Cyclobutadieneiron nitrosyl complexes

The air stable yellow-orange complexes of cyclobutadieneiron dicarbonyl nitrosyl hexafluorophosphate, R₄C₄Fe(CO)₂NO]⁺PF^-₆; R = H, CH₃, Ph, were prepared by the reaction of R₄C₄Fe(CO)₃ and nitrosonium hexafluorophosphate. These complexes undergo facile monocarbonyl substitution reactions with various Lewis bases (L) to afford products of the type R₄C₄Fe(CO)(NO)L]⁺PF^-₆, R = H, L = Ph₃P, Ph₃As, Ph₃Sb or R = Ph; L = Ph₃P, Ph₃As; a dicarbonyl substitution product of the type R₄C₄Fe(NO)L₂]⁺PF^-₆, R = Ph; L = (PhO)₃P, was also isolated and characterized.