Cobalt metallacycles. Part 16. X-Ray structures of 4-iminocobaltacyclobutene complexes

Abstract

Three 4-iminocobaltacyclobutene complexes, [[graphic omitted](NC₆H₄Me-p)}(η⁵-C₅H₅)(PPh₃)] have been analysed by single-crystal X-ray analyses. Crystals of (1)(R¹= Ph, R²= CO₂Me; CH₂Cl₂ solvate) are triclinic, space group P, with a= 12.381(3), b= 13.987(4), c= 11.209(4)Å, α= 91.16(3), β= 103.30(2), γ= 77.14(2)°, Z= 2, and R= 0.066 for 3 055 reflections. Crystals of (2)(R′= Me, R²= CO₂Me) are monoclinic, space group P2₁/c, with a= 12.062(5), b= 14.945(4), c= 17.817(5)Å, β= 113.70(4)°, Z= 4, and R= 0.052 for 2 842 reflections. Crystals of (3)(R¹= CO₂Me, R²= Ph) are triclinic, space group P, with a= 12.271(6), b= 13.216(5), c= 10.833(4)Å, α= 96.07(3), β= 98.77(4), γ= 102.23(3)°, Z= 2, and R= 0.048 for 4 324 reflections. The Co–C(R¹) distance in these complexes depends on the bulkiness of the substituent R¹, varying from 1.966(8)Å for R¹= Ph (1), to 1.931(5)Å for R¹= CO₂Me (3), and to 1.908(7)Å for R¹= Me (2). In all cases the substituent of the imino group, C₆H₄Me-p, is located syn with respect to the metal. Treatment of (1) with methyl iodide gives a cationic complex which has been isolated as [[graphic omitted](NMeC₆H₄Me-p)}(η⁵-C₅H₅)(PPh₃)]PF₆(4). Crystals of (4) are triclinic, space group P, with a= 13.658(3), b= 14.142(2), c= 10.517(3)Å, α= 94.42(2), β= 95.39(1), γ= 102.62(1)°, Z= 2, and R= 0.082 for 2 314 reflections. The methyl group originating from methyl iodide is bound to the imino nitrogen. Metallacyclobutadiene character in (4) is apparent from the shorter metal–carbon bonds and more averaged C–C distances than in the parent complex (1).