Dinuclear palladium(II) and platinum(II) complexes of a readily accessible bicyclic diphosphane

The one-step synthesis (33 % isolated yield) of a novel bicyclic diphosphane, [P(CH2)2NC6H4(4-NMe2)]2, P−P(NMe2), from the reaction of [P(CH2OH)4]Cl and H2NC6H4(4-NMe2) in methanol is described. Surprisingly, P−P(NMe2) displays excellent air/solution stability (towards H2O, CH3OH) and can also function efficiently as a bridging ligand. Hence reaction of P−P(NMe2) with [Pd(μ−Cl)(η3-allyl)]2 (η3-allyl=C3H5, C4H7) or [Pd(μ−Cl)(κ2−C9H12N)]2 affords the singly-bridged complexes {Pd(Cl)(η3-allyl)}2 {μ-P−P(NMe2)} 1 a/1 b and {Pd(Cl)(κ2−C9H12N)}2{μ-P−P(NMe2)} 1 c whereas treatment with [MX2(η4-cod)] (M=Pd, Pt; X=Cl, Br, I, Me; η4-cod=cycloocta-1,5-diene) gave (MX2)2{μ-P−P(NMe2)}2 2 a–e in high yields. Protonation of 2 a–d with HBF4 ⋅ OEt2 gave the corresponding dimethylammonium salts 3 a–d. Single crystal X-ray studies have been undertaken on P−P(NMe2), 1 b, 2 a, 2 b ⋅ 2CDCl3, 2 d, 2 e, 3 a ⋅ 12CD3CN and 3 b ⋅ 12CD3CN. The P−P bond lengths in free/coordinated P−P(NMe2) remain similar across all compounds studied here and no M ⋅⋅⋅ M contacts were observed within the planar M2P4 ring. In 3 a/3 b the BF4− anion displays a unique secondary interaction with the inorganic six-membered M2P4 core.