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

Ether-functionalised aminophosphines Ph2PNHR [R=CH2CH2OCH3 L-1, CH2CH(OCH3)(2) L-2, CH2CH2CH2OCH3 L-3 or C6H4OCH3-2 L-4] were prepared from the reaction of Ph2PCl and the amine RNH2 in the presence of triethylamine. Reaction of L1-4 with [MCl2(cod)] (M=Pd or Pt) or [PtBr2(cod)] gave the complexes [MCl2L2] (1, M=Pd, L=L-1; 2, M=Pd, L=L-2; 3, M=Pd, L=L-3; 4, M=Pd, L=L-4; 5, M=Pt, L=L-1; 6, M=Pt, L=L-2; 7, M=Pt, L=L-4) and [PtBr2(L-1)(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(L-1)(2)][BF4](2) 9 and cis-[PtL2][BF4](2) (L=L-1; 10 or L-4 11) containing bidentate P,O-co-ordinated ligands whereas reaction of 1 with one equivalent of AgBF4 gave exclusively [{Pd(mu-Cl)(L-1)(2)}(2)][BF4](2) 12, containing only unidentate aminophosphine ligands. Reaction of 5 and 8 with NaNO2 led to formation of cis-[PtX(NO2)(L-1)(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 L1-4 with [{M(dmba)(mu-Cl)}(2)] (M=Pd or Pt; Hdmba=N,N-dimethylbenzylamine) gave [M(dmba)ClL] (16, M=Pd, L=L-1; 17, M=Pd, L=L-2; 18, M=Pd, L=L-3; 19, M=Pd, L=L-4; 20, M=Pt, L=L-1; 21, M=Pt, L=L-2; 22, M=Pt, L=L-4). 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=L-1; 24, M=Pt, L=L-1; 25, M=Pt, L=L-4). 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)(mu-PPh2O)}(2)] 30 which was characterised by X-ray crystallography.