Recent advances in transition metal catalysed dehydropolymerisation of amine boranes and phosphine boranes

Amine–Borane Dehydropolymerization: Challenges and Opportunities

“…For brevity, closely related phosphine-borane dehydrocoupling is not discussed in detail,b ut concepts and catalysts developed in either field serve as useful comparisons. [5,23,24] in detail by Manners (Figure 1). [1,27] Since then,t he number of catalysts capable of effecting such polymerizations has grown considerably,w ith homogeneous and heterogeneous examples now spanning the periodic table.…”

“…[1,2] In the ten years since, considerable progress has been made in understanding and developing this methodology for the synthesis of main-group polymericm aterials. [3][4][5][6][7][8] Challenges remain, however,i nb oth fundamental mechanistic understanding and translating this to the production of tailored new materials.…”

“…There are now many catalysts known that are capable of the very efficient dehydrogenation of amine-boranes, including transition-metal complexes, s-blockc ompoundsa nd maingroup Lewis acids. [5][6][7] The challenge in catalytic amine-borane dehydropolymerization, then, is not to effect dehydrogenation but rather to do so with ah igh degree of control to afford well-defined polymeric products in the subsequentB ÀNc oupling steps, in an overall atom efficient manner and with high compositional purity.T his Concept article serves to outline the currentp osition of amine-borane dehydropolymerization, and identify key challenges and opportunities that the community may find useful to consider as the field develops. For brevity, closely related phosphine-borane dehydrocoupling is not discussed in detail,b ut concepts and catalysts developed in either field serve as useful comparisons.…”

“…[1,27] Since then,t he number of catalysts capable of effecting such polymerizations has grown considerably,w ith homogeneous and heterogeneous examples now spanning the periodic table. [5][6][7] We will focus on homogeneous systems here,a nd selected examples are showni n Figure 1. Examples of early and mid-transition-metal catalysts include Manners'T iCl 2 Cp* 2 /2 nBuLi system, [28] and Kawano's Mn(h 5 -C 5 H 5 )(CO) 3 and Cr(h 6 -C 6 H 6 )(CO) 3 complexes under photolytic conditions.…”

A d10 Ag(i) amine–borane σ-complex and comparison with a d8 Rh(i) analogue: structures on the η1 to η2:η2 continuum

“…1 For example, amine-borane σcomplexes, 2 exemplified by [M]⋯H 3 B•NRH 2 ( Fig. 1), are key intermediates in the catalytic dehydropolymerisation of amine-boranes that leads to the formation of B-N polymeric materials, [3][4][5] B-B coupling 6 or hydroboration reactions. 7 H 3 B•NMe 3 is often used as a model substrate for such processes as it provides insight into the initial binding step of the amine-borane, there being no protic N-H available for onward reaction.…”