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Mono and Bis Carbene Neodymium(III) Spirocyclic Complexes with a Cumulene Carbon Metal Structure

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Mono and Bis Carbene Neodymium(III) Spirocyclic Complexes with a Cumulene Carbon Metal Structure Journal of Organometallic Chemistry 895 (2019) 7e14 Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem Mono and bis carbene neodymium(III) spirocyclic complexes with a cumulene carbon metal structure * ** Jingwei Li a, Jianguo Zhao a, , Guibin Ma a, b, , Robert McDonald b, Ronald G. Cavell b, 1 a Institute of Carbon Materials Science, Shanxi Datong University, Datong, Shanxi Province, 037009, PR China b Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada article info abstract Article history: The formation of metal carbon cumulene structures is rare in synthesis chemistry because properties of Received 20 March 2019 the carbene carbon and metal must match properly, such as an electron rich PCP carbene and late Received in revised form transition metals containing d, f rich orbitals, or lanthanide metals. In this study, we performed the first 17 May 2019 step reaction of [Li C(Ph P ¼ NSiMe ) ](1) with NdCl in 1:1 M ratio in situ, with subsequent addition of Accepted 18 May 2019 2 2 3 2 3 second molar ratio of 1 to the reaction solution to generate bis carbene neodymium organometallic Available online 20 May 2019 compound of [Nd{C(Ph2P ¼ NSiMe3)2}2][Li(THF)n](2). The anion of this isolated compound 2 formed a rare linear carbene metal cumulene structure (C]Nd ¼ C) demonstrated by crystal structure determi- Keywords: Carbene nation. In order to synthesize a mono carbene neodymium compound with bis(diphenyliminophos- ¼ Neodymium(III) phorane)methandiide (1) to compare its bonding feature to the reactions of [Li2C(Ph2P NSiMe3)2](1) Spirocyclic complexes with NdCl3 and CpTl in THF, eventually crystal structure analysis showed that generated another neo- Cumulene carbon metal structure dymium organometallic complexes of [Cp2Nd{CH(Ph2P ¼ NSiMe3)2}2](3), unexpected the methandiide carbon of PCP ligand was protonated. Furthermore, DFT calculations demonstrated the presence of multiple bonding interaction in the carbon metal cumulene structure (C]Nd ¼ C). NBO analysis revealed that the average overall C]Nd double bond contains 21.19% carbon and 14.43% Nd component respec- tively, indicating it is a covalent conjugated multiple bonding system. To the best of our knowledge, it is the first structural example of PCP carbene neodymium compound with the cumulene structure (C] Nd ¼ C) unit. © 2019 Elsevier B.V. All rights reserved. 1. Introduction real metal-carbon multiple bond character have been widely described in the past few years [3e5]. Lanthanide metal carbene complex chemistry is a rapidly The reactions of various metal species with developing area in the last few decades because of its potential bis(diphenyliminophosphorane)-methandiide, [Li2L] (1), formed by application to catalysis and organic synthesis, most notably the use double deprotonation of the backbone methylene of dppm has of lanthanide alkyls and hydrides as single-component catalysts for generated interesting chemistry [6]. We want to focus on its reac- olefin polymerization [1]. Two-electron carbene donors to metal tion with different metals to design and synthesize complexes in ions formation of typical single bond (M À C) carbene-metal com- devising geometry, and to study their unique bonding behaviour plexes also play a central role in catalytic organometallic chemistry, and reactivity. In a past decade, it has been demonstrated that these such as lanthanide N-heterocyclic carbene (NHC) complexes types of spirocyclic pincer ligands (PCP) have abundant chemical including neodymium are effective regioselective CeH activation bonding properties and reactivities with transition metals, catalysts [2]. Lanthanide and actinide f-element complexes with lanthanide and actinide metals, as well as main group elements. Examples include the formation of complexes containing either single (CÀM) or double (C ¼ M) carbeneÀmetal bonds, or formation of monomeric and bimetallic complexes, some of which showed * Corresponding author. great catalytic activities [6]. Recently, the synthesis of bis(carbene) ** Corresponding author. Institute of Carbon Materials Science, Shanxi Datong metal complexes has been conducted, and some of these complexes University, Datong, Shanxi Province, 037009, PR China. ¼ ¼ E-mail addresses: [email protected] (J. Zhao), [email protected] (G. Ma). form the cumulene carbon metal structure (C M C), such as the 1 Deceased December 1, 2017. first crystal structure characterization of Tm(III) complex with SCS https://doi.org/10.1016/j.jorganchem.2019.05.018 0022-328X/© 2019 Elsevier B.V. All rights reserved. 8 J. Li et al. / Journal of Organometallic Chemistry 895 (2019) 7e14 ligand (Ph2SPCPSPh2/C]Tm]C) [3d]. As far as we know, only two was added into the reaction solution. The mixture turned into a anion crystal structures of Dy(III) and Ce(III) with bis(carbene) clear dark green solution. The filtered THF solution was evaporated 2- þ ligand of [C (Ph2P ¼ NSiMe3)2] and cation potassium (K ) coordi- on a dynamic vacuum line and the remaining powder was dis- nated by 18-crown-6 ether and two THF were reported in the solved in 10 ml ether. The undissolved solid of LiCl was removed by literature [4a,4b] to also contain cumelene carbon metal structures centrifugation. The dark-green solution was evaporated under (C]Dy]CorC]Ce ¼ C). For lanthanide neodymium(III) carbene vacuum to half of the volume. The solution was kept inside the complex, only one crystal structure of bis(iminophosphranyl) PCP freezer (À20 C) for a few days, during which dark-green crystals ligand ([H2C(Ph2P ¼ NSi(i-Pr)2] was reported in literature where formed. The top liquid was taken and dried under vacuum. The the structure unit of C]Nd-CH was presented [3e]. product of 3 was obtained (0.062 g, yield 75.0%). Anal. Calcd for In this research, we have extended our study of this PCP C41H49N2NdP2Si2: C, 59.18; H, 5.94; N, 3.36. Found: C, 60.16; H, 5.69; 1 [Li2C(Ph2P ¼ NSiMe3)2] (Li2L) electron rich carbene ligand to the N, 3.32. H NMR(THF-d8): d 7.92 (t, phenyl), 7.54 (d, phenyl), 7.30 (t, 13 1 31 lanthanide neodymium, and in the course of the study we have phenyl), À0.13 (s, -Si(CH3)3). C{ H, P} NMR (THF-d8): d 132.0(s, discovered a rare example of the neodymium metal center bonding phenyl), 130.1(s, phenyl), 129.1(s, phenyl), 127.2(s, phenyl/C5H5), 31 1 directly to two PCP carbenes to form a rare linear cumulene carbon 3.62 (s, Si(CH3)3) (notes: carbide signal was not resolved). P{ H} metal structure (C]Nd ¼ C). NMR(THF-d8): d 18.68 (s). IR data: 3076s, 3058s, 2950s, 2894 m, 1590w, 1483w, 1435s, 1256s, 1246s, 1115s, 1092s, 1071 m, 1030w, 2. Experimental 1014s, 996w, 848s, 830s, 764s, 696 m. 2.1. General considerations 2.4. Crystal structure determination All manipulations were performed either in an Ar-filled glove Suitable crystals of 2 to 3 were mounted on glass fibers by box or under an Ar or N2 atmosphere using standard Schlenk means of mineral oil, and data were collected using graphite- techniques. Solvents were dried over appropriate drying agents and monochromated MoKa radiation (0.71073 Å) on a Bruker PLAT- degassed by three freeze-pump-thaw cycles prior to use. The FORM/SMART 1000 CCD diffractometer. Programs for diffractom- organolithium compound [Li2-1]2 (1) was prepared according to eter operation, data collection, data reduction and absorption our published procedures [7a,7b]. Warning!!! The toxicity of correction were all supplied by Bruker. The structure was solved by thallium and its compounds has been previously discussed [7c], direct methods using Patterson Search/Structure Expansion [8a], and must be handled very carefully. NMR spectra were recorded at and these structures were all refined using full-matrix least- 2 ambient temperature using THF-d8 or toluene-d8 solutions of the squares on F (SHELXL-97)[8b-8c]. All non-hydrogen atoms in the complexes on a Varian i400 spectrometer (161.9 MHz for 31P, structure compound were refined with anisotropic displacement 100.6 MHz for 13C) and referenced to residual solvent proton (1H), parameters. Selected crystal data and structure refinement details 13 31 solvent ( C), external 85% H3PO4 ( P). Elemental analyses were for 2e3 are listed in Table 1. carried out at Analytical and Instrumentation Laboratory, Depart- ment of Chemistry, University of Alberta. 2.5. Computational details 2.2. Synthesis of [{C(Ph2P ¼ NSiMe3)2}2Nd][Li(C4H8O)4] (2) The geometric optimization and energy calculations were per- formed with the Gaussian03 program [9] based on the density To THF solution (10 ml) of [Li2-1]2 (0.115 g, 0.10 mmol) was functional theory (DFT) method. DFT calculations were performed ** added anhydrous NdCl3 (0.025 g, 0.10 mmol) as a solid in a single using the B3PW91 [9] functional, the SDD basis set on Nd, 6-311G portion at room temperature. The resulting solution was stirred at basis set on P, N and 6-31G* basis set on Si, C and H. The partial room temperature for 2 h, during which the mixture turned into a outside phenyl rings were replaced with methyl and methyl was clear light green solution. The filtered THF solution was evaporated replaced with H. The SDD basis is constructed with a quasir- on a dynamic vacuum line and the remaining powder was dis- elativistic effective core potential that allows the incorporation of solved in 10 ml ether. The undissolved solid of LiCl was removed by scalar relativistic effects in nonrelativistic calculation. centrifugation. The yellow-green solution was evaporated under vacuum to half of the volume and a few drops of dry toluene was 3. Results and discussion added. The solution was kept inside the freezer (À20 C) for a few days, during which yellow-green crystals formed.
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