelate ligands.