Pairing lithium and manganese(II) to form lithium manganate [Li2Mn(CH2SiMe3)4] enables the efficient direct Mn–I exchange of aryliodides, affording transient (aryl)lithium manganate intermediates which in turn undergo spontaneous C−C homocoupling at room temperature to furnish symmetrical (bis)aryls in good yields under mild reaction conditions. The combination of EPR with X‐ray crystallographic studies has revealed the mixed Li/Mn constitution of the organometallic intermediates involved in these reactions, including the homocoupling step which had previously been thought to occur via a single‐metal Mn aryl species. These studies show Li and Mn working together in a synergistic manner to facilitate both the Mn–I exchange and the C−C bond‐forming steps. Both steps are carefully synchronized, with the concomitant generation of the alkyliodide ICH2SiMe3 during the Mn–I exchange being essential to the aryl homocoupling process, wherein it serves as an in situ generated oxidant.

While alkali metal zincates have shown promising utility in organic synthesis, frequently these compounds are prepared in situ, and their identities remain blurred. Herein, the synthesis of a new family of sodium zincates featuring the chelating silyl(bis)amido ligand {Ph 2 Si(NAr*) 2 } 2− (Ar* = 2,6-diisopropylphenyl) is presented. Using a synchronized bimetallic approach, 2fold deprotonation of Ph 2 Si(NHAr*) 2 (1) by mixed-metal base NaZn(HMDS) 2 R (2) [R = CH 2 SiMe 3 ; HMDS = N(SiMe 3 ) 2 ] afforded the solvent-separated ion pair alkyl zincate [{Ph 2 Si(NAr*) 2 Zn(R)} − {Na(THF) 6 } + ] (3), showing a clear preference for 2 to react as bis(amide) base via its two Zn−N bonds rather than reacting using its alkyl group. Alternatively, a stepwise approach using two single-metal bases sequentially, NaR and Zn(HMDS) 2 affords the tris(amido) zincate [{Ph 2 Si(NAr*) 2 Zn(HMDS)} − {Na-(THF) 6 } + ] (6). Formation of 6 takes place by initial monosodiation of 1, furnishing the amido-amine [{Ph 2 Si(NHAr*)(NAr*)-Na} 2 ] (5), which in turn undergoes a co-complexation and deprotozincation step with Zn(HMDS) 2 . Using 2,4,6trimethylacetophenone (7) as a case study, the ability of sodium zincates 3 and 6 to access zinc enolates was investigated, affording sodium zincates [{(THF)NaZnR[OC(CH 2 )Mes] 2 } 2 ] (8) and [{(THF)NaZn(OC(CH 2 )Mes) 3 } 2 ] (9), respectively. These studies revealed that the chelating silyl(bis)amide {Ph 2 Si(NAr*) 2 } 2− far from being an innocent spectator is an effective base for the deprotonation of 7, showing an unexpected superior kinetic basicity than the CH 2 SiMe 3 alkyl group when part of sodium heteroleptic zincate 3. The bimetallic constitution of enolates 8 and 9 contrasts with that of all-sodium [{(THF)Na(OC( CH 2 )Mes)} 4 ] (10) obtained by reacting the homoleptic alkylzincate NaZnR 3 (4) with 7, with the concomitant elimination of ZnR 2 . Revealing the divergent behavior of Mg versus Zn in these bimetallic systems, reaction of 7 with the magnesium analog of 3, [{Ph 2 Si(NAr*) 2 Mg(R)} − {Na(THF) 6 } + ] (11), produces magnesiate enolate [{Ph 2 Si(NAr*) 2 Mg(O(CH 2 )Mes)(THF)} − {Na-(THF) 5 } + ] (12), where the chelating silyl(bis)amide ligand is retained and metalation of the ketone is actioned by the alkyl group.

Combining a bulky bis(amide) and a reactive one-coordinate TMP (2,2,6,6-tetramethylpiperidide) ligand, a new mixed K/Zn heteroleptic base has been developed for regioselective zincation of fluoroarenes. This special ligand set allows...

A new method for regioselective zincations of challenging N-heterocyclic substrates such as pyrimidines and pyridazine was reported using bimetallic bases TMPZnX•LiX (TMP = 2,2,6,6-tetramethylpiperidyl; X = Cl, Br). Reactions occurred under mild conditions (25-70 °C, using 1.75 equivalents of base without additives), furnishing 2-zincated pyrimidines and 3-zincated pyridazine, which were then trapped with a variety of electrophiles. Contrasting with other s-block metalating systems, which lack selectivity in their reactions even when operating at low temperatures, these mixed Li/Zn bases enabled unprecedented regioselectivities that cannot be replicated by either LiTMP nor Zn(TMP) 2 on their own. Spectroscopic and structural interrogations of organometallic intermediates involved in these reactions have shed light on the complex constitution of reaction mixtures and the origins of their special reactivities.

Bimetallic complexes combining an alkali‐metal with a lower electropositive metal have demonstrated unique chemical profiles which can be rationalised in terms of chemical cooperativity. Advancing the rational design of these types of complexes, a adaptable method is described to prepare a new family of potassium metal(ates) containing the highly sterically demanding silyl(bis)amide {Ph2Si(NAr*)2}2− (Ar*=2,6‐diisopropylphenyl). Using a sequential deprotonative co‐complexation approach, mono‐metallation of Ph2Si(NHAr*)2 (1) is accomplished using potassium alkyl KCH2SiMe3 yielding [{Ph2Si(NHAr*)(NAr*)K}∞] (2), which, in turn, undergoes co‐complexation with the relevant M(CH2SiMe3)2 (M=Mg, Zn, Mn) enabling metallation of the remaining NHAr* group to furnish silylbis(amido) alkyl potassium metal(ates) [{Ph2Si(NAr*)2M(THF)x(CH2SiMe3)}−{K(THF)y}+] (M=Zn, x=0, y=4, 3; M=Mg, x=1, y=3, 4; and M=Mn, x=0, y=4, 5). Reactivity studies of potassium manganate 5 with the amine HMDS(H) (HMDS=N[SiMe3]2 revealed the kinetic activation of the remaining alkyl group on Mn furnishing [K(THF)2{Ph2Si(NAr*)2}Mn(HMDS)] (6). The structures of these bimetallic complexes along with that of the potassium precursor 2 have been established by X‐ray crystallographic studies.