New palladacycles containing terdentate [C,N,O]n- (n = 0, 1, 2) or tetradentate [N,C,O,N′]n- in = 1, 2 ligands. the first 1,2-dihydroquinazoline-4-yl complexes

Article abstract of DOI:10.1021/om800205g

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 = 'Bubpy (1), N,N,N,′N′-tetramethylethylenediamine = tmeda (2)). These complexes react with PPh₃ (1:2) to give trans-[PdI(Ar)(PPh ₃)₂] (3) or with TlTfO (TfO = CF₃SO ₃) to give [Pd{C,C-C₆H₄{NH=C(Me)CHC(O)Me}-2] (N^N)]TfO (N^N = 'Bubpy (4), tmeda (S)), which, in turn, react with neutral monodentate ligands (L, 1:1) to give complexes [Pd(Ar)(N^N)(L)] (N^N = 'Bubpy, L = PPh₃ (6), NAN = 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 [Pd ₂I₂(CNXy)₄] (9, Xy = C₆H ₃Me₂-2,6) or trans-[PdI₂(Ct=NH ^tBu)Ar}(CN^tBu)] (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 5reacts with XyNC(1:1) to give the dimeric complex [Pd{μ-N,C,N′,O-N(Xy){=CC ₆H₄{NC(Me)CHC(Me)O}-2} }]₂ (13), which reacts with excess HTfO to give [Pd[μ-N,C,N′,O-N(Xy) ({=CC₆H ₄ (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)C ₆H₄{N=C-(Me)CH₂C(O)Me }-2} (PPh ₃)J(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)OJ-2}L]X (X/R/L = ClO₄/Bu/BuNC (21), ClO₄ZXyZXyNC (22), TfO/ XyZPPh ₃ (23)), analogues of 19 or 20, respectively. The reaction of 21 with Na₂CO₃ (2:1) allowed the synthesis of [Pd(C,N,O-C(=N ^tBu)C₆H₄{NC(Me)CHC(Me)O}-2}(CN^tBu)] (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-dihydroquinazoline4-yl complexes trans-[PdI₂{C(=NXy)C(Me){CH₂C(O)Me}NHC₆H ₄-2}(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)NC ₆H₄C=NXyJ} {μ-N,C,N,′ O-N(XyH=CC ₆H₄(NC(Me)CH₂C(Me)O}}]TfO (14b) were obtained alongside those of 14a, and the corresponding crystal structure was also solved.