Darstellung, Struktur und Eigenschaften von harnstoffverbrückten cyclischen Phosphoniumsalzen mit Phosphor‐Phosphor‐, Phosphor‐Arsen‐, Phosphor‐Antimon‐und Phosphor‐Zinn‐Bindung

Preparation, Structure, and Properties of Urea‐Bridged Cyclic Phosphonium Salts with Phosphorus‐Phosphorus, Phosphorus‐Arsenic, Phosphorus‐Antimony, and Phosphorus‐Tin Bonds N ‐[ tert 1‐Butyl(phenyl)phosphanyl]‐ N,N ′‐dimethyl‐ N ′‐(trimethylsilyl)urea ( 2 ) reacts with organodichlorophosphanes with cleavage of the Si – N bond to form the cyclic phosphanylphosphonium chlorides 3a – i containing the grouping [λ 3 P – λ 4 P + ]Cl – . Evidence was obtained for the existence of an equilibrium in solution between the ionic phosphonium structure 3 and a covalent form. The position of the equilibrium is determined by the nature of the group R at λ 3 P. Reaction of the phosphonium salts 3a – i with Na[BPh 4 ] furnished the phosphonium tetraphenylborates 4a – i containing the grouping [λ 3 P – λ 4 P + ][BPh 4 ] – . In the reaction of 2 with organodichloroarsanes the arsanyl‐phosphonium chlorides 5a and 5b with the grouping [λ 3 As – λ 4 P + ] were formed. By treatment of 5a and 5b with Na[BPh 4 ] the corresponding tetraphenylborates 6a and 6b were produced. Further cyclic phosphonium salts containing a heteroatom‐phosphorus bond with the complex chloro anions [AsCl 4 ] – , [SbCl 4 ] – , and [Me 2 SnCl 4 ] 2– were formed in the reaction of 2 with the chlorides AsCl 3 , SbCl 3 and Me 2 SnCl 2 . – The structures of 4h and 6a were confirmed by low‐temperature X‐ray crystal structure determination; the P – P bond length of 4h is 222.3(2) pm, the P – As bond length of 6a 234.6, 234.1(2) pm in two independent cations.