Gyroscope-like platinum(IV) complexes of the macrocyclic dibridgehead diphosphine P((CH2)14)3P

Abstract

Reactions of the platinum(II) dihalide complexes trans-Pt(X)2(P((CH2)14)3P)(X=Cl,trans-4;Br,trans-6) and excess X2 give the platinum(IV) tetrahalide complexes trans-Pt(X)4(P((CH2)14)3P)(trans-5,trans-7) in 84-95% yields. Their crystal structures are determined and the PtXn conformations and bond lengths compared to those of trans-4 and trans-6. In one instance, a reaction of trans-6 and MeMgBr (2.4 equiv) gave not the precedented productcis-Pt(Me)2(P((CH2)14)3P), but rather a small amount of the platinum(IV) tetramethyl complextrans-Pt(Me)4(P((CH2)14)3P) (trans-8), as verified crystallographically and by diagnostic NMR signals. Independent syntheses were attempted. Reactions of trans-5 or trans-7 with excesses of common sources of Me– were unsuccessful. Thus, the free dibridgehead diphosphine P((CH2)14)3P, which can incorporate PtX2 to give trans-4 or trans-6, was treated with the PtMe4 source Pt2Me8(µ-SMe2)2. However, this gave instead the isomeric species cis-8, and attempts to establish cis/trans equilibria were unsuccessful.