om800205g_si_006.cif (13.9 kB)

New Palladacycles Containing Terdentate [C,N,O]n (n = 0, 1, 2) or Tetradentate [N,C,O,N′]n (n = 1, 2) Ligands. The First 1,2-Dihydroquinazoline-4-yl Complexes

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posted on 14.07.2008 by José Vicente, María Teresa Chicote, Antonio Jesús Martínez-Martínez, Peter G. Jones, Delia Bautista
The reaction of IC6H4{NHC(Me)CHC(O)Me}-2 (IAr) with [Pd2(dba)3]·dba (“Pd(dba)2”, dba = dibenzylideneacetone) gives, in the presence of bidentate ligands N^N (1:1:1), cis-[PdI(Ar)(N^N)] (N^N = 4,4′-tert-butyl-2,2′-bipyridine = tBubpy (1), N,N,N′,N′-tetramethylethylenediamine = tmeda (2)). These complexes react with PPh3 (1:2) to give trans-[PdI(Ar)(PPh3)2] (3) or with TlTfO (TfO = CF3SO3) to give [Pd{C,C-C6H4{NHC(Me)CHC(O)Me}-2}(N^N)]TfO (N^N = tBubpy (4), tmeda (5)), which, in turn, react with neutral monodentate ligands (L, 1:1) to give complexes [Pd(Ar)(N^N)(L)] (N^N = tBubpy, L = PPh3 (6), N^N = tmeda, L = PPh3 (7), tBuNC (8)). The reaction of IAr with “Pd(dba)2” and RNC (R = Xy, tBu) in 1:1:2 molar ratio produces a mixture containing [Pd2I2(CNXy)4] (9, Xy = C6H3Me2-2,6) or trans-[PdI2{C(NHtBu)Ar}(CNtBu)] (10), respectively, but using an excess of RNC (1:1:5 molar ratio), complexes trans-[PdI{C(NR)Ar}(CNR)2] (R = tBu (11), Xy (12)) are obtained instead. Complex 5 reacts with XyNC (1:1) to give the dimeric complex [Pd{μ-N,C,N′,O-N(Xy){CC6H4{NC(Me)CHC(Me)O}-2}}]2 (13), which reacts with excess HTfO to give [Pd{μ-N,C,N′,O-N(Xy){CC6H4{NC(Me)CH2C(O)Me}-2}}]2(TfO)2 (14a) or with neutral monodentate ligands (L) to give neutral mononuclear pincer complexes [Pd{C,N,O-C(NXy)C6H4{NC(Me)CHC(Me)O}-2}(L)] (L = PPh3 (15), tBuNC (16a), XyNC (17)), which react with excess of HTfO to give the corresponding dicationic [Pd{C,N,O-C(NHXy)C6H4{NC(Me)CH2C(O)Me}-2}(PPh3)](TfO)2 (18) or monocationic pincer derivatives [Pd{C,N,O-C(NHXy)C6H4{NC(Me)CHC(Me)O}-2}(CNR)]TfO (R = tBu (19), Xy (20)), respectively. The reaction of complex 11 or 12 with AgClO4 (1:1) or that of 14a with PPh3 (1:2) affords [Pd{C,N,O-C(NHR)C6H4{NC(Me)CHC(Me)O}-2}L]X (X/R/L = ClO4/tBu/tBuNC (21), ClO4/Xy/XyNC (22), TfO/Xy/PPh3 (23)), analogues of 19 or 20, respectively. The reaction of 21 with Na2CO3 (2:1) allowed the synthesis of [Pd{C,N,O-C(NtBu)C6H4{NC(Me)CHC(Me)O}-2}(CNtBu)] (16b). The reaction of 1 or 3 with HI and XyNC in 1:1:2 or 1:1:1 molar ratio, respectively, produces the first 1,2-dihydroquinazoline-4-yl complexes trans-[PdI2{C(NXy)C(Me){CH2C(O)Me}NHC6H4-2}(L)] (L =XyNC (24), PPh3 (25)). The crystal structures of complexes 1, 3, 5, 7, 10, 13, 14a, 17, 21, 22, and 24 have been determined. Single crystals of complex [Pd{μ-O,N,C,N′-OC(Me)CHC(Me)NC6H4CNXy}{μ-N,C,N′,O-N(Xy){CC6H4{NC(Me)CH2C(Me)O}-2}}]TfO (14b) were obtained alongside those of 14a, and the corresponding crystal structure was also solved.

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