Formation and properties of phosphaquinomethane tungsten(0) complexes - isolation and conversion of primary radical coupling products.

A rational approach to phosphaquinomethane metal(0) complexes, based on dearomatization of the phenylene unit in [W(CO)](R)P(Cl)-CH-CPh, is described, including theoretical studies on mechanisms and structures. Furthermore, the first phosphaquinone tungsten complex with reversible redox properties is reported thus illustrating the beneficial stabilization of ligation.

Coordination chemistry of a low-coordinate non-metal element: the case of electrophilic terminal phosphinidene complexes.

3-Imino-azaphosphiridine complex 1 reacts with carbon monoxide to give 1,3-azaphosphetidinone complex 2, whereas with isocyanides 3a,b substitution occurred to yield complexes 4a,b. Oxidation of 1 using elemental sulfur afforded the first 1,3,2-thiazaphosphetidine-4-imine complex 5. DFT calculations provide insight into a manifold of pathways based on a common intermediate, a carbodiimide-to-phosphinidene complex, leading to P-N and P-C bond insertion products as well as ligand substitution products.

Stimuli-Responsive Frustrated Lewis-Pair-Type Reactivity of a Tungsten Iminoazaphosphiridine Complex.

Reactions of 3-imino-azaphosphiridine complexes 1 a,b with carbodiimides 2 a,b, isocyanates 3 a,b, and carbon dioxide are described. Whereas exchange of the carbodiimide unit occurs in the first case, an overall ring expansion takes place with phenyl isocyanate (3 a) and carbon dioxide to yield complexes 4 and 5 bearing novel 1,3,5-oxazaphospholane ligands; the isopropyl derivative 3 b did not react under these conditions. DFT calculations provide insight into the pathway of the reaction with carbon dioxide with model complex 1 c, revealing effects of initial non-covalent interactions with the substrate onto the ring bonding, thus triggering an initially masked frustrated Lewis-pair-type behavior.

Going for strain: synthesis of the first 3-imino-azaphosphiridine complexes and their conversion into oxaphosphirane complex valence isomers.

Reaction of a Li/Cl phosphinidenoid complex with N,N'-dialkyl carbodiimides yielded the novel 3-imino-azaphosphiridine complexes; reaction with water led selectively to the first stable valence isomer of an oxaphosphirane complex.

Unprecedented ring-ring interconversion of N,P,C-cage ligands.

The novel N,P,C-cage complexes 5 a-f and 6 a-f have been obtained by the reaction of the P-pentamethylcyclopentadienylphosphinidene complex 2, generated thermally from 2H-azaphosphirene complex 1, with N-methyl-C-arylcarbaldimines 3 a-f. Li/Cl phosphinidenoid complex 8 reacted with 3 a,b to give N,P,C-cage complexes 6 a,b, whereas with 3 c-f, complexes 6 c-f were obtained in negligible amounts only. Both types of ligand N,P,C-cage structures 5 and 6 were found to be in an unprecedented equilibrium, with 5 a,f as the predominant species.

The azaphosphiridine to terminal phosphinidene complex rearrangement--looking for non-covalent interactions of a highly reactive species.

Azaphosphiridine complexes 4a,a', intermediates in the reaction of P-C5Me5 substituted Li–Cl phosphinidenoid complex 2 and C-furyl carbaldimine 3, rearranged selectively to give the novel N,P,C-cage complex 5a. Transient terminal phosphinidene complex 7a was trapped with phenyl acetylene (8) forming the new N,P,C-cage complex 9. DFT calculations provide evidence for a thermally allowed aza-phospha-Cope rearrangement that led to the P-amino substituted phosphinidene complex 7a, which is stabilized by non-covalent interactions in addition to typical through-bond electronic effects.