Isomer Interconversion Studied through Single-Crystal to Single

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Isomer Interconversion Studied through Single-Crystal to SingleCrystal Transformations in a Metal−Organic Framework Matrix Michael T. Huxley,† Rosemary J. Young,†,‡ Witold M. Bloch,† Neil R. Champness,*,‡ Christopher J. Sumby,*,† and Christian J. Doonan*,† †

Department of Chemistry and Centre for Advanced Nanomaterials, The University of Adelaide, Adelaide 5005, Australia School of Chemistry, The University of Nottingham, Nottingham NG7 2RD, U.K.

‡

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S Supporting Information *

ABSTRACT: Careful changes to the primary coordination sphere of an organometallic species can modify its chemical and physical properties, potentially providing accessible coordinating sites for catalysis or modifying its photophysical properties. Here we show, via a series of single-crystal to single-crystal (SC-SC) transformations, the modification of the primary coordination sphere of a Mn(CO)3Br species that has been postsynthetically incorporated into a metal−organic framework ([Mn3L2L′] (1), where L = bis(4-carboxyphenyl-3,5-dimethylpyrazolyl)methane). By simply changing the pore solvates, and hence the secondary coordination sphere from polar (EtOH) to nonpolar (toluene, THF), the MOF-tethered species is converted from an ion pair to a charge-neutral complex with a coordinated bromide ligand. Coordinating solvents such as acetonitrile and benzonitrile compete as ligands and coordinate to the Mn(I) center. The demonstration of interconversion of ionization and solvation isomers allows the preparation of materials for facile anion exchange, in the cases where bromide remains uncoordinated, or when the bromide is coordinated to the MOF-tethered Mn-carbonyl species, a charge-neutral species is generated whose spectrum is red-shifted, offering potentially lower energy photolysis for photoinduced CO release.

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metalation (PSMet)11 and modifications (PSM) with retention of single crystallinity.12−14 Furthermore, near-quantitative metalation of the host framework is reliably achieved; thus, the resulting metal centers can be readily structurally characterized using single-crystal X-ray diffraction (SCXRD), which offers remarkable insight into their chemistry. We have previously taken advantage of these properties to comprehensively study the organometallic transformations of a Rh(I) dicarbonyl complex15 and demonstrated a structural basis for chemoselective “click” chemistry reactions which take place within the pores of 1.16 There are few examples where such exquisite insight into the structures and chemistry of PSMet MOFs is obtainable.17−20 It is worth noting at this point that the single-crystal to single-crystal (SC-SC) transformations observed for 1 are quite different from those commonly reported for MOFs;21−23 typically SC-SC transformations of MOFs involve notable changes in structure, including changes in connectivity and topology. MOF 1, however, only undergoes very subtle changes to its overall framework structure, which allows these SC-SC transformations of the

INTRODUCTION Isomerization in transition-metal complexes is a foundational concept in coordination and organometallic chemistry.1,2 Isomers are chemically distinct species that have a different connectivity (structural isomers) or spatial arrangements (stereoisomers) of the same atoms. Isomers of transitionmetal complexes can display markedly different physical properties and chemical reactivity,3,4 display different cellular responses and hence therapeutic properties (e.g., cisplatin),5−7 or provide insight into chemical transformations.1,8−10 Among structural isomers for coordination complexes, solvation and/ or ionization isomers result from the interchange of ligands within the primary coordination sphere with those in the secondary coordination environment; the former involve exchange of solvent and the latter exchange of anionic ligands. 1,2 Indeed, Werner’s investigations of products displaying these archetypal forms of isomerism in chromium(III) and cobalt(III) chloride complexes helped establish the field of coordination chemistry.3,4 In this work we study isomer interconversions about a Mn(CO)3Br moiety tethered to a metal−organic framework (MOF) crystalline matrix. The platform material in which this chemistry occurs is a flexible MOF, [Mn3L2L′] (1; where L = bis(4-carboxyphenyl3,5-dimethylpyrazolyl)methane, which features a vacant N,N′chelation site arising from a partially noncoordinated L moiety (L′)). MOF 1 is capable of undergoing postsynthetic © XXXX American Chemical Society

Special Issue: Organometallic Chemistry within Metal-Organic Frameworks Received: June 16, 2019

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DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

Figure 1. (a) Flexible ligand (L) employed to prepare MOF 1. (b) Representation of the coordination site in the MOF pore. (c) Scheme showing the conversion of the charged complex 1·[Mn(CO)3(H2O)]Br (center) (formed upon metalation of 1 with [Mn(CO)5Br] in ethanol) to the corresponding neutral complex 1·[Mn(CO)3Br] (right) upon solvent exchange with toluene or THF. When a strongly coordinating solvent such as PhCN is introduced, water is displaced and the nitrile ligand is observed in the coordination sphere (left). The inset shows the “intermediate” species observed in toluene with the bromide anion disordered over the axial sites (lower:upper ratio (adjacent CH2) of 0.22:0.18 on a mirror plane with the remainder of the Br in the pore).

Figure 2. Distances between the tethered Mn(I) complex, the main bromide anion site, and adjacent features of the MOF pore highlighted by a dotted line for the complexes (a) 1·[Mn(CO)3Br], (b) 1·[Mn(CO)3(H2O)]Br, and (c) 1·[Mn(CO)3(PhCN)]Br. A truncated view of the adjacent Mn(I) complex (along the c axis channel) is shown to illustrate the position of the noncoordinated bromide anion in (b) and (c) between the two Mn(I) centers. Pertinent distances α, β, γ, and δ are specified in the text.

complex 1·fac-[Mn(CO)3N3], which participates in click chemistry. Herein, we report SC-SC observations of solvation/ ionization isomerization occurring at the postsynthetically grafted metal center inside the crystalline phase of MOF 1. In particular, we show the reversible conversion of the charged complex 1·[Mn(CO)3(H2O)]Br to the neutral species 1· [Mn(CO)3Br] via exchange of the ethanol pore solvate for a nonpolar solvent. SCXRD structures of crystals determined immediately after exposure to toluene show that the bromide anion is disordered over both axial sites of the Mn(I) center, whereas after time (and visible light exposure) a single species can be observed. As this chemistry occurs within the reference frame of the MOF support, we can postulate the steps involved in the transformation: in this case, ligand exchange followed by rearrangement of the coordination sphere to the thermodynamically favored species. We further demonstrate that the polarity of the guest molecules in the MOF pores dictate the isomer that is observed; polar solvents favor the charged

local postsynthetically introduced metal coordination environment to occur in a facile manner, with limited crystal degradation. Studying the isomerization of transition-metal complexes, within the pore environment of a MOF, presents an intriguing hybrid of solid-state and solution properties.10,14 The metal centers, along with their primary coordination sphere, are tethered to a relatively rigid solid-state structure, facilitating characterization by SCXRD, but are suspended in the solventfilled cavities that permeate through the MOF structure (the secondary coordination sphere and bulk solvent). This solvated pore environment is dynamic, such that the solvent and chemistry of the MOF pore can influence the primary coordination sphere, leading to SC-SC transformations. We recently reported the metalation of 1 with [Mn(CO)5Br], which gives rise to the unusual charged complex 1·fac[Mn(CO)3(H2O)]Br.16 In this material the noncoordinated bromide anion resides in the MOF pore and undergoes facile anion exchange with azide to form the corresponding azide B

DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX

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Organometallics Table 1. Effect of Dielectric Constant (ε) on ν(CO) and λmax for 1·[Mn(CO)3Br]a solvent

ε

MeCN PhCN EtOH acetone iPA THF toluene

37.5 26 24.5 20.7 17.9 7.58 2.38

ν(CO)b (cm−1) 2041, 2021, 2040, 2039, 2039, 2029, 2029, 2026,

(2029), 1953, 1921 1937, 1909 1951, 1921 (2031), 1952, 1916 (2031), 1948, 1924 1951, 1906 1953, 1899 1927, 1901

structure

form

λmax (nm)

1·[Mn(CO)3(H2O)]Br and 1·[Mn(CO)3(CH3CN)]Br 1·[Mn(CO)3(PhCN)]Br 1·[Mn(CO)3(H2O)]Br

ion pair (and coordinated CH3CN) coordinated PhCN ion pair

374

1·[Mn(CO)3Br] 1·[Mn(CO)3Br] [Mn(CO)3Br(bpzm)]

neutral complex neutral complex molecular analogue

380

a

The IR data for the molecular analogue [Mn(CO)3Br(bpzm)] (where bpzm = bis(3,5-dimethylpyrazolyl)methane) are shown for comparison. The most prominent bands are given, and minor IR components are shown in parentheses.

b

polar ethanol (dielectric constant (ε = 24.5) with nonpolar solvents could destabilize the ion pair and promote the formation of the corresponding neutral complex 1·[Mn(CO)3Br].24,25 With this in mind, we performed solvent exchange of the MOF crystals with toluene (ε = 2.38), during which the material retained its bright yellow color and crystallinity (Figure SI2.1). IR spectroscopy revealed a subtle shift in the ν(CO) bands: the symmetric stretching mode shifted from 2040 cm−1 in EtOH to 2028 cm−1 in toluene, which suggests incorporation of bromide into the coordination sphere of the Mn(I) center (more back-donation). SCXRD studies of the material following toluene exchange confirmed the successful formation of the neutral complex 1·[Mn(CO)3Br]. This occurs with minimal changes to the unit cell parameters (see Tables S3.4.1 and S3.4.2) and overall MOF structure with no changes in MOF connectivity. The coordination sphere possesses a facial geometry with bromide occupying the axial site opposite to that previously occupied by water in 1·[Mn(CO)3(H2O)]Br (and adjacent to the methylene hinge of L) (Figure 1 and Figure SI3.2.1). The migration of bromide to the opposing axial site is likely driven by stabilizing interactions between the supporting ligand and bromide; the nonsymmetrical profile of the bis(3,5dimethylpyrazolyl)methane means that the two axial sites are inequivalent, one being more enclosed by the adjacent pyrazole moieties and the other closer to the CH2 hinge of the linker. Residual electron density in the site previously occupied by the bromide anion in the charged complex was modeled as a bromide (and refined to an occupancy of ca. 16%), suggesting that the formation of the neutral complex is not quantitative in toluene (at least if the crystal is exposed to atmospheric moisture). Furthermore, when crystals of 1·[Mn(CO)3Br] were washed with ethanol, the original charged complex was regenerated. To gain insight into the isomerization process, a crystal of 1· [Mn(CO)3Br] shortly after exchange with toluene was also studied by SCXRD. The structure, which has the expected coordinated bromide ligand, displays an intermediate in the isomerization process with the coordinated bromide disordered across both axial sites (Figure 1 inset and Figure SI3.2.2). The disorder across the lower:upper (where upper corresponds to being adjacent to the CH2 hinge) sites was refined as 0.22:0.18 (on a mirror plane with the remainder in the pore). Given the relationships to the starting ion pair 1· [Mn(CO)3(H2O)]Br form and the final 1·[Mn(CO)3Br] species, this suggests that exchange at the water site occurs prior to rearrangement to the most stable complex species. Considering the notable differences in the structures obtained in ethanol and toluene, we expanded our inves-

complex. This isomerization process can be readily monitored by IR spectroscopy through observation of changes in the CO stretching bands, providing a quick guide to the form of the guest Mn(CO)3X species. Finally, competing donor solvents such as acetonitrile and benzonitrile also coordinate to the Mn center, precluding bromide coordination and resulting in the formation of a charged complex. In combination, these observations represent a fascinating demonstration of how the MOF pore environment influences the coordination sphere of framework-bound transition-metal complexes and illustrate the importance of elucidating the complete structure of postsynthetically metalated MOFs.

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RESULTS AND DISCUSSION MOF 1 contains a free N,N′-coordinating site comprising the pyrazole donors of one in every three molecules of L. Metalation of 1 with [Mn(CO)5Br] was performed in EtOH at 50 °C and has been described previously.16 The reaction yields the metalated product 1·[Mn(CO)3(H2O)]Br in the form of bright yellow crystals. Through judicious choice of the conditions, the framework retains crystallinity during this process, allowing the coordination sphere of the Mn(I) center to be fully elucidated via SCXRD. The six-coordinate Mn complex exhibits a fac geometry with a water molecule in the axial coordination site that is opposite the methylene hinge of L (Figure 1c), and bromide residing in the MOF pore adjacent to the Mn(I) center. The bromide anion occupies a cavity within the MOF pore and is stabilized by a number of CH···Br weak hydrogen bonds (C−Br distances in the range 2.80−3.14 Å; Figure 2b). The presence of a separated ion pair for this complex is unusual; all related diimine manganese tricarbonyl bromide complexes are neutral, including an analogous discrete molecular complex possessing the same donor set, [Mn(CO)3Br(bis(3,5-dimethylpyrazolyl)methane)].16 Thus, it is evident that by tethering the Mn(I) complex to the MOF structure we are able to access an unusual coordination environment in which the bromide resides in the MOF pore. Further inspection of the X-ray crystal structure highlights that the Mn(I) centers line the pores of the MOF and are separated by approximately 13 Å, with the bromide anions residing in the aforementioned cavity between the Mn(I) centers (Br−O distances of 5.11 and 4.53 Å from the water or CO axial sites of the Mn(I) center, respectively; Figure 2). We posit that the MOF provides an environment in which both the cation and the anion are “solvated” by the MOF framework, or polar EtOH molecules, thereby stabilizing the ion pair. Given that the solvent guest molecules within the MOF pores can be exchanged to alter the secondary coordination sphere of the complex, we anticipated that the exchange of C

DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX

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Organometallics tigation by exchanging the solvate for samples of 1·[Mn(CO)3(H2O)]Br using a variety of solvents with different dielectric constants, including tetrahydrofuran (THF), acetonitrile (MeCN), acetone, toluene, isopropyl alcohol (iPA), and benzonitrile (PhCN). X-ray crystallography revealed that dry THF promotes the formation of the neutral complex 1· [Mn(CO)3Br] with only a small amount of residual noncoordinated bromide apparent in the electron density map (Figure SI3.2.4). Again, the overall MOF structure is largely unchanged. The coordination sphere of the Mn(I) center is identical to that observed in toluene, containing a bromide anion bound to the less hindered axial site and three facially disposed carbonyl ligands. The position of the bromide ligand is consistent with observations and calculations for octahedral Rh(III) complexes coordinated within the N,N-coordinating site of 1.15 Given that the IR stretches of the CO ligands are sensitive to the nature of the axial coordinating group, we measured the IR spectra of 1·[Mn(CO)3(H2O)]Br following exposure to a range of solvents (Table 1, starting with crystals containing ethanol). These data are also compared with the IR spectrum of the molecular analogue [Mn(CO)3Br(bpzm)] (where bpzm = bis(3,5-dimethylpyrazolyl)methane), which shows stretches at 2026, 1927, and 1901 cm−1. IR spectroscopy on the MOFbound species revealed that solvents with intermediate polarity, such as acetone and iPA, give rise to a spectrum that contains two distinct symmetric stretching modes (Figure 3). This suggests that two species are present under these conditions, most likely the neutral and charged complexes. Generally, the proportion of the neutral complex (assigned to the 2028 cm−1 band) increases as the solvent polarity decreases. The differences between the stretches of the molecular complex [Mn(CO)3Br(bpzm)] and the neutral complex within the MOF, 1·[Mn(CO)3Br], are attributable to differences in the chemical environments of the two complexes; [Mn(CO)3Br(bpzm)] has a close-packed structure, whereas in 1·[Mn(CO)3Br] the organometallic moiety is exposed to toluene solvates. The obvious exceptions to this trend are benzonitrile and acetonitrile, two strongly coordinating solvents. Despite possessing a polarity greater than ethanol, acetonitrile produces two bands in the IR. The first band at 2041 cm−1 likely corresponds to a charged complex, and we postulate that the second band at 2029 cm−1 would correspond to the complex in which acetonitrile had replaced the axially coordinated water26 (high-quality SCXRD data are not available, as acetonitrile has deleterious effects on the crystal quality for this sample). To test this hypothesis, we washed a sample of 1·[Mn(CO)3(H2O)]Br with THF, and then benzonitrile and subsequently collected a single-crystal X-ray structure. Refinement of the data revealed that benzonitrile is indeed part of the coordination sphere of the Mn(I) center and occupies the more open of the axial coordination sites about the fac-1·[Mn(CO)3(PhCN)] complex, i.e. the axial site occupied by CO in 1·[Mn(CO)3(H2O)]Br (Figure 1 and Figure SI3.2.4). The noncoordinated bromide anion forms strong anion−π contacts27 with the PhCN ligand. IR spectroscopy revealed a single strong symmetric stretching band at 2021 cm−1, which we attribute to the benzonitrile complex 1·[Mn(CO)3(PhCN)]Br. On closer examination of the IR spectra, it can be observed that, as the polarity of the solvent decreases, the A′ symmetric stretching band at 2040 cm−1 decreases in intensity while a new band appears at 2029 cm−1, consistent with the

Figure 3. (a) ν(CO) modes observed in the IR spectra of fac[Mn(CO)3]+ complexes and the corresponding stretching behavior. (b) IR spectra of 1·[Mn(CO)3X]Y (X = H2O, Y = Br; X = Br, Y = nothing) after soaking in various solvents for 24 h. The material was synthesized in ethanol and subsequently exchanged with a different solvent over the course of 24 h. The ν(CO) bands of the complex in ethanol are labeled A−C and highlighted with a vertical line. The solid-state IR spectrum for the molecular analogue [Mn(CO)3Br(bpzm)] (where bpzm = bis(3,5-dimethylpyrazolyl)methane) is shown for comparison.

conversion of the charged complex 1·fac-[Mn(CO)3(H2O)] Br into the neutral complex 1·fac-[Mn(CO)3Br]. The A″ symmetric stretch (ca. 1950 cm−1) remains relatively unchanged, as it purely involves the equatorial CO ligands, while the antisymmetric stretching mode does appear to shift toward a lower wavelength with decreasing polarity. Acetonitrile and benzonitrile are the key exceptions. Despite MeCN having the highest polarity, the IR spectrum displays two symmetric stretching modes which likely arise from nitrile coordination to the axial site rather than the formation of a neutral complex. This is supported by SCXRD data for 1· [Mn(CO)3(PhCN)]Br, where a coordinated PhCN ligand is observed. The samples of MOF analyzed by IR spectroscopy (Figure 3) have been subjected to extended solvent exchange (five washes over the course of 24 h) to ensure quantitative conversion. To elucidate time scales for these transformations, specifically the conversion of 1·fac-[Mn(CO)3(H2O)]Br (EtOH) into the neutral complex 1·fac-[Mn(CO)3Br] (toluene), we examined samples at selected time points and washing stages. We first probed the exchange occurring in a sample of 1·fac-[Mn(CO)3(H2O)]Br exposed to one aliquot of toluene only, for 120 min (Figure SI4.1). Analysis of digested samples of the MOF crystals shows that the quantity of ethanol rapidly declines to approximately 20% of the pore content but D

DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX

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Organometallics

MOF-tethered complex in a systematic manner. Small variations in the tethered complex’s coordination sphere leads to changes in spectroscopic properties of the materials. These changes are important in terms of defining the reactive properties of the Mn(CO)3Br moiety16 and may also affect the photoinduced loss of CO, which is important for the development of PhotoCORMs.28,29 Indeed, we anticipate that the ability to tune the chemical environment and spectroscopic properties of coordination complexes is important across a variety of applications.

does not decrease further (no further washing steps were undertaken). IR spectroscopy reveals that the Mn(I) coordination sphere also undergoes a rapid transformation, with new CO stretching bands appearing near 1830−1950 cm−1 within 15 min and a new stretch at 2029 cm−1 (characteristic of 1·fac-[Mn(CO)3Br]) growing in place of the original band at 2041 cm−1. To more accurately represent the actual conversion, a sample of 1·fac-[Mn(CO)3(H2O)]Br was subjected to five washing steps (see section 4 in the Supporting Information for a description of the procedure). This second experiment shows that complete pore exchange of EtOH for toluene (within detection limits) is achieved after 45 min (three washes) (Figure SI4.2). Furthermore, the IR spectra show that the exchange progresses via a series of carbonyl intermediates, likely including the disordered form of 1·fac-[Mn(CO)3Br] before producing the ordered complex after 24 h. Solid-state UV−visible data on the different solvated MOF samples were measured, with the charged MOFs showing a λmax value at ca. 374 nm and the neutral complex slightly redshifted with a λmax value at ca. 380 nm. Given the broad adsorption for this metal−ligand charge transfer (MLCT) band, and the limited difference between the two species, the different solvates are not distinguishable by this method (Figure S1). Notably, in both of the charged complexes depicted in Figure 1, the bromide anion resides in the same position within the MOF pore. The close contacts among the anion, Mn(I) complex, and surrounding MOF structure are highlighted in Figure 2. The distance between the anion and depicted atoms (α, β, γ) for the complexes 1·[Mn(CO)3(H2O)]Br and 1· [Mn(CO)3(PhCN)]Br are 3.02, 5.11, 2.80 Å and 2.86, 4.44, 2.82 Å, respectively (the shortest two distances in each structure representing weak C−H···Br hydrogen bonding). The closest contact between the benzonitrile and adjacent MOF structure (δ) is 2.81 Å, a relatively short anion−π contact.27 The similarity between the distances described above highlights how the bromide resides in a “pocket” within the MOF structure between Mn(I) cations (Mn−Br distances: 6.15 and 6.93 Å in 1·[Mn(CO)3(H2O)]Br) and interacts with the backbone of the MOF structure. In 1·[Mn(CO)3(H2O)]Br the presence of a polar solvent likely stabilizes this charged cation, while in 1·[Mn(CO)3(PhCN)]Br the presence of a strong ligand (PhCN) promotes the retention of a charged motif. In conclusion, we have shown that the chemistry of a Mn(CO)3Br species that has been postsynthetically incorporated into MOF 1 is notably different from the behavior of the discrete molecular analogue [Mn(CO)3Br(bpzm)] in the solid state. For the MOF-tethered complex, changing the MOF pore contents by solvent exchange enables modification of the primary coordination sphere of the Mn(CO)3Br species. For example, modifying the secondary coordination sphere from polar (EtOH) to nonpolar (toluene, THF) converts the MOFtethered species from an ion pair to a charge-neutral complex via SC-SC transformations. In addition, coordinating solvents such as acetonitrile and benzonitrile compete as ligands to displace the bromide. The molecular species [Mn(CO)3Br(bpzm)] crystallizes from EtOH (without EtOH solvate)16 as the charge-neutral complex, whereas in the MOF, presumably due to retaining its secondary coordination sphere of EtOH, the complex is an ion pair. Our studies demonstrate the ability to tune the coordination sphere, and isomer composition, of a

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EXPERIMENTAL SECTION

General Experimental Methods. Unless otherwise stated, all chemicals were obtained from commercial sources and used as received. THF was distilled from Na/benzophenone and degassed with Ar prior to use. The compounds [Mn(CO)3Br(bpzm)] (where bpzm = bis(3,5-dimethylpyrazolyl)methane),16 MOF 1,12 and 1· [Mn(CO)3(H2O)]Br16 were prepared by methods reported previously. 1·[Mn(CO)3(H2O)]Br was stored in the dark, and the samples were exposed to minimal light during handling to prevent the evolution of CO. Solid-state UV−vis spectra were recorded using a Cary 5000 UV−vis−NIR spectrophotometer equipped with a Harrick Praying Mantis diffuse reflection spectroscopy attachment. The sample was dispersed in KBr for analysis. Infrared (IR) spectra were collected on a PerkinElmer Spectrum Two instrument, with the sample dispersed between two NaCl disks in Nujol. Solvent Exchange of 1·[Mn(CO)3(H2O)]Br. Single crystals of 1· [Mn(CO)3(H2O)]Br (15 mg) suspended in ethanol were transferred to an 8 mL glass vial. The ethanol was replaced with 5 mL of fresh solvent (toluene, acetonitrile, isopropyl alcohol, acetone, benzonitrile, or THF) a total of five times, with the crystals allowed to soak for 1 h between each washing step. Major bands in the IR spectrum of each species are reported below. 1·[Mn(CO)3(H2O)]Br (EtOH): IR νmax (cm−1, Nujol) 2040 (s, CO), 1951 (s, CO), 1921 (s, CO), 1608 (CO), 1553, 1511, 1408, 1306, 1272. 1·[Mn(CO)3(H2O)]Br and 1·[Mn(CO)3(MeCN)]Br (MeCN): IR υmax (cm−1, Nujol) 2041 (CO), 1951 (CO), 1921 (CO), 1608 (CO), 1553, 1509, 1407, 1376, 1304, 1273. 1·[Mn(CO)3(H2O)]Br (isopropyl alcohol): IR νmax (cm−1, Nujol) 2039 (CO), 1948 (CO), 1924 (CO), 1608 (CO), 1555, 1509, 1407, 1377, 1342, 1304, 1273. 1·[Mn(CO)3(H2O)]Br (acetone): IR νmax (cm−1, Nujol) 2039 (CO), 1952 (CO), 1916 (CO), 1613 (CO), 1556, 1376, 1305, 1274. 1·[Mn(CO)3Br] (toluene): IR νmax (cm−1, Nujol) 2029 (s, CO), 1953 (s, CO), 1899 (s, CO), 1608 (CO), 1552, 1510, 1407, 1303, 1272. 1·[Mn(CO)3Br] (THF): IR νmax (cm−1, Nujol) 2029 (s, CO), 1951 (s, CO), 1906 (s, CO), 1613 (CO), 1555, 1305, 1274. 1·[Mn(CO)3(PhCN)]Br (benzonitrile): IR νmax (cm−1, Nujol) 2021 (CO), 1937 (CO), 1909 (CO), 1604 (CO), 1554, 1509, 1403, 1303, 1271. [Mn(CO)3Br(bpzm)]: IR νmax (cm−1, Nujol) 2026 (CO), 1927 (CO), 1901 (CO), 1456, 1376, 1288, 1041, 808. Single-Crystal X-ray Crystallography. Single crystals were mounted in Paratone-N oil on a nylon loop or in Fomblin oil on a MiTeGen micromount. Single-crystal data for: 1·[Mn(CO)3Br] after THF (1·[Mn(CO)3Br] (THF)) or toluene (1·[Mn(CO)3Br] (toluene)) exposure were collected at 100 K on the MX1 beamline at the Australian Synchrotron using the Blue-ice software interface (λ = 0.7108 or 0.7109 Å),30,31 those for 1·[Mn(CO)3Br] (toluene, disordered) were collected at 150 K on an Oxford Diffraction Xcalibur diffractometer with an Eos CCD area detector (λ = 0.71073 Å), and those for 1·[Mn(CO)3(PhCN)]Br were collected on an Agilent SuperNova diffractometer at 120 K with an AtlasS2 CCD area detector using Cu Kα radiation (λ = 1.54184 Å). Absorption corrections were applied using empirical methods; the structures were E

DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX

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Organometallics solved by direct methods using SHELXS or SHELXT32 and refined by full-matrix least-squares on F2 by SHELXL,33 interfaced through the program X-Seed34 or Olex.35 In general, all non-hydrogen atoms were refined anisotropically and hydrogen atoms were included as invariants at geometrically estimated positions, unless specified otherwise in additional details in the Supporting Information. X-ray experimental data are given in Tables S3.4.1 and S3.4.2. Figures were produced using the program CrystalMaker. CIF data have been deposited with the Cambridge Crystallographic Data Centre, CCDC reference numbers CCDC 1920928−1920931 (1·[Mn(CO)3Br] (toluene), 1920930; 1·[Mn(CO)3Br] (toluene, initial), 1920931; 1· [Mn(CO) 3 Br] (THF), 1920929; 1·[Mn(CO) 3 (PhCN)]Br, 1920928).

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications Web site. (PDF). Crystallographic information files (cif). The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/ acs.organomet.9b00401. UV−visible spectroscopic data, powder X-ray diffraction data, additional information on the single-crystal structures, and IR spectroscopic and NMR digestion data (PDF) Accession Codes

CCDC 1920928−1920931 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail for N.R.C.: [email protected]. *E-mail for C.J.S.: [email protected]. *E-mail for C.J.D.: [email protected]. ORCID

Neil R. Champness: 0000-0003-2970-1487 Christopher J. Sumby: 0000-0002-9713-9599 Christian J. Doonan: 0000-0003-2822-0956 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS W.M.B., C.J.S., and C.J.D. gratefully acknowledge the Australian Research Council for funding (DE190100327, DP160103234, and DP190101402). N.R.C. gratefully acknowledges support from the UK Engineering and Physical Sciences Research Council (EP/S002995/1). Aspects of this research were undertaken on the MX1 beamline at the Australian Synchrotron, Victoria, Australia.

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DOI: 10.1021/acs.organomet.9b00401 Organometallics XXXX, XXX, XXX−XXX