Coordination-driven self-assembly, structures, and dynamic properties of diplatinum hexatriynediyl and butadiynediyl complexes in which the sp carbon chains are shielded by Sp(3) carbon chains: Towards endgroup-endgroup interactions

Sequential reactions of trans-(C6F5)(P-tol(3)P),Pt(C C)(3)SiEt3 (PtC6,SiEt3) with nBU(4)N(+) F- (THF/methanol), PtCl, KPF6/tBuOK, and CuCl give trans,trans-[(C6F5){(p-tol(3)P)(2)}Pt(C C)(3)Pt{(Pp-tol(3))(2)}(C6F5)] (PtC6Pt) in 95% yield on multigram scales. Reactions of PtC6Pt and Ar2P(CH2)mPAr(2) afford substitution products trans,trans-[(C6F5){(Ar2P(CH2)mPAr(2))}Pt(C C)(3)Pt- {(Ar2P(CH2)(m) PAr2)}(C6F5)] (PtC6Pt-m/Ar; m/Ar=8/p-tol, 78%; 10/Ph, 82%; 11/Ph, 69%; 12/Ph, 57%; 1.4/p-tol, 57%; 14/p-C6H4-tBu, 71%), in which the diphosphines span the square planar platinum endgroups. An analogous reaction with PEt, gives a tetrakis PEt3 complex Pt'C6Pt' (72%). The crystal structures Of PtC6Pt, Pt'C6Pt', PtC6Pt-10/Ph, PtC6Pt-11/Ph, and PtC6Pt-14/p-tol or solvates thereof are compared. In PtC6Pt, the endgroups can avoid van der Waals contact, and define angles of 0 degrees. In PtC6Pt-14/p-tol, the sp(3) chains twist around the sp chain in a chiral double-helical motif, with an endgroup/endgroup angle of 189 degrees. The sp(3) chains are too short to adopt analogous conformations in the other complexes, but laterally shield the sp chain. NMR spectroscopy shows that the helical enantiomers of PtC6Pt-14/p-tol rapidly interconvert in solution at low temperature. A crystal structure of PtC4Pt shows endgroups that are in van der Waals contact and define an angle of 41 degrees. Reactions with Ar2P-(CH2)(8)PAr2 give PtC4Pt-8/Ar (Ar=Ph, 53%; p-tol, 87%). Low-temperature NMR spectroscopy establish non-helical chiral conformations. Electrochemical oxidations of the diplatinum complexes are analyzed, the reversibilities of which decrease with increasing sp chain length.