Nickel(0) Complexes of Polyunsaturated Azamacrocyclic Ligands

Abstract

A series of nickel(0) complexes, 3, 4, and 5, containing unsaturated 15-membered azamacrocyclic ligands have been synthesized. Structural characterization of the complexes is based on NMR spectroscopy, X-ray diffraction analysis, and differential scanning calorimetry. In addition, the catalytic activity of the complexes in the Suzuki–Miyaura cross-coupling of arylboronic acids and aryl halides has been tested.

Transition-metal-catalyzed Suzuki–Miyaura cross-coupling reactions: a remarkable advance from palladium to nickel catalysts

“…Very recently, Roglans and co-workers 55 reported a class of Ni (0) complexes derived from polyunsaturated azamacrocyclic ligands (Fig. 6).…”

Nickel(0) Complexes of Acyclic Polyunsaturated Aza Ligands

“…When the ring adopts the C 2 -symmetrical twist conformation, as in Ni(0)− triazacyclopentadeca-3,8,13-triene VII, the high-field shift of the axial protons Ha is less (VII: δ(H) 2.84). 10 For the asymmetric pseudo-azametallacyclohexanic rings involving an alkene and an alkyne function in a "half-chair" conformation, the Ha high-field shift for NCHeHa connected to the alkene function in the chairlike region is again large (VIII: δ(H) 2.00), while that for NCHeHa connected to the alkyne function in the flat part is small (VIII: δ(H) 4.13). The equatorial protons He (δ(H) 4.52−4.66) appear little affected by the conformation of the chelate.…”

“…Complex 4 represents a hitherto rare example of a structurally characterized (L 2 Ni) 2 (μ-RCCR′)-type complex (L = alkene) in which two CC bonds lie in one CC−Ni plane and two others perpendicular to the second plane. 10 The principal features of the structure of acyclic dinuclear 4 correspond to those of the cyclic dinuclear IX and, neglecting the Ni2(cod) moiety, also to those of the cyclic mononuclear VIII. Without the Ni2(cod) group, 4 can also be viewed as a rough model for structure of the acyclic mononuclear C s -3 which seems to be present in solution (eq 1).…”

“…In a recent collaboration we succeeded in synthesizing the Ni(0)−triazacyclopentadeca-3,8,13-triene VII and the Ni(0)− triazacyclopentadeca-3,8-dien-13-yne VIII, which respectively represent derivatives of IV and V. Complex VIII reacted further with Ni(cod) 2 to give dinuclear IX. 10 The structure of VIII is C s -symmetrical and resembles a chair, with the 15-membered ring providing the seat, the two SO 2 -tolyl (tosyl, Ts) groups at NCH 2 CCCH 2 N representing the front legs, and the other tosyl group forming the back rest (Figure 1). The coordination geometry at Ni is trigonal planar with the CC bond and the midpoints of both CC bonds lying in the plane, but the CC bonds are twisted by 21°out of the plane about their midpoints.…”

Recent Developments in the Suzuki-Miyaura Reaction: 2010–2014

“…In 2012, Roglans and Pörschke reported on the use of a series of nickel (0) complexes of polyunsaturated azamacrocyclic ligands ( 39 and related structures, Figure 5) for the SMR of arylboronic acids and aryl halides [80]. The same year, Fu and co-workers reported the use of carbamates, sulphonamides and sulfones as directing groups in Ni-catalyzed SMR, achieving the asymmetric coupling of unactivated alkyl electrophiles at room temperature (Scheme 5) [81].…”