In a high‐yield one‐pot synthesis, the reactions of [Cp*M(η5‐P5)] (M=Fe (1), Ru (2)) with I2 resulted in the selective formation of [Cp*MP6I6]+ salts (3, 4). The products comprise unprecedented all‐cis tripodal triphosphino‐cyclotriphosphine ligands. The iodination of [Cp*Fe(η5‐As5)] (6) gave, in addition to [Fe(CH3CN)6]2+ salts of the rare [As6I8]2− (in 7) and [As4I14]2− (in 8) anions, the first di‐cationic Fe‐As triple decker complex [(Cp*Fe)2(μ,η5:5‐As5)][As6I8] (9). In contrast, the iodination of [Cp*Ru(η5‐As5)] (10) did not result in the full cleavage of the M−As bonds. Instead, a number of dinuclear complexes were obtained: [(Cp*Ru)2(μ,η5:5‐As5)][As6I8]0.5 (11) represents the first Ru‐As5 triple decker complex, thus completing the series of monocationic complexes [(CpRM)2(μ,η5:5‐E5)]+ (M=Fe, Ru; E=P, As). [(Cp*Ru)2As8I6] (12) crystallizes as a racemic mixture of both enantiomers, while [(Cp*Ru)2As4I4] (13) crystallizes as a symmetric and an asymmetric isomer and features a unique tetramer of {AsI} arsinidene units as a middle deck.

Insertion and functionalization of gallasilylenes [LPhSi–Ga(Cl)LBDI] (LPh = PhC(NtBu)2; LBDI = [{2,6-iPr2C6H3NCMe}2CH]) into the cyclo-E5 rings of [Cp*Fe(η5-E5)] (Cp* = η5-C5Me5; E = P, As) are reported.

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.

A missing family of the extremely air sensitive tripentelyltrielanes was discovered. Their stabilisation was achieved by using the bulky NHC IDipp (NHC=N‐heterocyclic carbene, IDipp=1,3‐bis(2,6‐diisopropylphenyl)‐imidazolin‐2‐ylidene). The tripentelylgallanes and tripentelylalanes IDipp ⋅ Ga(PH2)3 (1 a), IDipp ⋅ Ga(AsH2)3 (1 b), IDipp ⋅ Al(PH2)3 (2 a) and IDipp ⋅ Al(AsH2)3 (2 b) were synthesised by salt metathesis of IDipp ⋅ ECl3 (E=Al, Ga, In) with alkali metal pnictogenides such as NaPH2/LiPH2 ⋅ DME and KAsH2, respectively. Moreover, the detection of the first NHC‐stabilised tripentelylindiumane IDipp ⋅ In(PH2)3 (3) was possible by multinuclear NMR spectroscopy. Initial investigations of the coordination ability of these compounds resulted in the successful isolation of the coordination compound [IDipp ⋅ Ga(PH2)2(μ3‐PH2{HgC6F4}3)] (4) by reaction of 1 a with (HgC6F4)3. The compounds were characterised by multinuclear NMR spectroscopy as well as single crystal X‐ray diffraction studies. Supporting computational studies highlight the electronic features of the products.

The redox chemistry of [Cp‴Ni(η 3 -As 3 )] (A), an end-deck cyclo-As 3 complex, is explored in terms of systematically accessing a series of Ni 2 As 3 triple-decker compounds. While oxidation of A affords the cationic complex [{Cp‴Ni} 2 (μ,η 3:3 -AsOne-electron reduction of 1 and one-electron oxidation of 2 yield the neutral compound [{Cp‴Ni} 2 (μ,η 3:3 -As 3 )] (3), representing the missing link between 1 and 2, which is corroborated electrochemically. The cyclo-As 3 ligand in 2 undergoes bond weakening and splitting of one As−As bond upon stepwise oxidation to 3 and 1, finally displaying an allylic As 3 ligand. In-depth experimental studies shed light onto the reaction pathway of the oxidation of A, and additional DFT computations give insight into the electronic structure of the obtained complexes.