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. 2024 Apr 2;63(15):6998–7006. doi: 10.1021/acs.inorgchem.4c00605

Synthesis and Characterization of a Terminal Iron(II)–PH2 Complex and a Series of Iron(II)–PH3 Complexes

Samantha Lau †, Mary F Mahon †,*, Ruth L Webster ‡,*
PMCID: PMC11022175  PMID: 38563561

Abstract

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Reported is the reaction of a series of iron(II) bisphosphine complexes with PH3 in the presence of NaBArF4 [where BArF4 = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate]. The iron(II) bisphosphine reagents bear two chlorides or a hydride and a chloride motif. We have isolated six different cationic terminal-bound PH3 complexes and undertaken rigorous characterization by NMR spectroscopy, single crystal X-ray diffraction, and mass spectrometry, where the PH3 often remains intact during the ionization process. Unusual bis- and tris-PH3 complexes are among the compounds isolated. Changing the monophosphine from PH3 to PMe3 results in the formation of an unusual Fe7 cluster, but with no PMe3 being ligated. Finally, by using an iron(0) source, we have provided a rare example of a terminally bound iron–PH2 complex.

Short abstract

Presented is a procedurally simple method for the release of small quantities of PH3 gas under inert atmosphere conditions. We have employed this method for the preparation of a series of PH3-ligated iron(II) bisphosphine complexes, along with an example of a terminal iron–phosphide complex, which is formed by oxidative addition to Fe(0). When PH3 is swapped for PMe3, it is clear that sterics play a role in the coordination chemistry.

Introduction

Bisphosphine ligands are ubiquitous in catalysis and coordination chemistry. Iron bisphosphine complexes have been of interest to several research groups because of their propensity to catalyze C–C bond-forming reactions and there is a wealth of information that can be gained through simple ligand modification.1−9 Synthesis of simple iron bisphosphine complexes featuring ligands such as 1,1-bis(diphenylphopshino)methane (dppm),10−12 1,1-bis(diphenylphosphino)ethane (dppe),13,14 and 1,2-bis(dimethylphosphino)ethane (dmpe)15 are a good starting point from which to study fundamental reactivity. For example, iron complexes chelated by dmpe have been studied extensively in the activation of CO216−19 and N2,20−23 along with X–H bond activation (X = H,24 B,25 C,26 and N27,28).

The inherent dangers of working with PH3, a toxic and flammable gas, has meant this area of research has been restricted to those equipped with specialized equipment.29 However, there has been renewed interest in the use of PH3 as a P1 source with more accessible methods to form and consume PH3in situ appearing in the literature.30−33 Pertinent to this work, and to the best of our knowledge, there is only one report of a single crystal X-ray diffraction study of an isolated iron complex bearing the Fe–PH3 motif, [(CO)4Fe(PH3)] (Figure 1a).34,35 Similarly, although there are a handful of examples of metals (across the s-, d-, p-, and f-block) bearing terminal –PH2 ligands,36−57 there are no examples where iron is the metal; the few examples of structurally characterized iron–PH2 complexes exist as bridging species or employ iron as a Lewis acid to support the PH2 moiety.34,35,58,59 Notably, these iron complexes always contain CO ligands.

Figure 1.

Figure 1

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(a) Previous examples of isolated single crystal X-ray diffraction data of iron complexes bearing Fe–PH3 and Fe–PH2 motifs and (b) isolated iron(II) bisphosphine complexes from reactions with PH3.

We herein disclose the synthesis and isolation of a library of iron bisphosphine cationic complexes bearing PH3 as well as the direct P–H activation of PH3 by [Fe(dmpe)2N2] to give a rare example of a terminal iron–phosphide complex (Figure 1b).

Results and Discussion

Our studies on the reactivity of PH3 with iron bisphosphine complexes were inspired by recent work by Ball and co-workers.31 Their work on the application of PH3 demonstrated a procedurally simple method to generate and consume PH3in situ from the digestion of cheap and commercially available Zn3P2 with concentrated HCl. However, the digestion of Zn3P2 using concentrated HCl is not a suitable method for the release of PH3 when applications involve air- and moisture-sensitive reagents due to the presence of H2O, along with challenges associated with degassing. To overcome this drawback, we have modified the procedure of Ball and co-workers. Anhydrous p-toluenesulfonic acid (p-TsOH) is a suitable acid because it has a pKa close to HCl, is a solid with a high melting point, and the ZnOTf byproduct from the digestion process is benign to the reaction conditions. Distillation from this digestion reaction in either dichloromethane or fluorobenzene shows clean generation of PH3 by multinuclear NMR spectroscopy (δP = −243 ppm, q, 1JPH = 186 Hz) with no formation of P2H460 and no detectable transfer of the acid or byproduct.

Due to the poor σ-donating ability of PH3, we targeted cationic iron complexes with a bulky, weakly coordinating counteranion to aid isolation. One equiv of [Fe(dppm)2Cl2] reacts with 1 equiv of NaBArF4 [ArF = 3,5-bis(trifluoromethyl)phenyl] in the presence of in situ generated PH3 in either CH2Cl2 or fluorobenzene at room temperature to generate 1 ([Fe(dppm)(Cl)(PH3)][BArF4]) exclusively, which is isolated as a pink/purple crystalline solid (Scheme 1a). In CD2Cl2, an isolated sample of 1 displays two resonances in the 31P{1H} NMR spectrum, δP = 10.1 ppm (doublet, 2JPP = 47.1 Hz for dppm) and δP = −64.7 ppm (pentet, 2JPP = 46.1 Hz for PH3) which are consistent with chloride abstraction and subsequent ligation of PH3 to the vacant site to give the trans-isomer of 1. The corresponding Fe–PH3 signal is also observed in the 1H NMR spectrum at 3.02 ppm (doublet of pentet, 1JHP = 344.35 Hz and 3JHP = 4.64 Hz). The signals for PH3 in both the 31P and 1H NMR spectra are significantly downfield compared to those of free PH3. In addition, ESI-MS of 1 shows a monocation without PH3 at m/z = 859.1421 (calcd 859.1426) with the correct isotopic pattern. This may allude to the labile nature of PH3 in this complex during the nebulization process. Single crystal X-ray diffraction of 1 shows an Fe1–Cl1 distance of 2.3016(7) Å and an Fe1–P5 distance of 2.1945(7) Å (Scheme 1b).

Scheme 1. (a) Formation of 1 from Reaction of [Fe(dppm)2Cl2] with NaBArF4 and PH3; The BArF4 Counter Anion Is Removed from the Scheme for Clarity and (b) Structure of the Cation in Compound 1 (CCDC 2329812).

Scheme 1

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Ellipsoids are depicted at 30% probability. Hydrogen atoms, with the exception of those, which are phosphorus-bound, have been omitted for clarity. Phenyl substituents are depicted as wireframes, also for visual ease.

Repeating the same procedure for the monochloride analogue [Fe(dppm)2(H)(Cl)] gives 2 ([Fe(dppm)2(H)(PH3)][BArF4]) exclusively when CH2Cl2 is used as the solvent (Scheme 2a). An isolated sample of complex 2 displays two resonances in the 31P{1H} NMR spectrum at δP = 30.6 ppm (doublet, 2JPP = 32.7 Hz for dppm) and δP = −89.7 ppm (pentet, 2JPP = 32.7 Hz for PH3). The retention of the iron hydride in complex 2 is observed at δH = −4.23 ppm as a pentet of doublets (2JHP = 46.2 and 10.7 Hz). Here the expected trans-coupling, for H–Fe–PH3, is smaller than the cis-coupling for Fe–H with the four phosphorus environments associated with the two dppm ligands. This is unexpected and may allude to weak binding of the PH3 ligand. A direct comparison can be made with the reported iridium cationic complex, [Ir(CO)(PEt3)2(PH2)(PH3)]+, where the iridium hydride is assigned trans to the PH3 moiety based on coupling constants.61 Here Ebsworth and Mayo ascribe the 2JHP = 140.7 Hz to trans-coupling for H–Ir–PH3 and 2JHP = 9.5 Hz to cis-coupling for H–Ir–PH2. It is also worth noting there have been reports of octahedral trans-iron hydride phosphaalkyne complexes bearing bisphosphine ligands which show that both the cis and trans2JHP of these systems can exhibit similar magnitudes.62,63 Pleasingly, the single crystal X-ray diffraction data for 2 allows the position of the iron hydride to be located freely on the Fourier transform map, trans to the PH3 group confirming the connectivity of 2. Repeating the same reaction but using fluorobenzene as the solvent in the presence of PH3, gives a mixture of complexes 2 and 3 ([Fe(dppm)2(PH3)2][BArF4]2), which form with varying ratios each time. Attempts to cleanly form 3 by changing the stoichiometry to 2 equiv NaBArF4 and leaving the chloride abstraction for 1 week before addition of PH3 gives 3 as the major species but still with some contamination by 2. Complex 3 is a dicationic Fe(II) complex with two PH3 groups ligated to the iron center trans to each other. Both 2 and 3 crystallize out in the same solvent system as yellow and orange crystalline materials respectively which can be mechanically separated allowing single crystal X-ray diffraction to corroborate the identity of 3 as trans-[Fe(dppm)2(PH3)2]2+. In contrast to complex 1, ESI-MS of complexes 2 and 3 gives the intact monocationic and dicationic iron complexes with one and two PH3 still ligated to the iron centers, respectively. It is worth noting that there are even fewer reports of isolated transition metal complexes ligated by multiple PH3 ligands. A search of the Cambridge Structural Database reveals that five out of the seven structurally characterized complexes bear CO as ancillary ligands,35,64−66 the exceptions being an iridium boron cluster complex67 and trans-[RuCl2(PH3)4].68

Scheme 2. (a) Reactivity of [Fe(dppm)2(H)(Cl)] with NaBArF4 and PH3 under CH2Cl2 and C6H5F to Give Different Product Distributions; The BArF4 Counter Anions Are Removed from the Scheme for Clarity; (b) One of the Cations Present in the Structure of Compound 2 (CCDC 2329813)a; and (c) Structure of the Cation in Compound 3 (CCDC 2329814).

Scheme 2

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Ellipsoids are depicted at 30% probability; hydrogen atoms, with the exception the hydride and of those which are phosphorus-bound, have been omitted for clarity; phenyl substituents are depicted as wireframes, also for visual ease.

Ellipsoids are depicted at 30% probability. Hydrogen atoms, with the exception of those, which are phosphorus-bound, have been omitted for clarity. Phenyl substituents are depicted as wireframes, also for visual ease. Symmetry operations: 1 – x, 3 – y, 1 – z.

The formation of 3 is not entirely understood under these reaction conditions but following the reaction by in situ NMR spectroscopy provides some insight. Addition of 1 equiv [Fe(dppm)2(H)(Cl)] with 1 equiv NaBArF4 in fluorobenzene in the absence of PH3 results in an intractable number of signals in the 31P{1H} NMR spectrum after 1 week. A shorter reaction time does not lead to a cleaner reaction. This includes a broad signal at δP = 24 ppm. By 1H NMR spectroscopy a broad signal from δH = −8.50 to −9.50 ppm is observed. Both signals correspond closely to the reported signal for trans-[Fe(dppm)2H2] in CD2Cl2.12 Therefore, one can envisage that the generated 5-coordinate cationic iron intermediate, formed from the initial chloride abstraction, can react with another molecule of itself to form [Fe(dppm)2H2] and an iron dicationic intermediate that is capable of binding two PH3 ligands to form complex 3. Single crystal X-ray diffraction studies on complex 2 (Scheme 2b) show little difference in the Fe1–P5 bond distance compared to 1 [2.197(1) Å in 2, 2.1945(7) Å in 1]. The Fe1–H1 bond distance is 1.39(3) Å. In contrast, the Fe–P3 distance in complex 3 is 2.2351(6) Å, much longer than that observed in complexes 1 and 2 (Scheme 2c).

As stated (vide supra), we do not observe the formation of 3 starting from [Fe(dppm)2Cl2]. This reaction exclusively forms 1 in either CH2Cl2 or C6H5F.

Selected bond angles associated with the dppm ligand for complexes 1, 2, and 3 are presented in Table 1. From these data, we can observe that the P–Fe–P bond angles are narrowest for complex 1, whereas the P–C–P bond angles around the dppm ligand are wider for the D2h symmetrical complex 3.

Table 1. Selected Bond Angles for Complexes 1, 2, and 3.

complex P1–Fe1–P2 (deg) P3–Fe1–P4 (deg) P1–C–P2 (deg) P3–C–P4 (deg)
1 73.68(2) 73.85(2) 96.7(1) 95.7(1)
2 75.03(3) 74.28(3) 94.1(2) 93.2(2)
3 74.18(2) n/a 97.2(1) n/a
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By using dppe, the reaction of 1 equiv [Fe(dppe)2(H)(Cl)] with 1 equiv NaBArF4 in the presence of PH3 in CH2Cl2 at room temperature gives the expected cationic complex 4 ([Fe(dppe)2(H)(PH3)][BArF4], Scheme 3a). An isolated sample of 4 displays two resonances in the 31P{1H} NMR spectrum at δP = 84.7 ppm (doublet, 2JPP = 28.7 Hz for dppe) and δP = −91.4 ppm (pentet, 2JPP = 28.2 Hz for PH3). In the 1H NMR spectrum, the corresponding Fe–PH3 signal is observed at δH = 3.24 ppm (dp, 1JHP = 319.2 Hz, 3JHP = 5.3 Hz), and the Fe–H signal is observed at δH = −10.99 ppm (pd, 2JHP = 47.8 and 16.5 Hz). Again, the smaller trans-H–Fe–PH3 coupling is observed compared to the cis-coupling to dppe, akin to what is observed for complex 2. Both single crystal X-ray diffraction and ESI-MS unambiguously confirm the assignment of complex 4 as trans-[Fe(dppe)2(H)(PH3)]+. When this reaction is repeated in fluorobenzene additional peaks are observed in both 1H and 31P{1H} NMR spectra showing a new species (5, vide infra) is formed in the reaction. Complex 4 can be isolated as yellow crystals with 5 forming orange crystals, allowing for mechanical separation of the two species. Single crystal X-ray diffraction studies on 4 show an elongated Fe1–H1 bond distance compared to that of the narrow bite-angle congener, 2. Fe1–H1 in complex 4 is 1.54(2) Å, while the bond distance between Fe1 and the PH3 unit is also elongated at 2.2006(7) Å. Comparing the Fe1–Pdppm in 2 to the Fe–Pdppe bond distances in 4 shows slightly larger bond distances in the dppe complex, potentially indicating that dppe is more weakly coordinating and thus preventing backbonding into PH3, hence the larger Fe–PH3 bond distance. 2: Fe1–P1 2.226(1), Fe1–P2 2.2179(9), Fe1–P3 2.2360(9), and Fe1–P4 2.2139(9) Å. 4: Fe1–P1 2.2568(8), Fe1–P2 2.2798(6), Fe1–P3 2.2427(6), and Fe1–P4 2.2589(8) Å.

Scheme 3. (a) Formation of 4 from Reaction of [Fe(dppe)2(H)(Cl)] with NaBArF4 and PH3; The BArF4 Counter Anion Is Removed from the Scheme for Clarity; and (b) Structure of the Cation in Compound 4 (CCDC 2329815).

Scheme 3

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Ellipsoids are depicted at 30% probability. Hydrogen atoms, with the exception of the hydride and of those, which are phosphorus-bound, have been omitted for clarity. Phenyl substituents are depicted as wireframes, also for visual ease.

When 1 equiv [Fe(dppe)2Cl2] is reacted with 1 equiv NaBArF4 in either fluorobenzene or CH2Cl2 (Scheme 4a,b), the same peaks attributed to 5 ([Fe(dppe)2(Cl)(PH3)3][BArF4]) are observed by multinuclear NMR spectroscopy. Characterization of this species by single crystal X-ray diffraction reveals the formation of an unusual cationic iron tris-PH3 complex (5, Scheme 4c). Complex 5 is not stable in CH2Cl2 with decomposition observed within 1 h by NMR spectroscopy through loss of PH3. Complex 5 displays well-resolved splitting patterns in both 1H and 31P{1H} NMR spectra allowing for identification of the axial and equatorial PH3 ligands. For example, in the 31P{1H} NMR spectrum, the equatorial-PH3 displays a resonance at δP = −75.4 ppm with a splitting pattern dtd; 2JPP = 114.9 Hz (trans-PPh2), 2JPP = 57.4 Hz (axial-PH3) and 2JPP = 47.8 Hz (cis-PPh2). Surprisingly, ESI-MS of 5 measures a monocation at m/z = 591.0289 Da (calcd 591.0303 Da) with the correct isotopic pattern showing all three PH3 ligands still intact in the complex during the nebulization process. The single crystal data for this complex show that the PH3 units that sit trans to each other have longer Fe1–P distances [Fe1–P3 2.221(1) Å, Fe1–P4 2.223(1) Å], whereas the PH3 ligand that lies trans to one arm of the dppe ligand has Fe1–P5 2.263(1) Å.

Scheme 4. (a) Formation of 4 and 5 from [Fe(dppe)2(H)(Cl)]; (b) Formation of 5 from [Fe(dppe)2Cl2]; The BArF4 Counter Anion Is Removed from the Scheme for Clarity; and (c) Structure of the Cation in Compound 5 (CCDC 2329816).

Scheme 4

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Ellipsoids are depicted at 30% probability. Hydrogen atoms, with the exception of those, which are phosphorus-bound, have been omitted for clarity. Phenyl substituents are depicted as wireframes, also for visual ease.

To investigate the effect of ancillary ligand sterics the [Fe(dmpe)2Cl2] precursor15 was synthesized as a direct comparison to [Fe(dppe)2Cl2]. 1 equiv [Fe(dmpe)2Cl2] reacts with 1 equiv NaBArF4 in either CH2Cl2 or fluorobenzene resulting in the expected formation of complex 6 ([Fe(dmpe)2(Cl)(PH3)][BArF4], Scheme 5). In CD2Cl2, the 31P resonance for Fe–PH3 is observed at δP = −64.8 ppm (pentet, 2JPP = 51.9 Hz). Identification of complex 6 is further corroborated by single crystal X-ray diffraction and ESI-MS characterization. Unlike [Fe(dppe)2Cl2], which forms 5, no additional iron species are formed in this reaction, as observed by NMR spectroscopy. A comparison of the single crystal data obtained for 6 to that obtained for the monochloride complex 1 shows that the dmpe ligand moderately influences bond metrics. For complex 1 we observe Fe1–Cl1 2.3016(7) Å, Fe1–P5 2.1945(7) Å, whereas for complex 6 we observe bond contraction at chloride with Fe1–Cl1 2.2758(7) Å and bond elongation at phosphorus with Fe1–P5 2.2127(7) Å.

Scheme 5. Formation of 6 from Reaction of [Fe(dmpe)2Cl2] with NaBArF4 and PH3; The BArF4 Counter Anion Is Removed from the Scheme for Clarity and (b) Structure of the Cation in Compound 6 (CCDC 2329817).

Scheme 5

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Ellipsoids are depicted at 30% probability. Hydrogen atoms have been omitted for clarity. (The hydrogens attached to P5 could not be reliably located in this structure).

The steric crowding around the iron center is further examined when [Fe(dppm)2Cl2] and [Fe(dppe)2Cl2] are reacted with NaBArF4 and PMe3 (Scheme 6a,c). In both instances, no analogous 6-coordinate cationic iron species are observed, and instead, the 1H NMR spectra show paramagnetic signals within the spectral window +150 to −200 ppm. In the case of dppm, an unusual cationic iron cluster with one BArF4 anion is isolated and analyzed by single-crystal X-ray diffraction analysis. Iron cluster 7 ([Fe7Cl12(dppm)6][BArF4], Scheme 6b) contains seven iron centers, all in an octahedral geometry with the central iron ligated by six bridging chlorides. Alternatively, when [Fe(dppe)2Cl2] is reacted under the same conditions, the cationic intermediate 5-coordinate species 8 ([Fe(dppe)2(Cl)][BArF4]) is isolated as the product from initial chloride abstraction with NaBArF4 (Scheme 6d). Noticeable for both reactions is that the strongly σ-donating PMe3 ligand is not coordinated, indicating that a specific steric pocket size range favors the encapsulation of PH3 by these cationic iron complexes.

Scheme 6. (a) Formation of Iron Macrocyclic Species 7; (b) The Structure of the Cation in Compound 7 (CCDC 2329818); (c) Formation of Cationic 5-Coordinate Iron Complex; and (d) The Structure of the Cation in Compound 8 (CCDC 2329819).

Scheme 6

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Ellipsoids Are Depicted at 30% Probability; Hydrogen Atoms Have Been Omitted for Clarity and Phenyl Substituents Are Depicted as Wireframes, Also for Visual Ease; Symmetry Operations: 12 – x, 1 – y, 1 – z.

Ellipsoids are depicted at 30% probability. Hydrogen atoms have been omitted for clarity and phenyl substituents are depicted as wireframes, also for visual ease.

So far only cationic iron–PH3 complexes have been isolated; based on the high levels of reaction control and selectivity we have observed, we hypothesized that with judicious selection of the iron complex we would be able to undertake oxidative addition of PH3 and generate an iron–PH2 complex. Field and co-workers have previously reported on the reaction of [Fe(dmpe)2Cl2] with hydrazine in the presence of the reductant KC8 to form an intermediate Fe(0) complex.28 Inspired by this study, the analogous Fe(0) complex [Fe(dmpe)2(N2)] was treated with an excess of PH3 in C6D6. Following agitation at room temperature for 24 h, complex 9 is formed ([Fe(dmpe)2(H)(PH2)], Scheme 7). Pleasingly, rather than simple ligand substitution of N2 with PH3, activation of the P–H bond across the iron center is achieved to give a terminal iron phosphide complex. Complex 9 has been characterized by single crystal X-ray diffraction confirming the trans-conformation of the structure and represents the analogous structure reported by Fox and Bergman on an iron-amido complex, trans-[Fe(dmpe)(H)(NH2)].27 Fox and Bergman reported that both the cis and trans isomers of the iron amido complex were observed in equilibrium in a 1:4 ratio by multinuclear NMR spectroscopy. In this reaction with PH3, a minor peak in the 1H NMR spectrum of the crude reaction mixture at δH = −13.94 ppm is suspected to correspond to the Fe–H resonance for cis-[Fe(dmpe)2(H)(PH2)]. It is likely the cis-isomer forms initially in the reaction, which quickly rearranges to the more favored trans-isomer over time. The iron hydride is observed at δH = −18.57 ppm as a pentet (2JHP = 48.14 Hz). No trans-PH2–Fe–H coupling is observed, similar to the comparative complex trans-[W(H)(PPh2)2(dppe)2] reported by Field and co-worker where only the coupling from the hydride to dppe was observed as a pentet.69 It has been noted trans-R2P–M–H geometries are rare and indeed only a handful have been characterized extensively.51,69,70,71 Complex 9 displays an Fe1–H1 distance of 1.48(4) Å and an Fe1–P5 distance of 2.337(1) Å. In comparison and as expected, Scheer’s bridged iron species displays much shorter Fe–P bond distances (Fe1–P1 2.2159 Å and Fe1–P2 2.2205 Å),34 which is in line with the bridging environment of the phosphide in that complex.

Scheme 7. (a) P–H Activation of PH3 by [Fe(dmpe)2N2] Complex and (b) One of the Molecules Present in the Structure of Compound 9 (CCDC 2329820).

Scheme 7

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Ellipsoids are depicted at 30% probability. Hydrogen atoms, with the exception of the hydride and of those which are phosphorus-bound, have been omitted for clarity. The disordered component has not been included, also for visual ease.

Conclusions

To summarize, we have modified a procedurally simple method31 for the generation of PH3 to allow the synthesis and isolation of highly sensitive iron bisphosphine complexes. Use of NaBArF4 to form cationic iron complexes has aided synthesis and isolation and as a result, we have isolated six Fe(II)bisphosphine–PH3 complexes. In one case, we have been able to prepare an iron complex bearing three PH3 ligands. Changing the ancillary bisphosphine ligand from dppm to dppe changes the PH3 coordination stoichiometry. However, changing the bisphosphine ligand has little effect on bond metrics, but when a bulkier monophosphine is employed (PMe3 rather than PH3) the effects of sterics are clear, and PMe3 fails to ligate. Finally, the use of an Fe(0) source has allowed us to isolate and characterize what we believe to be a very rare, or indeed unique, example of a terminal iron–PH2 complex. Looking forward, the PH3 complexes could be employed as PH3 transfer agents, and their reactivity compared to free-PH3 studied, while the Fe–PH2 complex could act as a catalytic intermediate in PH2 functionalization reactions; the onward reactivity of these complexes is currently being studied in our lab.

Acknowledgments

R.L.W. also acknowledges the provision of funding from the Yusuf Hamied Department of Chemistry at the University of Cambridge.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.inorgchem.4c00605.

  • Synthetic procedures and analysis data (PDF)

Author Contributions

The manuscript was written through contributions of all authors.

Funding awarded by the EPSRC (S.L., R.L.W.) and the Leverhulme Trust (R.L.W.).

The authors declare no competing financial interest.

Notes

PH3 is a toxic and flammable gas. Use of a PH3 monitor is highly recommended for any synthesis involving PH3 in addition to the usual safety protocols in place.

Supplementary Material

ic4c00605_si_001.pdf (1.5MB, pdf)

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