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.