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

摘要

Insertion of CO into the Pd-C_(aryl) bond of complexes [PdI{C _6H_4{NHC(Me)CHC(O)Me}-2}(N^N)] afforded the benzoyl derivatives [PdI{C(O)C_6H_4{NHC(Me)CHC(O)Me}-2}(N^N)] [N^N = 4,4′-di-tert-butyl-2,2′-dipyridyl (tBubpy) (1a), N,N,N′,N′-tetramethylethylenediamine (tmeda) (1b)]. The reactions of [Pd{C,C-C_6H_4{NH=C(Me)CHC(O)Me}-2}(tmeda)]OTf (OTf = CF_3SO_3) with excess CO and tmeda (2:1) or HOTf (1:1) produced the dinuclear benzoyl complex [{Pd{C,N,O-{C(O)C_6H _4{NC(Me)CHC(O)Me}-2}_2(μ-tmeda)] (2) or [Pd _2{μ-O,C,N,O′-{O=CC_6H_4{NC(Me)CHC(O)Me}- 2}_2}] (3), respectively. The latter reacted with anionic or neutral ligands to give complexes Bu_4N[{Pd{C,N,O-{C(O)C_6H _4{NC(Me)CHC(O)Me}-2}_2(μ-OH)] (4), Q[Pd{C,N,O-{C(O) C_6H_4{NC(Me)CHC(O)Me}-2}}Cl] [Q = PPN (5a), NMe_4 (5b)], or [{Pd{C,N,O-{C(O)C_6H_4{NC(Me)CHC(O)Me}-2}L] (L = CN~tBu (6a), CNXy (6b), PPh_3 (6c), NH3 (6d), NH_2Me (6e), MeCN (6f), dmso (6g)), respectively. The reaction of dimethylacetylenedicarboxylate (DMAD) with [PdI{C_6H _4{NHC(Me)CHC(O)Me}-2}(tmeda)] (1:1) afforded [PdI{C_6H _4{NHC(Me)C{Z-C(CO_2Me)=CH(CO_2Me)}C(O)Me}}-2} (tmeda)] (7Z), resulting from the insertion of the alkyne into the C(sp 2)-H bond of the enaminone substituent. 7Z isomerized into the E analogue (7E) 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_6H_4{NC(Me)C{C(CO_2Me)= CHCO_2Me)}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_6H_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_6H _4{NC(Me)C{C(CO_2Me)=CHCO_2Me)}C(O)Me}-2}(CNXy)] OTf (10) or [Pd{C,N,O-{C(=NXy)C_6H_4{N(dmoc)}-2](CNXy)] ·Hpic (11; Hpic = picric acid), respectively. The crystal structures of complexes 2, 3, 5a, 6b, 6c, 6e, 7Z, 7E, and 10 have been determined.