Benzene dihydridobis triphenylphosphine molybdenum

All reactions are carried out in an inert atmosphere. Solutions of (//6-benzene)dihydridobis(triphenylphosphine)molybdenum should be handled in an inert atmosphere other than nitrogen to avoid contaminating the product with the dinitrogen complex [Mo[P(C6H5)3]2(fj6-C6H6)]2N2. 

Bis( /6-benzene)molybdenum (2 g, 7.94 mmol) in ca. 400 mL of dry benzene is treated with 1.5 mL (18.43 mmol) of allyl chloride which has been freshly distilled from P4O10. The solution is warmed to 45° in a water bath. The solution rapidly turns a red-violet color and small, purple crystals separate. After 1 hr at 40° the solution is cooled to 6° for 30 min and the light-purple supernatant liquid is decanted. The solid is washed with 100 mL of 95 % ethanol and dried in vacuo. The yield of di-/i-chloro-bis[( /3-allyl)(t/6-benzene)molybdenum(ll)] is 1.5-1.7 g (75-85%). The solid is ground to a fine powder and transferred to a solution of 3 g (11.47 mmol) of triphenyl-phosphine in 100 mL of benzene. The mixture is stirred under reflux for 1 hr, and the red-purple solution is cooled and filtered. One hundred milliliters of 95 % ethanol is added, and the solution is concentrated to a volume of about 75 mL in vacuo. The solution is then cooled to —15° for 1 hr, and the supernatant is carefully decanted. The small, purple crystals are washed with 100 mL of 95 % ethanol and are dried in vacuo. The yield of ( 73-allyl)chloro( 76-benzene)(triphenylphosphine)molybdenum is 2.4 2.8 g (60-70% yield based on bis( /6-benzene)molybdenum). The solid is ground 

The methyldiphenylphosphine analog can be prepared in an analogous manner except that hot benzene is used for the recrystallization of the neutral compound. 

One gram (1.7 mmol) of ( /6-benzene)tris(dimethylphenylphosphine)-molybdenum synthesized as described in Sec. C is dissolved in 10 mL (135.0 mmol) of freshly distilled, deoxygenated trifluoroacetic acid to give a yellow solution. Four milliliters (33.0 mmol) of 65% aqueous hexafluoro-phosphoric acid is added, and the solution is concentrated slowly in vacuo to a volume of about 5 mL. Very small, yellow crystals are produced. The mixture is centrifuged and the mother liquor is decanted off. The solid is washed three times with 5-mL portions of cold (0°) water and is dried in vacuo. The yield is ca. 1.1 g [75% yield based on ( /6-benzene)tris(di-methylphenylphosphine)molybdenum]. Anal. Calcd. for C30H39P 5F 12Mo C, 40.9 H, 4.7. Found C, 40.5 H, 4.9. 

Submined by TAKASHI ITOt and AKIO YAMAMOTOt Checked by WILLIAM SILVERTHORN  

---