Synthesis and Reactivity of [PdCl₂{<i>C,N</i>-C₆H₄C(NHXy)NH₂-2}] and Neutral Palladium 1,2-Dihydroquinazolinium-4-yl Complexes: Depalladation Reactions

The complex [Pd­{C,N,O-C­(NXy)­C6H4{NC­(Me)­CHC­(Me)­O}-2}­PPh3] (A) reacts with aqueous HCl and H2O2 or with aqueous HCl (HCl:Pd = 2, 3) to produce the complexes [PdCl2{C,N-C­(NHXy)­C6H4NH2-2}] (1), cis-[PdCl2{C­(NHXy)­C6H4NH2-2}}­(PPh3)] (2c), and [PdCl2{C­(NHXy)­C6H4NH3-2}­PPh3]Cl (3), respectively. The reactions of complex 1 with L (neutral C- or P-donor ligands) give [PdCl2{C­(NHXy)­C6H4NH2}-2}­L] (2). Dehydrochlorination of 2a (L = CNtBu) occurred upon heating to give [PdCl­{C,N-C­(NXy)­C6H4NH2-2}­L] (4). The complexes [PdCl­{C,N-C­(NXy)­C6H4NH2-2}­PPh3]­X (X = ClO4 (5), TfO (5′)) were obtained by reacting 2c with AgClO4 or TlTfO (TfO = CF3SO3), respectively. When 1 was reacted with NEt3, a dehydrochlorination/dimerization process occurred, giving [Pd2Cl2{μ-N,C,N′-C­(NXy)­C6H4NH2-2}2] (6a), which, in turn, reacted in two steps with TlTfO and NaOAc to give [Pd2(OAc)2{μ-N,C,N’-C­(NXy)­C6H4NH2-2}2] (6b). The reaction of 1 with 1 equiv of a neutral ligand L and a carbonyl compound (acetone, RCHO, or R′(CHO)3) affords the neutral 1,2-dihydroquinazolinium-4-yl complexes cis-[PdCl2{C­(NXy)­CMe2NHC6H4-2}­L] (7), cis-[PdCl2{C­(NXy)­CH­(R)­NHC6H4-2}­PPh3] (8), and [{cis-PdCl2{C­(NXy)­CHNHC6H4-2}­CNXy}3{μ3-C6H3(C6H4-4)3-1,3,5}] (9)), respectively. Depalladation of compounds 7 occurred when they were heated with TlTfO, to give 2-Me-4-xylyliminium-1,4-dihydroquinoline triflate (10a). The complexes trans-[PdI­{C­(NXy)­CMe2NHC6H4-2}­(CNXy)2]­TfO and trans-[PdI­{C­(NXy)­C6H4NH2-2}­(CNXy)2] react in two steps with AgTfO and PhCCH/NEt3 to give the depalladated species 2,2-dimethyl-3-xylyl-4-phenylethynyl-1,2-dihydroquinazolinium triflate (11) and H2NC6H4{C­(NXy)­CCPh}-2 (12), respectively. Complex 11 reacts with KtBuO or Tl­(acac) to give the dinuclear complex [Pd2{μ-C,N-C­(NXy)­C6H4NH-2}­{C,N-C­(NXy)­C6H4NH2-2}­(CNXy)3] (13).