σ-vs π-bonding in manganese(II) allyl complexes

Laura K. Engerer, Christin N. Carlson, Timothy P. Hanusa, William W. Brennessel, Victor G. Young

Research output: Contribution to journalArticle

8 Scopus citations

Abstract

Reaction of two equivalents of K[1,3-(SiMe 3) 2C 3H 3] (= K[A′]) with MnCl 2 in THF produces the allyl complex A′ 2Mn(thf) 2; if the reaction is conducted in ether, the solvent-free heterometallic manganate species K 2MnA′ 4 is isolated instead. With the related allyl K[1,1′,3-(SiMe 3) 3C 3H 2] (= K[A″]), reaction with MnCl 2 in THF/TMEDA produces the corresponding adduct A″ 2Mn(tmeda). In the solid state, both A′ 2Mn(thf) 2 and A″ 2Mn(tmeda) are monomeric complexes with σ-bonded allyl ligands (Mn-C = 2.174(2) and 2.189(2) Å, respectively). In contrast, K 2MnA′ 4 is a two-dimensional coordination polymer, in which two of the allyl ligands on the Mn cation are σ-bonded (Mn-C = 2.197(6), 2.232(7) Å) and the third is π-bonded (Mn-C = 2.342(7)-2.477(7) Å). Both σ-allyls are π-coordinated to potassium cations, promoting the polymer in two directions; the π-allyl ligand is terminal. Density functional theory (DFT) calculations indicate that isolated high-spin (C 3R 2H 3) 2Mn (R = H, SiMe 3) complexes would possess π-bound ligands. A mixed hapticity (π-allyl)(σ-allyl) MnE structure would result with the addition of either a neutral ligand (e.g., THF, MeCN) or one that is charged (Cl, H). Both allyl ligands in a bis(allyl)manganese complex are expected to adopt a σ-bonded mode if two THF ligands are added, as is experimentally observed in A′ 2Mn(thf) 2. The geometry of allyl-Mn(II) bonding is readily modified; DFT results predict that [(C 3H 5)Mn] + and (C 3H 5)MnCl should be σ-bonded, but the allyl in (C 3H 5)MnH is found to exhibit a symmetrical π-bonded arrangement. Some of this behavior is reminiscent of that found in bis(allyl)magnesium chemistry.

Original languageEnglish (US)
Pages (from-to)6131-6138
Number of pages8
JournalOrganometallics
Volume31
Issue number17
DOIs
StatePublished - Sep 10 2012

Fingerprint Dive into the research topics of 'σ-vs π-bonding in manganese(II) allyl complexes'. Together they form a unique fingerprint.

Cite this