Isolable N-heterocyclic carbene adducts of the elusive diiodophosphine

Reactions of PH-substituted phosphinidene-imidazolylidenes with I₂ afford isolable NHC-adducts of the transient diiodophosphine PHI₂. 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.

Synthesis, spectroscopic characterisation and transmetalation of lithium and potassium diaminophosphanide-boranes

A secondary diaminophosphane-borane (Et₂N)₂PH(BH₃) was prepared from a chlorophosphane precursor and LiBH₄ and metalated by reaction with anion bases (n-BuLi, KN(SiMe₃)₂) to yield the corresponding metal diaminophosphanide-boranes [(Et₂N)₂P(BH₃)]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 LiH₃B-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.

Molecular qubits based on potentially nuclear-spin-free nickel ions

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+. (d₂₀-PPh₄)[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 (HNEt₃)[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.