Ytterbium(III) Triflate
Properties
| State | Solid (hygroscopic) |
| Color | White to pale yellow |
| Solubility | Very soluble in water, acetonitrile, DMF, DMSO, THF, alcohols, acetone |
| Melting Point | 100-120 °C (dehydrates); decomposes >350 °C |
About Ytterbium(III) Triflate
Ytterbium(III) triflate is a white, fiercely hygroscopic salt — Yb(CF3SO3)3, anhydrous molar mass 620.23 g/mol — and it's the most-cited lanthanide-triflate Lewis acid in modern organic synthesis. The commercial form is the hydrate Yb(OTf)3·xH2O, typically the nonahydrate. Shu Kobayashi at the University of Tokyo published the seminal Mukaiyama aldol paper in 1991 showing that this catalyst worked in water, and that single result rewrote the playbook for Lewis-acid catalysis. Conventional Lewis acids — TiCl4, AlCl3, BF3 — hydrolyze on contact with even trace moisture, so for decades "dry conditions" were a non-negotiable cost of doing business. Yb(OTf)3 stays catalytically active at 0.01-5 mol% in wet THF, aqueous acetonitrile, and even pure water. Published applications now span Mukaiyama aldol, Mannich, Diels-Alder and aza-Diels-Alder, Michael additions, Friedel-Crafts acylation, glycosylation in carbohydrate synthesis, and enantioselective variants with chiral pybox or bipyridine ligands. The triflate anion is so weakly coordinating that Yb(III) sits in solution as a bare electrophilic center, and the catalyst is recoverable by aqueous extraction after workup.
Where you'll encounter it
If you've ever run a Mukaiyama aldol in a teaching lab and been told you didn't need to flame-dry your flask, you were probably using Yb(OTf)3 — that's the catalyst that took Lewis-acid chemistry out of the glovebox and onto the open bench. In a process-development lab, the appeal is even more practical: you can run the reaction in 10:1 THF/water, do an aqueous workup, evaporate the aqueous layer, and recover the catalyst as a recyclable solid for the next batch. Pharmaceutical process groups have used Yb(OTf)3 in API synthesis at kilogram scale precisely because it tolerates the residual moisture you can't economically remove from bulk solvents. In a glycochemistry lab, it activates trichloroacetimidate or thioglycoside donors for stereoselective glycosylation under conditions that would destroy a more sensitive promoter like TMSOTf.
Common Uses
- Water-tolerant Lewis-acid catalyst for Mukaiyama aldol, Mannich, and aza-Diels-Alder reactions at 0.01-5 mol%
- Green-chemistry catalyst for aqueous and wet-organic carbonyl activation, recoverable by aqueous extraction
- Mild promoter for glycosylation in carbohydrate and glycopeptide synthesis where TMSOTf is too aggressive
- Chiral Lewis-acid scaffold when paired with pybox or bisoxazoline ligands for enantioselective C-C bond formation
- Pharmaceutical process catalyst at kilogram scale for water-tolerant Friedel-Crafts and Michael chemistry
Safety Information
GHS: Skin corrosion/irritation Category 2 (H315), Eye irritation Category 2A (H319), STOT SE Category 3 respiratory tract irritation (H335). Acute toxicity at typical 1-5 mol% catalyst loading is low — the hazardous behavior is irritation from the triflate anion, not lanthanide toxicity. There is no specific OSHA PEL for ytterbium triflate; treat as a moderate skin/eye irritant and follow the general particulate-not-otherwise-regulated limit of 15 mg/m3 total dust. Standard lab PPE: nitrile gloves, splash goggles, lab coat, work in a fume hood when weighing the dry powder. Store sealed under desiccant — moisture uptake will turn the bottle into a syrupy mass within hours of being left open.
This safety summary is for educational reference only and may not be complete. It is not a substitute for Safety Data Sheets (SDS), medical advice, or professional chemical safety guidance. Always consult appropriate SDS and qualified professionals before handling chemicals.