Reactivity of dinuclear palladium phosphine 1-azaallyl complexes

The reactivity of two dinuclear palladium complexes, [PdMe(P^AzA)] 2 (1; P^AzA = [Ph 2 P(C 6 H 4 )NCHC(CH 3 ) 2 ] – ) and [Pd(P^AzA)] 2 (2), toward small molecules was evaluated. First, an optimized synthesis of 2 was demonstrated, which involved P^AzA ligand coordination to the Pd(I) dinuclear precursor [Pd(MeCN) 3 ] 2 [BF 4 ] 2 . Complexes 1 and 2 were treated with the Lewis bases pyridine and CO. With pyridine, the Pd(II) complex 1 afforded a mononuclear py adduct Pd(P^AzA)(py) (3), while the Pd(I) complex 2 underwent disproportionation to give Pd(P^AzA) 2 (4) and Pd black. With CO, 1 decomposed while 2 followed Lewis base-induced disproportionation. Both 1 and 2 reacted with H 2 to heterolytically cleave the small molecule by metal-ligand cooperative bond activation. Similar bond activation of the polarized O–H bonds of PhOH and H 2 O was observed. The heterolytic cleavage reactions permitted isolation and characterization of select reaction products. Dinuclear Pd(I) complex 2 reacted with H 2 to afford mononuclear [Pd(Ph 2 P(C 6 H 4 )NCH 2 C(CH 3 ) 2 CH( i-Pr)N(C 6 H 4 )PPh 2 )] (5), in which H 2 addition occurred to the ligand framework. Dinuclear Pd(II) complex 1 reacted with PhOH to afford the mononuclear phenoxide complex Pd(Me)(OPh)(P^Imine) (6; P^Imine = [Ph 2 P(C 6 H 4 )N=CH( i-Pr)]). The reactions of 1 and 2 show the importance of both the supporting ligand and metal oxidation states to dictate preferred reaction outcomes of dinuclear complexes.