Rhenium carbonyl complexes. Synthesis and characterisation of NN′-diarylamidines, R′NHC(R)NR′(R = H, Me, or Ph, R′= Ph or C6H4Me-p), and related carbamoyl derivatives

Abstract

NN′-Diarylacetamidines R′NHC(Me)NR′, NN′-diarylbenzamidines R′NHC(Ph)NR′, and NN′-diarylformamidines R′NHC(H)NR′(R′= Ph or C₆H₄Me-p) react thermally or photolytically with [Re(CO)₅X] and/or [{Re(CO)₄X}₂](X = Cl or Br) to afford air-stable, white complexes, [Re(CO)₄{R′NC(R)NHR′}X], containing monodentate amidine ligands. The corresponding lithioamidines (R = Me or Ph) gave white carbamoyl complexes [Re(CO)₄{CON(R′)C(R)NR′}], which are converted thermally to NN′-bidentate [Re(CO)₄{R′NC(R)NR′}] and ortho-metallated [[graphic omitted]₆H₃R″}{R′NC(R)NHR′}](R″= H or Me). The latter complexes are also formed by further reaction of the carbamoyl complexes with the corresponding amidine. The carbamoyl complexes react with PPh₃ to form [Re(CO)₃(PPh₃){R′NC(R)NR′}]. Lithioamidines in excess react with [Re(CO)₅X](X = Cl or Br) complexes to give adducts formulated as Li⁺[Re(CO)₃{CON(R′)C(R)NR′}₂]^–. The new complexes are characterised, and structural data obtained by i.r. and n.m.r. spectroscopy.