The Parent Cyclopentadienyltin Cation, Its Toluene Adduct, and the Quadruple-Decker [Sn3Cp4]2+

Bis(tetrelocenes) - fusing tetrelocenes into close proximity

We report the synthesis and structure of two bis(germanocenes) and a bis(stannocene), obtained by the reaction of unsymmetric ansa bis(cyclopentadienyl) ligands with germanium and tin dichloride. DFT calculations show that the formation of these bis(tetrelocenes) is energetically favoured over the formation of the corresponding [1]tetrelocenophanes. In the crystal structure authenticated structural motif, the two tetrel(II) centers are forced into close proximity to each other, resulting in weak donor-acceptor interactions, according to Natural Bond Orbital (NBO) and Atoms in Molecules (AIM) analyses.

Utilization of a Tris(carbene)borate Ligand for Umpolung Reactivity of a Nucleophilic Tin(II) Cation Salt

We show that a tris(carbene)borate (TCB) ligand, namely [PhB(^tBuIm)₃]^- ([PhB(^tBuIm)₃]^- = phenyltris(3-tert-butylimidazol-2-ylidene)borato), is capable of stabilizing an unprecedented nucleophilic Sn(II) cation salt. Unlike known Sn(II) cations, the strong electron-donating ability of [PhB(^tBuIm)₃]^- makes the cationic tin atom electron-rich, σ-donating yet slightly π-accepting, which allows for the ensuing facile oxidation with o-chloranil and S₈ as well as coordination with coinage metals. The former oxidations give the Sn(IV) cation salts, while the latter reactions produce the metal complexes. The electronic structures of these species are thoroughly probed by quantum chemical computations. These results uncover an added role for TCB ligands in isolating unprecedented p-block species.

Phosphanyl-substituted tin half-sandwich complexes†

Phosphanyl-substituted tin(ii) half sandwich complexes are reported. Due to the Lewis acidic tin center and Lewis basic phosphorous atom they form head-to-tail dimers. Their properties and reactivities were investigated both experimentally and theoretically. Furthermore, related transition metal complexes of these species are presented.

Phosphanyl-substituted tin(ii) half sandwich complexes are reported, which exhibit Lewis acidic tin atoms and Lewis basic phosphorous atoms and form head-to-tail dimers.

Cationic dialanes with fluxional π-bridged cyclopentadienyl ligands

Unique π-cyclopentadienyl bridged dialanes are synthesized as complex salts with aluminate anions by comproportionation of aluminocenium cations [Al^III(Cp)(Cp*)]⁺/[Al^IIICp₂]⁺ with [(Al^ICp*)₄]. Very short Al-Al bond lengths occur in positively charged Al₂⁴⁺ fragments. Intriguingly, the prepared asymmetric dialane shows a unique fluxional coordination of the cyclopentadienyl ligands.

Silole and germole complexes of lanthanum and cerium

Using dianionic metallole ligands (silole or germole) and the cyclooctatetraendiide dianion, heteroleptic lanthanide multi-decker complexes have been prepared. Due to the heteroatom of the metallole ligands intermolecular bridging between the sandwich complexes takes place. Our work highlights that different combinations of the lanthanide and heterocycle lead to different intermolecular interactions including a dimeric La-silole sandwich complex, a La-germole ladder-type polymeric species and a Ce-germole coordination polymer.

Stack by Stack: From the Free Cyclopentadienylgermanium Cation Via Heterobimetallic Main-Group Sandwiches to Main-Group Sandwich Coordination Polymers

Heterobimetallic cationic sandwich complexes [M(μ-Cp)M'Cp]+ of group 13 (M=Ga, In) and group 14 (M'=Ge, Sn) elements have been prepared as [WCA]- salts (WCA=Al(ORF )4 ; ORF =OC(CF3 )3 ). Their molecular structures include free apical gallium or indium atoms. The sandwich complexes were formed in the reactions of [M(HMB)]+ [WCA]- (HMB=C6 Me6 ) with the free metallocenes [M'Cp2 ]. Their structures are related to known stannocene and stannocenium salts; the unprecedented germanium analogues, namely the free germanocenium cation [GeCp]+ and the corresponding triple-decker complex cation [CpGe(μ-Cp)GeCp]+ , are described herein. By variation of the reaction conditions, these sandwich complexes can be transformed into the group 13/14 mixed cationic coordination polymer [{In(HMB)(μ-SnCp2 )}n ][WCA]n . This polymeric chain motif was also successfully replicated by the synthesis of complexes [{Ga/In(HMB)(μ-FeCp2 )}n ][WCA]n containing FeCp2 as a bridging ligand.

Synthesis, detailed geometric analysis and bond-valence method evaluation of the strength of π-arene bonding of two isotypic cationic prehnitene tin(II) complexes: [{1,2,3,4-(CH3)4C6H2}2Sn2Cl2][MCl4]2 (M = Al and Ga)

From solutions of prehnitene and the ternary halides (SnCl)[MCl4] (M = Al, Ga) in chloro-benzene, the new cationic SnII-π-arene complexes catena-poly[[chlorido-aluminate(III)]-tri-μ-chlorido-4':1κ2 Cl,1:2κ4 Cl-[(η6-1,2,3,4-tetra-meth-yl-benzene)-tin(II)]-di-μ-chlorido-2:3κ4 Cl-[(η6-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-3:4κ4 Cl-[chlorido-aluminate(III)]-μ-chlorido-4:1'κ2 Cl], [Al2Sn2Cl10(C10H14)2] n , (1) and catena-poly[[chlorido-gallate(III)]-tri-μ-chlor-ido-4':1κ2 Cl,1:2κ4 Cl-[(η6-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-2:3κ4 Cl-[(η6-1,2,3,4-tetra-methyl-benzene)-tin(II)]-di-μ-chlorido-3:4κ4 Cl-[chlor-ido-gallate(III)]-μ-chlorido-4:1'κ2 Cl], [Ga2Sn2Cl10(C10H14)2] n , (2), were isolated. In these first main-group metal-prehnitene complexes, the distorted η6 arene π-bonding to the tin atoms of the Sn2Cl2 2+ moieties in the centre of [{1,2,3,4-(CH3)4C6H2}2Sn2Cl2][MCl4]2 repeating units (site symmetry ) is characterized by: (i) a significant ring slippage of ca 0.4 Å indicated by the dispersion of Sn-C distances [1: 2.881 (2)-3.216 (2) Å; 2: 2.891 (3)-3.214 (3) Å]; (ii) the non-methyl-substituted arene C atoms positioned closest to the SnII central atom; (iii) a pronounced tilt of the plane of the arene ligand against the plane of the central (Sn2Cl2)2+ four-membered ring species [1: 15.59 (11)°, 2: 15.69 (9)°]; (iv) metal-arene bonding of medium strength as illustrated by application of the bond-valence method in an indirect manner, defining the π-arene bonding inter-action of the SnII central atoms as s(SnII-arene) = 2 - Σs(SnII-Cl), that gives s(SnII-arene) = 0.37 and 0.38 valence units for the aluminate and the gallate, respectively, indicating that comparatively strong main-group metal-arene bonding is present and in line with the expectation that [AlCl4]- is the slightly weaker coordinating anion as compared to [GaCl4]-.

Facile and systematic access to the least-coordinating WCA [(RFO)3Al-F-Al(ORF)3]- and its more Lewis-basic brother [F-Al(ORF)3]- (RF = C(CF3)3)

By reaction of the Lewis acid Me3Si-F-Al(ORF)3 with a series of [PF6]- salts, gaseous PF5 and Me3Si-F are liberated and salts of the anion [F-Al(ORF)3]- ([f-al]-; RF = C(CF3)3) can be obtained. By addition of another equivalent of Me3Si-F-Al(ORF)3 to [f-al]-, gaseous Me3Si-F is released and salts of the least coordinating anion [(RFO)3Al-F-Al(ORF)3]- ([al-f-al]-) are formed. Both procedures work for a series of synthetically useful cations including Ag+, [NO]+, [Ph3C]+ and in very clean reactions with 5 g batch sizes giving excellent yields typically exceeding 90%. In addition, the synthesis of Me3Si-F-Al(ORF)3 has been optimized and scaled up to 85 g batches in an one-pot procedure. These anions could previously only be obtained by difficult to control decomposition reactions of [Al(ORF)4]- or by halide abstraction reactions with Me3Si-F-Al(ORF)3, generating relatively large countercations that are unsuited for further use as universal starting materials. Especially [al-f-al]- is of interest for the stabilization of reactive cations, since it is even weaker coordinating than [Al(ORF)4]- and more stable against strong electrophiles. This bridged anion can be seen as an adduct of [f-al]- and Al(ORF)3. Thus, it is similarly Lewis acidic as BF3 and eventually reacts with nucleophiles (Nu) from the reaction environment to yield Nu-Al(ORF)3 and [f-al]-. This prevents working with [al-f-al]- salts in ethereal or other donor solvents. By contrast, the [f-al]- anion is no longer Lewis acidic and may therefore be used for reactions involving stronger nucleophiles than the [al-f-al]- anion can withstand. Subsequently it may be transformed into the [al-f-al]- salt by simple addition of one equivalent of Me3Si-F-Al(ORF)3.

Taming the Cationic Beast: Novel Developments in the Synthesis and Application of Weakly Coordinating Anions

This Review gives a comprehensive overview of the most topical weakly coordinating anions (WCAs) and contains information on WCA design, stability, and applications. As an update to the 2004 review, developments in common classes of WCA are included. Methods for the incorporation of WCAs into a given system are discussed and advice given on how to best choose a method for the introduction of a particular WCA. A series of starting materials for a large number of WCA precursors and references are tabulated as a useful resource when looking for procedures to prepare WCAs. Furthermore, a collection of scales that allow the performance of a WCA, or its underlying Lewis acid, to be judged is collated with some advice on how to use them. The examples chosen to illustrate WCA developments are taken from a broad selection of topics where WCAs play a role. In addition a section focusing on transition metal and catalysis applications as well as supporting electrolytes is also included.

Approaching monocoordination at a silver(i) cation

A series of highly electrophilic [(NHC)Ag]⁺ complexes (NHC = N-heterocyclic carbene) have been prepared which approach the limit of monocoordination for silver(i).

Two synthetic approaches for the preparation of tin(ii) dications

Facile access to weakly coordinated Sn(ii) salts is provided by reaction of NO[Al(OR^F)₄] with tin metal. Further use is indicated.