Ether functionalised aminophosphines: synthesis and co-ordination chemistry of palladium(II) and platinum(II) complexes

Abstract

Ether-functionalised aminophosphines Ph₂PNHR [R = CH₂CH₂OCH₃L¹, CH₂CH(OCH₃)₂L², CH₂CH₂CH₂OCH₃L³ or C₆H₄OCH₃-2 L⁴] were prepared from the reaction of Ph₂PCl and the amine RNH₂ in the presence of triethylamine. Reaction of L^1–4 with [MCl₂(cod)] (M = Pd or Pt) or [PtBr₂(cod)] gave the complexes [MCl₂L₂] (1, M = Pd, L = L¹; 2, M = Pd, L = L²; 3, M = Pd, L = L³; 4, M = Pd, L = L⁴; 5, M = Pt, L = L¹; 6, M = Pt, L = L²; 7, M = Pt, L = L⁴) and [PtBr₂(L¹)₂] 8. X-Ray crystallographic analyses of complexes 1 and 2 indicated the presence of bifurcated hydrogen bonds between the NH protons and both the chloride ligands and the ether oxygen atoms. Reaction of 1, 5 and 7 with two equivalents of AgBF₄ led to formation of trans-[Pd(L¹)₂][BF₄]₂9 and cis-[PtL₂][BF₄]₂ (L = L¹; 10 or L⁴11) containing bidentate P,O-co-ordinated ligands whereas reaction of 1 with one equivalent of AgBF₄ gave exclusively [{Pd(μ-Cl)(L¹)₂}₂][BF₄]₂12, containing only unidentate aminophosphine ligands. Reaction of 5 and 8 with NaNO₂ led to formation of cis-[PtX(NO₂)(L¹)₂] (X = Cl 13 or Br 14). Shielding of one of the NH protons with respect to 5 and 8 suggested loss of N–H⋯X hydrogen bonding and this was confirmed by an X-ray crystallographic analysis of 14. Reaction of L^1–4 with [{M(dmba)(μ-Cl)}₂] (M = Pd or Pt; Hdmba = N,N-dimethylbenzylamine) gave [M(dmba)ClL] (16, M = Pd, L = L¹; 17, M = Pd, L = L²; 18, M = Pd, L = L³; 19, M = Pd, L = L⁴; 20, M = Pt, L = L¹; 21, M = Pt, L = L²; 22, M = Pt, L = L⁴). The crystal structure of 16 reveals a similar bifurcated hydrogen bond to those observed in 1 and 2, whereas the structure of 18 shows the N–H⋯Cl interaction to be present but the N–H⋯O interaction absent. Reaction of 16, 20 and 22 with AgBF₄ gave the bidentate P,O-co-ordinated complexes [M(dmba)L]BF₄ (23, M = Pd, L = L¹; 24, M = Pt, L = L¹; 25, M = Pt, L = L⁴). Displacement of the co-ordinated ether oxygen was achieved by reaction of 24 and 25 with CO and of 25 with xylyl isocyanide and acetonitrile. Attempts to recrystallise 24 led instead to isolation of the dinuclear species [{Pt(dmba)(μ-PPh₂O)}₂] 30 which was characterised by X-ray crystallography.