Isolation of the key intermediates of base-promoted borylene–carbonyl coupling reactions

Abstract

The terminal alkylborylene complex [(h 5 -C 5 H 5 )(OC) 2 Mn]BtBu] (1) reacts with trimethylphosphine and CO to form a borylene-carbonyl coupling productThis reactivity can be extended to nitrogen-and carbon-based ligands to form similar complexes and IMe, 8). The key intermediates of these reactions were found to be neutral, Lewis base-stabilized borylenes of the form [(h 5 -C 5 H 5 )(OC) 2 Mn]B(tBu)(L)] (L ¼ 4-dimethylaminopyridine (DMAP), 4, 3,5-lutidine, 5 and :C[N(Me)CH] 2 (IMe), 6, which have been isolated and fully characterized. They can be synthesized from simple addition of the base to the parent borylene 1. The coordination of the base to the boron center seems to facilitate a rearrangement of the t-butyl borylene substituent.

Interactions of Isonitriles with Metal–Boron Bonds: Insertions, Coupling, Ring Formation, and Liberation of Monovalent Boron

“…In an attempt to determine the effect of the sequential addition of different Lewis bases to base‐stabilized borylene complexes, the NHC‐stabilized, isobutyl‐substituted borylene complex 3 (prepared by the thermal isomerization of NHC‐stabilized tert ‐butylborylene complex 2 ) was treated first with one molar equivalent of CNMes* at room temperature for four hours, followed by the addition of one molar equivalent of the NHC 1,3‐dimethylimidazol‐2‐ylidene (IMe). Upon the addition of the carbene, the solution turned bright red, and crystallographic‐quality yellow crystals of 10 (Scheme ) were obtained after removal of the solvent, washing with hexane, and recrystallization from benzene.…”

Activation of boryl-, borylene and metalloborylene complexes by isonitriles

“…9,10 Similarly, reactions of the borylene complex [(Z 5 -C 5 H 5 )(OC) 2 MnQBtBu] with Lewis bases yielded the acid-base adducts [(Z 5 -C 5 H 5 )(OC) 2 MnQB(L)tBu] (L = lutidine, dimethylaminopyridine, IMe). 11 However, reactions of boryls and borylenes with isonitriles showed different reactivity patterns, which is not altogether surprising, as there are documented differences between the reactivities of isonitriles and Lewis bases such as carbenes, phosphine and amines that extend beyond simple differences in basic strength. This is perhaps most well documented in the propensity for isonitriles to affect insertions into metal-element 12 and element-element bonds, 13 including metal boryls, 14 as well as boron-boron, 15 boron-hydride 16 and boronhalide bonds.…”

“…The reaction of 5 with the three equivalents of CyNC led to isolation of a yellow solid with an 11 B NMR shift at À8.8 ppm. Crystals suitable for X-ray diffraction were obtained from a concentrated toluene solution, revealing a [2.3]-spiro species (6, Fig.…”

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

“…The BÀNb ond (148.4(6) pm) is shorter than BÀNs ingle bonds (151.8(3)-159.6(2) pm). [52,53] However, it is longer than BÀN double bonds and thus can be described as ap artial BÀN double bond (142.9(7)-144.4(5) pm). [51,52,54] Both the NÀC1 (116.1(5) pm) and the C1ÀS( 158.3(5) pm) bonds are within the normalrange for double bonds of their respective type.…”