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

The reaction of IC 6 H 4 {NHC(Me)CHC(O)Me}-2 (IAr) with [Pd 2 (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 = t Bubpy ( 1 ), N,N,N′,N′ -tetramethylethylenediamine = tmeda ( 2 )). These complexes react with PPh 3 (1:2) to give trans -[PdI(Ar)(PPh 3 ) 2 ] ( 3 ) or with TlTfO (TfO = CF 3 SO 3 ) to give [Pd{ C,C -C 6 H 4 {NH═C(Me)CHC(O)Me}-2}(N^N)]TfO (N^N = t Bubpy ( 4 ), tmeda ( 5 )), which, in turn, react with neutral monodentate ligands (L, 1:1) to give complexes [Pd(Ar)(N^N)(L)] (N^N = t Bubpy, L = PPh 3 ( 6 ), N^N = tmeda, L = PPh 3 ( 7 ), t BuNC ( 8 )). The reaction of IAr with “Pd(dba) 2 ” and RNC (R = Xy, t Bu) in 1:1:2 molar ratio produces a mixture containing [Pd 2 I 2 (CNXy) 4 ] ( 9, Xy = C 6 H 3 Me 2 -2,6) or trans -[PdI 2 {C(═NH t Bu)Ar}(CN t Bu)] ( 10 ), respectively, but using an excess of RNC (1:1:5 molar ratio), complexes trans -[PdI{C(═NR)Ar}(CNR) 2 ] (R = t Bu ( 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){═CC 6 H 4 {NC(Me)CHC(Me)O}-2}}] 2 ( 13 ), which reacts with excess HTfO to give [Pd{μ- N,C,N′,O -N(Xy){═CC 6 H 4 {N═C(Me)CH 2 C(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)C 6 H 4 {NC(Me)CHC(Me)O}-2}(L)] (L = PPh 3 ( 15 ), t BuNC ( 16a ), XyNC ( 17 )), which react with excess of HTfO to give the corresponding dicationic [Pd{ C,N,O -C(═NHXy)C 6 H 4 {N═C(Me)CH 2 C(O)Me}-2}(PPh 3 )](TfO) 2 ( 18 ) or monocationic pincer derivatives [Pd{ C,N,O -C(═NHXy)C 6 H 4 {NC(Me)CHC(Me)O}-2}(CNR)]TfO (R = t Bu ( 19 ), Xy ( 20 )), respectively. The reaction of complex 11 or 12 with AgClO 4 (1:1) or that of 14a with PPh 3 (1:2) affords [Pd{ C,N,O -C(═NHR)C 6 H 4 {NC(Me)CHC(Me)O}-2}L]X (X/R/L = ClO 4 / t Bu/ t BuNC ( 21 ), ClO 4 /Xy/XyNC ( 22 ), TfO/Xy/PPh 3 ( 23 )), analogues of 19 or 20, respectively. The reaction of 21 with Na 2 CO 3 (2:1) allowed the synthesis of [Pd{ C,N,O -C(═N t Bu)C 6 H 4 {NC(Me)CHC(Me)O}-2}(CN t Bu)] ( 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 -[PdI 2 {C(═NXy)C(Me){CH 2 C(O)Me}NHC 6 H 4 -2}(L)] (L =XyNC ( 24 ), PPh 3 ( 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 6 H 4 C═NXy}{μ- N,C,N′,O -N(Xy){═CC 6 H 4 {NC(Me)CH 2 C(Me)O}-2}}]TfO ( 14b ) were obtained alongside those of 14a, and the corresponding crystal structure was also solved.