Unsymmetrical organodiplatinum(II) and organodiplatinum(IV) complexes containing bis(diphenylphosphino)methane as bridging ligand: general approaches for synthesis and characterization by multinuclear NMR studies

摘要

Reaction of cis-[PtR_2(Sme_2)_2] (R = Ph or p-MeC_6H_4) with [Pt{(CH_2)_4} (dppm = Ph_2PCH_2PPh_2) gave the unsymmetrical cis, cis-diaryl-dialkyl diplatinum(II) complexes cis,cis-[R_2Pt(#mu#-dppm)PtMe-_2], 1a and 2a, or cis,cis-[R_2Pt(#mu#-SMe_2)(#mu#-dppm)Pt{(CH_2)_4}], 1b and 2b, respectively. complexes 1a and 2a were also prepared by reaction of [PtMe_4(#mu#-SMe_2)_2] with [PtR_2(dppm)]. The unsymmetrical complex cis,cis-[Me_2Pt(#mu#-SMe_2)(#mu#-dppm)Pt{(CH_2)}_4] (3b) was prepared by the same method using [Pt{(CH_2) _4}(dppm)] and [Pt_2Me_4(#mu#-SMe_2)_2]. The symmetrical complex cis,cis[Me_2Pt(#mu#-SMe_2)(#mu#-dppm)PtMe_2] (3a) was prepared by reaction of [Pt_2Me_4(#mu#-SMe_2)_2] with either one equivalent of dppm or [PtMe_2(dppm)]. The complexes 2 and 3 reacted with MeI to give the unsymmetrical diplatinum(IV) complexes fac,fac-[R_2MePt(#mu#-I)_2(#mu#-dppm)PtMeR'_2] (4a, R = R' = Me; 4b, R = Me, R'-2 = (CH_2)_4; 5a, R = p-MeC_6H_4, R' = Me; 5b, R = p-MeC_6H_4. R'_2 = (CH_2)_4). The reactions probably occurred by a S_N2-type mechanism and the entering Me groups stereoselectively remained in the equatorial positions (Pt-P taken as axial direction), unless for fac-PtMe_3 moiety that Me scrambling was taken place. Reaction of cis,cis-dialkyl-dialkyl diplatinum(II) complexes 3 with one equivalent of dppm gave bis(dppm-bridged) complexes cis,cis-[R_2Pt (#mu#-dppm)_2PtR'_2] (6a, R = R' = Me; 6b, R = Me, R'_2 = (CH_2)_4). The complexes were fully characterized using multinuclear (~1H-, ~(13)C{~1H}-, ~(31)P{~1H}-, ~(195)Pt{~1H}-) NMR spectroscopy.