Chloro- p-fluorophenyldiimide -bis triethylphosphine platinum II Tetrafluoroborate

frans-CHLORO- (p-FLUOROPHENYLDIIMIDE) -BIS(TRIETHYLPHOSPHINE)PLATINUM(II) TETRAFLUOROBORATE 

In this preparation it is desirable to use freshly prepared diazonium salt and thoroughly purified platinum hydride. The 

A solution of 1.92 ml. of freshly distilled p-fluoroaniline (b.p. 187-189°C.) and 10 ml. of 48% tetrafluoroboric acid is stirred at 0°C. in a 50-ml. beaker while a solution of 1.68 g. of sodium nitrite and 3 ml. of water is added over a period of 15 minutes. p-Fluorobenzenediazonium tetrafluoroborate precipitates as white crystals. The mixture is filtered, and the crystals are washed with 3 ml. of cold concentrated fluoroboric acid, 3 ml. of cold ethanol, and 30 ml. of ether. Yield is 3.8 g. vn-n = 2274 cm.-1. 

A suspension of 2.10 g. of the freshly prepared diazonium salt and 50 ml. of ethanol is stirred in a 200-ml. Erlenmeyer flask and cooled to 0°C. while a solution of 4.7 g. of fcww-chloro-hydrido-bis(triethylphosphine) platinum (II) in 25 ml. of ethanol is added over a period of 10 minutes. The mixture becomes yellow immediately and is stirred at 0°C. for 10 minutes. At this point, yellow crystals of the aryldiimide complex usually separate. The mixture is filtered, and the filtrate is cooled to —78°C. to give a second crop of the diimide complex. Occasionally crystallization does not occur immediately. In this situation, the mixture is cooled to — 78°C. directly, and the crystals which form are filtered and washed with ether. In either case the total yield is about 4.9-5.4 g. (72-78%). (The checkers reported an 87% yield with a melting point of 105-108°C. with decomposition.) The purity of this material is adequate for most preparatory purposes. Further purification may be accomplished by conversion to the arylazoplatinum compound (Sec. D) followed by reprotonation with concentrated aqueous fluoroboric acid, HBF4. 

The p-fluorophenyldiimide complex is moderately stable at room temperature when pure but is best stored at — 78°C. It melts with decomposition to a red liquid at 105-106°C. The NH proton is moderately acidic (pKa 4.5) and exchanges rapidly with D20 and D2.4 The complex is readily soluble in alcohols, ketones, ethers, and chloroform and even has some solubility in benzene. 

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A solution of 1.38 g. of irons-chloro-(p-fluorophenyldiimide)-bis(triethylphosphine)platinum(II) tetrafluoroborate in 10 ml. of methanol is stirred and cooled to 0°C. in a 50-ml. Erlenmeyer flask while a solution of 0.27 g. of sodium acetate trihydrate in 5 ml. of 50% aqueous methanol is added over a period of 1 minute. The mixture becomes red immediately, and a violet precipitate forms. The mixture is stirred for 5 minutes at 0°C. and then is filtered promptly. After drying under vacuum to remove methanol, recrystallization from hexane (about 30 ml.) gives rose-colored needles (m.p. 116-117°C.) of trans-chloro-... 

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