Cyclic Ruthenium(II)−Halocarbon Complexes Derived from Ru(II)‐Induced Cyclization of Homopropargylic Halopyridines: Mechanism, Bonding and Reactivity

The activation of various homopropargylic pyridines by cis‐[RuII/OsII(dppm)2Cl2] (dppm=1,1‐bis(diphenylphosphino)methane) has previously been shown to generate a diverse array of metallacycles and metalated heterocyclic complexes. However, a minor structural modification of introducing a halide onto the pyridyl group of the alkyne substrate resulted in the formation of unprecedented Ru(II)/Os(II)−haloquinolizine complexes. These complexes display (1) κ2(X,C)‐haloquinolizine chelates arising from the cycloisomerization of HC≡CC(OH)(CH2(6‐X‐2‐py))(Ph) on [RuII/OsII(dppm)2]2+ moieties via a vinylidene pathway, (2) five‐membered Ru/Os−X−C−N−C rings (X=F, Cl, Br) ortho‐ and peri‐fused to quinolizinium skeletons, and (3) uncommon M−X−R bonding interactions that are atypical in coordination complexes. Despite being divalent and integrated into a five‐membered Ru−X−C−N−C ring system, the X atoms in the Ru(II) complexes are susceptible to substitution by O in the presence of −OH, resulting in the formation of quinolizinium‐fused ruthenaoxazole complexes. Overall, this work highlights the importance of considering metal−halocarbon bonding interactions in catalytic or coordination designs. Cyclic metal−haloquinolizine complexes derived from the cyclization of homopropargylic halopyridines on Ru(II) and Os(II) centers display unusual metal−halocarbon bonding interactions and reactivity. Unprecedented κ2(X,C)‐haloquinolizinium (X=F, Cl, and Br) ligated Ru(II) complexes were synthesized via Ru(II)‐promoted rearrangement and cyclization of homopropargylic halopyridines. These cyclic Ru(II)−halocarbon complexes, featuring rare M−X−R bonding interactions, undergo nucleophilic aromatic substitution to yield quinolizinium‐fused metallaoxazole complex. This work highlights the importance of metal−halocarbon bonding interactions in catalytic and coordination design.