Functionalization, Fragmentation, and Expansion of cyclo-PR Ligands.

In this study, three isolobal complexes of the form [{LM}(η-PR)] ({LM}  = {CpMo(CO)} (A), {Cp'''Ni} (B), {Cp'''Co} (C), R = Ph, iPr; Cp''' = 1,2,4-BuCH) are reacted with nucleophilic carbenes (L). While C does not show any reactivity, the cationic complexes A and B undergo addition reactions. The respective products [CpMo(CO)(η-PRL)] (1a - d) and [Cp'''Ni(η-PRL)] (3a - d) show different geometries for the L-PPR ligands. Their reactivity towards EtO results in either a simple addition (for 1) or a complex addition, ring-opening, rearrangement sequence (for 3). Moreover, [Cp'''Ni(η-IDippPP(OEt)PPPr)] (4) could be methylated by the reaction with MeOTf, which affords an iso-tetraphosphine ligand, marking the first example of complete functionalization of a polyphosphorus ligand to a complexed phosphine. Mechanistic studies shed light upon the fundamental principles, which differentiate the influence of the isolobal {CpMo(CO)}, {Cp'''Ni}, and {Cp'''Co} transition metal units. Lastly, 3a-d were chosen as model substrates for further nucleophilic functionalization. In this regard, 3 reacts with [CN] in a [3+1] fragmentation reaction affording the dimerized species [{Cp'''Ni}(μ,η-cyclo-P(PR))] (6a: R = Ph, 6b: R  =  Pr) together with IDippP-CN. In contrast, the reaction with [ECO] (E = P, As) led to an extension of the pnictogen framework yielding [Cp'''Ni(η-EPPhIDipp)] (8a: E = P, 8b: E = As).