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The halogen-free synthesis of oligosilazanes has been observed upon dehydrocoupling silanes with ammonia at 25 °C using [(2,6-iPr2PhBDI)Mn(µ-H)]2. Extending this methodology to polymethyl-hydrosiloxanes afforded thermally robust polysiloxazane solids, and the dehydrocoupling of 1,3,5,7-tetramethylcyclotetrasiloxane with ammonia afforded a polysiloxazane having a weight-average molecular weight of 4300 g/mol. A representative oligosilazane has been applied to a copper surface and found to afford a 20 μm thick coating that resists corrosion after 24 h under water. Addition of ammonia to [(2,6-iPr2PhBDI)Mn(µ-H)]2 allowed for characterization of the catalyst resting state, [(2,6-iPr2PhBDI)Mn(µ-NH2)]2, which has been found to mediate Si‒N dehydrocoupling. 

Although silane diamine copolymers have captured the attention of the catalysis community, the optimization of their synthesis and end uses have yet to be explored. In this study, a well-defined Earth-abundant metal catalyst, [(2,6-iPr2PhBDI)Mn(µ-H)]2, has been found to couple organosilanes to diamines to prepare networks that feature varied silane substitution and diamine chain lengths. By performing dehydrocoupling in the absence of solvent with 0.01 mol% catalyst loading, substrate utilisation turnover frequencies of up to 300 s-1 have been achieved at early reaction times, the highest Si–N dehydrocoupling activity ever observed. These networks have been employed as absorbents for common organic solvents, a property that had not been studied for this class of materials. By incorporating a long-chain hydrophobic linker, one network has been found to absorb 7.7× its orginal mass in THF and recycling has been demonstrated upon solvent removal. Controlling the degree of dehydrocoupling also offered an opportunity to deposit coatings from freshly-prepared silane diamine polymer solutions and monitor their integrity upon curing in air. While uniform and persistent coatings have been obtained from 1,6-hexanediamine derived polymers, the need to prepare dilute solutions that have a short shelf-life and the tackiness associated with extended dry times have been identified as potential limitations. 

The electronic structure of a dimeric manganese hydride catalyst supported by β-diketiminate ligands, [( 2,6-iPr2Ph BDI)Mn(μ-H)] 2 , was investigated with density functional theory. A triple bond between the manganese centres was anticipated from simple electron-counting rules; however, calculations revealed Mn–Mn Mayer bond orders of 0.21 and 0.27 for the ferromagnetically-coupled and antiferromagnetically-coupled extremes, respectively. In accordance with experimentally determined Heisenberg exchange coupling constants of −15 ± 0.1 cm −1 (SQUID) and −10.2 ± 0.7 cm −1 (EPR), the calculated J 0 value of −10.9 cm −1 confirmed that the ground state involves antiferromagnetic coupling between high spin Mn( ii )-d 5 centres. The effect of steric bulk on the bond order was examined via a model study with the least sterically-demanding version of the β-diketiminate ligand and was found to be negligible. Mixing between metal- and β-diketiminate-based orbitals was found to be responsible for the absence of a metal–metal multiple bond. The bridging hydrides give rise to a relatively close positioning of the metal centres, while bridging atoms possessing 2p orbitals result in longer Mn–Mn distances and more stable dimers. The synthesis and characterization of the bridging hydroxide variant, [( 2,6-iPr2Ph BDI)Mn(μ-OH)] 2 , provides experimental support for these assessments. 

The manganese hydride dimer, [( 2,6-iPr2Ph BDI)Mn(μ-H)] 2 , was found to mediate nitrile dihydroboration, rendering it the first manganese catalyst for this transformation. Stoichiometric experiments revealed that benzonitrile insertion affords [( 2,6-iPr2Ph BDI)Mn(μ-NCHC 6 H 5 )] 2 en route to N , N -diborylamine formation. Density functional theory calculations reveal the precise mechanism and demonstrate that catalysis is promoted by monomeric species.