Synthesis and reactions of 1,3-bis(diphenylphosphino-κP)-2-methylallyl complexes of platinum

Abstract

Treatment of [PtX₂(cod)](cod = cycloocta-1,5-diene) with the diphosphine (Ph₂PCH₂)₂CCH₂ gives the complexes [PtX₂{(Ph₂PCH₂)₂CCH₂}](X = Cl 1a or Me 1c). The dichloro complex can be converted to give the corresponding diiodo complex by metathesis and isomerised by base (NaOH–EtOH) to give [PtCl₂(Ph₂PCH₂CMeCHPPh₂)]2a. Treatment of complexes 1a, 1c or 2a with LiMe gives [PtMe₂{(Ph₂PCH)₂CMe}]^–3, containing a symmetrical anionic diphosphine, which reacts with MeOH to give [PtMe₂(Ph₂PCH₂CMeCHPPh₂)]2b. Treatment of 1a or 2a with equimolar amounts of Cl₂ produces the corresponding tetrachloroplatinum(IV) complexes 4 and 5, whilst treatment of 1c with MeI gives [PtMe₃I{(Ph₂PCH₂)₂CCH₂}]6; 4–6 are all unstable in solution with respect to reductive elimination reactions, 4 and 5 giving 1a and 2a respectively whilst 6 gives [PtMeI{Ph₂PCH₂)₂CCH₂}]. Treatment of 3 with electrophilic reagents such as MeI, PhCH₂Br, SiMe₃Cl or PPh₂Cl gives complexes [PtMe₂(Ph₂PCHRCMeCHPPh₂)](R = Me 7a, PhCH₂7b, SiMe₃7c or PPh₂7d). Treatment of the salt [Pt{(Ph₂PCH₂)₂CCH₂}₂]Cl₂9 with NaBH₄ gives the platinum(0) compound [Pt{(Ph₂PCH₂)₂CCH₂}₂]9, whilst with LiBu–Me₂NCH₂CH₂NMe₂ it gives the unusual platinum(II) complex [[graphic omitted]HPPh₂}₂]10, in which the Pt is bonded to two P and two C atoms and two of the phosphorus atoms are uncomplexed.