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.