Complexes of 2,3-bis(diphenylphosphino)propene with PtII, PdII and RuII: synthesis, characterisation and rearrangements to complexes of cis-1,2-bis(diphenylphosphino)propene

Abstract

Treatment of [PdCl2(PhCN)2] with 1 equivalent of 2,3-bis(diphenylphosphino)propene (2,3-dpppn) in CH2Cl2 gave [PdCl2(2,3-dpppn)] 1 together with some [PdCl2(1,2-dpppn)] 2 [1,2-dpppn = cis-1,2-bis(diphenylphosphino)propene]. Treatment of 1 with an excess of benzylamine did not lead to addition to the double bond, but resulted in complete isomerisation to 2, as monitored by 31P-{1H} and 1H NMR spectroscopy. Metathesis of 2 with NaI in acetone gave [PdI2(1,2-dpppn)] 3. Platinum(II) complexes [PtCl2(2,3-dpppn)] 4 and [PtCl2(1,2-dpppn)] 5 were prepared and characterised analogously. Treatment of 2 or 5 with an excess of MeLi gave [PdMe2(1,2-dpppn)] 6 and [PtMe2(1,2-dpppn)] 7 respectively, and treatment of 5 with hydrazine hydrate and an excess of HCCPh in ethanol gave [Pt(CCPh)2(1,2-dpppn)] 8. Treatment of [PdCl2(PhCN)2] with 2 equivalents of AgBF4 and 2 equivalents of 2,3-dpppn gave a mixture of at least four isomeric complexes, probably cis- and trans-[Pd(2,3-dpppn)2][BF4]2 and cis- and trans-[Pd(1,2-dpppn)2][BF4]2. On treatment with benzylamine, this mixture was converted into a ca. 1∶1 mixture of two isomers, which NMR spectroscopic evidence suggested were cis- and trans-[Pd(1,2-dpppn)2][BF4]2 9. Similarly, treatment of [PtCl2(PhCN)2] with AgBF4–2,3-dpppn gave cis- and trans-[Pt(1,2-dpppn)2][BF4]2 10. A crystal structure determination was performed on the trans isomer, isolated on recrystallisation of the mixture from MeCN–Et2O. Treatment of [RuCl2(PPh3)3] with 2 equivalents of 2,3-dpppn gave a very insoluble complex, trans-[RuCl2(dpppn)2] 11. Treatment of [RuCl(η5-C5H5)(PPh3)2] with 2,3-dpppn in refluxing benzene gave [RuCl(η5-C5H5)(1,2-dpppn)] 12. The formulation of 12 was confirmed by a single-crystal structure determination.