[N-(tert-butyl)(3,5-dimethylphenyl)-amido](VI) propylidyne could be produced through the following synthetic routes.

A. N-(3,5-Dimethylphenyl)-tert-butylamine (1). A 500-mL, three-necked, round-bottomed flask is equipped with two glass stoppers, a magnetic stir bar and a reflux condenser fitted with a gas inlet connected to an argon-vacuum manifold. The flask is flame-dried under vacuum, then filled with argon. After evacuating and backfilling with argon three times, the flask, in which a positive flow of argon is maintained throughout the entire procedure, is sequentially charged with sodium tert-butoxide (19.22 g, 0.20 mol), 2-(dicyclohexylphosphino)biphenyl (0.50 g, 1.4 mmol), [Pd₂(dba)₃] (0.65 g, 0.71 mmol), toluene (200 mL), tert-butylamine (18.0 mL, 0.17 mol) and 5-bromo-1,3-dimethylbenzene (19.4 mL, 0.14 mol). The resulting viscous red reaction mixture is heated at 80 °C in an oil bath for 12 h while maintaining positive argon pressure. The solution color changes from dark red to orange red with white solids precipitating out. The mixture is transferred to a 500-mL, one-necked, round-bottomed flask and concentrated to a residue by rotary evaporation (water bath temperature 50–55 °C) before cooling down to room temperature. (250 mL) and brine (80 mL) are added to the residue. After separation, the aqueous layer is extracted with tert-butyl methyl ether (2 × 250 mL), the combined organic layers are dried (MgSO₄), filtered and concentrated by rotary evaporation, and the crude product is purified by distillation under vacuum (bp 50–53 °C, 10-3 mbar, oil bath temperature 70 °C) affording aniline 1 as colorless liquid (21.8 g, 86%).

B. N-(3,5-dimethylphenyl)-tert-butylamide etherate (2). A 500-mL, three-necked, round-bottomed flask is equipped with a magnetic stirring bar, two glass stoppers and a pressure-equalizing dropping funnel fitted with a gas inlet connected to an argon-vacuum manifold. The flask is flame-dried under vacuum, then filled with argon. After evacuating and backfilling with argon three times, the flask is charged with substituted aniline 1 (11.3 g, 63.7 mmol) and n-hexane (220 mL) under argon purge. The solution is cooled to -78 °C in a dry ice-acetone bath and a solution of n-BuLi (1.6 M in hexanes, 48 mL, 76.8 mmol) is added via the dropping funnel over 10 min. After the addition is complete, the mixture is stirred for 12 h during which time it is gradually warmed to room temperature; a white precipitate forms upon warming. The dropping funnel is replaced by a distillation head and condenser and all volatiles are removed under vacuum (approximately 7.5 mmHg) at room temperature without exposing the contents to the open atmosphere. Then ether (25 mL) and n-hexane (50 mL) are added to the remaining viscous liquid causing further precipitation of a white solid. The resulting suspension is kept at -30 °C under argon for 12 h. The white solids of lithium anilide etherate (2•Et₂O) formed are collected by filtration under argon, washed with cold n-hexane (2 × 10 mL) and dried under vacuum (10-3 mbar) to give lithium N-(3,5-dimethylphenyl)-tert-butylamide etherate as colorless crystals (9.41 g, 57%). The filtrate is concentrated under vacuum to approximately half of its volume and slowly cooled to -78 °C to give a second crop of the product which is isolated by filtration under argon as described above (3.48 g, 21%).

C. [MoCl₃(THF)₃](3). A 500-mL, two-necked, round-bottomed flask equipped with a magnetic stir bar, a glass stopper and a gas inlet connected to the argon/vacuum line is flame-dried and back-filled with argon. While maintaining a positive argon pressure, the flask is charged with acetonitrile (250 mL). Molybdenum pentacarbonyl (MoCl₅) (51.17 g, 160 mmol) is then added in portions over a period of 20 min, causing a gentle warming of the mixture. The resulting suspension is stirred for 20 h at ambient temperature. The solid material is filtered off and is carefully rinsed with acetonitrile (50 mL) before it is dried under vacuum (10-3 mbar) to give MoCl₄(MeCN)₂ as a red-brown solid (47.5 g, 93%). This material is re-dispersed in THF (200 mL) and the suspension is stirred for 3.5 h under argon. The resulting complex is filtered off under argon, the solid is carefully washed with pentane (100 mL) and dried under vacuum (10-3 mbar) to give MoCl4(THF)₂ as orange-brownish crystals (53.30 g, 94%).

A 500-mL, two-necked, round-bottomed flask equipped with a magnetic stir bar, a glass stopper and a gas inlet connected to the argon/vacuum line is flame-dried and back-filled with argon. This flask is charged with the MoCl₄(THF)₂ complex (53.30 g, 140 mmol), THF (300 mL) and tin shot (107.3 g, 0.904 mol), and the resulting suspension is stirred for 30 min, resulting in a slight exotherm (a temperature of approximately 30 °C is reached). Stirring is then discontinued to allow the remaining tin to settle. Upon gentle manual swirling, leaving the metallic tin at the bottom of the flask, the supernatant suspension (liquid and all solids except metallic tin) is decanted, the solid material is collected by filtration under argon, the product is carefully rinsed with pentane (100 mL) and dried under vacuum (10-3 mbar), affording MoCl₃(THF)₃ as an orange solid (51.2 g, 88%).

D. Tris[N-(tert-butyl)(3,5-dimethylphenyl)-amido]molybdenum(III) (4). A 500-mL two-necked, round-bottomed flask equipped with a magnetic stir bar, a glass stopper and a gas inlet connected to the argon/vacuum manifold is flame-dried under vacuum and back-filled with argon. The flask is then charged with [MoCl₃(THF)₃] ₃ (7.96 g, 19.0 mmol) by removing a stopper and adding the solid, followed by Et₂O (300 mL), which is transferred by syringe. The resulting suspension is cooled to -30 °C with an acetone/dry ice bath before anilide 2 (9.79 g, 38.0 mmol) is added through removal of the stopper. The resulting mixture is stirred for 3 h during which time it is allowed to reach room temperature and the solution turns dark red. The suspension is filtered under argon into a flame-dried 500-mL, two-necked, round-bottomed flask to remove LiCl; the solid is rinsed with ether (15 mL). With one neck equipped with a rubber septum and the other one connected via a cold-trap to the vacuum line, the filtrate is concentrated under reduced pressure (7.5 mmHg) to approximately 1/6 of its original volume (50 mL). The remaining solution is cooled to - 30 °C for 16 h, causing the separation of dark red crystals. The supernatant liquid is decanted off while keeping a positive argon pressure, and the remaining dark-red, crystalline molybdenum trisamide 4 is dried under vacuum (10-3 mbar) (4.28 g, 55%).

E. Tris[N-(tert-butyl)(3,5-dimethylphenyl)-amido]molybdenum(VI) propylidyne (5). A 250-mL, two-necked, round-bottomed flask equipped with a rubber septum, a magnetic stirring bar, and a gas inlet connected to the argon/vacuum manifold is flame-dried and back-filled with argon. Molybdenum trisamide 4 (5.31 g, 8.48 mmol), magnesium turnings (2.54 g, 106 mmol) and THF (160 mL) are added to the flask by removal of the septum. To the stirred solution, 1,1-dichloropropane (1.7 mL, 17 mmol) is added dropwise via syringe within 5 min, resulting in a color change from red to dark amber. The resulting mixture is stirred for 2.5 h at room temperature under argon. The rubber septum is replaced by a distillation head connected to the vacuum line, the solvent is removed under reduced pressure (approximately 7.5 mmHg), and the residue is redissolved in pentane (100 mL). After vigorous stirring/manual shaking, the solid precipitate (MgCl₂) and excess magnesium turnings are removed by filtration under argon. The filtrate is concentrated to approximately 1/10 of its volume and slowly cooled to -78 °C, causing the molybdenum propylidyne complex to precipitate. The supernatant is removed via cannula and the remaining beige crystals are dried under vacuum (10-3 mbar) (3.08 g, 54%).