Ring expansion vs. addition – reactivity of a cyclo-P₄ complex towards pnictogenium cations

Abstract

A systematic reactivity study of the cyclo-P4 complexes [CpRTa(CO)2(4-P4)] towards pnictogenium cations results in the formation of functionalised interpnictogen cations. Phosphenium ions insert into one of the P–P bonds to...

Electrophilic Functionalization of a Hexaphosphabenzene Ligand in [(Cp*Mo)2(μ,η6 : 6‐P6)]

“…So far, however, this methodology has only yielded singly functionalized E n ligand complexes. [17][18][19]21,22] Examples of multi-and regioselectively functionalized E n ligand complexes generated by this method are still unknown. Therefore, the group 16 electrophile precursor PhSeBr in combination with A and the abstracting agent Tl [26,27] was selected.…”

“…The in situ halide abstraction with suitable Tl + salts was assumed to be the most promising route [17–19,21,22] to generate reactive electrophiles. So far, however, this methodology has only yielded singly functionalized E n ligand complexes [17–19,21,22] .…”

“…The in situ halide abstraction with suitable Tl + salts was assumed to be the most promising route [17–19,21,22] to generate reactive electrophiles. So far, however, this methodology has only yielded singly functionalized E n ligand complexes [17–19,21,22] . Examples of multi‐ and regioselectively functionalized E n ligand complexes generated by this method are still unknown.…”

“…This dependency was demonstrated by functionalizations of [{CpMo(CO) 2 } 2 (μ,η 2 : 2 ‐PE)] (E=P, As, Sb) with group 14 electrophiles (Scheme 1, IV ), showing the selective substitution of the E n ligand by the electrophile [17] . In contrast, the reaction of [Cp'''Ni(η 3 ‐P 3 )] (Cp'''=η 5 ‐1,2,4‐ t Bu 3 C 5 H 2 ) (Scheme 1, V ) as well as [Cp'''Ta(CO) 2 (η 4 ‐P 4 )] with in situ generated phosphenium ions reveal an insertion into one P−P bond of the cyclo ‐P 3 and cyclo ‐P 4 ligand, respectively [18,19] . Interestingly, more extended polyphosphorus frameworks such as [Cp*Fe(η 5 ‐P 5 )] (Cp*=η 5 ‐C 5 Me 5 ) (Scheme 1, VI ) [20,21] or the very recently reported [{Cp'''Ta} 2 (μ,η 2 : 2 : 2 : 2 : 1 : 1 ‐P 8 )] ( VII ) [22] exclusively show mono‐substitution at the P n ligand.…”

“…[17] In contrast, the reaction of [Cp'''Ni(η 3 -P 3 )] (Cp''' = η 5 -1,2,4-t Bu 3 C 5 H 2 ) (Scheme 1, V) as well as [Cp'''Ta(CO) 2 (η 4 -P 4 )] with in situ generated phosphenium ions reveal an insertion into one PÀ P bond of the cyclo-P 3 and cyclo-P 4 ligand, respectively. [18,19] Interestingly, more extended polyphosphorus frameworks such as [Cp*Fe(η 5 -P 5 )] (Cp* = η 5 -C 5 Me 5 ) (Scheme 1, VI) [20,21] or the very recently reported [{Cp'''Ta} 2 (μ,η 2 : 2 : 2 : 2 : 1 : 1 -P 8 )] (VII) [22] exclusively show mono-substitution at the P n ligand. Despite the previously reported examples of electrophilic functionalizations of E n ligand complexes with main group electrophiles, no detailed investigations have so far been undertaken for the prototypical hexaphosphabenzene ligand in [{Cp*Mo} 2 (μ,η 6 : 6 -P 6 )] [23] (A).…”