The first trivalent rare-earth metal phosphinidene complex was reported in 2008, but a divalent rare-earth metal phosphinidene complex has not been reported to date. Herein, we report the synthesis and structural characterization of divalent ytterbium alkyl/phosphido/phosphinidene, phosphido/phosphinidene, and phosphinidene complexes. These three complexes were obtained through a stepwise synthesis using a divalent ytterbium dialkyl complex as the starting material. The alkyl/phosphido/phosphinidene, phosphido/phosphinidene, and phosphinidene complexes are all polymetallic, and the number of ytterbium centers in the complexes increases from 4 to 5 to 6. DFT calculations indicate the presence of Yb-P single bonds in the complexes, with additional pi delocalization evidenced by the presence of ring critical points in the Yb-P-Yb-P diamond cores at the Quantum Theory of Atoms in Molecules level. The phosphido/phosphinidene complex reacts with one equivalent of 1-isocyanoadamantane (AdNC) to afford a divalent ytterbium complex through selective insertion of AdNC into one Yb-P(phosphinidene) bond. In contrast, treatment with an excess of AdNC leads to complete insertion into all Yb-P(phosphinidene) bonds and redox reactions at the Yb(ii) centers, yielding a structurally intriguing mixed-valence Yb(ii)/Yb(iii) complex.

Bredt's rule has long defined the limits of bridgehead alkenes, and the synthesis of highly strained members of this class remains a formidable challenge. Herein, we report the synthesis, structure,...

A naphthalene and amino-substituted silacyclopropanyl potassium, [(Me3Si)(DIPP)NSi(C10H8)K(THF)2]2 (N-SiK), was synthesized. Reactions of N-Si-K with ytterbium(II) iodide [L1Yb(THF)(mu -I)]2 (L1 = [MeC(NDIPP)CHC (Me)(NCH2CH2NMe2)]- , DIPP = 2,6-(iPr)2C6H3), [L2Yb(mu -I)]2 (L2 = [tBuC(NDIPP)CHC(tBu) (NCH2CH2NMe2)]- ), or [L3Yb(mu -I)]2 (L3 = [MeC(NDIPP)CHC(Me)(NCH2CH2N(Me)CH2CH2NMe2)]- ) afforded the corresponding ytterbium(II) silacyclopropanyl complexes 1-3. Complexes 2 and 3 were characterized by single crystal X-ray diffraction. Complexes 2 and 3 are less stable than complex 1 and decompose at room temperature. Complex 1 reacts with 2 equivalents of triphenylphosphine sulfide to produce an ytterbium(II) complex [Yb{MeC(NDIPP)C(Si(NDIPPSiMe3)S2)HC(Me)(NCH2CH2NMe2)}]2 (4) and releases naphthalene and PPh3. Complex 2 reacts with 3 equivalents of 1-isocyanoadamantane to provide an unusual ytterbium(III) complex [L2Yb{N(Ad)C}2Si(CN)NDIPP(SiMe3)] (5) through multiple steps.

Although the development of tetravalent lanthanide complexes has accelerated recently, it still lags far behind that of their trivalent congeners. Herein, we report the synthesis and structural characterization of the first tetravalent lanthanide phosphido complexes, [(ImtBuN)3CeIVP(SiMe3)Ar] (Ar = C6H5 (1), C6H3-2,6-iPr2 (2)). Single-crystal X-ray diffraction reveals a pyramidal geometry around the phosphorus atom in 1, whereas a trigonal planar geometry and a shorter Ce-P distance in 2 suggest the presence of a Ce-P π-interaction alongside the σ-bond. Computational studies corroborate these findings, revealing polarized Ce-P bonds with significant double-bond character. Notably, f-orbital contributions are substantial for both σ-type (28-51%) and π-type (67%) bonding interactions. Preliminary reactivity studies demonstrate that complex 1 undergoes addition reactions with AdN3 and Ph2CN2, rather than redox processes.

Anionic ketenes [RCCO]- exhibit two resonance forms: ketenyl anions and ynolate anions. While ketenyl complexes have been isolated and characterized, crystalline ynolate complexes remain elusive. Herein, we report the first lanthanide ynolate complex, namely, the europium ynolate complex. A σ-bond metathesis reaction of Me3Si(H)CN2 with a europium(II) hydrido or alkyl complex yields a europium(II) nitrilimine, which reacts with CO to provide a europium(II) ynolate complex. Single-crystal X-ray diffraction and DFT calculations confirm the dominance of the ynolate resonance form, showing two orthogonal π orbitals between the C-C unit and a significant negative charge (-0.83) on the oxygen atom. Reactivity studies demonstrate C-centered trapping products with trimethylsilyl trifluoromethanesulfonate, benzophenone, isothiocyanate, and carbodiimide. Mechanistic DFT analysis of the carbodiimide reaction reveals a gradual shift from ynolate to ketenyl anion, enhancing reactivity for [2 + 2] cyclization.

The metal-substituted silylenes are of high interest, as the theoretical studies indicated that the silylenes with electropositive substituents have a small Δ E S−T (singlet-triplet energy gap) or even the ground-state triplets. However, such compounds are highly unstable, and only two transient alkali metal-substituted silylenes M( t Bu 3 Si)Si: (M = Li, K) were generated by photoextrusion of the alkali metal-substituted silacyclopropenes and merely studied by spectroscopic method (EPR) at low temperature (14 to 50 K). Herein, we report the generation of transient zinc-substituted silylenes from zinc silacyclopropanyl complexes under very mild and convenient conditions. The generated transient zinc-substituted silylenes are highly reactive and undergo intermolecular cycloaddition with alkenes for the synthesis of zinc-substituted Si-heterocyclic compounds. If there is no substrate, the zinc-substituted silylenes attack the C–C bonds of the β-diketiminato ligands and break the C–C bonds. DFT studies further highlight the silylene nature of the zinc-substituted silylene and a very small Δ E S−T (4.4 kcal/mol).

Utilizing strong-field ligands to construct highorder axial local symmetry can help improve the performance of single-molecule magnets (SMMs). Three mono(imidazolin-2-iminato) dysprosium(III) complexes {[Dy(Im Dipp N)(THF) 5 ][BPh 4 ] 2 } (1), {[Dy (Im Dipp N)(py) 5 ][BPh 4 ] 2 } (2) and {[Dy(Im Ad N)(THF) 5 ] [BPh 4 ] 2 } (3) (Im Dipp NH = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-imine, Im Ad NH = 1,3-di(adamantan1-yl)imidazolin-2-imine) were synthesized, in which five neutral solvent molecules behave as auxiliary ligands to fill the remaining coordination space. The significantly shortened strong axial Dy-N bond (2.0598(18)-2.085(4) & Aring;) together with very weak auxiliary neutral ligands provides an ideal pseudo mono-coordinate ligand field. Notably, combining with enhanced axial molecular symmetry, complexes 1-3 exhibit better performance than previously reported bis(imidazolin-2-iminato) SMMs, demonstrating the potential of utilizing only one strongfield ligand and providing insightful clues for further molecular design.

The first examples of RE/Si FLPs (RE: rare-earth metal, FLPs: frustrated Lewis pairs), namely Yb/Si FLPs were synthesized, where Yb⋯Si distances are in the range of 3.55 to 3.72 Å. These FLPs react with triphenylphosphine sulfide and aryl isocyanide to produce novel silylyne group transfer products through dissociation of naphthalene.

The rare-earth elements are generally trivalent, but some, like cerium, praseodymium, and terbium, can also exhibit the tetravalent state. However, tetravalent rare earth (RE) metal-carbon sigma-bond complexes remain elusive and have not been synthesized without the use of chelating ligands to stabilize them. In contrast, the synthesis of numerous trivalent RE-C bond complexes has been achieved and reported. Herein, we report the first synthesis and structural characterization of a complete series of cerium(IV) alkyl, aryl, and alkynyl complexes without chelate-assisted stabilization. The CeIV-C IV -C sigma-bond complexes are synthesized from reactions of imidazolin-2-iminato cerium(IV) chlorides with lithium alkyl, aryl, or alkynyl reagents, and they have all been characterized by single crystal X-ray diffraction. The investigation of the decomposition of cerium(IV) alkyl complexes shows the generation of alkyl radicals, indicating a homolytic cleavage mechanism of CeIV-C(sp3) IV -C(sp 3 ) sigma-bond, which is significantly different from the decomposition mechanism of the REIII- III - C(sp3) 3 ) sigma-bond. Quantum theoretical studies were performed to provide insights into the CeIV-C(spn) IV -C(sp n ) (n n = 1, 2, 3) sigma-bonding properties as well as the high 13 C{ 1 H} nuclear magnetic resonance (NMR) chemical shifts of CeIV-C IV -C signals. The electronic influence of the supporting ligands was also studied theoretically, which revealed that the strong electron -donating imidazolin-2-iminato ligand enhanced the energylevel match of the Ce(IV) 5d orbitals with the alkyl group. This energy -level match strategy provides insights into the preparation of RE complexes with unusual chemical bonds.

ConspectusAs phosphorus analogues of alkylidene (or carbene) and imido (or nitrene) complexes, phosphinidene complexes have received great attention not only for their fundamental scientific merits but also for their ability to build new phosphorus-containing molecules. A large number of phosphinidene complexes in bridging, mononuclear, or terminal coordination modes have been synthesized, and their reactivity has been extensively explored. However, the synthesis of rare-earth metal (scandium, yttrium, and lanthanide metal) phosphinidene complexes lagged behind the transition metal and actinide congeners for decades. Rare-earth metal ions are among the hardest Lewis acids, whereas phosphinidene ligands are soft Lewis bases; rare-earth metal-phosphinidene coordination is thus mismatched based on the Pearson's HSAB principle. The bridging rare-earth metal phosphinidene complexes were not reported until 2008, and the synthesis of the mononuclear and terminal species is even more challenging, which has only recently been achieved.Our group reported a bis(μ2-phosphinidene)dineodymium complex in 2008. In the following >10 years, we have been pursuing the terminal rare-earth metal phosphinidene complexes. Due to the high instability of rare-earth metal-phosphorus multiple bonds, the synthesis and stabilization of these complexes are extremely difficult. Finally, by using suitable phosphinidene ligands and supporting ligands, we obtained the first mononuclear rare-earth metal phosphinidene complex in 2018 and the first terminal rare-earth metal phosphinidene complex in 2020. In these more than ten years of research, we have also found some interesting reactivity of the rare-earth metal phosphinidene complexes. The rare-earth metal bridging phosphinidene complexes can act as two-electron reductants based on the oxidative coupling of two phosphinidene ligands into a diphosphene ligand. The mononuclear rare-earth metal phosphinidene complexes catalyze the hydrogenation of terminal alkenes under mild conditions, and the joint experimental/DFT studies indicate that the hydrogenation reaction proceeds in a 1,2-addition/elimination mechanism rather than the common σ-bond metathesis mechanism. These reactivities are new and important for the rare-earth metal complexes. In addition, the ligand design in our study may contribute to the synthesis of rare-earth metal-arsenic multiple bonding complexes and alkaline-earth metal-phosphorus multiple bonding complexes, which have not yet been realized. Herein, we present an account of our investigations into rare-earth metal phosphinidene complexes, a trip from bridging one to terminal one. To give the readers an overall image of the development of the rare-earth metal phosphinidene complexes, some findings from other researchers are also included.

In principle, catalytic dehydrogenative silylation and mono/dihydrosilylation tandem reactions of terminal alkynes with hydrosilanes provide gem-disilylated alkenes or gem-trisilylated alkanes, but very little progress has been made. Herein, we report organo-calcium-complex-catalyzed dehydrogenative silylation and mono/ dihydrosilylation tandem reactions of terminal alkynes with hydro-silanes in one pot, which produce gem-disilylated alkenes in moderate yields and gem-trisilylated alkanes in high yields. We also briefly demonstrate that the synthesized gem-disilylated alkenes can be easily transformed into other organosilanes.

Model calculations indicate that the increasement of Ueff becomes tiny when N–Dy–N angle is large. Thus, the construction of near-linear two-coordinate dysprosium(III) SMMs with high Ueff and TB using bulky imidazolin-2-iminato ligands is feasible.

Alkynylsilanes are an important class of organic compounds and dehydrogenative coupling of hydrosilanes with terminal alkynes provides a convenient and simple route to alkynylsilanes. On the other hand, calcium is an abundant, biocompatible, and environmentally friendly element and using organocalcium complexes as catalytic reagents in organic synthesis recently attracted increasing attentions. Here we report an organocalcium complex‐catalyzed dehydrogenative coupling of hydrosilanes with terminal alkynes. With a calcium alkyl complex [LCaCH 2 SiMe 3 ] (L=[MeC(NDipp)CHC( t Bu)NCH 2 CH 2 N(Me)CH 2 CH 2 NMe 2 ] − , Dipp=2,6‐( i Pr) 2 C 6 H 3 ) as the catalyst, the reactions of n ‐HexSiH 3 with terminal alkynes provide trialkynylsilanes and those of Et 2 SiH 2 with terminal alkynes give monoalkynylsilanes efficiently.

The trivalent rare-earth metal hydrido and imido complexes are of versatile reactivity, and many such complexes have been synthesized. However, no example of a rare-earth metal complex bearing both hydrido- and imido-ligands has been reported. Herein, we report the first rare-earth metal complex bearing both hydrido- and imido-ligands, namely a hydrido- and imido-bridged dinuclear ytterbium(III) complex. The complex was synthesized via an unprecedented redox reaction of divalent rare-earth metal hydrido complex with azido compound. DFT calculation indicated that the N2 release from azido compound in the presence of ytterbium(II) is a kinetically facile process because of the cooperative effects of the two metal centers. The reactivity of the hydrido- and imido-bridged dinuclear ytterbium(III) complex was also explored, which showed the redox, addition and σ-bond metathesis reactivities.

The ligand field greatly affects the redox properties of cerium. Herein, cerium(III) and cerium(IV) complexes supported by imidazolin-2-iminato ligands were synthesized and structurally characterized, and their electrochemical properties were investigated. Silylamine elimination of cerium(III) amide Ce{N(SiMe3 )2 }3 with imidazolin-2-imine ImR NH (R=Mes, tBu, iPr) provided imidazolin-2-iminato cerium(III) complexes, [(ImMes N)(ImMes NH)Ce{N(SiMe3 )2 }2 ] (1), [(ImtBu N)2 (ImtBu NH)Ce{N(SiMe3 )2 }] (2) and [(ImiPr N)2 (ImiPr NH)Ce(μ-ImiPr N)]2 (4) in 71-85% yields. These cerium(III) complexes were successfully oxidized by Ph3 CCl or C2 Cl6 to afford imidazolin-2-iminato cerium(IV) chlorides, [(ImMes N)2 Ce{N(SiMe3 )2 }Cl] (5), [(ImtBu N)3 CeCl] (6) and [(ImiPr N)2 Ce(μ-ImiPr N)Cl]2 (7) in 70%-76% yields. All complexes were characterized by the single-crystal X-ray diffraction, which showed that 1, 2, 5 and 6 are monomers while 4 and 7 are dimers. The electrochemical studies indicated that the Ce(III/IV) couples for 5 and 6 are more negative than those of silylamido cerium(IV) complexes, and the Ce(III/IV) couples for 1 and 2 have a similar trend.

Rare-earth metal complexes have been used as catalysts for many types of reactions. However, the mechanistic studies showed that basically, these various reactions proceeded with sigma-bond metathesis of RE-E bond (RE: rare-earth metals; E: main group elements) or RE ions acting as Lewis acid centers to activate the polar functional groups of the substrates. In this article, a lutetium phosphinophosphinidene complex, with Lu=P double-bond character, was synthesized and structurally characterized. This lutetium complex and our previously reported scandium phosphinophosphinidene complexes were able to catalyze the hydrogenation of terminal alkenes under mild conditions, and the lutetium complex showed higher catalytic activity than the scandiumones. More interestingly, isotopic labeling experiments indicated that the catalytic reaction proceeded through an addition/elimination mechanism rather than the traditional sigma-bond metathesis mechanism. Density functional theory calculations provided insights into the 1,2-addition/elimination mechanism and regioselectivities of the H-2 addition to the Lu=P double bond of the lutetium phosphinophosphinidene complex and the anti-Markovnikov alkene insertion into the Lu-H bond of the lutetium phosphinophosphido hydride intermediate. [GRAPHICS] .

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

While the chemistry of trivalent rare-earth metal hydrido complexes has been well developed in the past 40 years, that of the divalent rare-earth metal hydrido complexes remains in its infancy because of the synthetic challenge of such complexes. In this paper, we report the synthesis and structural characterization of a divalent ytterbium hydrido complex supported by a bulky β-diketiminato-based tetradentate ligand. This hydrido complex is a dimer containing two μ-hydrogen ligands, and it easily undergoes a hydrido shift reaction to form a new divalent ytterbium hydrido complex that contains only one hydrido bridge. Furthermore, this hydrido complex reacts with pyridine and pyridine derivatives, showing versatile reactivity [Yb-H addition to pyridine, hydrido shift to ancillary ligand, and ytterbium(II)-center-induced redox reaction with bipyridine]. This hydrido complex reacts with Ph3P═O, resulting in a P-CPh cleavage of Ph3P═O and an elimination of C6H6; on the other hand, the reaction with Ph3P═S is a hydrido coupling-based redox reaction. The reactions of this hydrido complex with 1 and 2 equiv of PhSSPh clearly indicate that the hydrido coupling-based redox reaction is prior to the ytterbium(II) oxidation-based redox reaction.

The first isolation and structural characterization of a rare-earth metal-terminal imido complex were reported in 2010, but a rare-earth metal-terminal phosphinidene complex is still absent, to date. Herein, we report the synthesis and structure of the first example of a rare-earth-terminal phosphinidene complex, namely the scandium boronylphosphinidene complex. Single-crystal X-ray diffraction shows that the complex has a much shorter Sc-P bond length as compared to that in a related scandium boronylphosphido complex, 2.381(1) Å vs 2.564(1) Å. DFT calculations indicate the presence of a strong Sc-P π interaction in this complex, which is in striking contrast to the weak interaction found in the phosphido complex. A preliminary reactivity study demonstrates that the scandium-terminal boronylphosphinidene complex behaves as a nucleophilic phosphinidene complex.