Stepwise Stress‐Induced Transformations of Metal‐Organic Polyhedral Cluster‐Based Assemblies: Where Conformational and Supramolecular Features Meet

Abstract

Understanding the factors governing the formation of supramolecular structures and phase transitions between various forms of molecular crystals is pivotal for developing dynamic, stimuli‐responsive materials and polymorph‐controlled syntheses. Here, we investigate the pressure‐induced dynamic of both the intrinsic molecular structure and the supramolecular network of a predesigned polyhedral oxo‐centered zinc cluster incorporating monoanionic N,N’‐diphenylformamidinate and featuring N‐bonded phenyl groups in close proximity to the primary coordination sphere. We demonstrate that the model oxo cluster is prone to undergoing pressure‐induced conformational transformations of the secondary coordination sphere and simultaneous stepwise (initially every second polyhedral molecule undergoes the conformational transformations) and reversible transitions from an ambient phase α to high‐pressure phases β and γ, as single‐crystal‐to‐single‐crystal events. The observed phase transitions illustrate the key role of an interplay between the low‐energy conformation perturbations and cooperative intra‐ and intermolecular noncovalent interactions.

Factors controlling the structure of alkylzinc amidinates: on the role ofN-substituents

“…[19][20][21] For example, we observed an interesting solvatomorphism and pressureinduced dynamic behavior of an N,N′-diphenylformamidinate (dipf ) stabilized zinc-oxido cluster, originated in high adaptability of its secondary coordination sphere comprising numerous N-bonded phenyl rings. 20 Interestingly, in this case, the aromatic subunits not only mediated intermolecular CH-π interactions but their conformational movement gradually absorbed compression strain induced by the increasing pressure, which promoted stepwise phase transitions (Fig. 2b) and thus these observations provided a profound understanding of the multistep single-crystal-to-single crystal phase transitions at the atomic level.…”

“…2,[12][13][14][15] The nature and reactivity of heteroleptic alkylzincs are often not only determined by the primary coordination sphere (i.e., the array of the direct metal-ligands interactions) but they can be strongly influenced by the secondary coordination sphere interactions of the metal environment, 16,17 which includes organic skeletons of supporting ligands or external functionalities attached to the internal scaffolds that not only provide a specific steric environment but may participate in an array of noncovalent interactions and be very effective in the construc-tion of supramolecular assemblies. [18][19][20][21] Hence, many of the important transformations involving alkylzinc compounds are still not well understood, such as, among others, the fascinating autocatalytic Soai reaction, 5,7 and the oxygenation of organozincs, which mechanism has been under debate for over 160 years. 22,23 In this view, a more in-depth understanding of the multifaceted chemistry of alkylzinc species is crucial for the development of new, more efficient reaction systems.…”

Tetrahedral M4(μ4-O) Motifs Beyond Zn: Efficient One-Pot Synthesis of Oxido–Amidate Clusters via a Transmetalation/Hydrolysis Approach

“… 34 − 37 Another approach based on well-defined precursors utilizes diorganozinc species, which are reacted with the appropriate proligand, and then are exposed to dioxygen 38 − 40 or undergo hydrolysis by addition of a stoichiometric amount of water ( Figure 2 b). 3 , 5 , 6 , 16 , 18 , 19 , 21 , 41 − 44 In the hydrolytic transformation, the high Brønsted basicity of alkylzinc moieties is not only used to generate O 2– ions but also facilitates initial deprotonation of the proligand. This approach enabled the synthesis of μ 4 -oxido complexes incorporating a wide range of organic ligands, namely, carboxylates, 5 , 16 , 21 phosphinates, 18 , 19 , 42 amidates, 23 amidinates, 6 , 26 , 41 , 43 and guanidinates.…”

“… 3 , 5 , 6 , 16 , 18 , 19 , 21 , 41 − 44 In the hydrolytic transformation, the high Brønsted basicity of alkylzinc moieties is not only used to generate O 2– ions but also facilitates initial deprotonation of the proligand. This approach enabled the synthesis of μ 4 -oxido complexes incorporating a wide range of organic ligands, namely, carboxylates, 5 , 16 , 21 phosphinates, 18 , 19 , 42 amidates, 23 amidinates, 6 , 26 , 41 , 43 and guanidinates. 44 Despite the wide scope of applied [Zn 4 (μ 4 -O)] 6+ core coating ligands, this relatively universal approach for Zn–oxido complexes is essentially non-transferable to the related transition-metal systems.…”

“…For example, the most common zinc-oxido carboxylates are easily prepared by either thermal decomposition of zinc carboxylates via elimination of the corresponding anhydride or in alkaline solutions of zinc salts with water acting as a source of the O 2– ion. ,, An increased control over the process of zinc-oxido carboxylates formation was achieved by using homoleptic zinc carbamates as well-defined precursors acting simultaneously as water deprotonation agents (Figure a). − Another approach based on well-defined precursors utilizes diorganozinc species, which are reacted with the appropriate proligand, and then are exposed to dioxygen − or undergo hydrolysis by addition of a stoichiometric amount of water (Figure b). ,,,,,,,− In the hydrolytic transformation, the high Brønsted basicity of alkylzinc moieties is not only used to generate O 2– ions but also facilitates initial deprotonation of the proligand. This approach enabled the synthesis of μ 4 -oxido complexes incorporating a wide range of organic ligands, namely, carboxylates, ,, phosphinates, ,, amidates, amidinates, ,,, and guanidinates . Despite the wide scope of applied [Zn 4 (μ 4 -O)] 6+ core coating ligands, this relatively universal approach for Zn–oxido complexes is essentially non-transferable to the related transition-metal systems.…”