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(CH 2 ) 2 NC 6 H 4 (4‐NMe 2 )] 2 , P−P(NMe 2 ) , from the reaction of [P(CH 2 OH) 4 ]Cl and H 2 NC 6 H 4 (4‐NMe 2 ) in methanol is described. Surprisingly, P−P(NMe 2 ) displays excellent air/solution stability (towards H 2 O, CH 3 OH) and can also function efficiently as a bridging ligand. Hence reaction of P−P(NMe 2 ) with [Pd(μ−Cl)(η 3 ‐allyl)] 2 (η 3 ‐allyl=C 3 H 5 , C 4 H 7 ) or [Pd(μ−Cl)(κ 2 −C 9 H 12 N)] 2 affords the singly‐bridged complexes {Pd(Cl)(η 3 ‐allyl)} 2 {μ ‐P−P(NMe 2 ) } 1 a / 1 b and {Pd(Cl)(κ 2 −C 9 H 12 N)} 2 {μ ‐P−P(NMe 2 ) } 1 c whereas treatment with [MX 2 (η 4 ‐cod)] (M=Pd, Pt; X=Cl, Br, I, Me; η 4 ‐cod=cycloocta‐1,5‐diene) gave (MX 2 ) 2 {μ ‐P−P(NMe 2 ) } 2 2 a – e in high yields. Protonation of 2 a – d with HBF 4  ⋅ OEt 2 gave the corresponding dimethylammonium salts 3 a – d . Single crystal X‐ray studies have been undertaken on P−P(NMe 2 ) , 1 b , 2 a , 2 b  ⋅ 2CDCl 3 , 2 d , 2 e , 3 a ⋅  12CD 3 CN and 3 b ⋅  12CD 3 CN. The P−P bond lengths in free/coordinated P−P(NMe 2 ) remain similar across all compounds studied here and no M ⋅⋅⋅ M contacts were observed within the planar M 2 P 4 ring. In 3 a / 3 b the BF 4 − anion displays a unique secondary interaction with the inorganic six‐membered M 2 P 4 core.