Monomeric C,N‐Chelated Germanium Hydrides in N–C Bond Cleavage

Abstract

The synthesis of the monomeric organogermanium(II) hydrides [(LGeH)M(CO)5] [M = Cr (4), W (5)] by utilizing the C,N‐chelating ligand L {L = [2‐(CH2NEt2)‐4,6‐tBu2C6H2]–} was explored. Stabilization of the GeH terminal bond in 4 and 5 was accompanied by a combination of electronic and steric protection of ligand L. The reactivity of the GeH terminal bond was also investigated, and attempts to reduce the polar C≡N bond in tBuNC provided an unexpected N–C bond‐cleavage reaction yielding organogermanium(II) cyanides [(LGeCN)M(CO)5] [M = Cr (6), W (7)] instead of a hydrogermylation reaction.

Reactivity of Monomeric N→Ge Coordinated Germanium(II) Hydrides

“…The WBI Ge‐TM for 3–6 were predicted to be in the range of 0.74–0.79 showing a significant covalent character of the Ge→TM interactions (cf. 0.76 and 0.79 for 1 and 2 , respectively) . The WBIs of the Ge–H bond reach higher values of 0.86 and 0.87 for 9 and 10 , respectively.…”

“…The starting compounds {(LGeH)M(CO) 5 } (M = Cr ( 1 ), W ( 2 )) were prepared according to the literature procedure . Subsequent treatment with 3,5‐di‐ tert ‐butyl‐ ortho ‐quinone and 3,4,5,6‐tetra‐chloro‐ ortho ‐quinone yielded compounds {[(L H )Ge(κ 2 ‐O 2 ‐3,5‐ t Bu 2 C 6 H 2 )]M(CO) 5 } (M = Cr ( 3 ), W ( 4 )) and {[(L H )Ge(κ 2 ‐O 2 ‐3,4,5,6‐Cl 4 C 6 )]M(CO) 5 } (M = Cr ( 5 ), W ( 6 )) (Scheme ) as the products of the hydrogermylation of a C=O bond.…”

“…Particular focus was put on describing the nature of the Ge–O bond both in TM coordinated 1,3,2‐benzodioxagermylenolato anions ( 3–6 ) and 1,3,2‐benzodioxagermoles ( 9 and 10 ). The geometries of all compounds were fully optimized at the M06/cc‐pVDZ(‐PP) level, which was chosen on the basis of our previous studies on the starting compounds 1 and 2 . The agreement between the measured and calculated structural parameters is very good (Table , Figures S2, S3 in SI).…”

“…These studies laid the foundation of the field of the monomeric germanium hydrides and clearly demonstrated that these systems may be considered as an alternative for the transition metal‐based catalysts in the reduction processes. We have recently synthesized monomeric organogermanium(II) hydrides {(LGeH)M(CO) 5 } (M = Cr ( 1 ), W ( 2 ), L = [2‐(CH 2 NEt 2 )‐4,6‐ t Bu 2 ‐C 6 H 2 ] – ), where the Ge H terminal bond was protected by the combination of the electronic and steric effects of the ligand L (Figure C) . However, attempts to reduce C≡N bond in t BuNC provided an unexpected N–C bond cleavage reaction .…”

“…We have recently synthesized monomeric organogermanium(II) hydrides {(LGeH)M(CO) 5 } (M = Cr ( 1 ), W ( 2 ), L = [2‐(CH 2 NEt 2 )‐4,6‐ t Bu 2 ‐C 6 H 2 ] – ), where the Ge H terminal bond was protected by the combination of the electronic and steric effects of the ligand L (Figure C) . However, attempts to reduce C≡N bond in t BuNC provided an unexpected N–C bond cleavage reaction . Here we report further investigations of 1 and 2 in the hydrogermylation of activated ketones ( ortho ‐quinones) and a terminal alkyne (HC≡CCO 2 Me).…”