The Difficulty of Coordinating Mutually<i>trans</i>Phosphine and Aryl Ligands in Palladium Complexes and Its Relation to Important Coupling Processes. Syntheses and Crystal Structures of a Family of Palladium Phosphino, Triflato, Perchlorato, and Aquo-2-(arylazo)aryl Complexes

Abstract

The reaction between [Pd(C6H3NNR-2, X-5)Cl]2 and phosphines gives [Pd(C6H3NNTo-2,Me-5)Cl(L)] [To = C6H4Me-4, L = PEt3 (1a), PPh2Me (1b)] or trans-[Pd(C6H3N2To-2,Me-5)ClL2] (L = PEt3 (2a), PPh2Me (2b), L2 = bis(diphenylphosphino)methane = dppm (2c)) or trans-[Pd(C6H3N2X-2, R-5)Cl(μ-dppm)]2 (X = Me, R = To (3a); X = H, R = Ph (3b)), depending on the molar ratio of the reagents. Tl(OTf) (OTf = O3SCF3), AgClO4, or AgSbF6 react with 1a,b, 2a, 2c, or 3a to give, variously, [Pd(C6H3NNTo-2,Me-5)(Y)(L)] (L = PEt3, Y = TfO (4a); L = PPh2Me, Y = TfO (4b), ClO4 (4b‘)), trans-[Pd(C6H3N2To-2,Me-5)(OTf)(PEt3)2] (5), [Pd(C6H3N2To-2,Me-5)(η1-dppm)(η2-dppm)]TfO (6), or [Pd(C6H3NNR-2,X-5)(η2-dppm)]Y (X = Me, R = To, Y = TfO (7a)). Complexes [Pd(C6H3NNR-2,X-5)(η2-dppm)]SbF6 (X = Me, R = To (7a‘); X = H, R = Ph (7b)) can be prepared by reacting [Pd(C6H3NNR-2,X-5)Cl]2 with AgSbF6 and dppm. Complex 4b‘ reacts with PPh2Me to give [Pd(C6H3N2To-2,Me-5)(PPh2Me)3]ClO4 (8). Attempts to obtain single crystals of 4a, [Pd(C6H3NNR-2,X-5)(PPh3)(Me2CO)]ClO4, or 7b lead to different products. From 4, an insertion into the Pd−OTf bond of one molecule of water gives [Pd(C6H3NNTo-2,Me-5(OH2···OTf)(PEt3)] (9) while substitution of the acetone molecule by two water molecules occurs in the second case to give [Pd(C6H3NNTo-2,Me-5){(μ3-OH2)(···OClO3)(···OH2)}(PPh3)] (10). Finally, ready oxidation in the air of 7b gives [Pd(C6H4NNPh-2)(η2-dppmO)]SbF6 (11) [dppmO = bis(diphenylphosphino)methane monoxide]. [Pt(PPh3)3] reacts with [Hg(C6H3N2To-2, Me-5)Cl] to give trans-[Pt(C6H3N2To-2,Me-5)Cl(PPh3)2] (12), which in turn reacts with Tl(OTf) to give [Pt(C6H3NNTo-2,Me-5)(PPh3)2]TfO (13). Crystal structures of 2c·1/2CH2Cl2, 4b‘, 5, 6, 7a, 9, 10, and 11·2MeOH have been determined.