s-Block Metal Complexes

The coordination chemistry of the s-block metals spans diverse fields, ranging from shielded coordination compounds over hydride to organometallic complexes for diverse applications. New developments pertain, not only to the lithium and magnesium chemistry with inspiring examples, such as heterobimetallic or heteroleptic complexes with special reactivity patterns, but the heavy s-block metals have progressively gained attention in various fields. Subvalent magnesium(I) derivatives are increasingly being used for reduction reactions, turbo-Grignard reagents show enhanced reactivity and tolerance toward functional groups, hydrides act as hydrogen storage materials, heavy Grignard reagents are available by straight forward procedures—just to name a few examples. Quantum chemical calculations deal with unique bonding situations and the relevance of d-orbital participation has been discussed to understand structure-reactivity relationships. Especially the complexes of the heavy alkaline earth metals are catalytically active in diverse reactions, promoting hydrofunctionalization reactions and Lewis acid catalysis. This Special Issue aims to highlight the structural and chemical diversity of s-block metal complexes, as well as the broad field of applications

Bis(2,4,6-trimethyl­phen­yl)zinc(II)

The title compound, [Zn(C9H11)2] or Mes2Zn (Mes = mesityl = 2,4,6-trimethyl­phen­yl), crystallizes with a quarter of a mol­ecule in the asymmetric unit. The ZnII atom is in a strictly linear environment with a Zn—C bond length of 1.951 (5) Å. Due to the imposed 2/m symmetry, both aromatic rings are coplanar. One of the methyl groups is disordered over two equally occupied positions

A hydrogen-bridged adduct 3,4,6,7,8,9-hexa­hydro-2H-pyrimido[1,2-a]pyrimidin-1-ium [1,3-bis­(tert-butyl­dimethyl­sil­yloxy)-1,3-bis­(pyridin-2-yl)propan-2-yl­idene]nitro­nate acetonitrile monosolvate

The title compound, C7H14N3 +·C25H40N3O4Si2 −·CH3CN, was obtained by the reaction of 2-nitro-1,3-di(pyridin-2-yl)-1,3-di(tert-butyl­dimethyl­sil­yloxy)propane with 1,3,4,6,7,8-hexa­hydro-2H-pyrimido[1,2-a]pyrimidine. Two hydrogen bonds stabilize the Lewis acid/base pair of the nitro­nate and the guanidinium moiety with N⋯O distances of 2.772 (3) and 2.732 (3) Å. Both hydrogen atoms are more closely bound to the guanidinium [N—H distances of 0.83 (3) and 0.93 (3) Å] than to the nitro­nate moiety. The nitro­nate is double-bonded to the respective carbon with an N=C bond length of 1.316 (3) Å

Synthesis and Structure of a New Bulky Hybrid Scorpionate/Cyclopentadienyl Ligand and its Lithium Complex

Abstract The reaction of 5‐(1‐adamantyl)‐3‐methyl‐1 H ‐pyrazole with dibromomethane yields a product mixture of bis(3‐adamantyl‐5‐methylpyrazolyl)methane (H 2 C(Pz Ad,Me ) 2 , 2 a ), (3‐adamantyl‐5‐methylpyrazolyl)‐(3‐methyl‐5‐adamantylpyrazolyl)methane ((H 2 C(Pz Ad,Me )(Pz Me,Ad ), 2 b ) and bis(3‐methyl‐5‐adamantylpyrazolyl)methane (H 2 C(Pz Me,Ad ) 2 , 2 c ). Lithiation of sterically congested H 2 C(Pz Ad,Me ) 2 ( 2 a ) and subsequent addition of diphenylfulvene yields lithium 1,1‐bis(3‐adamantyl‐5‐methylpyrazolyl)‐2,2‐diphenyl‐2‐ethyl‐ cyclo pentadienide, [(thf)Li{Cp−CPh 2 −CHPz Ad,Me }] ( 3 ) which is unable to form a thf adduct but can be hydrolyzed to H 5 C 5 −CPh 2 −CHPz Ad,Me ( 4 ). Adamantyl groups in 5‐position of bis(pyrazolyl)methane, i. e. 2 b and 2 c , prohibit formation of a fulvene adduct. For comparison reasons, [{H 5 C 5 −CPh 2 −CHPz Me2 }LiI] ( 1 b ) has been prepared via protolysis of (thf)lithium 1,1‐bis(3,5‐dimethylpyrazolyl)‐2,2‐diphenyl‐2‐ethyl‐ cyclo pentadienide, [(thf)Li{Cp−CPh 2 −CHPz Me2 }] ( 1 a ), in the presence of calcium iodide.imag

Synthesis, Structure, and Stability of Lithium Arylphosphanidyl‐diarylphosphane Oxide

The reaction of LiP(H)Tipp ( 2a ) and KP(H)Tipp ( 2b , Tipp = C 6 H 2 ‐2,4,6‐ i Pr 3 ), which are accessible via metalation of Tipp‐PH 2 ( 1 ), with bis(4‐ tert ‐butylphenyl)phosphinic chloride yields Tipp‐P=P(OM)Ar 2 [M = Li ( 3a ) and K ( 3b )]. These complexes show characteristic chemical 31 P shifts and large 1 J PP coupling constants. These compounds degrade with elimination of the phosphinidene Tipp‐P: and the alkali metal diarylphosphinites M–O–PAr 2 [M = Li ( 4a ) and K ( 4b )]. The phosphinidene forms secondary degradation products (like the meso and R,R/S,S ‐isomers of diphosphane Tipp‐P(H)–P(H)Tipp ( 5 ) via insertion into a P–H bond of newly formed Tipp‐PH 2 ), whereas the crystallization of [Tipp‐P=P(OLi)Ar 2 · LiOPAr 2 · LiCl · 2Et 2 O] 2 (i.e. [ 3a·4a· LiCl · 2Et 2 O] 2 ) succeeds from diethyl ether. The metathesis reactions of LiP(Si i Pr 3 )Tipp and LiP(Si i Pr 3 )Mes (Mes = C 6 H 2 ‐2,4,6‐Me 3 ) with Ar 2 P(O)Cl yield Ar*‐P=P(OSi i Pr 3 )Ar 2 (Ar* = Mes, Tipp) which degrade to Ar 2 POSi i Pr 3 and other secondary products.image John Wiley & Sons, Ltd

2-(Benzoyl­amino­meth­yl)pyridinium chloride

The title compound, C13H13N2O+·Cl−, (1), was obtained as a colorless crystalline by-product during the synthesis of N-(2-pyridylmeth­yl)benzoyl­amine (2). The C—O bond length of 1.231 (2) Å in the benzoyl unit of (1) is slightly elongated in comparison with isolated C=O double bonds as also observed for (2) [1.237 (2) Å]. The N—C bond length of 1.345 (2) Å in the benzoic acid amide unit indicates the formation of an allylic O—C—N system and is very similar to the N—C bond lengths [1.345 (2) Å] of the pyridyl group. A further delocalization of charge from this allylic system into the phenyl fragment does not occur, which can be deduced from a characterisitc C—C single bond length of 1.499 (2) Å between these fragments. A dimer is formed via N—H⋯Cl hydrogen bonds. The two rings make a dihedral angle of 105.0 (2)

One‐Step Synthesis and Schlenk‐Type Equilibrium of Cyclopentadienylmagnesium Bromides

Abstract In the in situ Grignard metalation method (iGMM), the addition of bromoethane to a suspension of magnesium turnings and cyclopentadienes [C 5 H 6 (HCp), C 5 H 5 ‐Si( i Pr) 3 (HCp TIPS )] in diethyl ether smoothly yields heteroleptic [(Et 2 O)Mg(Cp R )(μ‐Br)] 2 (Cp R =Cp ( 1 ), Cp TIPS ( 2 )). The Schlenk equilibrium of 2 in toluene leads to ligand exchange and formation of homoleptic [Mg(Cp R ) 2 ] ( 3 ) and [(Et 2 O)MgBr(μ‐Br)] 2 ( 4 ). Interfering solvation and aggregation as well as ligand redistribution equilibria hamper a quantitative elucidation of thermodynamic data for the Schlenk equilibrium of 2 in toluene. In ethereal solvents, mononuclear species [(Et 2 O) 2 Mg(Cp TIPS )Br] ( 2’ ), [(Et 2 O) n Mg(Cp TIPS ) 2 ] ( 3’ ), and [(Et 2 O) 2 MgBr 2 ] ( 4’ ) coexist. Larger coordination numbers can be realized with cyclic ethers like tetrahydropyran allowing crystallization of [(thp) 4 MgBr 2 ] ( 5 ). The interpretation of the temperature‐dependency of the Schlenk equilibrium constant in diethyl ether gives a reaction enthalpy ΔH and reaction entropy ΔS of −11.5 kJ mol −1 and 60 J mol −1 , respectively.Cyclopentadienylmagnesium bromides are accessible with high yields by a fast and smooth one‐pot synthesis. In hydrocarbons and in ethereal solvents a dissociative Schlenk equilibrium is operative interconverting heteroleptic compounds into homoleptic congeners. imag

Bis[(2-pyridylmeth­yl)(triisopropyl­silyl)amido]zinc(II)–toluene–tetra­hydro­furan (4/2/1)

The transamination reaction of (2-pyridylmeth­yl)(triiso­propyl­silyl)amine with bis­{bis­(trimethyl­silyl)amido}zinc(II) yields the colorless title solvate, [Zn(C15H27N2Si)2]·0.5C7H8·0.25C4H8O. The title compound was crystallized from toluene and tetra­hydro­furan. There are two independent mol­ecules in the asymmetric unit. In each mol­ecule, the Zn atom is tetra­hedrally coordinated by four N atoms. The two mol­ecules differ in the orientation of the isopropyl groups. The mol­ecules show large N—Zn—N angles [143.0 (2) and 145.7 (2)° between the amide groups]

Alkaline‐earth metal dimesitylphosphinites and their ether adducts – A structural study in solution and in the crystalline state

Abstract Alkaline‐earth metalation of dimesitylphosphane oxide Mes 2 P(O)H ( 1 ) in ethereal solvents with dialkylmagnesium and alkylmagnesium bromide as well as the homoleptic bis(trimethylsilyl)amides of calcium, strontium, and barium yields [(L)MgR(μ‐OPMes 2 )] 2 (L/R=thf/Et ( 2‐Et ), Et 2 O/Br ( 2‐Br )), [(thf) 3 Ca(hmds)(OPMes 2 )] ( 3‐hmds ), [(thf) 3 Mg(OPMes 2 ) 2 ] ( 2‐thf ) and [(thf) 4 Ae(OPMes 2 ) 2 ] (Ae=Ca ( 3‐thf ), Sr ( 4‐thf ), and Ba ( 5‐thf )), depending on the applied stoichiometry. Exchange of thf ligands in 3‐thf by oligodentate ethers allows isolation of [(thf) 2 (dme)Ca(OPMes 2 ) 2 ] ( 3‐dme ), [(thf) 2 (diglyme)Ca(OPMes 2 ) 2 ] ( 3‐diglyme ) and [(thf)(triglyme)Ca(OPMes 2 ) 2 ] ( 3‐triglyme ). Contrary to this finding, oligodentate amines are unable to substitute ligated thf ligands in 3‐thf . In ethereal solutions, the heteroleptic complexes 2‐Et , 2‐Br and 3‐hmds show Schlenk‐type equilibria, interconverting these compounds into their homoleptic counterparts.imag

In Situ Grignard Metalation Method for the Synthesis of Hauser Bases

The in situ Grignard Metalation Method ( i GMM) is a straightforward one‐pot procedure to quickly produce multigram amounts of Hauser bases R 2 N‐MgBr which are valuable and vastly used metalation reagents and novel electrolytes for magnesium batteries. During addition of bromoethane to a suspension of Mg metal and secondary amine at room temperature in an ethereal solvent, a smooth reaction yields R 2 N‐MgBr under evolution of ethane within a few hours. A Schlenk equilibrium is operative, interconverting the Hauser bases into their solvated homoleptic congeners Mg(NR 2 ) 2 and MgBr 2 depending on the solvent. Scope and preconditions are studied, and side reactions limiting the yield have been investigated. DOSY NMR experiments and X‐ray crystal structures of characteristic examples clarify aggregation in solution and the solid state