| Abstract
| - Deuterium variable-temperature T1 measurements have been performed for a series ofrhenium carbonyl clusters containing doubly and triply bridging deuterides, namely Re2(μ-D)2(CO)8 (1), Re3(μ-D)3(CO)12 (2), Re4(μ3-D)4(CO)12 (3), [NEt4][Re3(μ-D)4(CO)10] (4), [NEt4][Re3(μ-D)3(μ-Cl)(CO)10] (5), and [NEt4][Re3(μ-D)4(CO)9] (6). The deuterium quadrupolar couplingconstants (DQCC) of the deuteride ligands have been evaluated for compounds 1−5, whilethe fluxionality of 6 hampered such a determination. The experimental DQCC of compound3 (21.8 kHz) was, until now, the smallest found for organometallic compounds. Overall theDQCC values span a 4-fold range, and their fine-tuning depends on the bridging mode ofthe deuteride ligands (μ3 vs μ), the local unsaturation degree of the Re atoms bridged by thedeuteride, and the presence of other bridging ligands. The experimental DQCC's of rheniumderivatives and those of bridging deuterides in Cr, W, and Os clusters linearly correlatewith the respective metal−hydrogen stretching frequencies.
- The deuterium quadrupolar coupling constant (DQCC) of bridging deuterides cannot be taken as indicative of ionic character of the M−H bond (as suggested for terminal hydrides), since its value is affected by other molecular features, such as the electronic unsaturation and the bridging mode (μ3 vs μ) of the deuteride ligands. A linear correlation between the DQCC values and the M−H−M stretching frequencies is observed.
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