Synthesis of metallacycles by 1,3-dipolar cycloaddition reactions between low-valent metal carbonyls and aryl nitrile N-oxides

Article abstract of DOI:10.1021/om00093a012

Reaction of low-valent metal carbonyl complexes with aryl nitrile N-oxides leads to the synthesis of novel five-membered metallacycles by 1,3-dipolar cycloaddition of the aryl nitrile N-oxide to the M-CO bond of the low-valent metal carbonyl complex. The syntheses of these metallacycles from metallacarborane carbonyl anions [closo-3-PPh₃-3-(CO)-3,1,2-MC₂B₉H ₁₁]^- (M = Ir, Rh) and [closo-2-PPh₃-2-(CO)-2,1,7-RhC₂B₉H ₁₁]^- and a number of pentamethylcyclopentadienyl and cyclopentadienyl complexes of Co, Rh, and Ir of the type (η⁵-C₅R₅)LM(CO) (R = H, Me; L = PPh₃, PMe₃, CO) and the metal carbonyl anions M(CO)₅^- (M = Mn, Re) are described. The syntheses of these metallacycles proceed in good yield (50-85%). The factors influencing the chemical and thermal stability of these metallacycles are discussed, and single-crystal X-ray diffraction studies of the metallacycles [PPN] [closo-2-(PPh₃)-2-{η²-C(m-FC₆H ₄)-NOC(=O)-}-2,1,7-RhC₂B₉H₁₁] ([PPN]·5b) and (η⁵-C₅Me₅)(PMe₃)Rh{η ²-C(p-FC₆H₄)NOC(=O)-} (9) are reported and their structures discussed. Crystallographic data for 9: space group P2₁/c; a = 9.0376 (7) A?, b = 14.8675 (13) A?, c = 16.1965 (14) A?, β = 99.074 (3)°, V = 2149 A?³, and Z = 4. For PPN·5b: space group P1; a = 12.910 (5) A?, b = 13.270 (5) A?, c = 18.402 (7) A?, α = 88.24 (3)°, β = 109.46 (3)°, γ = 83.89 (3)°, V = 2948 A?³, and Z = 2.