Synthesis and Reactivity of a Cyclooctatetraene‐Like Polyphosphorus Ligand Complex [Cyclo‐P₈]

Abstract

The thermolysis of Cp'''Ta(CO) 4 with white phosphorus (P 4 ) gives access to [{Cp'''Ta} 2 (μ,η 2 : 2 : 2 : 2 : 1 : 1 -P 8 )] (A), representing the first complex containing a cyclooctatetraene-like (COT) cyclo-P 8 ligand. While ring sizes of n > 6 have remained elusive for cyclo-P n structural motifs, the choice of the transition metal, coligand and reaction conditions allowed the isolation of A. Reactivity investigations reveal its versatile coordination behaviour as well as its redox properties. Oxidation leads to dimerization to afford [{Cp'''Ta} 4 (μ 4 ,η 2 : 2

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

“…The in situ halide abstraction with suitable Tl + salts was assumed to be the most promising route [17][18][19]21,22] to generate reactive electrophiles. So far, however, this methodology has only yielded singly functionalized E n ligand complexes.…”

“…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.…”

“…[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).…”

Synthesis of Carbene-Stabilized PNPN Fragments and Their Carbene-Dependent Redox Properties

“…Phosphorus mononitride (PN) is a molecule of long-standing fundamental intrigue, − owing both to it being the first phosphorus compound detected in interstellar media , and its isoelectronic relationship with small molecules of critical importance, such as N 2 , CO, and HCCH. In spite of this, the synthesis of PN-containing compounds is limited (Chart ), − due to its proclivity to undergo uncontrolled oligomerization to insoluble, ill-defined, material. , As linear and cyclic oligomers of PN should be isoelectronic with polyenes and polyaromatic hydrocarbons, respectively, and accordingly may exhibit interesting electronic properties, they are attractive synthetic targets of both fundamental and applied interest. ,,, While numerous compounds consisting of catenated, low-valent, heavy pnictogens such as phosphorus and arsenic are known, ,− their synthesis is often dependent on the direct functionalization of elemental P 4 or As 4 , preventing the direct transposition of these strategies to PN. Further, compounds containing linear chains of more than three nitrogen atoms are far rarer, , owing to their thermodynamic and kinetic instabilities toward dinitrogen extrusion, and, to our knowledge, no general strategies for the controlled synthesis for low-valent heteropnictogen chains are known.…”

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

“…17 Surprisingly, a much larger cyclo-P 8 complex can be functionalised with arsenium ions in an addition reaction, affording salts of the exotic cation [{Cp 0 0 0 Ta} 2 (m,Z 2 : 2:2 : 2 : 1 : 1 : 1 : 1 -P 8 AsCy 2 )] + . 18 Despite the precedent for the synthetic utility of pnictogenium ions for the preparation of transition metal-stabilised polyphosphorus cations, a systematic evaluation of the reactivity trend from lighter phosphenium to its heavier homologues is still missing. Most notably, the reactivity of polyphosphorus complexes towards stibenium ions is completely unexplored to the best of our knowledge.…”