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Aluminium(I) anion-supported zero-valent palladium complexes


Monovalent group 13 element anions, such as boryl [BR2] and aluminyl [AlR2] anions, serve as nucleophiles to form diverse group 13 element-containing molecules. Although transition-metal complexes bearing group 13 ligands are accessible via salt metathesis with these anions, zero-valent transition-metal complexes have never been reported. In the present study, the synthesis, isolation and characterization of palladium complexes in the zero-oxidation state featuring one, two and three anionic aluminium ligands are reported. The Pd(0) complexes result from the ligand exchange reaction between bis(tri-tert-butylphosphoranyl)palladium and cyclic (alkyl)(amino)aluminium (CAAAl) anions. X-ray crystallographic and spectroscopic analyses, with the aid of quantum chemical calculations, disclose the highly negatively charged Pd centre, polarized Pd(δ)–Al(δ+) covalent bond, as well as the pronounced σ-donor and π-acceptor properties of the CAAAl ligand. Remarkably, 3K[Pd(0)(CAAAl)3] readily reacts with bis(pinacolato)diboron, leading to a bis(boryl)bis(aluminyl)Pd(II) complex via an unprecedented oxidative addition of the B–B bond to the Pd centre.

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Fig. 1: Examples of TM-aluminyl complexes in +I and +III oxidation state generated from Al(I) anions and Pd(0) complexes from the present study.
Fig. 2: Synthesis and structures of compounds 2, 3 and 5.
Fig. 3: Bonding analysis of compounds 2′, 3′ and 5.
Fig. 4: Deformation density plots and energy decomposition.
Fig. 5: Reaction of 5 with B2pin2.
Fig. 6: Reaction of 5 with 1-AdCN.

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Data availability

Crystallographic data for the structures reported in this article have been deposited at the Cambridge Crystallographic Data Centre under deposition nos. CCDC 2266523 (2), 2266524 (3), 2266525 (5) and 2266526 (6) and 2297129 (7). Copies of the data can be obtained free of charge via Additional synthetic methods, NMR spectra, IR data, single-crystal X-ray diffraction data and computational details are available in the Supplementary Information.


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R.K. acknowledges financial support from NTU, Nippon Shokubai and the Singapore Ministry of Education (MOET2EP10220-0002). R.K. thanks L. Yongxin (NTU) for assistance with the X-ray diffraction analysis.

Author information

Authors and Affiliations



C.Y. and K.K. performed the synthetic experiments, analysed the data and performed the theoretical analyses. L.Z. assisted with the experimental and computational studies. C.Y. and K.K. contributed equally to the present study. R.K. conceived and supervised the project. C.Y., K.K. and R.K. wrote the manuscript.

Corresponding author

Correspondence to Rei Kinjo.

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The authors declare no competing interests.

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Nature Synthesis thanks Martyn Coles and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Peter Seavill, in collaboration with the Nature Synthesis team.

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Supplementary information

Supplementary Information

Experimental details, Supplementary Figs. 1–40 and Tables 1–18.

Supplementary Data 1

X-ray crystallographic data for compound 2, CCDC 2266523.

Supplementary Data 2

X-ray crystallographic data for compound 3, CCDC 2266524.

Supplementary Data 3

X-ray crystallographic data for compound 5, CCDC 2266525.

Supplementary Data 4

X-ray crystallographic data for compound 6, CCDC 2266526.

Supplementary Data 5

X-ray crystallographic data for compound 7, CCDC 2297129.

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Yan, C., Koshino, K., Zhu, L. et al. Aluminium(I) anion-supported zero-valent palladium complexes. Nat. Synth (2024).

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