Low‐Coordinate Monomeric Zinc Hydride Complexes with Encapsulating Dipyrromethene Ligands and Reactivity with B(C₆F₅)₃

Abstract

The dipyrromethene (DPM) ligand is the key to isolation of monomeric Zn hydride complexes with tricoordinate zinc centers. A range of RDPM ligands with various substituents in the pole position (1,9‐positions) were prepared: R = tBu, adamantyl (Ad), mesityl (Mes), 2,6‐diisopropylphenyl (DIPP), 2,4,6‐triphenylphenyl (Mes*), or 9‐anthracenyl (Anth). Reaction of the ligands with Et2Zn gave a series of (RDPM)ZnEt complexes, which were converted with I2 to the corresponding (RDPM)ZnI compounds. The latter reacted by salt metathesis with KN(iPr)HBH3 to the series of Zn hydride complexes (RDPM)ZnH. For ligands with the larger Mes* and Anth substituents, (RDPM)ZnEt was converted to (RDPM)ZnOSiPh3, which after reaction with PhSiH3 gave the hydrides. While Zn hydride complexes with R = tBu or Ad are dimeric, all complexes with aryl‐substituents are monomeric. The aryl groups span a cavity around the metal, blocking dimerization and causing a high‐field shift of the 1H NMR signals due to the ASIS effect. Attempted abstraction of the hydride with B(C6F5)3 led to cleavage of the B‐C6F5 bond.

Molecular Main Group Metal Hydrides

“…In contrast to the thermally robust complex ( Dipp Nacnac)ZnH (366), the tetrazinc hydride complex 375 can release H 2 in organic solvents at temperatures as low as 20 °C. 493 495,496 Soon after, the same group replaced the flanking Dipp groups in the Dipp (385) with the hydride sources PhSiH 3 and Me 2 NH•BH 3 , respectively (Scheme 76). 499 Westerhausen and coworkers prepared the amido-pyridine zinc(II) hydride adducts [{RZn} 2 {μ-N(CH 2 Py) 2 }(μ-H)] (R = Me, CH 2 SiMe 3 , CH(SiMe 3 ) 2 ; Py = 2-pyridyl, 386−388) with the trimethylsilylmethyl derivative (387) 502 Compound 390 reacts nearly instantaneously with trifluoromethylacetophenone and benzaldehyde via hydride insertion, 502 a transformation that is reminiscent of this group's use of twocoordinate germanium(II) and tin(II) hydrides as extremely active hydroboration catalysts (see Section 6.3).…”

Molybdenum(VI) bis-imido Complexes of Dipyrromethene Ligands

“…For example, because of the steric profile of DPMs, the coordinated metal ions are well-shielded, thereby efficiently inhibiting dimerization processes, which can be detrimental to catalytic activity . Furthermore, DPM ligands can be considered as “cut-in-half” porphyrins, wherefore they are able to stabilize metal ions in a large variety of oxidation states or to be redox-active themselves and have unique UV–vis as well as fluorescent properties. − It is therefore no surprise that this ligand scaffold is valuable in many areas of synthetic and physical chemistry including light-harvesting arrays (especially in combination with boron-dipyrromethenes (BODIPYs)), − metal ion sensing, coordination polymers, and metal organic frameworks. − In recent years, on the basis of the seminal work by Betley and co-workers, − their use as ligands in late transition-metal chemistry, ,− main-group chemistry, − and even actinide chemistry , has experienced a renaissance (Figure , left and middle).…”

2-Anilidomethylpyridine-Derived Three-Coordinate Zinc Hydride: The Journey Unveils Anilide Backbone’s Reactive Nature

“…< 4 ( A – E ; Figure ) are rare. Harder’s A and B with a trigonal planar geometry use bidentate LX-type ligands . The L and X are disjoint in Robertson and Hevia’s C and in Stephan’s D . Jones’ E is the only example of a two-coordinate zinc hydride that employs a “super bulky” anilide ligand (X-type) .…”