| Abstract
| - The nucleophilic molybdenum nitride (Et2NCS2)3MoN (1) reacts with the electrophilic osmium nitride TpOsNCl2 (2) predominantly by nitride coupling to give N2 and the heterobimetallic μ-nitrido complex TpOsCl2(μ-N)Mo(S2CNEt2)3 (3). Mixed-metal coupling takes place in preference to osmium−osmium coupling despite the thermodynamic advantage enjoyed by the latter, suggesting that nitride coupling (and by implication, its microscopic reverse, dinitrogen cleavage) can be accelerated by enhancing its polar character.
- The nucleophilic molybdenum nitride (Et2NCS2)3MoN (1) reacts with the electrophilic osmium nitride complex TpOsNCl2(2, Tp = hydrotris(1-pyrazolyl)borate) to produce molecular nitrogen. Reaction of 1 at the nitride is accompaniedby a substantial amount of reaction at a sulfur atom of the dithiocarbamate ligand, forming the osmium thionitrosylcomplex TpOs(NS)Cl2 (4). Labeling experiments establish that the N2 produced comes specifically (>96%) frommixed-metal (molybdenum−osmium) coupling. The major transition-metal-containing product of the reaction is theμ-nitrido complex TpOsCl2(μ-N)Mo(S2CNEt2)3 (3), where the bridging nitride derives primarily (82%) from the osmiumnitride 2. The μ-nitrido complex 3 has been characterized crystallographically, and shows a nitride bridge that isvery asymmetric (Mo−N = 1.721(3) Å, Os−N = 1.906(3) Å), with less multiple bonding toward osmium and moretoward molybdenum. Heterometallic coupling is much faster than either homometallic coupling reaction, in particularthe osmium−osmium coupling, despite the greater oxidizing power of osmium over molybdenum. The origin andimplications of this kinetic effect on nitride coupling and dinitrogen cleavage are discussed.
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