Preparation and phosphorus-31 and selenium-77 NMR spectra of platinum and palladium complexes of a P2N4Se2 ring
The reaction of 1,5-Ph4P2N4Se2 with Pt(PPh&(CH2=CH2) or Pd(PPh3)l in toluene at 0 OC produces the 92- Se,Se'-bonded complexes M(PPh3)2( 1,5-Ph4P~N4Sez) (2a, M = Pt; 2b, M = Pd) characterized by their 3IP and "Se NMR spectra. Simulation of the 77Se NMR spectra gave detailed coupling information for 2a and 2b. Heating 2a or 2b in boiling toluene produces the corresponding ~2-Se,N-p,r11-Se'-bonded dimers [M(PPh3)( 1,5-Ph&N4- Sez)12 (3a, M = Pt; 3b, M = Pd). Variable-temperature 31P NMR spectra of 3a reveal a fluxional process which is proposed to involve a [ 1,3]-metallotropic shift. The reaction of 1,5-Ph4P2N4Se2 with [PtC12(PEt3)]2 in CHzCl2 produces the #-N-bonded adducts [PtClZ(PEt3)],(1,5-Ph4PzN4Se2) (4a, n = 1; 5, n = 2). The two PtC12(PEt3) groups in 5 are attached to distal nitrogen atoms of the P2N4Se2 ring, which retains a folded structure with d(Se-Se) = 2.594 A. Treatment of 4a with Pt(PPh3)2(CHyCH2) produces the pZ,s3-Se,Se',N-bonded complex Pt(PPh3)z( 1,s- PhP2Nfie2) [PtC12(PEt3)] identified by "PNMR spectroscopy. Reaction of [Li[Ph&NBe2Ph](THF)]z, generated from the combination of 1,5-Ph4P~N4Sez and phenyllithium in THF, with cis-PtCl~(PEt3)~ yields the +Se-bonded complex trans-PtCl(PEt3)z(PhdP2N&e2Ph)(7a). Variable temperature 31P NMR spectra of 7a reveal a two-site exchange process involving the two PEt3 ligands, which is proposed to occur via rotation about the PtSe bond. Line-fitting analysis yielded the thermodynamic parameters for this process.
Chivers, T., Hilts, R. W., Doxsee, D. D., Parvez, M. (1993). Preparation and nuclear magnetic resonance characterization of N-bonded complexes of platinum(II) with phosphorus-nitrogen rings containing three-coordinate chalcogens: X-ray structure of [PtCl2(PEt3)]2(Ph4P2N4Se2Et2). Canadian Journal of Chemistry, 71(11), 1821–1827. https://doi.org/10.1139/v93-227
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