Chemistry of metal – boron double bonds

Abstract

This article provides an overview of the recent developments in the area of transition metal complexes featuring metal-boron double bonds. In particular, emphasis has been placed on studies focused on the exploration of patterns of reactivity.

Bis(borylene) Complexes of Cobalt, Rhodium, and Iridium [(η5-C5H5)M(BNX2)2] (X = Me, SiH3, SiMe3): A Bonding Analysis

“…Synthesis, structure, bonding, and reactivity of transition metal borylene complexes have been a provocative subject since the first report of structurally characterized terminal transition metal borylene complexes in 1998. , So far a number of structurally characterized terminal transition metal borylene complexes have been reported (Table ) and a number of interesting review articles have been written during these periods by Braunschweig et al − and Aldridge et al − Additionally, a number of base-stabilized adducts formed by the coordination of a Lewis base (main group or transition metal) to the two- or three-coordinate boron center have also been reported. , …”

Structure and Bonding Energy Analysis of Cobalt, Rhodium, and Iridium Borylene Complexes [(η5-C5H5)(CO)M(BNX2] (X = Me, SiH3, SiMe3) and [(η5-C5H5)(PMe3)M{BN(SiH3)2}] (M = Co, Rh, Ir)

“…So far 12 structurally characterized neutral terminal transition metal borylene complexes − and nine terminal cationic transition metal borylene complexes − (see Charts 1 and 2 of the Supporting Information, respectively) have been reported. Additionally, a number of base-stabilized adducts formed by the coordination of a Lewis base (main group or transition metal) to the two- or three-coordinate boron center have also been prepared. − Understanding the nature of M−borylene bonding in these species is of utmost importance and could lead to synthesis of new transition metal−borylene complexes with interesting reactivity.…”

Crystal Nucleation Using Surface-Energy-Modified Glass Substrates

“…Table 2 shows average crystallization onset times for the protein thaumatin (n = 15) on 20 mm grid and circular surface energy modifications using sitting drop vapor diffusion (see Supporting Information for details). The unmodified control surface produced thaumatin crystals on average at 44(12) h, with the CC5 motif of concentric circles producing little apparent reduction in crystallization time with a similar value of 39( 14) h. The grid-based surface energy modifications gave progressively faster crystallization onset times of 37 (14), 33 (16), and 32(15) h for G5, G6, and G18, respectively, affording a reproducible maximum reduction of 27% in crystallization onset times for the G18 surface.…”

“…Similarly, by analyzing the crystallization onset times for the protein bovine pancreatic trypsin (BPT; n = 17) in Table 3, it can be seen that the surface controls produced crystals at 41 (14) h and that the CC5 substrate again shows little improvement in crystallization onset time at 41(13) h vs control. The grid motifs G5, G18, and G6 show decreasing crystallization onset times of 34 (16), 30(12), and 27(12) h, respectively, and the surface energy profile of G6 produces the largest overall reduction in crystallization onset times for BPT of 34%.…”

“…The identification of solid form variants including polymorphs, solvates, and hydrates continues to be an important and regulated aspect of small molecule API development because these different solids can have very different dissolution characteristics that can affect in vivo drug performance. − ,, The needs for such crystal form screening are broad-based and will persist given that ≈90% of APIs are crystalline materials , and that ≈50–80% of small molecule APIs exhibit polymorphism at some point from discovery through manufacturing. − The many unpredictable aspects of polymorphism, and of solid form variation in general, underpin the need for rational approaches to improving crystallization outcomes for small molecule APIs, and advances here can be anticipated to help minimize the costly economic penalties incurred from untimely polymorphic transformations (e.g., Norvir, Avalide, etc.). As importantly, enhanced crystal nucleation can create value in the form of new intellectual property for commercially relevant API compositions and by making solid form screening more complete and time efficient.…”