Cyclometallated [C,N,O] Complexes as Metalloligands: Synthesis and Structural Characterisation of New Di‐, Tri‐, Tetra‐ and Pentanuclear Heterometallic Complexes

Abstract

AbstractReaction of the Schiff‐base ligands 4‐(4‐NC5H4)C6H4C(H)=N(C6H3OH‐2‐tBu‐5) (a) and (4‐NC5H4)C(H)=N(C6H3OH‐2‐tBu‐5) (b) with palladium(II) acetate in toluene at 60 °C gave the tetranuclear orthometallated palladium complexes 1a and 1b, respectively, as air‐stable solids. Treatment of 1a and 1b with triphenylphosphane gave the mononuclear species 2a and 2b upon splitting of the polynuclear structure. Reaction of 1a with the tertiary diphosphanes Ph2P(CH2)4PPh2 (dppb), Fe(C5H4PPh2)2 (dppf), Ph2PC(H)=C(H)PPh2 (t‐dppe) and Ph2P(CH2)6PPh2 (dpph), and 1b with dppb and dppf, in a 1:2 molar ratio gave complexes 3a–6a and 3b and 4b, respectively. Reaction of 2a, 4a and 6a with hexacarbonylchromium or ‐tungsten and 2b and 3b with hexacarbonylchromium, ‐molybdenum or ‐tungsten in thf under UV activation gave complexes 7a–12a and 5b–10b, respectively, which contain an M(CO)5 fragment coordinated to the pyridine nitrogen atom. Treatment of 2b with [RuCl2(CO)(dmf)(PPh3)2] in chloroform at room temperature for 2 d afforded 11b. Treatment of ligands (2‐NC5H4)C(H)=N(C6H4OH‐2) (c) and (2‐NC5H4)C(H)=N(C6H3OH‐2‐tBu‐5) (d) with palladium(II) acetate yielded the mononuclear palladium acetate complexes 1c and 1d, respectively. Treatment of 1c and 1d with aqueous sodium chloride, or, alternatively, treatment of c and d with K2[PdCl4], gave chloropalladium complexes 2c and 2d, respectively. Treatment of 2c and 2d with silver perchlorate and triphenylphosphane in acetone gave the mononuclear phosphane complexes 3c and 3d, respectively.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)