Direct nitration of aryl groups σ-bound to ruthenium(II)

A new method has been developed for the preparation of nitroaryl transition metal complexes using copper(II) nitrate in the presence of acetic anhydride (Menke conditions) to directly nitrate an aryl group which is already σ-bound to a transition metal centre. Under these conditions ruthenium(II) aryl complexes of the type: (where R1=R2=H; R1=H, R2=CH3; R1=CH3, R2=H) react to yield three distinct types of nitroaryl-containing products (I–III). The preparation and characterisation of these compounds are described. X-ray crystallographic data for one example of each of the three types of compound, are also reported. The compounds that have been studied crystallographically are Ru(C6H4NO2-4)(η2-O2CCH3)(CO)(PPh3)2 (1a), C45H37NO5P2Ru·(CH2Cl2)0.5, a = 20.254(5), b=19.437(8), c=22.629(3) A, β=115.390(10)°, monoclinic, space group C2/c, Z=8; Ru(C6H4N[O]O-2)- Cl(CO)(PPh3)2 (4a), C43H34ClNO3P2Ru, a=9.331(3), b=12.443(2), c=16.346(3) A, α=82.81(2), β=85.03(2), γ=74.76(2)°, triclinic, space group P1, Z=2; Ru(C6H2CH3-2,NO2-4,N[O]O-6)Cl(CO)(PPh3)2 (5b), C44H35Cl- N2O5P2Ru·(CH2Cl2)2, a=19.497(3), b=14.502(3), c=19.340(5) A, β=122.79(1)°, monoclinic, space group Cc, Z=4.