Generation of Group VI Piano‐Stool and Triple‐Decker Complexes from [(IMes)₂PtH(Cl‐boratabenzene)] Species

Abstract

Species [(IMes)2Pt(H)(1‐Cl‐2‐SiMe3–BC5H4)] (1) was used as the source of the Cl‐boratabenzene anion for coordination to group VI transition metals, resulting in the formation of piano‐stool complexes [(η6‐1‐Cl‐2‐SiMe3–BC5H4)M(CO)3]– [M = Cr (2), Mo (4), W (5)] and a homodimetallic triple‐decker complex [(CO)3Cr(η6‐1‐Cl‐2‐SiMe3–BC5H4)Cr(CO)3]– (3). All species were spectroscopically characterized and the first X‐ray structure of a Cl‐boratabenzene species is reported.

The 9‐Borataphenanthrene Anion

“…Upon mixing, the solution color immediately changed from yellow to red. In situ 11 BNMR spectroscopy revealed an upfield shift of the boron resonance from 40.4 ppm to 30.5 ppm, consistent with the formation of an h 6 -boratabenzene complex [49,50,52] with complete conversion of 1 in 75 minutes.Coordination of dibenzo-18-crown-6 to the potassium ion allowed for the isolation and crystallographic characterization of the pianostool complex 1•Cr(CO) 3 (Figure 8). Theborataphenanthrene ligand coordinates to the chromium center through the central BC 5 ring.T he FT-IR spectrum of the piano-stool complex 1•Cr(CO) 3 exhibits carbonyl stretching bands at 1903, 1821, and 1769 cm À1 ,which are similar to the chromium boratabenzene complex Na[(MeBC 5 H 5 )Cr(CO) 3 ]( u CO = 1910, 1820, 1776 cm À1 ).…”

The 9‐Borataphenanthrene Anion

“…Upon mixing, the solution color immediately changed from yellow to red. In situ 11 BNMR spectroscopy revealed an upfield shift of the boron resonance from 40.4 ppm to 30.5 ppm, consistent with the formation of an h 6 -boratabenzene complex [49,50,52] with complete conversion of 1 in 75 minutes.Coordination of dibenzo-18-crown-6 to the potassium ion allowed for the isolation and crystallographic characterization of the pianostool complex 1•Cr(CO) 3 (Figure 8). Theborataphenanthrene ligand coordinates to the chromium center through the ).…”

“…Boratabenzenes have been extensively studied as polyhaptic ligands for transition metals since their discovery in 1970 by Herberich and co‐workers . The corresponding complexes and related compounds have been applied in fields that span olefin polymerization catalysis, asymmetric synthesis, and single‐ion magnets .…”

Construction of Boron-Containing Aromatic Heterocycles

“…113,115 Compound 227b was also applied as a source of the Clboratabenzene ligand for coordination to group VI transition metals. 116 Reaction of freshly prepared 227b with L 3 M(CO) 3 (M = Cr, Mo, W; L = CO, MeCN) generated the corresponding piano stool complexes 231 (Scheme 66). Interestingly, when (MeCN) 3 Cr(CO) 3 was reacted with 227b a second homodimetallic triple-decker complex 232 was obtained, which represents an extremely rare example in boratabenzene chemistry.…”