A useful ligand involving three pyridyl donor arms and fluorocarbon substituents surrounding the coordination pocket has been assembled and utilized in coinage metal chemistry. This tris(pyridyl)borate serves as an excellent...

The pyridine-based poly(pyridyl)borates are a recent addition to the scorpionate family. Furthermore, pyridyl ring substituted analogues are also rare. The synthesis of a bis(pyridyl)borate featuring trifluoromethyl substituted pyridyl donor arms and its utility in isocyanide and carbonyl chemistry of copper(I) and silver(I) have been described together with related molecules supported by a fluorinated tris(pyridyl)borate, and a comparison to the better-known poly(pyrazolyl)borate relatives. X-ray crystal structures of copper and silver complexes show that the B-arylated, bis-and tris(pyridyl)borate ligands use only two pyridyl moieties for metal ion coordination. Flanking B-aryl groups close to metal sites are also a common feature in copper and silver complexes supported by [Ph 2 B(6-(CF 3 )Py) 2 ] − and [t-BuC 6 H 4 B(6-(CF 3 )Py) 3 ] − . The CN stretching frequencies of the t-BuNC complexes of Cu(I) and Ag(I) are notably higher than that of the free t-BuNC. The CO stretch of the analogous fluorinated poly(pyridyl)borate ligand supported metal carbonyls lies closer to that of the free CO, indicating the presence of fairly Lewis acidic metal sites. Metal bound carbonyl stretching frequencies of comparable poly(pyridyl)borate and poly(pyrazolyl)borate have been utilized to gauge the relative donor properties of the two ligand families.

Bis- and tris-pyridyl borate ligands containing pyridyl donor arms, a methylated boron cap, and a fluorine-lined coordination pocket have been prepared and utilized in coinage metal chemistry. The tris­(pyridyl)­borate ligand has been synthesized using a convenient boron source, [NBu4]­[MeBF3]. These N-based ligands permitted the isolation of group 11 metal–ethylene complexes [MeB­(6-(CF3)­Py)3]­M­(C2H4) and [Me2B­(6-(CF3)­Py)2]­M­(C2H4) (M = Cu, Ag, Au). The gold complexes display the largest coordination-induced upfield shifts of the ethylene 13C resonance relative to that of the free ethylene in their NMR spectra, while the silver complexes show the smallest shift. Solid-state structures of five of these metal–ethylene complexes as well as the related free ligands were established by X-ray crystallography. Surprisingly, all three [MeB­(6-(CF3)­Py)3]­M­(C2H4) adopt the rare κ2 coordination mode rather than the typical κ3 coordination mode of facial capping tridentate ligands. Computational analyses indicate that κ2 coordination mode is favored over the κ3-mode in these coinage metal–ethylene complexes and point to the effects CF3-substituents have on κ2/κ3-energy difference. The M–C and M–N bond distances of [MeB­(6-(CF3)­Py)3]­M­(C2H4) follow the trend expected based on covalent radii of M­(I) ions. The calculated ethylene–M interaction energy of κ2-[MeB­(6-(CF3)­Py)3]­M­(C2H4) indicated that the gold­(I) forms the strongest interaction with ethylene. A comparison to the related poly­(pyrazolyl)­borates is also presented.

Given that pyrene represents one of the most versatile chromophores, the development of new selective routes for its functionalization and tuning of its emission properties is highly desirable. Pyrene‐based BN Lewis pair (LP)‐functionalized polycyclic aromatic hydrocarbons (PAHs) were prepared by regioselective Lewis base‐directed electrophilic aromatic substitution. The requisite 1,6‐dipyridylpyrene ligands were accessed by Suzuki–Miyaura cross‐coupling of 1,6‐bis(pinacolatoboryl)pyrenes with 2‐bromopyridine derivatives. Subsequent electrophilic borylation with BCl3 in the presence of AlCl3 and 2,6‐di‐tert‐butylpyridine as a hindered base produced the dichloroborane complexes, which were then in situ reacted with diphenyl or diethyl zinc. The presence or absence of alkyl chains in the 3,8‐positions of the pyrene moiety determined the position of the B−C bond formation (2,7 in the non‐K region versus 5,10 in the K region) and thereby also the size of the BN heterocycle (five‐ versus six‐membered). The impact of the regioisomeric borylation on the electrochemical, photophysical and structural properties was investigated and the conclusions supported by theoretical calculations. The rapid synthesis of derivatives that are borylated in the K region also suggests strong potential for the development of pyrene derivatives that are otherwise difficult to access.

The functionalization of polycyclic aromatic hydrocarbons (PAHs) via B ! NL ewis pair formation offers an opportunity to judiciously fine-tune the structural features and optoelectronic properties,tosuit the demands of applications in organic electronic devices,b ioimaging,a nd as sensitizers for singlet oxygen generation. We demonstrate that the N-directed electrophilic borylation of 2,6-di(pyrid-2-yl)anthracene offers access to linearly extended acene derivatives Py-BR (R = Et, Ph, C 6 F 5 ). In comparison to indeno-fused 9,10-diphenylanthracene,t he formal "BN for CC" replacement in Py-BR selectively lowers the LUMO,r esulting in am uchr educed HOMO-LUMO gap.A ne ven more extended conjugated system with seven six-membered rings in ar ow (Qu-BEt)i s obtained by borylation of 2,6-di(quinolin-8-yl)anthracene. Fluorinated Py-BPf shows particularly advantageous properties,i ncluding relatively lower-lying HOMO and LUMO levels,s trong yellow-green fluorescence,a nd effective singlet oxygen sensitization, while resisting self-sensitized conversion to its endoperoxide.