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Condensation of secondary 1,1'-diaminoferrocenes with phosphorus trihalides (PCl3 or PBr3) yielded either P-halo-1,3-diaza-2-phospha[3]ferrocenophanes or 1,1'-diaminoferrocenediyl-bis(dichlorophosphines), respectively. The latter provide controlled access to both [3]- and [4]ferrocene frameworks. Thus, reductive coupling with magnesium gave diaza-diphospha[4]ferrocenophane-annelated tetraphosphetanes, while a reaction with LiNMe2 produced a P-chloro-diazaphospha[3]ferrocenophane. Condensation of diaminoferrocenes and aminodichlorophosphines were mostly unselective, but afforded in one case a 3-amino[3]ferrocenophane. All reaction products were characterised by spectroscopic and single-crystal XRD studies. DFT studies indicate that the product selectivity in the reactions studied depends on a combination of kinetic and thermodynamic effects, which correlate subtly with the steric bulk of the N-substituents. Cyclic voltammetry measurements revealed that the ferrocenophanes can undergo multiple oxidation events, the first of which may according to DFT studies be located in both the ferrocene and aminophosphine units. The quantum chemical studies provided also insight into stereochemical aspects like ring strain in the ferrocenophane units.

N-Heterocyclic phosphenium (NHP) and nitrosonium (NO + ) ligands are often viewed as isolobal analogues that share the capability to switch between different charge states and thus display redox "noninnocent" behavior. We report here on mixed complexes [(NHP)M(CO) n (NO)] (M = Fe, Cr; n = 2, 3), which permit evaluating the donor/acceptor properties of both types of ligands and their interplay in a single complex. The crystalline target compounds were obtained from reactions of N-heterocyclic phosphenium triflates with PPN[Fe(CO) 3 (NO)] or PPN[Cr(CO) 4 (NO)], respectively, and fully characterized (PPN = nitride-bistriphenylphosphonium cation). The structural and spectroscopic (IR, UV-vis) data support the presence of carbene-analogue NHP ligands with an overall positive charge state and π-acceptor character. Even if the structural features of the M-NO unit were in all but one product blurred by crystallographic CO/NO disorder, spectroscopic studies and the structural data of the remaining compound suggest that the NO units exhibit nitroxide (NO - ) character. This assignment was validated by computational studies, which reveal also that the electronic structure of iron NHP/NO complexes is closely akin to that of the Hieber anion, [Fe(CO) 3 (NO)] - . The electrophilic character of the NHP units is further reflected in the chemical behavior of the mixed complexes. Cyclic voltammetry and IR-SEC studies revealed that complex [(NHP)Fe(CO) 2 (NO)] (4) undergoes chemically reversible one-electron reduction. Computational studies indicate that the NHP unit in the resulting product carries significant radical character, and the reduction may thus be classified as predominantly ligand-centered. Reaction of 4 with sodium azide proceeded likewise under nucleophilic attack at phosphorus and decomplexation, while super hydride and methyl lithium reacted with all chromium and iron complexes via transfer of a hydride or methyl anion to the NHP unit to afford anionic phosphine complexes. Some of these species were isolated after cation exchange or trapped with electrophiles (H + , SnPh 3 + ) to afford neutral complexes representing the products of a formal hydrogenation or hydrostannylation of the original M═P double bond.

Reactions of PH-substituted phosphinidene-imidazolylidenes with I 2 afford isolable NHC-adducts of the transient diiodophosphine PHI 2 . The products, which show a surprising structural diversity, are according to DFT studies best formulated as charge-transfer complexes of onio-substituted cationic phosphines with I - and are capable of reaction under formal transfer of an NHC-P + unit.

A secondary diaminophosphane-borane (Et 2 N) 2 PH(BH 3 ) was prepared from a chlorophosphane precursor and LiBH 4 and metalated by reaction with anion bases (n-BuLi, KN(SiMe 3 ) 2 ) to yield the corresponding metal diaminophosphanide-boranes [(Et 2 N) 2 P(BH 3 )]M (M = Li, K). Multinuclear NMR studies permitted the first spectroscopic characterisation of the metalation products and revealed the presence of monomeric (for M = Li) contact ion pairs in solution. NMR spectroscopic evidence that the ions in each pair interact via LiP- rather than LiH 3 B-interactions as had been inferred for a Ph-substituted analogue was confirmed by DFT studies, which revealed also that the borane coordination plays a decisive role in boosting the PH-acidity of the original secondary diaminophosphane precursor. Transmetalation of the potassium and lithium diaminophosphanide-boranes with Cu(i) and Zn(ii) chlorides afforded the first functional transition metal complexes of a P-heteroatom-functionalised phosphanide-borane ligand. Both products were fully characterised. Thermolysis of the Cu-complex induced a reaction which involved transfer of an NHC ligand from the metal to the phosphorus atom and yielded a phosphaalkene NHC[double bond, length as m-dash]PH (NHC = N-heterocyclic carbene) as the major phosphorus-containing product.

The reaction of an N-heterocyclic phosphenium complex of manganese with MeLi/Et 3 NHCl under formal addition of CH 4 to the Mn=P double bond can be reversed upon UV photolysis, providing a rare example for selective P-C(alkyl) bond activation. Action of LDA on the phosphenium complex does not proceed via attack at phosphorus but rather via C4-deprotonation to yield a unique P-analogue of an "abnormal" carbene. A transmetalation product of the original complex was fully characterized. The C-metalation is also applicable to bis-phosphenium complexes of other metals., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A neutral N-heterocyclic phosphenium complex of manganese was synthesised by a metathesis approach and characterised by IR, NMR, and XRD studies. The short P-Mn distance suggests a substantial metal-ligand double bond character. Reaction with a hydride produced an anionic phosphine complex, which was also characterised by IR and NMR spectroscopy and, after anion exchange, a single-crystal XRD study. Protonation of the anion occurs at the metal to yield a neutral phosphine metal carbonyl hydride, which releases dihydrogen upon irradiation with UV light. These reactions confirm the electrophilic nature of the phosphenium ligand and suggest that the title complex might undergo reactions displaying metal-ligand cooperativity. Surprisingly, reaction with ammonia borane (AB) did not proceed under transfer hydrogenation of the Mn=P double bond but through the catalytic dehydrogenation of AB. The phosphenium complex behaves here as a class II catalyst, which dehydrogenates AB to NH 2 BH 2 that was trapped with cyclohexene. Computational model studies led to the identification of two possible catalytic cycles, which differ in the regioselectivity of the initial AB activation step. In one case, the activation proceeds as cooperative transfer hydrogenation of the Mn=P bond, whereas in the other case a H + /H - pair is transferred to the phosphorus atom and a nitrogen atom of the phosphenium unit, resulting in a ligand-centred reaction in which the metal fragment acts merely as stabilising substituent. Unexpectedly, this pathway, which constitutes a new reaction mode for phosphenium complexes, seems to be better in accord with experimental findings on the course of the catalysis., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The outcome of the reduction of [(cod)PtX 2 ] (X = Cl, Br; cod = 1,5-cyclooctadiene) with N-heterocyclic phosphenium hydrides R NHP-H depends strongly on the steric demand of the N-aryl group R and the nature of X. Reaction of [(cod)PtCl 2 ] with Dipp NHP-H featuring bulky N-Dipp groups produced an unprecedented monomeric phosphenium metal(0) halide [( Dipp NHP)( Dipp NHP-H)PtCl] stabilized by a single phosphine ligand. The phosphenium unit exhibits a pyramidal coordination geometry at the phosphorus atom and may according to DFT calculations be classified as a Z-type ligand. In contrast, reaction of [(cod)PtBr 2 ] with the sterically less protected Mes NHP-H afforded a mixture of donor-ligand free oligonuclear complexes [{( Mes NHP)PtBr} n ] (n = 2, 3), which are structural analogues of known palladium complexes with μ 2 -bridging phosphenium units. All reductions studied proceed via spectroscopically detectable intermediates, several of which could be unambiguously identified by means of multinuclear ( 1 H, 31 P, 195 Pt) NMR spectroscopy and computational studies. The experimental findings reveal that the phosphenium hydrides in these multistep processes adopt a dual function as ligands and hydride transfer reagents. The preference for the observed intricate pathways over seemingly simpler ligand exchange processes is presumably due to kinetic reasons. The attempt to exchange the bulky phosphine ligand in [( Dipp NHP)( Dipp NHP-H)PtCl] by Me 3 P resulted in an unexpected isomerization to a platinum(0) chlorophosphine complex via a formal chloride migration from platinum to phosphorus, which accentuates the electrophilic nature of the phosphenium ligand. Phosphenium metal(0) halides of platinum further show a surprising thermal stability, whereas the palladium complexes easily disintegrate upon gentle heating in dimethyl sulfoxide to yield metal nanoparticles, which were characterized by TEM and XRD studies.

Molecular qubits with the longest coherence times thus far are based on nuclear-spin-carrying central ions. These nuclear spins can cause quantum state leakage, which is detrimental to quantum algorithm performance. We present two novel molecular qubits based on potentially nuclear spin-free Ni in the formal oxidation state 3+. (d 20 -PPh 4 )[Ni(mnt) 2 ] (Ni-mnt, mnt 2- = maleonitrile-1,2-dithiolate) possesses a coherence time of up to 38.7 μs at 7 K. Functionalization of the dithiolate ligand decreases the coherence time by a factor of only four in (HNEt 3 )[Ni(dip) 2 ] (Ni-dip, dip 2- = 3-(diphenylphosphoryl)-methylbenzene-1,2-dithiolate), indicating that monoanionic Ni-dithiolene complexes are promising and robust building blocks for polynuclear molecular qubit gates.

A synthetic protocol to synthesize 2-bromobenzo-1,3,2-dithiaboroles in one step from easily accessible benzene bis(isopropyl thioether)s has been developed. The reaction is remarkably specific in converting substrates with two adjacent (i)PrS moieties while leaving isolated thioether functions and other functional groups intact. On the basis of the spectroscopic detection or isolation of reaction intermediates, a mechanistic explanation involving a neighbor-group-assisted dealkylation as a key step is proposed. The resulting products featuring one or two dithiaborole units were isolated in good yields and fully characterized. Subsequent methanolysis, which was carried out either as a separate reaction step or in the manner of a one-pot reaction, gave rise to functionally substituted benzenedithiols. The feasibility of a methylphosphoryl-substituted benzenedithiol to act as a dianionic S,S-chelating ligand was demonstrated with the formation of paramagnetic Ni(III) and Co(III) complexes. Selective reduction of the phosphoryl group afforded a rare example of a phosphino dithiol which was shown to act as a monoanionic P,S-bidentate ligand toward Pd(II). All complexes were characterized by spectral data and X-ray diffraction studies, and the paramagnetic ones also by superconducting quantum interference device magnetometry.