MULTIMODE COORDINATION CHEMISTRY OF [R2P(X)CHNP(Y)R'2](2-N)- LIGANDS (X, Y = O, S, SE N = 1, 2) - SYNTHESIS AND P-31 NMR-SPECTROSCOPY OF PLATINUM COMPLEXES

Reactions of the bis(phosphine chalcogenides) CH2{P(X)R2}{P(Y)R'2} (X, Y = O, S, Se) and their derived anions [CH{P-(X)R2}{P(Y)R'2}]- with chloroplatinum complexes PtCl4(2-), [Pt2Cl4(PEt3)2], or [Pt2Cl2(PEt3)4]2+ result in a wide variety of coordination complexes. For example, when R = R' = Ph and X = Y = S, the following are all accessible in high yield: [PtCl(PEt3){CH2(P(S)Ph2)2-S,S}]+, [PtCl(PEt3){CH(P(S)Ph2)2-C,S}], [PtCl(PEt3){CH(P(S)Ph2)2-S,S}], [Pt(PEt3)2{CH2(P(S)-Ph2)2)-S,S}]2+, [Pt(PEt3)2{CH(P(S)Ph2)2-C,S}]+, [PtCl2{CH2(P(S)Ph2)2-S,S}], [Pt{CH2(P(S)Ph2)2-S,S}2]2+, and [Pt{CH(P-(S)R2)2-C,S}2]. A more limited range of complexes is also reported for X = Y = O, X = Y = Se, and X = O, Y = S. In general, the ligands exhibit at least five different coordination modes: (i) Bidentate X,Y coordination of neutral ligands; (ii) bidentate X,Y coordination of the anionic ligands; (iii) bidentate C,X coordination of the anions in a strained four-membered ring; (iv) monodentate C coordination of the anions; (v) complex C,S bridging mode involving a dianionic ligand and two metal centers. Interconversion reactions and characteristic P-31 NMR spectroscopy are described for all of the coordination modes, including dynamic NMR studies of the C,X modes. These last modes all exhibit some degree of fluxional behavior, involving an exchange of coordinated and noncoordinated P = X groups in essentially a classic "bimolecular" substitution reaction, except that the incoming ligand is actually part of one of the existing ligands.