Monohaloboryls (BHX⁻) as Bridging Ligands: Observable Dinuclear σ‐(Halo)boranyl Intermediates in the Synthesis of Metalloborylenes

Abstract

Upon treating transition-metal-dihaloboryl complexes of the form [L(n)MBX(2)] with K[(η(5)-C(5)H(5))MnH(CO)(2)], salt elimination occurs along with a migration of the Mn-bound hydride ligand onto the boron atom, thereby forming dinuclear σ-(halo)boranyl complexes of the form [L(n)M(μ-BHX)Mn(CO)(2)(η(5)-C(5)H(5))]. Most of these complexes react further at room temperature to lose HX and provide metalloborylene complexes [L(n)M-B = Mn(CO)(2)(η(5)-C(5)H(5))]; however, when ML(n) = Re(CO)(5) the σ-(halo)boranyl complex decomposes into unidentifiable products. We found through DFT calculations that two electronically and structurally distinct forms of the intermediate σ-(halo)boranyl complexes exist, one of which easily loses HX and one that does not.

Hydridoborylene Complexes and Di‐, Tri‐, and Tetranuclear Borido Complexes with Hydride Ligands

“…In all five hydridoborylene complexes, the WBIs of the BH interaction (0.50–0.59) are significantly higher than those of the MH bonds (0.29–0.37), which are lower than would be expected for terminal hydride ligands 9. These WBI values for the [MBH] triangle are very similar to those found in dinuclear complexes with bridging σ‐(halo)boryl ligands (BHX), in which the values for the MnH bonds are 0.26–0.28 and 0.58–0.62 for the BH bonds 10. Although the natural charges of the hydride ligands do not change at all in 3 a – c , 5 b , and c (0.06), there is a vast difference in charge at boron between the mononuclear (0.61–0.71) and dinuclear complexes (0.17, 0.23).…”

“…[9] These WBI values for the [MBH] triangle are very similar to those found in dinuclear complexes with bridging s-(halo)boryl ligA C H T U N G T R E N N U N G ands (BHX), in which the values for the Mn À H bonds are 0.26-0.28 and 0.58-0.62 for the B À H bonds. [10] Although the natural charges of the hydride ligands do not change at all in 3 a-c, 5 b, and c (0.06), there is a vast difference in charge at boron between the mononuclear (0.61-0.71) and dinuclear complexes (0.17, 0.23). This presumably stems from the smaller negative charge on the attached metal center (…”

Coordination and Dehydrogenation of Diphosphine–Borane Ph2PCH2PPh2·BH3 at a Heterometallic MoRe Center to Give an Agostic Boryl-Bridged Derivative

“…As noted above, the bridging boryl group in 5 can be viewed as -bound to Re and  2 -bound to Mo, via one of the BH bonds. In agreement with this, the ReB distance is now quite short, 2.38(2) Å, close to the reference value of 2.35 Å for a ReB single bond, 19 and comparable to the corresponding values measured in the mononuclear complexes [Re(CO)5(BCl2)] (2.189(16) Å), 28 and [Re(CO)5{B(NArCH)2}] (2.292 4Å), 29 which are the only other rhenium boryl complexes structurally characterized to date. As for the  2 -coordination to Mo, we find now a quite reduced MoHB angle of 94(4) o , and very short MoB separation of 2.31(1) Å, actually shorter than the reference value of 2.38 Å for a MoB single bond.…”

Active‐Site‐Matched Fluorescent Probes for Rapid and Direct Detection of Vicinal‐Sulfydryl‐Containing Peptides/Proteins in Living Cells

“…Pentacarbonylrhenate(–I) has been very often applied for the synthesis of complexes with transition metal M –Re bonds60 ( M = V, Ru, Os, Mn, Re, Au, Pt, Sm, Lu) as well as for metal clusters61 and for complexes with main group E –Re bonds62 ( E = B, Ga, In, Tl, Si, Ge, Sn, P). Remarkable complexes of the latter type are Tl[Re(CO) 5 ] 3 63 and Si[Re(CO) 5 ] 4 64 from TlI or SiI 4 , respectively.…”