Mechanistic insights of anionic ligand exchange and fullerene reduction with magnesium(i) compounds

Abstract

Exchange of anionic ligands on the Mg22+ ion via an associative mechanism can be facile and depends on ligand sterics and shape.

C−H Activation of Inert Arenes using a Photochemically Activated Guanidinato‐Magnesium(I) Compound

“…Although the formation of the unsymmetrical dimagnesium(I) compound 13 (and the other chemistry mentioned above) provides circumstantial evidence for the intermediacy of photochemically generated magnesium radical species in its formation, it should be emphasized that there are other possible routes to 13 . Indeed, previous reports have described similar scrambling reactions that occur under heating, or even rapidly at room temperature in the absence of irradiation when smaller magnesium(I) substituents are involved [25,26] . Stasch and co‐workers have provided evidence that dimagnesium(I) scrambling reactions can occur via an associative mechanism, which involves exchange of anionic β‐diketiminate or diiminophosphinate ligands between magnesium centres [26] .…”

“…Indeed, previous reports have described similar scrambling reactions that occur under heating, or even rapidly at room temperature in the absence of irradiation when smaller magnesium(I) substituents are involved. [ 25 , 26 ] Stasch and co‐workers have provided evidence that dimagnesium(I) scrambling reactions can occur via an associative mechanism, which involves exchange of anionic β‐diketiminate or diiminophosphinate ligands between magnesium centres. [26] Such a mechanism cannot be completely ruled out for the formation of 13 .…”

Calcium Hydride Reduction of Polycyclic Aromatic Hydrocarbons

“…Reactions of 2 with naphthalene,a nthracene and tetracene performed at 350 Kw ithin the cavity of aC WE PR spectrometer provided no evidence for the production of short lived hydrogen radicals.I ne ach case,h owever, signals (17), Ca1-C88 2.651(2), Ca1-C89 2.923(2), Ca1-C94 2.838(2), Ca1-C95 2.624(2), Ca1-C96 3.019(2), Ca2-N3 2.3492 (17),C a2-N4 2.4179(18), Ca2-C96 3.071(2), Ca2-C97 2.981(2), Ca2-C98 2.858(2), Ca2-C99 2.748(2), Ca2-C1002 .712(2), Ca2-C101 2.868(2), Ca3-N5 2.3902(18), Ca3-N6 2.4405 (19),C a3-C89 3.138(2), Ca3-C90 2.995(2), Ca3-C91, 2.875(2) Ca3-C92 2.804(2), Ca3-C93 2.801(2), Ca3-C94 2.964(2); N1-Ca1-N2 78.05 (6), N3-Ca2-N4 77.51(6), N5-Ca3-N6 78.73(6);(11)C a1-N1 2.3290(12), Ca1-N2 2.3412(12), Ca1-C30 2.7127(15), Ca1-C31 2.8973(15), Ca1-C32 2.7097 (14), Ca1-C33 2.7711 (14),C a1-C34 2.7660 (15);N1-Ca1-N2 76.92 (4). Symmetry operations to generate equivalent atoms 1Àx,1 Ày,1 Àz.…”

“…Tr eatment of anthracene by compound 6 also provides two-electron reduction and the formation of compound 8.W hile the electrochemical reduction potentials of 5 and 6 have never been determined, av ery recent report of the six electron reduction of C 60 by 6 indicates ar educing capability which is at least in the order of E 0 = À2.9 V( vs.S CE). [15] Consistent with this upper limit, however, such Mg I species are indefinitely stable in benzene (E 0 = ca. À3.4 V) and no evidence of reactivity with naphthalene (E 0 = ca.…”

Exohedral Cuprofullerene: Sequentially Expanding Metal Olefin Up to a C60@Cu24 Rhombicuboctahedron

“…As a spherical polyene system, the 30 CC bonds in C 60 provide an incredible possibility to bind 30 metal atoms in a saturated μ 30 -(η 2 ) 30 fashion to complete a C 60 @ M 30 icosi­dodecahedron with 20 vertex-shared M 3 -trigons (Scheme b). Up to now, the highest nuclearity is 6 in the reported exohedral metallo­fullerenes, such as 6:1 products through six η 2 or η 2 /η 5 interactions, − and 2:1 adducts through double (μ 3 -η 2 :η 2 :η 2 ) interactions. , It seems an impassable task to fulfill the saturated fashion using open-shell metals, because these metals show coordination numbers no less than 4, and the bulky steric crowding caused by the multiple auxiliary ligands will prevent more M 3 being coated on the neighbor hexagons and restrict the number of M 3 on the C 60 surface, in spite of numerous examples of (μ 3 -η 2 :η 2 :η 2 )-metallo­fullerenes . Therefore, minimizing the steric crowding surrounding the M 3 , for example, adopting the closed-shell Cu­(I) with low coordination number (no more than 4), and using anionic bridge ligands but not terminal ligands are believed to be effective strategies to achieve a high nuclear metallo­fullerene.…”