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Abstract Ferrocene1and its dianionic Fe(bis)(dicarbollide) analogue2are classical compounds that display unusual stability. These compounds are not known to undergo transmetallation chemistry of the Fe‐center and have been used extensively as chemical building blocks with consistent integrity. In this manuscript we describe the preparation of a charge compensated Fe(bis)(dicarbollide) species3 Feand its unprecedented transmetallation chemistry to Ir. Such reactions are hitherto unknown for any transition metal metallocene or metallacarborane complex. Additionally, we show that3 Fecan be deprotonated to afford the corresponding bis(NHC) Li‐carbenoid5that also displays unique reactivity. When5is reacted with [Ir(COD)Cl]₂it also undergoes a rapid transmetallation of the ferrocene “like” core to afford6but with the added twist that the Li‐carbenoid moiety stays intact and does not transmetalate. However, when6is subsequently treated with CuCl, the Li‐carbenoid transmetalates to Cu, which allows the controlled formation of the corresponding heterobimetallic Ir/Cu aggregate. Lastly, when Li‐carbenoid5is treated directly with CuCl, a double transmetallation occurs from both Fe to Cu and Li‐carbenoid to Cu, resulting in the trimetallic Cu cluster8. These novel reactions pave the way for new synthetic methods to build complicated polymetallic clusters in a controlled fashion. 

The combination of a boron Lewis acid and a decamethylsamarocene, specifically 9,10-Me 2 -9,10-diboraanthracene with (C 5 Me 5 ) 2 Sm II (THF) 2 , in toluene leads to cooperative reductive capture of N 2 . The product crystallizes as the salt, [(C 5 Me 5 ) 2 Sm III (THF) 2 ][(C 5 Me 5 ) 2 Sm III (η 2 -N 2 B 2 C 14 H 14 )], 1, which formally is comprised of an (NN) 2− moiety sandwiched between a [(C 5 Me 5 ) 2 Sm III ] 1+ metallocene cation and the diboraanthracene ditopic Lewis acid. 

Transition metal interactions with Lewis acids (M → Z linkages) are fundamentally interesting and practically important. The most common Z-type ligands contain boron, which contains an NMR active 11 B nucleus. We measured solid-state 11 B{ 1 H} NMR spectra of copper, silver, and gold complexes containing a phosphine substituted 9,10-diboraanthracene ligand (B 2 P 2 ) that contain planar boron centers and weak M → BR 3 linkages ([(B 2 P 2 )M][BAr F 4 ] (M = Cu (1), Ag (2), Au (3)) characterized by large quadrupolar coupling ( C Q ) values (4.4–4.7 MHz) and large span ( Ω ) values (93–139 ppm). However, the solid-state 11 B{ 1 H} NMR spectrum of K[Au(B 2 P 2 )] − (4), which contains tetrahedral borons, is narrow and characterized by small C Q and Ω values. DFT analysis of 1–4 shows that C Q and Ω are expected to be large for planar boron environments and small for tetrahedral boron, and that the presence of a M → BR 3 linkage relates to the reduction in C Q and 11 B NMR shielding properties. Thus solid-state 11 B NMR spectroscopy contains valuable information about M → BR 3 linkages in complexes containing the B 2 P 2 ligand. 

The water reactivity of the boroauride complex ([Au(B 2 P 2 )][K(18-c-6)]; (B 2 P 2 , 9,10-bis(2-(diisopropylphosphino)-phenyl)-9,10-dihydroboranthrene) and its corresponding two-electron oxidized complex, Au(B 2 P 2 )Cl, are presented. Au(B 2 P 2 )Cl is tolerant to H 2 O and forms the hydroxide complex Au(B 2 P 2 )OH in the presence of H 2 O and triethylamine. [Au(B 2 P 2 )]Cl and [Au(B 2 P 2 )]OH are poor Lewis acids as judged by the Gutmann–Becket method, with [Au(B 2 P 2 )]OH displaying facile hydroxide exchange between B atoms of the DBA ring as evidenced by variable temperature NMR spectroscopy. The reduced boroauride complex [Au(B 2 P 2 )] − reacts with 1 equivalent of H 2 O to produce a hydride/hydroxide product, [Au(B 2 P 2 )(H)(OH)] − , that rapidly evolves H 2 upon further H 2 O reaction to yield the dihydroxide compound, [Au(B 2 P 2 )(OH) 2 ] − . [Au(B 2 P 2 )]Cl can be regenerated from [Au(B 2 P 2 )(OH) 2 ] − via HCl·Et 2 O, providing a synthetic cycle for H 2 evolution from H 2 O enabled by O–H oxidative addition at a diboraanthracene unit. 

The boron-centered reactivity of the diboraanthracene-auride complex ([Au(B2P2)][K(18-c-6)]; (B2P2, 9,10-bis(2-(diisopropylphosphino)- phenyl)-9,10-dihydroboranthrene) with a series of organic carbonyls is reported. The reaction of [(B2P2)Au]– with formaldehyde or paraformaldehyde results in a head-to-tail dimerization of two formaldehyde units across the boron centers. In contrast, the reaction of [(B2P2)Au]– with two equivalents of benzaldehyde yields the pinacol coupling product via C–C bond formation. Careful stoichiometric addition of one equivalent of benzaldehyde to [Au(B2P2)]– enabled the isolation of an adduct corresponding to the formal [4+2] cycloaddition of the C=O bond of benzaldehyde across the boron centers. This adduct reacts with a second equivalent of benzaldehyde to produce the pinacol coupling product. Finally, the reaction of [Au(B2P2)]– with acetone results in a formal reductive deoxygenation with discrete hydroxo and 2-propenyl units bound to the boron centers. This reaction is proposed to proceed via an analogous [4+2] cycloadduct, highlighting the unique small molecule activation chemistry available to this platform. 

Borohydrides are widely used reducing agents in chemical synthesis and have emerging energy applications as hydrogen storage materials and reagents for the reduction of CO 2 . Unfortunately, the high energy cost associated with the multistep preparation of borohydrides starting from alkali metals precludes large scale implementation of these latter uses. One potential solution to this issue is the direct synthesis of borohydrides from the protonation of reduced boron compounds. We herein report reactions of the redox series [Au(B 2 P 2 )] n ( n = +1, 0, −1) (B 2 P 2 , 9,10-bis(2-(diisopropylphosphino)phenyl)-9,10-dihydroboranthrene) and their conversion into corresponding mono- and diborohydride complexes. Crucially, the monoborohydride can be accessed via protonation of [Au(B 2 P 2 )] − , a masked borane dianion equivalent accessible at relatively mild potentials (−2.05 V vs. Fc/Fc + ). This species reduces CO 2 to produce the corresponding formate complex. Cleavage of the formate complex can be achieved by reduction ( ca. −1.7 V vs. Fc/Fc + ) or by the addition of electrophiles including H + . Additionally, direct reaction of [Au(B 2 P 2 )] − with CO 2 results in reductive disproportion to release CO and generate a carbonate complex. Together, these reactions constitute a synthetic cycle for CO 2 reduction at a boron-based reaction center that proceeds through a B–H unit generated via protonation of a reduced borane with weak organic acids.