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

Reaction of the Schiff‐base ligands 4‐(4‐NC 5 H 4 )C 6 H 4 C(H)=N(C 6 H 3 OH‐2‐ t Bu‐5) ( a ) and (4‐NC 5 H 4 )C(H)=N(C 6 H 3 OH‐2‐ t Bu‐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 Ph 2 P(CH 2 ) 4 PPh 2 (dppb), Fe(C 5 H 4 PPh 2 ) 2 (dppf), Ph 2 PC(H)=C(H)PPh 2 ( t ‐dppe) and Ph 2 P(CH 2 ) 6 PPh 2 (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 [RuCl 2 (CO)(dmf)(PPh 3 ) 2 ] in chloroform at room temperature for 2 d afforded 11b . Treatment of ligands (2‐NC 5 H 4 )C(H)=N(C 6 H 4 OH‐2) ( c ) and (2‐NC 5 H 4 )C(H)=N(C 6 H 3 OH‐2‐ t Bu‐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 K 2 [PdCl 4 ], 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)