Binuclear platinum(II) complexes of 1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (P4) containing various bridging ligands as spacers between the P4 coordination units

Abstract

The former reported complex cis,meso-[Pt 2Cl 4P4] ( 1), where P4 is 1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane and which contains a chloro bridge only in solution, is fully characterized by an X-ray structure analysis: triclinic, P 1 ; a=8.395(2), b=11.675(2), c=13.717(3) Å, a=92.54(3), β=98.93(3), γ=109.28(3)°, R=0.059 for 2872 observed reflections ( F>6.0( F)). It shows an open-mode dimer with a Pt-Pt distance of 6.916(1) Å and a cis P4 configuration. A comparison with the X-ray structure of cis,rac-[Pt 2Cl 4P4] ( 2) is given. 2 also contains a chloro bridge only in solution, and these chloro bridges of 1 or 2 are replaced by hydride in rac-[Pt 2H 2(μ-H)P4](BF 4) ( 3), by pyridine in rac-[Pt 2Cl 2(μ-C 5H 5N)P4](BPh 4) 2 ( 4), by pyrazolate (Pz) in rac-[Pt 2Cl 2(μ-Pz)P4](BPh 4) ( 5), and by imidazolate (Im) in meso-[Pt 2Cl 2(μ-Im)P4](BPh 4) ( 6) and rac-[Pt 2Cl 2(μ- Im)P4](BPh 4) ( 7). In rac-[Pt 2Cl 2(μ-Cl)(μ-dppa)P4](BPh 4) ( 8), where dppa is 1,2-bis(diphenylphosphino)acetylene, an additional dppa bridge occurs. The complexes have been characterized by 195Pt{ 1H}, 31P{ 1H} and 1H NMR spectroscopy, elemental analyses and melting points. 3, 4, 5, 7 and 8 show that rac-P4 is flexible enough to allow the reaction with bridging ligands of very different sizes, whereas in the case of meso-P4 only the incorporation of imidazolate ( 6) is possible. This different behavior of meso- and rac-P4 is discussed with respect to the X-ray structures of 1 and 2, showing that completely different rotation isomers could be responsible for the observed reactivity. In meso-[Pt 2Cl(μ-Cl)(SnCl 3)P4](BPh 4) ( 9) the oxidative addition of SnCl 2 is only possible at a terminal PtCl bond.