A “Bottle-able” Phosphinidene

Base-Stabilized Phosphinidene Oxide, Imide and Sulfide

Oxidation of a base-stabilized phosphinidene (κ2 -NNP)P (12, NNP=phosphinoamidinate) with N2 O afforded a labile phosphinidene oxide (κ2 -NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N2 O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (κ2 -NNP)PO2 which was characterized by NMR and SC XRD. Trapping of 16 with tolyl isocyanate resulted in P=O/N=C metathesis, eventually affording a urea-ligated phosphine (κ1 -NNP)P(NTol)2 C=O (17) The mechanism of this reaction was elucidated by DFT calculations. Reactions of phosphinidene 12 with azides generated transient imines (NNP)P=NR, which in the case of R=Tol underwent cycloaddition with tolyl Isocyanate to afford the urea product 17, and in the case of R=SiMe3 reacts with N3 SiMe3 via the addition of N-Si across the P=N bond affording, after the extrusion of dinitrogen, a P,N-heterocyclic compound. Both products of the reactions with azides have been fully characterized, both in solution and the solid-state. Finally, reaction of phosphinidene 12 with one equivalent of sulfur resulted in the isolation of the base-stabilized phosphinidene sulfide (κ2 -NNP)P=S that has also been fully characterized.

Free Ethynylarsinidene and Ethynylstibinidene: Heavier Analogues of Nitrenes and Phosphinidenes

Until now, there has been very little experimental evidence for the existence of free arsinidenes and stibinidenes, apart from the hydrides, AsH and SbH. Here, we report on photogeneration of triplet ethynylarsinidene, HCCAs, and triplet ethynylstibinidene, HCCSb, from ethynylarsine and ethynylstibine, respectively, in solid argon matrices. The products were identified using infrared spectroscopy and the associated UV absorption spectra are interpreted with the aid of theoretical predictions.

An Isolable Gallium-Substituted Nitrilimine and its Reactivity with B-H, Si-H and B-B Bonds

Reaction of the Ga(I) compound NacNacGa (9) with the diazo compound N₂ CHSiMe₃ affords the nitrilimine compound NacNacGa(N-NCSiMe₃ )(CH₂ SiMe₃ ) (10). Carrying out this reaction in the presence of pyridine does not lead to C-H activation on the transient alkylidene NacNacGa=CHSiMe₃ but generates a metallated diazo species NacNacGa(NHN=CHSiMe₃ )(CN₂ SiMe₃ ) (13) that further rearranges into the isonitrile compound NacNacGa(NHN=CHSiMe₃ )(N(NC)SiMe₃ ) (15). Reactions of 10 with the silane H₃ SiPh and the borane HBcat furnished products of 1,3 addition to the nitrilimine moiety NacNacGa{N(ER_n )NCSiMe₃ }(CH₂ SiMe₃ ), whereas reaction with the diborane B₂ cat₂ gave the product of formal nitrene insertion into the B-B bond. DFT calculations suggest that the interaction of 9 with N₂ CHSiMe₃ proceeds through intermediate formation of an alkylidene compound that undergoes CH activation with a second molecule of N₂ CHSiMe₃ . Insertion into the B-B bond likely proceeds through an initial 1,3-addition of the diborane, followed by boryl migration to the former nitrene center.

Generation and reactivity of an elusive base-stabilised phosphinidene

Reduction of phosphorus dichloride 6, supported by the diaryloxyphenyl group (OCO) featuring two bulky phenoxy wingtips, by PMe₃, generates a reactive intermediate that behaves as a base-stabilized phosphinidene (OCO)P (5). Warming up a solution of this species in toluene to room temperature results in trimerization to give the isolable cyclic triphosphine [(OCO)P]₃, whereas in situ trapping with 2,3-dimethylbutadiene-1,3 afforded a 3,4-dimethylphospholene-3. Investigation of the reduction of 6 by the phosphine PMe₃ by NMR led to the observation of a persistent species between -10 °C and 10 °C. A DFT study of this process suggests that this compound cannot be the proposed phosphinidene 5, and is more likely the diphosphine (OCO)ClP-PCl(OCO) (12). Attempted reduction of 5 by the bulky carbene IPr resulted in unusual electrophilic substitution in the carbene olefin backbone by the chlorophosphinyl group.

Group 15 and 16 Nitrene-Like Pnictinidenes

Pnictinidenes are an increasingly relevant species in main group chemistry and generally exhibit proclivity for the triplet electronic ground state. However, the elusive singlet electronic states are often desired for chemical applications. We predict the singlet-triplet energy differences (ΔE_ST =E_Singlet -E_Triplet ) of simple group 15 and 16 substituted pnictinidenes (Pn-R; Pn=P, As, Sb, or Bi) with highly reliable focal-point analyses targeting the CCSDTQ/CBS level of theory. The only cases we predict to have favorable singlet states are P-PH₂ (-3.2 kcal mol^-1 ) and P-NH₂ (-0.2 kcal mol^-1 ). ΔE_ST trends are discussed in light of the geometric predictions as well as qualitative natural bond order analysis to elucidate some of the important electronic structure features. Our work provides a rigorous benchmark for the ΔE_ST of fundamental Pn-R moieties and provides a firm foundation for the continued study of heavier pnictinidenes.

Photochemical reactions of triplet phenylphosphinidene with carbon monoxide and nitric oxide

Here we report the photochemical reactions of triplet phenylphosphinidene with carbon monoxide and nitric oxide. The photolysis of phenylphosphirane in carbon monoxide-doped matrices enabled the first spectroscopic identification of phenylphosphaketene, the hitherto unreported phosphorus analogue of phenyl isocyanate. The hitherto undisclosed phosphinimine-N-oxyl radical formed upon UV irradiation of the phenylphosphinidene with nitric oxide in argon matrices at 10 K.

Imino-stabilised phosphinidene (or azaphosphole?) and some of its derivatives

Diiminophenyl (dimph) proved to be an excellent ligand platform to stabilise a low-valent phosphorus centre.