Ferrocene-bridged Pd–NCN pincer complexes

The meta-diaminoaryl ferrocene Fe[η5-C5H4(NCNH)]2 [NCNH=1-C6H3(CH2NMe2)2-3,5] (3) can be synthesised by the reaction of Fe[η5-C5H4(ZnCl)]2 (1) with I–C6H3(CH2NMe2)2-3,5 (2) in a 1:2 molar ratio in the presence of catalytic amounts of [Pd(PPh3)2]. The two meta-dimaminoaryl NCNH pincer units in 3 can be used to assemble multimetallic complexes. Thus, 3 produces on reaction with tBuLi and (Me2S)2PdCl2 trimetallic Fe[η5-C5H4(NCN–4-PdCl)]2 {NCN=1-C6H2(CH2NMe2)2-3,5} (6) along with heterobimetallic Fe[η5-C5H4(NCNH)][η5-C5H4(NCN–4-PdCl)] (5). Complex 6 contains two bis-ortho-chelated pincer NCN–PdCl units, whereas 5 possesses one bis-ortho-chelated NCN pincer entity and one non-metallated NCNH moiety. Complex 6 is the first example in organometallic chemistry in which two bis-ortho-chelated diaminoaryl palladium units are bridged via the respective para C-atoms spanned by a redox-active ferrocenyl building block.