Single crystals of [iPrMgCl(THF)] 2 [MgCl 2 (THF) 2 ] 2 were obtained by layering a THF solution of the "turbo Grignard" iPrMgCl•LiCl with Et 2 O at ambient temperature. The isolated 1:1 Grignard−MgCl 2 adduct is isostructural with crystalline compounds which were obtained from pure RMgCl solutions (R = Me, tBu, Ph, Bn). The structure of [iPrMgCl(THF)] 2 [MgCl 2 (THF) 2 ] 2 reveals an open-cube motif (monoclinic, P2 1 /c). When dioxane was added to a THF solution of iPrMgCl•LiCl, single crystals of [LiCl(THF) 2 ] 2 and [iPr 2 Mg(dioxane)] ∞ (monoclinic, C2/c) were isolated. From 1:1 mixtures of (Me 3 Si) 2 CHMgCl (DisylMgCl) and LiCl (prepared analogously to iPrMgCl•LiCl) two different Grignard compounds, the monomer [DisylMgCl(THF) 2 ] (monoclinic, P2 1 ) and the dimer [DisylMgCl(THF)] 2 (monoclinic, P2 1 /c), were isolated as single crystals. During our studies, two oxidation products of iPrMgCl and DisylMgCl, respectively, resulting from oxygen insertion, were obtained and structurally characterized. Colorless plates of [iPrMg(OiPr)] 4 (monoclinic, P2 1 /m) grew from a THF/benzene solution. The dimeric alkoxide {[DisylOMgCl][LiCl(THF) 2 ]} 2 (monoclinic, C2/c), which was obtained from DisylMgCl•LiCl by oxidation through residual oxygen, displays the only structure in which incorporation of LiCl in the molecular framework of a Mg alkoxide was observed.

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Two series of sterically demanding para-dimethoxyphenyl-substituted bis(pyrazol-1-yl)methane ligands have been synthesized, i.e., L2(R,R') = ((MeO)(2)C(6)H(3))C(H)(pz(R,R'))(2) and L3(R,R') = ((MeO)(2)C(6)H(3))C(Me)(pz(R,R'))(2) (R,R' = 3-Me,5-Me; 3-Ph,5-H; 3-tBu,5-H). In the solid state, already the sterically least encumbered derivative L2(Me2) is able to stabilize Co(II) complexes of the form [X(2)Co(L2(Me2))] (X = Cl, NO(3)); in solution, these complexes are at an equilibrium with the 1:2 species [Co(L2(Me2))(2)](2+). Oxidative demethylation of L3(Ph) and L3((t)Bu) with [Ce(NH(4))(2)(NO(3))(6)] leads to the corresponding para-benzoquinonyl-substituted bis(pyrazol-1-yl)methane ligands L4(Ph) and L4((t)Bu). Contrary to that, the methyl derivative L3(Me2) is transformed into the ortho-benzoquinone species L5(Me2), which still contains one methoxy substituent while one oxygen atom has been newly introduced. The formation of L5(Me2) requires (i) the admission of air, (ii) the presence of both methoxy substituents of L3(Me2), and (iii) the presence of (methyl) substituents both at the exocyclic carbon atom and at the 5- positions of the pyrazolyl rings. The parent ortho-hydroquinonyl-substituted bis(pyrazol-1-yl)methane ligand ((HO)(2)C(6)H(3))C(H)(pz(H,H))(2) is readily available from 3,4-dihydroxybenzaldehyde and (pz(H,H))(2)SO/pyridine.

To address challenges in the preparation of a key building block containing a difluorocyclopropane moiety, we have developed a new protocol for difluorocarbene generation that relies on a Krapcho-type dealkylation of ethyl bromodifluoroacetate (EBDFA), an inexpensive and readily available fluorinated feedstock. Application of DoE and kinetic modeling was used to understand key reaction parameters and identify an optimal process. We report two variants of this procedure that offer different processing advantages and that have both been scaled successfully multiple times to deliver hundreds of kilograms of the resulting difluorocyclopropane. To access a single enantiomer of the target compound, we have also developed a classical resolution strategy and recycling protocol for the undesired enantiomer to replace previous chromatographic methods for separation.

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