Diimide, and Hydrazine Complexes of Platinum

Submitted by GEORGE W. PARSHALL Cheeked by M. D. CURTISt and R. C. JOBf 

The reactions of arenediazonium salts with (rans-chlorohydrido-bis(triethylphosphine)platinum(II)1 give aryldiimide complexes which are precursors to new arylazoplatinum compounds2 and 

A solution of 20.8 g. (55 mmoles) of potassium tetrachloro-platinate(II) in 100 ml. of water is prepared in a 250-ml. suction flask with a nitrogen flow through the sidearm to provide an inert atmosphere. (The procedures work equally well at halfscale.) Triethylphosphine (15 ml., 100 mmoles) is added all at once and the mixture is stirred with a magnetic stirrer at room temperature for one hour. A pink-tan precipitate of tetrakis-(triethylphosphine)platinum(II)tetrachloroplatinate(II) forms. The mixture is heated on a steam bath for one hour. The pink salt dissolves, and a layer of pale yellow dichloro-bis(triethyl-phosphine)platinum forms on the liquid. The solid is filtered, washed with water, crushed in a mortar, and dried under 

The cis isomer of dichloro-bis(triethylphosphine)platinum(II) is a white crystalline solid with low solubility in benzene, ethanol, and acetone. It may be isomerized to an equilibrium mixture with the yellow trans isomer by heating to 180°C. or by exposure to sunlight in benzene solution.6 The trans isomer (m.p. 140-142°C.) is readily soluble in nonpolar organic solvents and can easily be separated from the equilibrium mixture by extraction with ether. 

It is desirable that pure as-dichloro complex be used in this preparation because the trans isomer is not reactive under these conditions and is difficult to separate from the hydride. 

---

The similarity between the hydrogen-deuterium exchange reaction of the aryldiimide- and arylhydrazine-platinum intermediates of this model and of N2ase is the best evidence for enzyme-bound diimide and hydrazine as intermediates (66). The correlation between the relative aflSnity of various ligands for N2ase and for some of the synthetic complexes of Fe, Co, Ni, Mo, Ru, Rh, Re, Os, and Ir that bind, but have not yet been shown to reduce, N2 (Table VIII) indicate that these metal complexes... 

---