Chromium carbonyl complexes with aryl mono- and oligogermanes: Ability for haptotropic rearrangement

The intra- and inter molecular inter-ring η 6 ⇌ η 6 -haptotropic rearrangements (IRHR), occurring by involving interactions to Ge atoms in arylgermanes, were investigated theoretically and experimentally. The new methods for the synthesis of non-symmetrical polyaromatic Ge compounds were elaborated. Digermane Ph 3 GeGeMe 2 Cl ( 2 ) was obtained from Ph 3 GeGeMe 2 NMe 2 ( 1 ) under action of Me 3 SiCl. Aryl digermane Ph 3 GeGeMe 2 (η 6 -C 6 H 5 )Cr(CO) 3 ( 4 ) was obtained after lithiation of (η 6 -C 6 H 6 )Cr(CO) 3 ( 3 ) with subsequent interaction with 2 . It was established that thermally induced intra molecular IRHR in 4 is not observed experimentally; at similar reaction conditions in the presence of tetralin C 10 H 12 ( 7 ) the bimolecular inter molecular IRHR occurs giving (η 6 -C 10 H 12 )Cr(CO) 3 ( 8 ). DFT analysis of the intra molecular IRHRs for model germane ( p -Tol) 2 Ge(H)(η 6 -Tol- p )Cr(CO) 3 ( MC1 ) and digermane Ph 3 GeGeH 2 (η 6 -C 6 H 5 )Cr(CO) 3 ( MC2 ) indicates a plausible effect of 3c-2e (agostic) Ge–H···Cr interaction on success of such rearrangement. The theoretical activation barrier is determined to be in the range of 35–37 kcal/mol. The model compound (η 6 -C 6 H 3 (GeHPh 2 )Me 2 - p )Cr(CO) 3 ( 12 ) was obtained from (η 6 -C 6 H 4 Me 2 - p )Cr(CO) 3 ( 11 ). The decomposition of 12 was observed under conditions of thermally induced IRHR. Molecular structures of 8 , 11 and 12 in a crystal were investigated by XRD. • A range of chromium carbonyl complexes with molecular aryloligogermanes was studied. • Inter molecular inter-ring haptotropic rearrangement was found for aryloligogermanes. • Intra molecular inter-ring haptotropic rearrangement in germanes was studied by DFT. • The presence of 3c-2e bonding is dramatic for IRHR in mono- and -digermanes.