[Pt]2Pb Trinuclear Systems: Impact of the Anionic Platinum Fragment on the Lead Environment and Photoluminescence†

A comparison of the solid structures of three novel trinuclear sandwich Pt2Pb systems (NBu4)2[{Pt(C≡CTol)4}2Pb(OH2)2] 1, [{Pt(bzq)(C≡CPh)2}2Pb] 2, and (NBu4)[{Pt(bzq)(C≡CC6H4−CF3-4)2}2Pb(O2ClO2)] 4 (NBu4[3·(O2ClO2)]) with that of the previously reported (NBu4)2[{Pt(C6F5)4}2Pb] 5 showed that the local environment of PbII is highly sensitive to the nature of the anionic platinate(II) precursors. The photoluminescence (PL) studies of all 1−5 complexes revealed a dependence of PL on the structure type. Thus, complexes 1 and 5 exhibit metal centered emissions (1, 497 nm, 77 K; 5, 539 nm, ϕ = 0.43, 298 K) related to the linear (5) or bent (1 Pt−Pb−Pt 149.9°) trinuclear entities. However, in complexes 2−4, that have unprecedented PbII···η1(C≡CR) bonding interactions and very short Pt···Pb and Pt···Pt distances, the emissive state in solid state (77 K) is attributed to a 3MLM′CT [Pt(1)π(C≡CR)→Pt(2)/Pb(sp)π*(C≡CR)] state mixed with some ππ* excimeric character in neutral complexes 2 (R = Ph) and 3 (R = C6H4−CF3-4)...