Reactivity of tetranuclear complexes of Pd(II) with potentially homo- and heterobidentate ligands

Abstract Reaction of the cyclometallated compounds [Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)-5-RC 6 H 3 ]}] 4 ( 1a : R = H, 1b : R =  t Bu) with the phosphine PPh 2 [2-(COH)C 6 H 4 ], in a complex/phosphine 1:4 molar ratio gave the mononuclear cyclometallated complexes [{Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)-5-RC 6 H 3 }}{PPh 2 [2-(HOC)C 6 H 4 ]}] ( 2a : R = H; 2b : R =  t Bu), upon cleavage of the tetranuclear structure. Treatment of complex 1a with the diarsine AsPh 2 (CH 2 ) 2 Ph 2 As (dppae) in a 1:2 or 1:4 molar ratio only yielded the dinuclear compound [{Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)C 6 H 4 ]}} 2 {μ-AsPh 2 (CH 2 ) 2 Ph 2 As}] ( 3a ), regardless the molar ratio used. Reaction of the cyclometallated tetramers with Ph 2 P(CH 2 ) 2 Ph 2 As (arphos) in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)C 6 H 4 ]}{PPh 2 (CH 2 ) 2 Ph 2 As-P}] ( 4a ) and [Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)-5- t BuC 6 H 3 ]}{PPh 2 (CH 2 ) 2 Ph 2 As-P}] ( 4b ), with the P, As ligand coordinated through the phosphorus atom, as air-stable solids. Treatment of 1a with arphos in a 1:2 molar ratio gave the dinuclear complex [{Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)C 6 H 4 ]}} 2 {μ-PPh 2 (CH 2 ) 2 Ph 2 As}] ( 5a ). Reaction of 1b with the diphosphine Ph 2 P(C 6 H 4 )O(C 6 H 4 )PPh 2 gave the dinuclear compound [{Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)- t BuC 6 H 3 ]}} 2 {μ-PPh 2 (C 6 H 4 )O(C 6 H 4 )Ph 2 P}] ( 6b ) for all the complex 1b /phosphine molar ratios tested. Reaction of the cyclometallated tetramer 1a with PPh 2 [4-(NMe 2 )C 6 H 4 ] (in 1:2 or 1:4 molar ratio) produced the mononuclear cyclometallated complex [Pd{2,3,4-(MeO) 3 C 6 HC(H) N[2-(O)C 6 H 4 ]}{PPh 2 [4-(NMe 2 )C 6 H 4 ]}] ( 7a ) as an air-stable solid.