3544 TableI.
a
"r Data of ML3 and ML4 Complexes
Relative to external 85
H3P04.
For this dissociation process, the free energy of activation is -12 kcal/mol. The marked basicity of Pt[P(C2H&I3 is well delineated by its interaction with ethanol and water. The tris complex dissolves in both solvents to form the previously reported1Ot11 cationic hydride, HPt[P(CzH~)3]3+which was isolated as the hexafluorophosphate salt by addition of ammonium hexafluorophosphate to the aqueous reaction mixture. The reaction of the tris complex with water is reversible; the tris complex was recovered by simple evaporation of the water. We find some parallel to the reactivity of Pt[P(C2H5)3]1in the chemistry of Ni[P(C2Hj)&. l ? This complex, an off-white crystalline compound, was formed almost quantitatively by reaction of bis(l,5cyclooctadiene)nickel(0) with triethylphosphine. It dissolved in hydrocarbon solvents with ligand dissociation to give intensely purple solutions of Ni[P(C2Hj)3]3. This tris complex reacted smoothly with chlorobenzene and with benzonitrile at room temperature to give the [ P ( C ~ H l~3 ) ~ ] ? corresponding ~ ~ ~ M ~ - C ~ H ~ N ~ Xcompounds. Work is in progress to examine other aspects of reactive dl0 complexes of Ni, Pd, and Pt.
change is rapid in solutions of PtL4 at room temperature, and no Pt-P coupling is observed. Tris(triethylphosphine)platinum(O) is an extraordinarily strong nucleophile and undergoes a wide range of oxidative-addition reactions. For example, addition of benzonitrile to a refluxing toluene solution of the tris complex gives within 15 min a high yield of trans-C6HSPt(CN)[P(C,H,),l,. Under similar conditions, the carbon-chlorine bond in chlorobenzene is cleaved with concomitant formation of trans-CsHjPtC1[P(C2Hj)3]2. In contrast, the tris-triphenylphosphine complex does not react with benzonitrile or chlorobenzene under these conditions.* These comparisons (10) M. J. Church and M. J. Mays, J . Chem. SOC.A , 3074 (1968). demonstrate the qualitatively different reactivities of (11) The proton nmr data are in accord with the previously reported aryl- and alkylphosphine complexes of platinum(0). data.10 The noise-decoupled 31P spectrum of the ethanol solution of the tris complex was found to consist of a doublet (6 - 18 ppm, J p p = 19 Like the arylphosphine complexes, the alkyl analogs Hz, J p t p = 2476 Hz) and a triplet (6 - 14 ppm, J p t r = 2003 Hz) with react with alkyl and allyl halides. We found that trisrelative intensities of 2 : 1. (12) C. S. Cundy, Ph.D. Thesis 1969, University of Bristol. (triethylphosphine)platinum(O) reacts vigorously with oxidative additions of chlorobenzenes have been re~ (13) ] ~ ) Similar +, allyl chloride at 25" to give ( ( T - C ~ H ~ ) P ~ [ P ( C ~ H ~ ) ported for N ~ ( C ? H I ) [ P ( C ? H ~ ) ~ ] Z . ~ ~ which was isolated as the tetrafluoroborate salt. (14) D. H. Fahey, J . Amer. Chem. Soc., 92,402 (1970); J. E. Dobson, R. G. Miller, and J. P. Wiggens, ibid., 93,554(1971). Hydrogen adds readily to the alkylphosphine-plati(15) Contribution No. 1807. num complexes to give five-coordinate hydrides. For D. H. Gerlach, A. R. Kane, G. W. Parshall example, the tris(triethy1phosphine)platinum complex, J. P. Jesson, E. L. Muetterties' in hydrocarbon solution, absorbed hydrogen at 25" to Ceirfral Research Deparimeut15 give H2Pt[P(C2HS)3]3.This novel hydride is thermally E. I. du Pottr de Nemoirrs a i d Conipairy unstable and decomposes within several days on standExperimeiltal Sratioii, Wilniitrgtori, Delawure 19898 ing in hydrocarbon solvent at -40". In solution this Receiwd April 26. 1971 hydride shows a single platinum-hydrogen infrared stretching frequency at 1766 cm-'. The 220-MHz proton nmr spectrum of the hydride region at -50" consists of a quartet at T 23.37 (JPH= 18 Hz) with Structure of Bilobalide, a Rare tert-Butyl Containing lgSPt satellites (JPtH= 635 Hz). The spectrum is Sesquiterpenoid Related to the Cla-Ginkgolides temperature dependent. On warming, the platinumSir: hydrogen coupling is lost above --30", and the specExtraction of a sesquiterpene closely related to the trum consists of three broad resonances with chemical diterpenoid ginkgolides1s2from leaves of Ginkgo biloba shifts and platinum-hydrogen coupling constants sub("fossil tree") was first reported in 19673 and then in With stantially unchanged from those found at -50". 1969 (bil~balide).~Structure 1 deduced for this biloincreasing temperature, the three lines sharpen and remain sharp to 80". The ligand-proton-decoupled 31P balide shows that it is a uniqus trilactone sesquiterpene having a tert-Bu group, which so far has been ennmr spectrum at -60" consists of a triplet (JPH= 18 countered only in the ginkgolides (cf. 10). Hz) with lg5Ptsatellites (.Iptp = 3060 Hz). These spectral data are consistent with, but do not define, a trigonal-bipyramidal structure with the hydrogen nuclei (1) (a) K. Nakanishi, Pure Appl. Chem., 14, 89 (1967); (b) M. Maruyama, A. Terahara, Y . Itagaki, and I
