Heterometallic Clusters with Cerium–Transition-Metal Bonding Supported by Nitrogen–Phosphorus Ligands

Ligands are known to play a crucial role in the construction of complexes with metal–metal bonds. Compared with metal–metal bonds involving d-block transition metals, knowledge of the metal–metal bonds involving f-block rare-earth metals still lags far behind. Herein, we report a series of complexes with cerium–transition-metal bonds, which are supported by two kinds of nitrogen–phosphorus ligands N[CH2CH2NHPiPr2]3 (VI) and PyNHCH2PPh2 (VII). The reactions of zerovalent group 10 metal precursors, Pd(PPh3)4 and Pt(PPh3)4, with the cerium complex supported by VI generate heterometallic clusters [N{CH2CH2NPiPr2}3Ce(μ-M)]2 (M = Pd, 2 and M = Pt, 3) featuring four Ce–M bonds; meanwhile, the bimetallic species [(PyNCH2PPh2)3Ce-M] (M = Ni, 5; M = Pd, 6; and M = Pt, 7) with a single Ce–M bond were isolated from the reactions of the cerium precursor 4 supported by VII with Ni(COD)2, Pd(PPh3)4, or Pt(PPh3)4, respectively. These complexes represent the first example of species with an RE–M bond between Ce and group 10 metals, and 2 and 3 contain the largest number of RE–M donor/acceptor interactions ever to have been observed in a molecule

Well-Defined Scandacyclopropenes: Synthesis, Structure, and Reactivity

Although transition metallacyclopropenes have been extensively explored for more than 40 years, their analogues of rare-earth metals have remained elusive. Herein, we report the synthesis of three isolable scandacyclopropenes, thus representing the first well-defined rare-earth metallacyclopropenes. Structural characterization and DFT calculations revealed a delocalized three-center two-electron (3c-2e) aromatic system. When scandacyclopropenes were treated with phenylacetylene or TMSN3, the scandium complex of bis-phenylacetylide or bis-azide was obtained, respectively. The reaction of scandacyclopropene with phenazine could provide the binuclear ring-opening scandium complex via 1,4-insertion of phenazine into one Sc–C bond and subsequent metathesis reaction. However, insertion of TMSNCO or N2O into one Sc–C bond of scandacyclopropenes gave a five- or six-membered scandacycle. In addition, scandacyclopropenes can serve as a two-electron reductive agent for PhSSPh and PhNNPh. These results show that scandacyclopropenes exhibit diversified and unique reactivity toward small molecules because of the strongly nucleophilic alkenediyl dianion and highly strained three-membered ring