SYNTHESIS AND P-31 NMR-STUDIES OF UNSYMMETRICAL CIS-DIPHOSPHINOALKENES AND THEIR COMPLEXES WITH NICKEL(II), PALLADIUM(II), AND PLATINUM(II)

Bis(phosphinoalkyne) complexes m-Cl2M(Ph2PC≡CR)2 (M = Pd, Pt; R = CF3, Ph, t-Bu) undergo a facile 1:1 reaction with secondary phosphines HPR'R˝ (R'R˝ = Ph, C2H4CN; R’ = Et, R˝ = Ph) to give stereospecifically the cis, 2-cis-phosphinoalk-1-ene complexes cis-Cl2M(Ph2PCH=C(R)PR'R˝). The uncoordinated diphosphinoalk-1-enes may be obtained by treatment of the corresponding Pt(II) complex with excess cyanide ion. Complexes cis-Cl2Ni(Ph2PCH==C(R)-PR'R˝) are obtained by reaction of cis-Ph2PCH=C(R)PR'R˝ with anhydrous nickel(II) chloride. The free diphosphinoalk-lenes and their Ni(II), Pd(II), and Pt(II) complexes are characterized by elemental analysis, mass spectrometry, IR, 1H NMR, and 31P NMR spectroscopy. Factors affecting 31P chemical shifts, coordination chemical shifts, and P-P couplings in these systems are discussed. © 1979, American Chemical Society. All rights reserved.