204860-41-3Relevant academic research and scientific papers
Unusually stable four-membered chelate rings in nickel(II), palladium(II), and platinum(II) complexes with the ligand 2,2-bis(diphenylphosphino)propane (2,2-dppp). Crystal and molecular structure of [PdI2(2,2-dppp)]·0.8CH2Cl2
Barkley, Jim,Ellis, Melanie,Higgins, Simon J.,McCart, Mark K.
, p. 1725 - 1731 (2008/10/08)
The ligand Ph2PC(CH3)2PPh2 (2,2-dppp) reacts with Ni(II) salts to give robust squareplanar chelate complexes [NiX2(2,2-dppp-P,?)] (X = Cl, 1; X = Br, 2) and the salt [Ni(2,2-dppp)2](ClO4)2 (3). The Pd(II) analogues [PdCl2(2,2-dppp)] (4), [PdI2(2,2-dppp)] (5), and [Pd(2,2-dppp)2](BF4)2 (6) have also been made. The crystal structure of 5 (obtained as 5·0.8CH2Cl2) has been determined by X-ray diffraction. The geminal C(CH3)2 group, when compared with related Ph2PCH2PPh2 (dppm) complexes, causes a small compression of the P-C-P chelate ring angle (to 91.3(3)° for 5). With [PtCl2(PhCN)2], 2,2-dppp affords [PtCl2-(2,2-dppp)] (7), which undergoes metathesis with NaI to give [PtI2(2,2-dppp)] (8), and [Pt-(2,2-dppp)2]Cl2 (9) was obtained by reaction of [PtCl2(PhCN)2] with 2 equiv of 2,2-dppp. Reactions were then attempted with 7 and 9, which are known to result in ring-opening reactions with the corresponding complexes of dppm, but in all cases, only 2,2-dppp chelate complexes could be isolated. Thus, treatment of 7 or 9 with excess MeLi gave exclusively [PtMe2(2,2-dppp)] (10) rather than cis,cis-[Pt2Me4(2,2-dppp)2]. Attempts to ring-open 10 with excess 2,2-dppp to give cis-[PtMe2(2,2-dppp- P)2] were unsuccessful. Treatment of 10 with 1 equiv of HCl or, better, treatment of [PtCl(Me)(1,5-cyclooctadiene)] with 2,2-dppp gave only mononuclear [PtCl(Me)(2,2-dppp)] (11) and no dimer of the type [MePt(a-2,2-dppp)2-(W-Cl)PtMe]Cl. Treatment of 7 with 2 equiv of NaCN in EtOH gave the chelate complex [Pt(CN)2(2,2-dppp)] (12) rather than trans,trans-[Pt2(CN)4(μ-2,2-dppp)2], and treatment of 7 with LiC≡CPh in thf or (better) H2NNH2·H2O/HC≡CPh in EtOH gave [Pt(C≡CPh)2(2,2-dppp)] (13), rather than trans trans-[Pt2(C≡CPh)4(μ-2,2-dppp)2]. Reaction of 7 with LiC≡CBun in thf likewise gave [Pt(C≡CBun)2(2,2-dppp)] (14) in low yield. The complexes were characterized by microanalyses (C, H, N and, in some cases, halide), infrared spectroscopy, 31P{1H} and 1H NMR spectroscopy, and fast atom bombardment mass spectrometry.
