Changing the Charge: Electrostatic Effects in Pd-Catalyzed Cross-Coupling

Abstract

A stable dianionic 14-electron Pd(0) complex supported by monoanionic carboranyl phosphines is reported. This complex rapidly undergoes the oxidative addition of Cl-C 6 H 5 at room temperature and is a competent catalyst for Kumada cross-coupling. The isosteric PdL 2 complex, supported by neutral o-carboranyl phosphines, does not display the same reactivity. The high reactivity of the dianionic Pd(0) complex toward chloroarenes can be explained by electrostatic effects that promote both formation of monophosphine-ligated LPd 0 and stabilization of the transition state during oxidative addition. This mode of stabilization is distinct from the wellknown π-arene interactions of biaryl phosphines, in that it occurs both on and off cycle. Communication pubs.acs.org/Organometallics

Transition Metal Complexes of a Monocarba‐closo‐dodecaborate Ligand via B–H Activation

“…Geometry optimization at the B97-D/Def2-TZVPD level of theory in acetonitrile gave key distances and angles consistent with the results from X-ray crystallography (Figure 2a). 1 H, 13 C and 11 B NMR spectroscopic data, calculated at the SO-ZORA/PBE0/QZ4P//B97-D/ Def2-TZVPD level of theory in acetonitrile, were also in agree- ment with the experimental values. Specifically, the 11 B NMR shifts of 10 are predicted to be -3.31, -15.6 and -6.1 ppm for B2, B9 and B12, while all other B vertices fall in the range of -11.2 to -13.8 ppm.…”

“…NMR spectra of 10 and 11 ( 1 H, 1 H{ 11 B}, 13 C{ 1 H}, 11 B, 11 B{ 1 H} and 11 B-11 B COSY) in CD 3 CN were fully consistent with the structures determined by X-ray crystallography. They remained unchanged over weeks at room temperature and over days at 50°C, indicating high inertness of both complexes; for a detailed assignment of 1 H, 13 C and 11 B signals, see the Supporting Information. Compounds 10 and 11 showed comparable 11 B resonances for vertices B12, B3-8/10,11 and B9, which appeared around -7.5, -10 to -15 and -16.5 ppm, respectively (Figure 3).…”

“…Lavallo's group observed that reaction of palladium precursor 3 with chlorobenzene afforded products 4 and 5 in a 9:1 ratio, 5 probably being the product of 4 via elimination of benzene. [13] Studies in our laboratory on the directing group-assisted B-H activation of the [CB 11 H 12 ]anion showed that amides 6 and 8 can selectively be transformed to iridium complexes 7 and 9. [14] In the present work we describe the preparation of rhodium and palladium complexes of 6, which were isolated in high yields and fully characterized.…”

Atomically Defined Monocarborane Copper(I) Acetylides with Structural and Luminescence Properties Tuned by Ligand Sterics

“…[10] Monocarborane B and its polyhalo and polyalkyl derivatives are best known as highly stable, extremely weakly coordinating anions. [12] The endo/exo-dianion [CB 11 H 11 -12-CC] 2À (C)f orms Au I complexes with two or four metal centers in combination with phosphine ligands, while the use of Ag I and pyridine ligands affords complicated structures featuringc ores from Ag 6 6 + to Ag 16 16 + . While many neutrald icarbaborane ligand systems have been explored,t he use of B as as ynthon in ligand design is much less developed.…”

“…While many neutrald icarbaborane ligand systems have been explored,t he use of B as as ynthon in ligand design is much less developed. [12] The endo/exo-dianion [CB 11 H 11 -12-CC] 2À (C)f orms Au I complexes with two or four metal centers in combination with phosphine ligands, while the use of Ag I and pyridine ligands affords complicated structures featuringc ores from Ag 6 6 + to Ag 16 16 + . [13, 14] Herein, we report the first Cu I complexes and nanoclusterso f C,c ontaining two to fourteen metal centers.…”