361440-52-0Relevant articles and documents
The origin of hindered rotation around the Pt-N bond in platinum amides
Albeniz,Calle,Espinet,Gomez
, p. 4211 - 4216 (2008/10/08)
Several platinum amides of formula trans-[PtCl(NHAr)(PEt3)2] (Ar = 3-FC6H4, 2; 4-FC6H4, 3; 4-ClC6H4, 4; 4-IC6H4, 5; 4-Cl,3-NO2-C6H3, 6) have been synthesized by reaction of [PtHCl(PEt3)2] with aryl azides. All the complexes feature planar arylamido moieties and hindered rotation around the N-aryl and Pt-N bonds have been detected and separately studied. The X-ray crystal structures of complexes 5 and 6 have been determined. Complex 5 crystallizes in the orthorhombic space group Pnma, with a = 23.806(4) A, b = 15.099(2) A, c = 6.7593(10) A α = β = γ = 90°, and Z = 4. Compound 6 shows an N-H·middot;middot;O(NO) hydrogen bond and it crystallizes in the monoclinic space group P2(1)/n, with a; = 12.215(3) A, b = 8.078(2) A, c = 13.052(4) A, α = γ = 90°, β = 90;057(6)°, and Z = 2. Except for Ar = 4-Cl,3-NO2-C6H3, the activation energies obtained for the complexes indicate that both dynamic processes occur simultaneously with a common barrier which originates in the multiple bond character of the N-aryl bond due to a strong π-donor behavior of the N atom in the N-aryl bond. The rotation about the Pt-N bond is unfavorable because of steric congestion with the planar amide, which can be overcome only when the aromatic ring can rotate. For the complex trans-[PtCl{NH(4-Cl,3-NO2-C6H3)} (PEt3)2] the barrier to rotation is mostly due to hydrogen bond interaction between the NO2 ortho substituent and the amide H atom.
