Platinum Oxoboryl Complexes as Substrates for the Formation of 1:1, 1:2, and 2:1 Lewis Acid–Base Adducts and 1,2‐Dipolar Additions

Abstract

The oxoboryl complex trans-[(Cy3 P)2 BrPt(B≡O)] (2) reacts with the Group 13 Lewis acids EBr3 (E=Al, Ga, In) to form the 1:1 Lewis acid-base adducts trans-[(Cy3 P)2 BrPt(B≡OEBr3 )] (6-8). This reactivity can be extended by using two equivalents of the respective Lewis acid EBr3 (E=Al, Ga) to form the 2:1 Lewis acid-base adducts trans-[(Cy3 P)2 (Br3 Al-Br)Pt(B≡OAlBr3 )] (18) and trans-[(Cy3 P)2 (Br3 Ga-Br)Pt(B≡OGaBr3 )] (15). Another reactivity pattern was demonstrated by coordinating two oxoboryl complexes 2 to InBr3 , forming the 1:2 Lewis acid-base adduct trans-[{(Cy3 P)2 BrPt(B≡O)}2 InBr3 ] (20). It was also possible to functionalize the B≡O triple bond itself. Trimethylsilylisothiocyanate reacts with 2 in a 1,2-dipolar addition to form the boryl complex trans-[(Cy3 P)2 BrPt{B(NCS)(OSiMe3 )}] (27).

Acid/Base-Free Acyclic Anionic Oxoborane and Iminoborane Bearing Diboryl Groups

“…In the 11 B NMR spectrum of 2 , two broad singlets at 54.4 and 25.8 ppm are observed, which suggests two types of tricoordinate boron atoms (Figure S3). The former singlet can be assigned to the boron atoms of the NHB units and is shifted upfield compared with that (69.5 ppm in C 6 D 6 and 68.5 ppm in CD 2 Cl 2 ) of 1 , while the latter singlet of the central boron atom, which is comparable to that (26.0 ppm in C 6 D 6 and 25.6 ppm in CD 2 Cl 2 ) of 1 , falls in the range of 18.7–32.3 ppm normally found in oxoboranes − and is shifted downfield with respect to those of acid-free oxoboranes I – III (20.7–24.3 ppm). The solid-state IR spectrum of 2 exhibits a band at 1462 cm –1 for the stretch BO vibration (Figure S7), which is lower than those of II (1581 cm –1 ) and III (1667 cm –1 ) and illustrates a relatively weaker BO bond in 2 .…”

“…In contrast to the well-known ketone compounds, oxoboranes (RBO) are prone to head-to-tail oligomerization because of the high polarity of the BO moiety. , Thus, monomeric oxoboranes are highly reactive and only observable in the gas phase, in argon matrix at low temperature, or by chemical trapping . In view of the electron-deficient boron center and the electron-rich oxygen atom, the employment of neutral or anionic ligands at the boron site and Lewis/Brønsted acids at the oxygen site have facilitated the isolation of base- and acid-stabilized oxoboranes. , Additionally, transition metal fragments have also been used by the groups of Braunschweig and Yamashita to stabilize the BO multiple-bonded compounds such as the base-free oxoboranes I (Chart a). In 2019, Aldridge and co-workers successfully isolated the first acid-free anionic oxoborane II , stabilized by a bulky N-heterocyclic ligand (Chart b) .…”

Advances in the development of complexes that contain a group 13 element chalcogen multiple bond

“…18 In addition, a variety of adducts between the platinum oxoboryl system and group 13 metal-based Lewis acids has been reported very recently. 19 Boron sulfur-and boron selenium double bond. Tokitoh et al, in their seminal work, described the reaction of a dithiastannaboretane (J) with 1,3-dienes at elevated temperature which afforded boron-sulfur heterocycles (K, Scheme 10).…”

A Tale of Two Stabilities: How One Boron Atom Affects a Switch in Bonding Motifs in CeO2Bx– (x = 2, 3) Complexes

“…With the ubiquity of carbon monoxide in organometallic compounds, integral in both catalysis and synthesis, there have been significant efforts to expand the breadth and specificity of their chemical reaches using isolobal and isoelectronic CO analogues. − Boronyl (BO – ) is one such example, ,, yet metal–(BO) n complexes have been largely elusive in non-gas-phase experiments, unlike other main group elements multiply bound to boron, for example, BN. , The highly polarized BO ligand acts as a strong nucleophile from the electron density localized on the O atom, with a tendency for cyclo-oligomerization with any nearby BO units. − Transition metals do stabilize small reactive functionalities like carbenes through electronic and steric effects, but only recently did Braunschweig and co-workers synthesize the first metal–BO complex, trans -[(Cy 3 P) 2 BrPtBO], in which the boronyl moiety is stabilized by a Pt­(II) center. This work inspired both experimentalists and theorists to explore several derivatives of trans -[(Cy 3 P) 2 BrPtBO] − as well as the potential stabilization of boronyls by other metals. ,− While some unexpected observations resulted, such as the synthesis of a trinuclear ruthenium complex capped with a BO unit, the general theme that has emerged is that an electron-rich metal center is necessary to stabilize the polar BO bond. And while B-centered polyboronyls have been previously observed and characterized in the gas phase, metal–boronyl complexes have yet to be observed with more than one boronyl ligand.…”