Multinuclear Silver Ethynide Supramolecular Synthons for the Construction of Coordination Networks

The invariant appearance of the μ₈ coordination mode for the C₄^2? dianion in its silver(I) complexes, with four silver(I) atoms attached to each terminal ethynide moiety, implies that the Ag₄?C?C? C?C?Ag₄ species may be considered as a new type of supramolecular synthon for the construction of 1D, 2D, and 3D coordination polymers. This Focus Review covers recent results on the synthesis and structural characterization of silver(I) arylethynide and alkylethynide complexes, which established the existence and utility of analogous polynuclear supramolecular synthons R? C?C?Ag_n (R=aryl or alkyl; n=4, 5) and Ag_n?C₂? R? C₂?Ag_n (R=p‐, m‐, o‐C₆H₄; n=4, 5). The interplay of silver–ethynide bonding, which can be classified into σ, π, and mixed (σ,π) types, with argentophilicity, π–π stacking, and other weak interactions highlights the complexity and challenge in building coordination networks of silver ethynide complexes.     

Structural variability of Ag(I) metal–organic networks: C–H⋯π and metal⋯π interactions

The synthesis and X-ray structural characterization of two silver(I) coordination polymers, [Ag₂(bpp)₂(Phdac)]·5H₂O (1) and [Ag₂(bpp)(HSSal)] (2), are reported, where bpp = 4,4′-trimethylene dipyridine, H₂Phdac = 1,4-phenylenediacetic acid, and H₃SSal = 5-sulfosalicylic acid. X-ray crystallography reveals that the structures are stabilized through hydrogen bonding interactions. The C–H?π and metal?π interactions of aromatic molecules play a crucial role in building a layered framework. Intricate combinations of the weak non-covalent interactions have been analyzed to explore cooperativity and competitiveness in the solid-state structures.     

A silver(I) coordination derivative of 2,3-dimethylthio-6-pyridyl tetrathiafulvalene,synthesis, crystal structure and electrochemical properties

A silver coordination compound [Ag(I)(DMT–TTF-py)₂CH₃CN] ClO₄?·?CH₂Cl₂ has been synthesized by reaction of DMT–TTF-py with AgClO₄. Structure analysis shows that the cations self-assemble to dimeric units through Ag?···?Ag interactions. Each silver(I) has a T-shaped AgN₃ coordination geometry. In the dimeric units, there are short C?···?S and C?···?C contacts between the two DMT–TTF-py molecules. The dimeric units are further assembled to a zigzag packing structure. The cyclic voltametric behavior of the ligand shows two-step reversible redox waves, which are shifted to lower values due to coordination to silver.     

基于2,4′-二羧基二苯甲酮构筑的具有一维梯状链和一维隧道的三维超分子体系

采用水热法设计合成了两个新型三维超分子化合物H₂L·H₂O (1)和[Ag(bpy)₂]·HL·H₂O (2) (其中bpy=2,2'-联吡啶, H₂L=2,4′-二羧基二苯甲酮),晶体结构分析表明,它们均是通过氢键采用不同的连接方式拓展而成。其中,化合物1 是2,4′-二羧基二苯甲酮和水分子通过O–H···O氢键形成的一维梯状链扩展构筑的三维超分子体系;化合物2 则是2,4′-二羧基二苯甲酮和水分子通过两种氢键形成含有一维隧道的三维超分子体系。有趣的是,[Ag(bpy)₂]⁺ 阳离子通过π–π 堆积和弱的Ag···Ag相互作用连在一起,进而以客体形式填充其中。荧光性质研究表明,由于存在bpy的螯合与堆积效应,化合物2相比配体和化合物1,其荧光发射峰发生红移。     

DFT studies on the mechanism of Ag2CO3‐catalyzed hydroazidation of unactivated terminal alkynes with TMS‐N3: An insight into the silver(I) activation mode

Silver‐mediated hydroazidation of unactivated alkynes has been developed as a new method for the synthesis of vinyl azides. Density functional theory calculations toward this reaction reveal that terminal alkynes with TMS‐N₃ participated hydroazidation proceed through HN₃ formation, deprotonation and silver acetylides formation, nucleophilic addition, and protonation of terminal carbon by AgHCO₃. It is also found that water molecules and activation modes of Ag (I) have a significant influence on the title reaction mechanism. Initially, catalyst Ag₂CO₃ coordinates preferentially with internal N atom of TMS–N₃ to assist water as hydrogen source and proton‐shuttle in facilitating HN₃ formation. Then, the regioselective anti‐addition of HN₃ to triple bond of active silver‐acetylide or ethynyl carbinols affords product vinyl azide via Ag–C σ‐bond activation or Ag…C π‐coordination activation modes, and the former one is more favorable. The origin of the difference regioselectivity is ascribed to the electronic and orbital effects of the reactive sites. Moreover, Ag₂CO₃ is the critical catalyst, acting as activator, base, and stabilizer to promote the HN₃ and vinyl azide formation. Water molecule plays an important role as proton shuttle to promote HN₃ and key active silver acetylides formation, thus improving the yield of product. © 2017 Wiley Periodicals, Inc.     

A two‐dimensional network formed by self‐associating silver(I) perchlorate with 3‐[4‐(2‐thienyl)‐2H‐cyclopenta[d]pyridazin‐1‐yl]benzonitrile

In the organometallic silver(I) supramolecular complex poly[[silver(I)‐μ₃‐3‐[4‐(2‐thienyl)‐2H‐cyclopenta[d]pyridazin‐1‐yl]benzonitrile] perchlorate methanol solvate], {[Ag(C₁₈H₁₁N₃S)](ClO₄)·CH₃OH}_n, there is only one type of Ag^I center, which lies in an {AgN₂Sπ} coordination environment. Two unsymmetric multidentate 3‐[4‐(2‐thienyl)‐2H‐cyclopenta[d]pyridazin‐1‐yl]benzonitrile (L) ligands link two Ag^I atoms through π–Ag^I interactions into an organometallic box‐like unit, from which two 3‐cyanobenzoyl arms stretch out in opposite directions and bind two Ag^I atoms from neighboring box‐like building blocks. This results in a novel two‐dimensional network extending in the crystallographic bc plane. These two‐dimensional sheets stack together along the crystallographic a axis to generate parallelogram‐like channels. The methanol solvent molecules and the perchlorate counter‐ions are located in the channels, where they are fixed by intermolecular hydrogen‐bonding interactions. This architecture may provide opportunities for host–guest chemistry, such as guest molecule loss and absorption or ion exchange. The new fulvene‐type multidentate ligand L is a good candidate for the preparation of Cp–Ag^I‐containing (Cp is cyclopentadienyl) organometallic coordination polymers or supramolecular complexes.     

Synthesis,crystal structure and ferromagnetic interactions of a silver(I) complex with imizadolyl-substituted nitroxide radicals

A silver(I) complex with nitronyl nitroxide, [Ag₂(NIT-R)₄(NO₃)₂]?·?CH₃OH [NIT-R?=?2-(5-methylimidazol-4-yl)-4,4,5,5-tetramethyl-2-imidazoline-1-oxyl-3-oxide], has been prepared and characterized by magnetic and single-crystal X-ray diffraction studies. In the complex, the silver(I) ion is coordinated with two monodentate nitronyl nitroxide radicals by the nitrogen of the imizadole ring. The silver(I) ion is two-coordinate and forms a dimer through Ag?···?Ag weak metal bonding interactions. The magnetic properties for the title complex have been investigated in the temperature range 2?～?300?K showing ferromagnetic interactions between the coordinated nitronyl nitroxides (J?=?3.64?cm^?1) and intermolecular antiferromagnetic interactions.     

Influence of Flexible Bis(benzimidazole) Derivatives on the Self‐assembly of Three Mixed Ligands Silver(I) Coordination Polymers

Three silver(I) coordination polymers namely, [Ag₄(L1)₂(1, 4‐ndc)₂]_n ( 1 ) {[Ag(L2)] · (1, 4‐Hndc) · H₂O}_n ( 2 ), and {[Ag(L3)(H₂O)] · (1, 4‐Hndc)}_n ( 3 ) [L1 = 1, 3‐bis(benzimidazol‐1‐ylmethyl)benzene, 1, 4‐H₂ndc = 1, 4‐naphthalenedicarboxylic acid, L2 = 1, 3‐bis(5, 6‐dimethylbenzimidazole‐1‐ylmethyl)benzene, L3 = 1, 4‐bis(5, 6‐dimethylbenzimidazole)butane], were hydrothermally synthesized and characterized by single‐crystal X‐ray diffraction analysis, elemental analysis, IR spectroscopy, thermogravimetric and XRPD analysis. Complex 1 displays a 1D tube‐like chain, which is packed into a 3D supramolecular network by π–π stacking interactions. Complex 2 features an infinite 1D linear chain. Complex 3 contains a 1D wave‐like chain, which is extended into a 3D supramolecular network through O–H ··· O hydrogen bonding interactions. Moreover, these coordination polymers exhibit catalytic properties for degradation of methyl orange in Fenton‐like processes.     

Bis(2‐pyridyl­methanol)­bis­(saccharinato)­zinc(II) and ‐cadmium(II) at 120 K: three‐dimensional structures containing both N‐and O‐coordinated ambi­dentate saccharinate ligands

The title complexes [M(sac)₂(mpy)₂] [sac is saccharinate (C₇H₄NO₃S) and mpy is 2‐pyridyl­methanol (C₆H₇NO)], with M = Zn^II and Cd^II, are isostructural and consist of neutral mol­ecules. The Zn^II or Cd^II cations are octahedrally coordinated by the two neutral mpy and two anionic sac ligands. The mpy ligand acts as a bidentate donor through the amine N and hydroxyl O atoms. The sac ligands exhibit an ambidentate coordination behaviour; one is N‐coordinated and the other is O‐coordinated within the same coordination octahedron. The crystal packing is determined by C—H?O‐type hydrogen bonding, as well as by weak py–py and sac–sac aromatic π–π‐stacking interactions.     

2‐Iodo‐N‐(3‐nitrobenzyl)aniline and 3‐iodo‐N‐(3‐nitrobenzyl)aniline exhibit entirely different patterns of supramolecular aggregation

In 2‐iodo‐N‐(3‐nitro­benzyl)­aniline, C₁₃H₁₁IN₂O₂, the mol­ecules are linked into a three‐dimensional structure by a combination of C—H?O hydrogen bonds, iodo–nitro interactions and aromatic π–π‐stacking interactions, but N—H?O and C—H?π(arene) hydrogen bonds are absent. In the isomeric 3‐iodo‐N‐(3‐nitro­benzyl)­aniline, a two‐dimensional array is generated by a combination of N—H?O, C—H?O and C—H?π(arene) hydrogen bonds, but iodo–nitro interactions and aromatic π–π‐stacking interactions are both absent.     

Anion Effects on the Formation of Silver(I) Complexes with the Flexible Ligand 4,4′‐Bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl

The reaction of 4,4′‐bis(1,2,4‐triazol‐1‐ylmethyl)biphenyl (btmb) with silver(I) salts of BF₄^–, NO₃^– and N₃^– led to the formation of four new silver(I) coordination polymers {[Ag(btmb)]BF₄}_n ( 1 ), {[Ag₂(btmb)₃](NO₃)₂(H₂O)₅}_n ( 2 ), [Ag₂(btmb)(N₃)₂]_n ( 3 ), and [Ag(btmb)(N₃)]_n ( 4 ). Their coordination number varies from 2 (in 1 ) to 3 (in 2 ), 4 (in 3 ), and 5 (in 4 ). Different from the single chain structure of 1 , complex 2 displays a 1D ladder‐like double chain framework, whereas complex 3 exhibits a 2D layered architecture. Complex 4 has the same anion as complex 3 but shows a different metal‐to‐ligand ratio and a 1D double‐zigzag chain structure. Both 3 and 4 have Ag ··· Ag argentophilic interactions. The ligand btmb adopts both cis or trans configuration in the studied complexes. A trans‐ or cis‐btmb ligand link silver ions with Ag ··· Ag distances of ≈?18 and 13 Å, respectively. BF₄^– and NO₃^– are non‐coordinating anions in 1 and 2 . N₃^– is the bridging anion in 3 (1,3‐bridging fashion) and 4 (1,1‐bridging fashion). These findings suggest that the coordination numbers around the Ag^I ion correlate to the coordination abilities of anions and the btmb to silver ratio. In addition, the influence of anions on thermal stability were also investigated. This work is a good example that nicely supports the less explored field of anion‐dependent structures of complexes with non‐pyridyl ligands.     

Syntheses,Crystal Structures and Cytotoxities of Silver (I) Complexes of 2,2′‐Bipyridines and 1,10‐Phenanthroline

The syntheses, characterizations and in vitro cytotoxities of seven soluble silver (I) compounds (1–7) with 2,2′‐bipyridine (bpy), 5,5′‐dimethyl‐2,2′‐bipyridine (dmbpy) and 1, 10‐phenanthroline (phen) are described. Two of the complexes, [Ag(dmbpy)(NO₃)] (1) and [Ag(dmbpy)]ClO₄(2), have been structurally established by single‐crystal X‐ray diffraction, which reveals the silver(I) atom in compound 1 is in a Y‐shape coordination geometry with two N atoms (av. Ag? N = 227.8 pm) from a chelate dmbpy ligand and an O atom (Ag? O=221.8(4) pm) from a monodentate nitrate. The Ag(I) atom in compound 2 is three‐coordinated by three N atoms, two of which are from a chelate dmbpy, and one from an acetonitrile ligand. The seven compounds showed strong cytotoxities in vitro to both normal and carcinoma cells.     

Three Dicyanidometallate(I)‐based Complexes Incorporating Hydrogen‐bonding, π–π Packing and d10–d10 Interactions with Auxiliary 2,2′‐Bipyridyl‐like Ligands

To investigate the influence of the non‐covalent interactions, such as hydrogen‐bonding, π–π packing and d¹⁰–d¹⁰ interactions in the supramolecular motifs, three cyanido‐bridged heterobimetallic discrete complexes {Mn(bipy)₂(H₂O)[Ag(CN)₂]}[Ag(CN)₂] ( 1 ), {Mn(phen)₂(H₂O)[Au(CN)₂]}₂[Au(CN)₂]₂ · 4H₂O ( 2 ), and {Cd(bipy)₂(H₂O)[Au(CN)₂]}[Au(CN)₂] ( 3 ) (bipy = 2,2′‐bipyridine, and phen = 1,10‐phenanthroline), which are based on dicyanidometallate(I) groups with 1:2 stoichiometry of metal ions and 2,2′‐bipyridyl‐like co‐ligands were synthesized and structurally characterized. In compound 1 , hydrogen bonding and π–π interactions governed the supramolecular contacts. In compound 2 , the incorporation of aurophilic, hydrogen bonding and π–π interactions result in a 3D supramolecular network. In compound 3 , hydrogen bonding and π–π stacking interactions result in a 2D supramolecular layer. In the three complexes, hydrogen‐bonding, π–π packing and/or d¹⁰–d¹⁰ interactions can play important roles in increasing the dimensionality of supramolecular assemblies.     

Ethyl 4‐do­decyl‐3,5‐di­methyl‐1H‐pyrrole‐2‐carboxyl­ate: intermolecular interactions in an amphiphilic pyrrole

The title compound, C₂₁H₃₇NO₂, is a new amphiphilic pyrrole with a long hydro­carbon chain, which will be used as a precursor for the synthesis of Langmuir–Blodgett films of porphyrins. Molecules related by an inversion centre are joined head‐to‐head into dimers by strong N—H?O hydrogen bonds. The dimers pack in the structure with their carbon chains parallel to one another, thereby forming alternating layers of carbon chains and pyrrole heads. The structure is further stabilized by two weak C—H?π intermolecular interactions, thereby saturating the hydrogen‐bonding capability of the aromatic π‐electron clouds.     

Syntheses and Structural Characterization of Four New Silver(I) Complexes with the N,N′(O)‐bidentate Bridging Ligands

Four new bridged silver(I) complexes, namely [Ag₂(μ₂‐teda)(μ₂‐fbc)₂] ( 1 ), [Ag₂(μ₂‐1,6‐dah)₂](bpdc) · 4H₂O ( 2 ), [Ag₂(μ₂‐2‐ap)(2‐ap)(bnb)] · 0.34H₂O ( 3 ), [Ag₂(μ₂‐pyc)₂(2‐apy)₂] · 0.5H₂O ( 4 ), have been synthesized and characterized by elemental analysis and crystallographic methods [fbc = 4‐fluorobenzoate, teda = triethylenediamine ( 1 ); bpdc = biphenyl‐4,4′‐dicarboxylate, 1,6‐dah = 1,6‐diaminohexane ( 2 ); bnb = 3,5‐binitrobenzoate, 2‐ap = 2‐aminopyrimidine ( 3 ); pyc = 3‐pyridinecarboxylate acid, 2‐apy = 2‐aminopyridine ( 4 )]. Complex 1 contains a 1D linear chain paralleling to the c‐axis, whereas in complex 2 silver(I) atoms were bridged by the 1,6‐dah ligand into a zigzag chain, further giving a 1D ribbon by weak Ag ··· Ag interactions. Complex 3 consists of a dinuclear silver(I) [Ag₂(μ₂‐2‐ap)(2‐ap)(bnb)] moiety and a lattice water molecule, forming a 3D network via a number of hydrogen‐bonding interactions such as N–H ··· O, N–H ··· N and C–H ··· O hydrogen bond and other weak interactions such Ag ··· Ag, Ag ··· N, N ··· O as well as O ··· O interaction. Similar to 3 , the asymmetric unit of 4 consists of one dinuclear silver(I) [Ag₂(μ₂‐pyc)₂(2‐apy)₂] moiety and half lattice water molecule, further generating a tetranuclear silver(I) {[Ag₂(μ₂‐pyc)₂(2‐apy)₂]₂ · H₂O} moiety. These moieties construct a 3D supramolecular network structure of 4 through N–H ··· O, O–H ··· O and C–H ··· O hydrogen bonds as well as other weak interactions such as Ag ··· O and N ··· O interactions.     

Strukturen ionischer Di(arensulfonyl)amide. 8. Natrium‐bis[di(4‐fluorbenzolsulfonyl)amido‐N]argentat: Ein Heterobimetallkomplex mit lamellarer Schichtstruktur und kurzen Zwischenschichtkontakten C–H···F–C

Structures of Ionic Di(arenesulfonyl)amides. 8. Sodium Bis[di(4‐fluorobenzenesulfonyl)amido‐N]argentate: A Heterobimetallic Complex Exhibiting a Lamellar Layer Structure and Short C–H···F–C Interlayer Contacts Na[Ag{N(SO₂–C₆H₄–4‐F)₂}₂] (monoclinic, C2/c, Z′ = 1/2) is the first heterobimetallic representative in a well‐documented class of layered inorgano‐organic solids where the inorganic component is comprised of metal cations and coordinating N(SO₂)₂ groups and the outer regions are formed by the aromatic rings of the di(arenesulfonyl)amide entities, which adopt a folded conformation approximating to mirror symmetry. The inversion‐symmetric bis(amido)argentate unit of the novel compound displays an exactly linear N–Ag–N core and short Ag–N bonds of 217.55(17) pm (at ?140 °C); the coordination number of the silver ion is extended to 2 + 6 by four internal and two external Ag···O secondary interactions. The polar lamella is constructed from rows of Na⁺ ions located on twofold axes, alternating with bis(amido)argentate strands reinforced by Ag···O interactions and weak C–H···O hydrogen bonds; Na⁺ is embedded in an O₆ environment. Adjacent layers are cross‐linked via short C–H···F–C contacts suggestive of weak hydrogen bonding enhanced by cooperativity.     

Silver(I) sulfate coordination polymers with 4,4′‐bipyridazine and pyridazino[4,5‐d]pyridazine

Poly[[μ₄‐4,4′‐bipyridazine‐μ₅‐sulfato‐disilver(I)] monohydrate], {[Ag₂(SO₄)(C₈H₆N₄)]·H₂O}_n, (I), and poly[[aqua‐μ₄‐pyridazino[4,5‐d]pyridazine‐μ₃‐sulfato‐disilver(I)] monohydrate], {[Ag₂(SO₄)(C₆H₄N₄)(H₂O)]·H₂O}_n, (II), possess three‐ and two‐dimensional polymeric structures, respectively, supported by N‐tetradentate coordination of the organic ligands [Ag—N = 2.208 (3)–2.384 (3) Å] and O‐pentadentate coordination of the sulfate anions [Ag—O = 2.284 (3)–2.700 (2) Å]. Compound (I) is the first structurally examined complex of the new ligand 4,4′‐bipyridazine; it is based upon unprecedented centrosymmetric silver–pyridazine tetramers with tetrahedral AgN₂O₂ and trigonal–bipyramidal AgN₂O₃ coordination of two independent Ag^I ions. Compound (II) adopts a typical dimeric silver–pyridazine motif incorporating two kinds of square‐pyramidal AgN₂O₃ Ag^I ions. The structure exhibits short anion–π interactions involving noncoordinated sulfate O atoms [O...π = 3.041 (3) Å].     

Silver(I) Double and Multiple Salts Containing the 1,3‐Butadiynediide Dianion: Coordination Diversity and Assembly with the Supramolecular Synthon Ag4⊂CC?CC⊃Ag4

A series of 13 silver(I) double and multiple salts containing 1,3‐butadiynediide, C₄^2?, were synthesized by dissolving the silver carbide Ag₂C₄ in a concentrated aqueous solution of one or more of the silver salts AgNO₃, AgCF₃CO₂, AgC₂F₅CO₂, AgF, AgBF₄, and AgPF₆. The 1,3‐butadiynediide anion invariably adopts a μ₄,μ₄ coordination mode in these compounds, which indicates that the Ag₄?C?C? C?C?Ag₄ moiety can be used as a new type of metalloligand supramolecular synthon for the construction of coordination networks. Fine‐tuning with various ancillary anionic ligands caused the Ag₄ aggregate at each ethynide terminus to adopt a butterfly‐shaped, planar, or barblike configuration, within which the silver–ethynide interactions can be classified into three types: σ, π, and mixed (σ,π). The effect of coexisting nitrile ligands and quaternary ammonium salts on supramolecular assembly with the above synthon was also explored. The hydrolysis of PF₆^? and BF₄^? led to the formation of the quadruple salt Ag₂C₄?4 AgNO₃?AgPF₂O₂?Ag₃PO₄ and a novel (F)₂(H₂O)₁₈ hydrogen‐bonded tape in the triple salt Ag₂C₄?2 AgF? 10 AgC₂F₅CO₂?CH₃CN?12 H₂O, respectively. The largest silver–ethynide cluster aggregate described to date, (C₄)₃@Ag₁₈, occurs in 3 Ag₂C₄? 12 AgC₂F₅CO₂?5[(BnMe₃N)C₂F₅CO₂]? 4 H₂O (Bn=benzyl).     

Nature of Noncovalent Carbon‐Bonding Interactions Derived from Experimental Charge‐Density Analysis

In an effort to better understand the nature of noncovalent carbon‐bonding interactions, we undertook accurate high‐resolution X‐ray diffraction analysis of single crystals of 1,1,2,2‐tetracyanocyclopropane. We selected this compound to study the fundamental characteristics of carbon‐bonding interactions, because it provides accessible σ holes. The study required extremely accurate experimental diffraction data, because the interaction of interest is weak. The electron‐density distribution around the carbon nuclei, as shown by the experimental maps of the electrophilic bowl defined by a (CN)₂C?C(CN)₂ unit, was assigned as the origin of the interaction. This fact was also evidenced by plotting the Δ²ρ(r) distribution. Taken together, the obtained results clearly indicate that noncovalent carbon bonding can be explained as an interaction between confronted oppositely polarized regions. The interaction is, thus electrophilic–nucleophilic (electrostatic) in nature and unambiguously considered as attractive.     

Factors that regulate the conformation of m-benziporphodimethene complexes: agostic metal-arene interaction, hydrogen bonding, and η2,π coordination

Group 12 and silver(I) tetramethyl‐m‐benziporphodimethene (TMBPDM) complexes with phenyl, methylbenzoate, or nitrophenyl groups as meso substituents were synthesized and fully characterized. The dimeric silver(I) complex displays an unusual η²,π coordination from the β‐pyrrolic C?C bond to the silver ion. All of the complexes displayed a close contact between the metal ion and the inner C(22)? H(22) on the m‐phenylene ring. The downfield chemical shifts of H(22) and large coupling constants between Cd^II and H(22) strongly support the presence of an agostic interaction between the metal ion and inner C(22)–H(22). Crystal structures revealed that the syn form is the predominant conformation for TMBPDM complexes. This is distinctively different from the exclusive anti conformation observed in m‐benziporphyrin and tetraphenyl‐m‐benziporphodimethene (TPBPDM) complexes. Evidently, intramolecular hydrogen‐bonding interactions between axial chloride and methyl groups stabilize syn conformations. Unlike the merely syn conformation observed in the solid‐state structures of TMBPDM complexes that contain an axial chloride, in solution these complexes display highly solvent‐ and temperature‐dependent syn/anti ratio changes. The observation of dynamic ¹H NMR spectroscopic scrambling between syn and anti conformations from the titration of chloride ion into the solution of the TMBPDM complex suggests that axial ligand exchange is a likely pathway for the conversion between syn and anti forms. Theoretical calculations revealed that intermolecular hydrogen‐bonding interactions between the axial chloride and CHCl₃ stabilizes the anti conformation, which explains the increased ratio for the anti form when dichloromethane or chloroform was used as the solvent.