Enhancing Reactivity of Directly íObservable B–H–Pt Interactions through Conformational Rigidity

Abstract

We report for the first time the direct syntheses of trimethylplatinum(IV) complexes supported by bis(pyrazolyl)dihydridoborate (Bp) and bis(3,5-dimethylpyrazolyl)dihydridoborate (Bp*) ligands from the corresponding dimethylplatinum(II) complexes. X-ray crystallographic and multinuclear NMR characterization of the trimethylplatinum(IV) complexes reveal agostic B-H-Pt interactions. Solid-state analysis reveals that BpPt IV Me 3 adopts a dinuclear structure featuring an intermolecular B-H-Pt bridge, whereas Bp*Pt IV Me 3 adopts a mononuclear structure [a]

B–N Cleavage in (9‐BBN)bis(pyrazolyl)borate NiII Complexes

“…Partial hydrolysis of [(BBN)Bp R ] – ligand has only two examples before,[4c], [4e] in which only one partial hydrolyzed ligand coordinated to the metal center. The other two similar examples were occurred in the [Ph 2 B(pz) 2 ]ML n complex.…”

“…Since first reported by Trofimenko, the poly(pyrazolyl)borates have been not only used as a general ligand to form stable complexes with metals across the periodic table and applied in various fields such as synthetic chemistry, catalysis, materials science, and biomimetics, but also famous for their innocence thus leaving the B–H or B–N bond intact . However, it has been pointed that sometimes modification of the ligand can occur in different ways: 1) ligand degradation to form pyrazole or pyrazolate derivatives, mainly due to the B–N bond cleavage; 2) ligand rearrangement, that is to say, exchange of the boryl group between the two nitrogen atoms of the pyrazolyl group, usually called 1,2‐borotropic shift; 3) hydrolysis or alcoholysis of the B–H or B–N moiety, yielding hydroxy‐ and alkoxy(pyrazolyl)borate complexes; and 4) insertion of aldehydes or ketones into the B–H bond or B–H functionalization of the bis‐ or tris(pyrazolyl)hydroborate complexes.…”

“…As a class of bis(pyrazolyl)borate ligands, the chemistry of (9‐BBN)bis(pyrazolyl)borate [(BBN)Bp R ] – is far less developed[4e], [5a], compared with its dihydrobis(pyrazolyl)borate counterparts . In addition, the rigid feature of BBN bicyclic system in [(BBN)Bp R ] – ligands usually causes the terminal hydrogen (α‐C–H) to be forced into close proximity to the metal center, forming agostic, or anagostic interactions.…”

“…This relatively new ligand combined with C–H ··· M interaction provides new potential to modulate the reactivity and catalytic applications of complexes of the type [(BBN)Bp R ]ML n . However, only limited examples of such type of complexes have been synthesized[4e], [5a], and their chemistry warrant further exploration.…”

Reversible PtII–CH3 deuteration without methane loss: metal–ligand cooperation vs. ligand-assisted PtII-protonation

“…According to DFT calculations, the barrier for the interconversion of 2 and 2' associated with TS12 is 11.9 kcal/mol, similar to that reported for other related squareplanar complexes. 13,54,62,63 Since complexes 2 and 2' are squareplanar Pt II complexes, the orientation of the OCH 3 fragment confers no energetic advantage, and thus, 2 and 2' are virtually isoergonic. The endo OCH 3 fragment, however, can enable protonation of the Pt II -centre of 2 by CD 3 OD to form Int11.…”