A novel access to phosphanylidene-phosphorane complexes via P-donor substitution and a detailed bonding analysis

Deciphering the direct heterometallic interaction in κ3-bis(donor)ferrocenyl-transition-metal complexes

Ligands featuring a 1,1'-bis(donor)ferrocene motif can adopt various binding modes. Among them, the κ3 binding mode, which involves interaction between the iron center of the ferrocene unit and the transition metal is the most unique. Although various examples highlight the interaction itself, the exact quantification of its strength remains uncertain. In our computational study, we systematically investigate the nature of this unique heterometallic bond, demonstrating that the electron density at the transition metal primarily governs the heterobimetallic interaction. On the other hand, the contribution of the ipso-carbon atoms of the cyclopentadiene ring is not negligible. We demonstrated that isodesmic reactions provide the most quantifiable data regarding the interaction. If the transition metal center is complexed with good electron-donor ligands or its positive charge is compensated by the negative charge of the ligands, the interaction with the electron-rich iron center recedes into the background. Finally, we highlighted the importance of the accurate computational description of these systems.

Oxaphosphiranes: isolable phosphorus-containing epoxide rings

Combining different heteroatoms in an epoxide-type ring having Lewis basic and acidic characteristics is challenging as it creates an increasing number of polar bonds and high ring strain energy. The first examples of isolable oxaphosphiranes, i.e., epoxide rings with a phosphorus atom, have been synthesized using a facile and effective protocol starting from [pentacarbonyl{dichloro(trityl)phosphane}molybdenum(0)] (trityl = CPh3), tert-butyllithium and commercially available fluorinated benzaldehydes. Reactions with various acids and bases will be described. Theoretical results unveil a singlet carbene-like FMO situation at phosphorus in oxaphosphirane, which is used to explain reaction mechanisms.

Nucleophilic Substitution at Phosphorus Centres - Old and Recent Studies and a Final Solution of Mechanistic and Related Stereochemical Problems

Among many problems of a fundamental value in the heteroatom chemistry the mechanism and stereochemistry of the nucleophilic substitution reaction at the phosphorus and other heteroatom centres have attracted great attention of phosphorus chemists already in the middle of the last century. This review, which does not have a comprehensive character, summarizes the selected original contributions aimed at solution of the mechanism of SN2-P reaction and its relationship with stereochemistry. The breakthrough in these studies was the Westheimer's concept and his rules which is presented at the beginning of this article. Next, a series of papers is presented where the stereochemistry of the substitution at phosphorus was investigated in cyclic five-, four- and six-membered ring phosphorus compound. The majority of these reactions have been found to occur with retention of the P-configuration. In the third part of this account, the selected examples of substitution reactions at phosphorus in acyclic compounds are discussed. As the results of all the investigations discussed did not allow to undoubtedly ascribe the mechanism (SN2 or A-E) to the investigated reactions, in the last part the SN-P reactions are presented, the mechanism of which has been established by combination of the stereochemical and DFT-studies.

Access to ligand-stabilized PH-containing phosphenium complexes

While the chemistry of phosphenium compounds, including metal complexes thereof, is very well established, few derivatives having a P-H bond have been described, yet. This work describes rational access to donor-stabilised phosphenium metal complexes possessing a P-H bond using protonation reactions of stable phosphinidene complex adducts. While most Brønsted-Lowry acids yield formal 1,1-addition products at the phosphorus centre under the loss of the donor, super-strong acids having weakly coordinating anions enable access to donor-stabilised P-H phosphenium complex salts. The latter possess N-methylimidazole as a donor (to phosphorus) and the N-P interaction has been studied theoretically.