π-Complexes as ligands in transition-metal compounds. Communication 7. Chromium π-arenecarbonyl complexes with azacymantrene as a two-electron ligand

Conclusions The previously unknown chromium -arenecarbonyl complexes containing -pyrrolylmanganesetricarbonyl as a two-electron ligand, C₆H₆Cr(CO)₂NC₄H₄Mn(CO)₃, Me₃C₆H₃Cr(CO)₂NC₄H₄Mn(CO)₃, and PhCOOMeCr(CO)₂NC₄H₄Mn(CO)₃, have been synthesized and characterized by spectroscopic methods.For Communication 6, see [6].Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2780–2782, December, 1985.     

The 13C NMR spectra of π-arenechromium carbonyl complexes

The ¹³C NMR spectra of π-arenechromium complexes XC₆H₅Cr(CO)₂L (where I, L  CO; II, L  PPh₃; X  aliphatic and aromatic substituents) were investigated. The effect of the nature of the substituent X on the chemical shifts of the carbon atoms of the aromatic ring in these complexes was analyzed.It was established that a correlation exists between δ(¹³C) and σ_R (Taft's constant) in complexes I, not only for C(4) nuclei but also for C(3) metal atoms, the difference being that the slopes of the corresponding curves are opposite.