Advances in PNP-ligated rare-earth-metal complexes: Reactivity and catalytic performances

Document Type : Mini Review


1 Petrochina Petrochemical Research Institute, Petrochina Company Limited, Beijing 102206, China

2 Provincial Key Laboratory of Polyolefin New Materials, College of Chemistry & Chemical Engineering, the Northeast Petroleum University, Daqing 163318, China


Due to the large ionic radius and high electro-positivity nature, rare earth metal complexes are difficult to stabilize and undergo pathways like ligand redistribution and intramolecular C-H activation. To solve such problems and retain reactive versatility, rare earth complexes supported by a variety of tridentate PNP pincer ligands have been explored. Such complexes can serve as perfect precursors for preparing ultra-active rare earth species containing two metal-carbon bands, let alone Ln=N and Ln=P multiple bonds. In addition, the combined stability and activity of the cation rare earth mediates made them the best catalysts for the polymerization of olefins and other non-polar hydrocarbon monomers, especially conjugated dienes. The practical utilization of rare earth metal catalysts for new materials production have also extensively explored by experts from the academic and industries. 


Main Subjects

  1. Koten G, Milstein D, Castonguay (2013) Organo­metallic pincer chemistry. Springer, 1-356
  2. Szabo KJ, Wendt OF (2014) Applications in Or­ganic Synthesis and Catalysis. Wiley-VCH, 1-302
  3. Benito-Garagorri D, Kirchner K (2008) Modular­ly designed transition metal PNP and PCP pincer complexes based on aminophosphines: Synthesis and catalytic applications. Acc Chem Res 41: 201- 213
  4. Van Der Vlugt JI, Reek JNH (2009) Neutral tri­dentate PNP ligands and their hybrid analogues: Versatile non-innocent scaffolds for homogeneous catalysis. Angew Chem Int Ed 48: 8832-8846
  5. Demott JC, Bhuvanesh N, Ozerov OV (2013) Frustrated Lewis pair-like splitting of aromatic C–H bonds and abstraction of halogen atoms by a cationic [(FPNP)Pt]+ Chem Sci 4: 642- 649
  6. Herbert DE, Miller AD, Ozerov OV (2012) Phosphorus(iii) cations supported by a PNP pin­cer ligand and sub-stoichiometric generation of p4 from thermolysis of a nickel insertion product. Chem Eur J 18: 7696-7704
  7. Kaita S, Hou Z, Wakatsuki Y (1999) Stereo­specific Polymerization of 1,3-butadiene with samarocene-based catalysts. Macromolecules 32: 9078-9079
  8. Kaita S, Hou Z, Nishiura M, Doi Y, Kurazumi J, Horiuchi AC, Wakatsuki Y (2003) Ultimately spe­cific 1,4-cis polymerization of 1,3-butadiene with a novel gadolinium catalyst. Macromol Rapid Commun 24: 179-184
  9. Kaita S, Doi Y, Kaneko K, Horiuchi AC, Wakat­suki Y (2004) An efficient gadolinium metallo­cene-based catalyst for the synthesis of isoprene rubber with perfect 1,4-cis microstructure and marked reactivity difference between lanthanide metallocenes toward dienes as probed by butadi­ene−isoprene copolymerization catalysis. Macro­molecules 37: 5860-5862
  10. Hou Z, Wakatsuki Y (2002) Recent developments in organolanthanide polymerization catalysts. Coord Chem Rev 231: 1-22
  11. Zeimentz PM, Arndt S, Elvidge BR, Okuda J (2006) Cationic organometallic complexes of scandium, yttrium, and the lanthanoids. Chem Rev 106: 2404-2433
  12. Nishiura M, Guo F, Hou Z (2015) Half-sandwich rare-earth-catalyzed olefin polymerization, car­bometalation, and hydroarylation. Acc Chem Res 48: 2209-2220
  13. Piers WE, Emslie DJH (2002) Non-cyclopentadi­enyl ancillaries in organogroup 3 metal chemistry: A fine balance in ligand design. Coord Chem Rev 233-234: 131-155
  14. Hänninen MM, Zamora MT, Hayes PG (2016) Rare earth pincer complexes: Synthesis, reac­tion chemistry, and catalysis. In: The privileged pincer-metal platform: Coordination chemistry & applications, Ed. G Van Koten, RA Gossage. Springer International Publishing, Cham. 93-177
  15. Fryzuk MD, Haddad TS (1988) Phosphine com­plexes of yttrium(III). Synthesis, reactivity and fluxional behavior of YCl[N(SiMe2CH2PMe2)2]2. J Am Chem Soc 110: 8263-8265
  16. Fryzuk MD, Haddad TS, Rettig SJ (1991) Phosphine complexes of yttrium, lanthanum, and lutetium. Synthesis, thermolysis, and flux­ional behavior of the hydrocarbyl derivatives MR[N(SiMe2CH2PMe2)2]2. X-ray crystal structure of [cyclic]Y[N(SiMe2CHPMe2)(SiMe2CH2PMe2)] [N(SiMe2CH2PMe2)2]. Organometallics 10: 2026- 2036
  17. Fryzuk MD, Giesbrecht G, Rettig SJ (1996) Synthesis and Characterization of the Five- Coordinate Scandium Dialkyl Complex­es ScR2 [N(SiMe2CH2PiPr2)2] (R = Me, Et, CH2SiMe3). Organometallics 15: 3329-3336
  18. Fryzuk MD, Giesbrecht GR, Rettig SJ (2000) Synthesis, characterization, and reactivity of scan­dium chloro, alkyl, aryl, and borohydride com­plexes, Sc(η5-C5H5)R[N(SiMe2CH2PiPr2)2] (R = Cl, Me, Ph, and BH4). Can J Chem 78: 1003-1012
  19. Masuda JD, Jantunen KC, Ozerov OV, Noonan KJT, Gates DP, Scott BL, Kiplinger JL (2008) A lanthanide phosphinidene complex: Synthesis, structure, and phospha-wittig reactivity. J Am Chem Soc 130: 2408-2409
  20. Scott J, Basuli F, Fout AR, Huffman JC, Mindiola DJ (2008) Evidence for the existence of a termi­nal imidoscandium compound: Intermolecular C-H activation and complexation reactions with the transient Sc=Nar species. Angew Chem Int Ed Engl 47: 8502-8505
  21. Wicker BF, Fan H, Hickey AK, Crestani MG, Scott J, Pink M, Mindiola DJ (2012) Evidence for the existence of terminal scandium imidos: Mechanistic studies involving imido–scandium bond formation and C-H activation reactions. J Am Chem Soc 134: 20081-20096
  22. Zatsepin P, Lee E, Gu J, Gau MR, Carroll PJ, Baik M-H, Mindiola DJ (2020) Tebbe-like and phos­phonioalkylidene and -alkylidyne complexes of scandium. J Am Chem Soc 142: 10143-10152
  23. Zabula AV, Qiao Y, Kosanovich AJ, Cheisson T, Manor BC, Carroll PJ, Ozerov OV, Schelter EJ (2017) Structure, electronics and reactivity of Ce(PNP) complexes. Chem Eur J 23: 17923- 17934
  24. Levine DS, Tilley TD, Andersen RA (2015) C–H bond activations by monoanionic, PNP-supported scandium dialkyl complexes. Organometallics 34: 4647-4655
  25. Levine DS, Tilley TD, Andersen RA (2017) Ef­ficient and selective catalysis for hydrogenation and hydrosilation of alkenes and alkynes with PNP complexes of scandium and yttrium. Chem Commun (Camb) 53: 11881-11884
  26. Friebe L, Nuyken O, Obrecht W (2006) Neodym­ium-based Ziegler/Natta catalysts and their ap­plication in diene polymerization. In Neodymium based Ziegler catalysts – fundamental chemistry, Ed. O Nuyken. Springer Berlin Heidelberg, Ber­lin, Heidelberg. 1-154
  27. Zhang L, Suzuki T, Luo Y, Nishiura M, Hou Z (2007) Cationic alkyl rare-earth metal complexes bearing an ancillary bis(phosphinophenyl)amido ligand: A catalytic system for living cis-1,4-po­lymerization and copolymerization of isoprene and butadiene. Angew Chem Int Ed Engl 46: 1909-1913
  28. Suzuki T, Zhang L, Hou Z (2008 May 15) Metal complex containing tridentate ligand and polym­erization catalyst comprising the Same, US Patent 2008/0114136A1
  29. Wang X, Kang X, Zhou G, Qu J, Hou Z, Luo Y (2017) DFT studies on cis-1,4-polymerization of dienes catalyzed by a cationic rare-earth metal complex bearing an ancillary PNP ligand. Poly­mers (Basel) 9: 53-67
  30. Wang L, Cui D, Hou Z, Li W, Li Y (2011) High­ly cis-1,4-selective living polymerization of 1,3-conjugated dienes and copolymerization with ε-caprolactone by bis(phosphino)carbazolide rare-earth-metal complexes. Organometallics 30: 760-767
  31. Liu B, Li S, Wang M, Cui D (2017) Coordination polymerization of renewable 3-methylenecyclo­pentene with rare-earth-metal precursors. Angew Chem Int Ed Engl 56: 4560-4564
  32. Jiang Y, Kang X, Zhang Z, Li S, Cui D (2020) Syndioselective 3,4-polymerization of 1-phe­nyl-1,3-butadiene by rare-earth metal catalysts. ACS Catalysis 10: 5223-5229
  33. You F, Zhai J, So Y-M, Shi X (2021) Rigid acri­dane-based pincer supported rare-earth complex­es for cis-1,4-polymerization of 1,3-conjugated dienes. Inorg Chem 60: 1797-1805
  34. Zhai J, You F, Xu S, Zhu A, Kang X, So Y-M, Shi X (2022) Rare-earth-metal complexes bearing an iminodibenzyl-PNP pincer ligand: Synthesis and reactivity toward 3,4-selective polymerization of 1,3-dienes. Inorg Chem 61: 1287-1296
  35. Ma R, Hu H, Li X, Zhou Y, Li H, Sun X, Zhang X, Mao G, Xin S (2022) PNP-ligated rare-earth metal catalysts for efficient polymerization of iso­prene. Catalysts 12: 1131
  • Receive Date: 28 February 2023
  • Revise Date: 04 April 2023
  • Accept Date: 05 April 2023
  • First Publish Date: 06 April 2023