ABSTRACT
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.
ABSTRACT
Although examples of multiple bonds between actinide elements and main-group elements are quite common, studies of the multiple bonds between actinide elements and transition metals are extremely rare owing to difficulties associated with their synthesis. Here we report the first example of molecular uranium complexes featuring a cis-[M â â ${{\rm{ \mathbin{{\stackrel{\textstyle\rightarrow} { {\smash{\rightarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }}}$ U â â ${{\rm{ \mathbin{{\stackrel{\textstyle\leftarrow} { {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }}}$ M] core (M=Rh, Ir), which exhibits an unprecedented arrangement of two M â â ${{\rm{ \mathbin{{\stackrel{\textstyle\rightarrow} { {\smash{\rightarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }}}$ U double dative bond linkages to a single U center. These complexes were prepared by the reactions of chlorine-bridged heterometallic complexes [{U{N(CH3 )(CH2 CH2 NPi Pr2 )2 }(Cl)2 [(µ-Cl)M(COD)]2 }] (M=Rh, Ir) with MeMgBr or MeLi, a new method for the construction of species with U-M multiple bonds. Theoretical calculations including dispersion confirmed the presence of two U â â ${{\rm{ \mathbin{{\stackrel{\textstyle\leftarrow} { {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }}}$ M double dative bonds in these complexes. This study not only enriches the U â â ${{\rm{ \mathbin{{\stackrel{\textstyle\leftarrow} { {\smash{\leftarrow}\vphantom{_{\vbox to.5ex{\vss}}}} } }} }}}$ M multiple bond chemistry, but also provides a new opportunity to explore the bonding of actinide elements.
ABSTRACT
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.
