Reactivity of ortho-β-Enaminone-phenyl Palladium Complexes. Insertion of CO into the Pd−C Bond to Give the First Acyl C,N,O-Pincer Complexes. Sequential Insertion of Dimethylacetylenedicarboxylate into the Enaminone C−H Bond and of Isocyanide into the Pd−C Bond. A New Photooxigenation/Cyclization Process

Insertion of CO into the Pd−C aryl bond of complexes [PdI{C 6 H 4 {NHC(Me)CHC(O)Me}-2}(N ∧ N)] afforded the benzoyl derivatives [PdI{C(O)C 6 H 4 {NHC(Me)CHC(O)Me}-2}(N ∧ N)] [N ∧ N = 4,4′-di- tert- butyl-2,2′-dipyridyl ( t Bubpy) ( 1a ), N,N,N′,N′ -tetramethylethylenediamine (tmeda) ( 1b )]. The reactions of [Pd{ C,C -C 6 H 4 {NH═C(Me)CHC(O)Me}-2}(tmeda)]OTf (OTf = CF 3 SO 3 ) with excess CO and tmeda (2:1) or HOTf (1:1) produced the dinuclear benzoyl complex [{Pd{ C,N,O- {C(O)C 6 H 4 {NC(Me)CHC(O)Me}-2} 2 (μ-tmeda)] ( 2 ) or [Pd 2 {μ- O,C,N,O′ -{O═CC 6 H 4 {NC(Me)CHC(O)Me}-2} 2 }] ( 3 ), respectively. The latter reacted with anionic or neutral ligands to give complexes Bu 4 N[{Pd{ C,N,O- {C(O)C 6 H 4 {NC(Me)CHC(O)Me}-2} 2 (μ-OH)] ( 4 ), Q[Pd{ C,N,O- {C(O)C 6 H 4 {NC(Me)CHC(O)Me}-2}}Cl] [Q = PPN ( 5a ), NMe 4 ( 5b )], or [{Pd{ C,N,O- {C(O)C 6 H 4 {NC(Me)CHC(O)Me}-2}L] (L = CN t Bu ( 6a ), CNXy ( 6b ), PPh 3 ( 6c ), NH 3 ( 6d ), NH 2 Me ( 6e ), MeCN ( 6f ), dmso ( 6g )), respectively. The reaction of dimethylacetylenedicarboxylate (DMAD) with [PdI{C 6 H 4 {NHC(Me)CHC(O)Me}-2}(tmeda)] (1:1) afforded [PdI{C 6 H 4 {NHC(Me)C{ Z- C(CO 2 Me)═CH(CO 2 Me)}C(O)Me}}-2}(tmeda)] ( 7 Z ), resulting from the insertion of the alkyne into the C(sp 2 )−H bond of the enaminone substituent. 7 Z isomerized into the E analogue ( 7 E ) when heated in toluene at 95 °C and reacted in two steps with AgClO 4 and XyNC (1:1:2) to give the C,N,O-pincer derivative Pd{ C,N, O-{C(═NXy)C 6 H 4 {NC(Me)C{C(CO 2 Me)═CHCO 2 Me)}C(O)Me}-2}(CNXy)] ( 8 ) as a mixture of the Z and E isomers. The latter complex converted, after a photochemical oxygenation, into the palladacycle [Pd{ C,N,O -{C(═NXy)C 6 H 4 {N(dmoc)}-2](CNXy)]·2CHCl 3 ( 9 ), where the imino substituent dmoc is the cycle 1,2-di(methoxycarbonyl)-3-oxocyclopent-1-ene-4-yl. Compound 8 or 9 reacted with triflic or picric acid to give the species Pd{ C,N, O-{C(═NHXy)C 6 H 4 {NC(Me)C{C(CO 2 Me)═CHCO 2 Me)}C(O)Me}-2}(CNXy)]OTf ( 10 ) or [Pd{ C,N,O -{C(═NXy)C 6 H 4 {N(dmoc)}-2](CNXy)]·Hpic ( 11; Hpic = picric acid), respectively. The crystal structures of complexes 2, 3, 5a, 6b, 6c, 6e, 7 Z, 7 E, and 10 have been determined.