Tetramethyldiphosphine

Preparations of the following three aliphatic chelating (dimethyl-phosphino) ligands illustrate the synthetic route and the procedure that can lead to a large number of new phosphine ligands. 

A carefully dried, 500-ml., three-necked, round-bottomed flask is fitted with a compact distillation head and condenser, a pressure-equalizing addition funnel, and a nitrogen gas inlet tube. TTie nitrogen passes out through the distillation head. If conventional stopcocks are used, they should be lubricated with fluorocarbon or silicone grease. 

Tetramethyldiphosphine disulfide (46.5 g., 0.25 mole) and 111 g. (0.50 mole plus 10% excess) of tributylphosphine are added directly to the three-necked flask. The funnel is replaced with a 

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Caution. Tetramethyldiphosphine and dimethylphosphine are toxic and spontaneously flammable in air. These reactions should be carried out in a purified nitrogen atmosphere and in a very good hood. 

Tetraethyl- and tetramethyldiphosphine disulfide (Orgmet, Inc., 300 Neck Rd. Haverhill, Mass. 01830), tributylphosphine (Carlisle Chemical Works, Inc., Reading, Ohio 45215), and 1,3-dichloropropane (Eastman Kodak Company, Rochester, N.Y. 14600) were obtained commercially and used without further purification. The first two reactants are completely inert to one another at room temperature and can be placed in the reaction vessel simultaneously. 

Tetramethyldiphosphine distills at 1S1°C. at ca. 750 torr. However, the vacuum distillation is preferred for safety also less frothing occurs at the lower temperature. 

A sodium dimethylphosphide solution is prepared as in Sec. B from 4.6 g. (0.20 mole) of sodium, 200 ml. of anhydrous liquid ammonia, and 12.2 g. (0.10 mole) of tetramethyldiphosphine. Then 36.5 g. (0.20 mole) of (3-chloropropyl)dimethylarsine11 is added dropwise to the reaction mixture. The color of the reaction mixture changes slowly from green to red and finally becomes colorless when the addition is complete. The liquid ammonia is allowed to evaporate into a hood at room temperature, and the remaining oil is distilled under vacuum b.p. 43-44°C./torr. The yield is ca. 26 g. (0.125 mole, 63%). 

Dimethylthiophosphinic bromide has been prepared by addition of elemental bromine to tetramethyldiphosphine disulfide suspended in carbon tetrachloride.1- The reaction is rather general in that alkyl or aryl groups other than methyl can be attached to the phosphorus atom to give products of the type... 

Figure 1 Three line-position and line intensity roadmaps as a function of rotation angle (deg), for rotations about three orthogonal rotation axes, obtained from solid-state 31P cross-polarization (CP) NMR spectra at fixed magnetic fields of 4.7 T, for single-crystals (space group C2/m) of TMPS (tetramethyldiphosphine sulfide). One sees the spectra from two site types occurring in abundance ratio 1 2, each with a spin-spin doublet structure. Taken from Ref. 31.

M. Gee, R. E. Wasylishen, K. Eichele and J. F. Britten, Phosphorus chemical shift tensors for tetramethyldiphosphine a 31P single-crystal NMR, dipolar-chemical shift NMR and ab initio molecular orbital study.. Phys. Chem. A, 2000,104,4598-4605. 

Diethyl (trimethylsilyl) phosphine has been prepared by the reaction of lithium diethylphosphide with chlorotrimethyl-silane in ether solution.4 The lithium diethylphosphide may be prepared by the reaction of an ether solution of phenyllithium with diethylphosphine.6 However, the dialkylphosphines are most conveniently prepared by the reduction of the corresponding tetraalkyldiphosphine disulfides with lithium tetrahydro-aluminate in ether.6 7 An alternative method for the preparation of dimethyl(trimethylsilyl)phosphine which eliminates the handling of the volatile dimethylphosphine involves the preparation of lithium dimethylphosphide from tetramethyldiphosphine. The latter is prepared by the reduction of tetramethyldiphosphine disulfide8 with tributylphosphine.9 The reaction of chlorotrimethylsilane with lithium dimethylphosphide is most conveniently carried out in a vacuum system without solvent at -78°. 

III) fluoride or by fluorination of the complex [(CH3)2-PCl2][AlCl4], formed by reaction of methyldichlorophos-phine, methyl chloride, and aluminum chloride with hydrogen fluoride. The compound is also formed upon reaction of tetramethyldiphosphine disulfide with antimony (III) fluoride.The latter procedure, which could be applied to synthesize numerous other trifluorophos-phoranes, is described below. 

The distillation flask is charged udth 49.0 g. (0.26 mole) of tetramethyldiphosphine disulfide and 10.3 g. (0.27 mole) of lithium hydroaluminate, and the flask is flushed with nitrogen. Four hundred milliliters of anhydrous dioxane (distilled from sodium) is added all at once through the addition funnel. The distillation column is adjusted to provide total reflux of the dimethylphosphine, and the reaction mixture is stirred for 4 hours. Moderately rapid hydrogen evolution occurs, and the... 

Nucleophilic Attack at Other Atoms.- Interest has continued in the synthesis of phosphine-borane adducts. Complexes of tetramethyldiphosphine with borane and various halogenoboranes have been used to generate a series of open-chain and cyclic phosphino-boranes. Adducts of 1,3,5-diazaphosphorinanes involving two... 

Tetramethyldiphosphine and hexafluoroacetone gave the phosphoranes (29), (30), and (31) in which the chiral centres at phosphorus led to doubling of resonances in their n.m.r. spectra. ... 

These products and others with different co-ordination at phosphorus are found to have the butterfly structures shown. The P—P bond of tetramethyldiphosphine disulphide (37) is readily broken by p-benzoquinone and by hydroxide ion. ... 

A 2-nitroalkylphosphinic ester (40) has been obtained by the interaction of dimethyl phenylphosphonite and a-nitroisopentene, although the true nature of the intermediate is open to question. The phosphinate (41) is obtained from p-benzo-quinone and tetramethyldiphosphine disulphide. Conventional reactions have been employed in the preparation of the macrocyclic compounds (42) and the perhydro-1,2-azaphosphorines (43). ... 

Phosphorus chemical shift and spin-spin coupling P-P tensors have been determined by Gee et al for tetramethyldiphosphine disulfide. 

From Metallated Phosphines. The preparations of a number of flexible aliphatic ligands, e.g. (6), containing the dimethylphosphino-group have been described, in which the sodium dimethylphosphide used was prepared from tetramethyldiphosphine, ... 

The desulphurization of diphosphine disulphides with tributylphosphine has been used to prepare tetramethyldiphosphine (19). ... 

The reactions of primary phosphines and the corresponding alkyl phosphides with a/ff-unsaturated ketones (25) have been discussed in some detail. " Tetrafluoroethylene with an excess of dimethylphosphine in the gas phase gives (26) by a reaction which is thought to be initiated by the bimolecular abstraction of a hydrogen atom from dimethylphosphine by tetrafluoro-ethylene. Tetrafluoroethylene also reacts with tetramethyldiphosphine by a radical process to give l,2-bis(dimethylphosphino)tetrafluoroethane (27). ... 

Various structural parameters and the conformation of biphosphine have been determined from the microwave spectra of biphosphine and deuteriated derivatives. Rotational isomerism in tetramethyldiphosphine has been detected using photoelectron spectroscopy. The dipole moments of a series of methyl-substituted triaryl phosphines have been measured. ... 

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