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

Reactions of the platinum(II) dihalide complexes trans - Pt (X) 2 ( P ( ( CH 2 ) 14 ) 3 P ) (X = Cl , trans - 4 ; Br, trans - 6 ) and excess X 2 give the platinum(IV) tetrahalide complexes trans - Pt (X) 4 ( P ( ( CH 2 ) 14 ) 3 P ) ( t rans - 5 , t rans - 7 ) in 84-95% yields. Their crystal structures are determined and the PtX n 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 product cis - Pt ( Me ) 2 ( P ( ( CH 2 ) 14 ) 3 P ) , but rather a small amount of the platinum(IV) tetramethyl complex trans - Pt ( Me ) 4 ( P ( ( CH 2 ) 14 ) 3 P ) ( 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((CH 2 ) 14 ) 3 P, which can incorporate PtX 2 to give trans - 4 or trans - 6 , was treated with the PtMe 4 source Pt 2 Me 8 ( & mu;SMe 2 ) 2 . However, this gave instead the isomeric species cis - 8 , and attempts to establish cis / trans equilibria were unsuccessful.

Automated summary

Reactions of platinum(II) dihalide complexes with excesses of halogens result in the formation of platinum(IV) tetrahalide complexes. Crystal structures are determined and compared to previous complexes. Unexpectedly, one reaction generated a platinum(IV) tetramethyl complex instead. Further attempts at synthesis and establishing cis/trans equilibria were unsuccessful.