Synthesis and Reactivity of Hetero‐Pnictogen Diazonium Analogs Stabilized by Transition Metal Units

Abstract

The reactivity of the mixed dipnictogen complexes [{CpMo(CO)2}2(μ,η2:2‐PE)] (E = P, As, Sb) towards different group 14 electrophiles is reported. The resulting library of cationic compounds [{CpMo(CO)2}2(μ,η2:2‐EPR)]+ (R = Mes (2,4,6‐C6H2Me3), CH3, CPh3, SnMe3) represents formally inorganic diazonium homologs which are stabilized by transition metal units. Modifying the steric and electronic properties of the electrophile drastically impacts the respective P‐R bond lengths and is accompanied by increasing (SnMe3>CPh3>CH3) the dynamic behavior in solution. In contrast to the well‐studied organic analogs, the prepared compounds are stable at room temperature. The subsequent reaction of the model substrate [{CpMo(CO)2}2(µ,η2:2‐P2Me)][OTf] ([OTf]‐ = [CF3SO3]‐) with different N‑heterocyclic carbenes (NHCs) leads to an addition at the unsubstituted P atom which is also predicted by computational methods. NMR spectroscopy confirms the formation of two isomers sync/gauche‐[{CpMo(CO)2}(μ,η2:1‐P(NHC)PMe){CpMo(CO)2}][OTf]. X‐ray crystallographic characterization and additional DFT calculations shed light on the spatial arrangement as well as on the possible formation pathways of the isomers.

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 [17–19,21,22] 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.…”

“…Depending on the electrophile used, different substitution patterns were achieved. 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] .…”