The Structure of the “Third‐Generation” Tris (pyrazolyl)borate Caesium Salt p ‐BrC 6 H 4 TpCs

Slow crystallisation at lowered temperature yielded crystals of the “third‐generation” tris (pyrazolyl)borate transfer agent p ‐BrC 6 H 4 TpCs (Tp′Cs) 1 (triclinic; P $\bar{1}$ ; a = 8.540(4), b = 15.045(6), c = 15.879(7) Å; α = 65.853(8), β = 88.457(8), γ = 75.056(8)°; V = 1791.4(13) Å 3 ; Z = 4). The central caesium ion in 1 interacts with three individual p ‐BrC 6 H 4 Tp ligands in two different chelating fashions.In particular, κ 1 ‐ N ‐coordination and η 5 ‐π‐coordination of pyrazole moieties as well as η 6 ‐π‐coordination of the p ‐BrC 6 H 4 substituent are observed. Further, comparable coordination of neighbouring caesium ions leads to the formation of polymeric structures connected by two bridging modes.