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The synthesis of the complexes [(q6-C6H6)Fe(CO)(L){=C(NHR')(R2)}]BF, [L = PPh,, P ( p -Tol),; R' = Me, CH,Ph; R2 = Me, Bu] is described. Photofragmentation voltammetry is used to demonstrate that the primary photoprocess is loss of the phosphine ligand in all four carbene complexes. A common intermediate is observed when the analogous aminocarbenes are studied.We have recently demonstrated that reversible phosphine rather than CO dissociation occurs in the homochiral amino-,, P(p-Tol),; R' = Me, Et; R' = CH,Ph].' The method used only provided indirect evidence for this process. Photofragmentation voltammetry has been successfully used to detect transient species in a variety of inorganic system^.^*^*^ The aminocarbenes [(q 5-C , H ,)Fe(CO)(L){ =C(NHMe)(Me)}] -BF, [L = PPh,, P(p-Tol),] were studied by this technique and direct evidence was found for initial loss of phosphine to produce a common residual iron inte~mediate.~ We describe herein the synthesis of these two compounds in addition to [(q5-C5H5)Fe(CO)(L){=C(NHCH2Ph)(Bu)}]BF, [L = PPh,, P(p-Tol),]. The full photofragmentation voltammetry studies on these four compounds is also presented. Paper 3/02382F

Photofragmentation volammetry is used to demonstrate directly the primary loss of P(Ar), from [ (q5-C,H,)Fe(CO)(PAr,)=C(NHMe)Me]+BF,-(Ar = phenyll andp-tolyl2) on irradiation withvisible light. In contrast, no loss of carbon monoxide is observed.Contrary to accepted dogma that complexes containing both phosphine and carbon monoxide ligands preferentially lose the latter on photolysis, we have recently reported that, on irradiation of aminocarbenes of the type [(q 5-C5H5)Fe(CO)-(PAr,)=C(NHR)R] + BF,-, the primary photoreaction is loss of the phosphine ligand. The primary process of phosphine loss was demonstrated indirectly by stereochemical techniques and phosphine exchange experiments. We describe here the use of photofragmentation voltammetry (PFV) to monitor this process directly for the complexes [(q 5-C5H5)Fe(CO)(PAr,)= C(NHMe)Me]+BF,-(Ar = phenyl 1 and p-tolyl 2): in each case distinctive fingerprints for the relevant free phosphine and for the common residual iron fragment are observed. BF, ' p k 3 Me c BF, ' ! J Paper 3/01371E