Coordination of 3,5‐Diisopropyl‐1,2,4‐triazolato and 5‐Phenyltetrazolato Ligands to the [K([18]crown‐6)]⁺ Fragment: Structural Insight into the Coordination of Nitrogen‐Rich Azolato Ligands to Single Metal Centers

Abstract

Durch asymmetrische η2‐Koordination über zwei Stickstoffdonoren binden die heterocyclischen Liganden in K([18]Krone‐6)‐diisopropyltriazolat und K([18]Krone‐6)‐phenyltetrazolat an das Kaliumion (siehe Bild). Die Verbindungen sind Beispiele für die seltene terminale η2‐Koordination stickstoffreicher Azolatliganden.

A Persistent Dipotassium 1,2,4‐Diazaphospholide Radical Complex: Synthesis, X‐Ray Structure, and Bonding

“…[13] The unequal K À N bond lengths in both are consistent with slipped h 2 -bonding [16] and may be compared with those found in [(h 2 ,h 4 -3,5-Ph 2 dp)K(Et 2 O)] n (KÀN 2.7504(15), 2.7348 (16) ) [11b] and in a pyrazolato potassium complex. [17] The difference in bond length may be due to interactions with the [18]crown-6 ligands.…”

Azide Chemistry – An Inorganic Perspective, Part II[‡][3+2]‐Cycloaddition Reactions of Metal Azides and Related Systems

“…[148,151,[208][209][210][211] (According to a more recent calculation on [K(18-crown-6)](η 2 -N 4 CPh), however, the Mulliken charges on the 1-and 2-nitrogen atoms are -.38 and -.20, respectively, i.e., N 1 is slightly more basic than N 2 , which follows the expected trend for a nitrogen atom bonded to one carbon atom and one nitrogen atom vs. a nitrogen atom bonded to two nitrogen atoms (see above) causing a certain asymmetry in the potassium-nitrogen distances.) [199] This explains why approximately equal abundances of N 1 -and N 2 -bonded 5R-tetrazolato complexes result from both, [3+2] cycloadditions mostly of azidopalladium(II) www.zaac.wiley-vch.de REVIEW and -platinum(II) complexes with nitriles, and simple anionic metathesis of the corresponding chloro complexes. In the latter the metal acts like an organic substituent in alkylations of 5-substituted tetrazolate salts which generally produce equilibrium mixtures of 1,5-and 2,5-disubstituted tetrazoles, [86,208,[212][213][214][215][216][217][218] whose relative amounts are controlled by electronic and steric factors.…”

“…[221,352] (Note that η 2 -bonding interactions with tetrazolato ligands have been ascertained in recent years both, in complex poly- 1.2.). [205,199] ) At least, an η 5 transition state as well as all η 3 states except one -η 3 (C,N 1 ,N 2 ) -could be excluded. Ligand dissociation and reentry mechanisms have also been eliminated by the 15 N-experiments.…”

“…Theoretical results demonstrate that particularly in early transition metal compounds there is a strong thermodynamic preference for this kind of coordination over the η 1 -mode. [198] In order to obtain discrete mononuclear complexes with (slipped) η 2 -bonded tetrazoles/tetrazolates, bulky ancillary ligands are required in the coordination sphere as, for instance, in [K(18-crown-6)](η 2 (N 1 ,N 2 )-N 4 CR) (R = Ph, pyrrolidinyl, Bu t ), [199] or in [Ba (18- [198] For the most part, however, coordinative saturation both in simple binary compounds and in the realm of tetrazole-based metal-organic coordination polymers (MOCPs) (see particularly section 1.3. ), is achieved by tetrazolato bridge formation.…”

Elevated‐Temperature Metathesis Syntheses of Structurally Novel Alkali‐Metal Tetrakis(3,5‐di‐tert‐butylpyrazolato)lanthanoidate(III) Complexes: Toluene‐Coordinated Discrete Bimetallic Complexes and Supramolecular Chains

“…Although Na À N bond differences of up to 0.6 ä (above) strain the concept of the longer distance as bonding, it gains support from there being a bonding carbon atom (C(13,25)) at a comparable distance as part of the p-NNC interaction. In addition, unsymmetrical h 2 -R 2 pz or h 2 -triazolate coordination with MÀN bond-length differences of 0.45 ä for AlÀN, [52] and approximately 0.60 ä for K À N bonding, [53] (but not 0.70 ä for Mg À N in [Mg(tBu 2 pz) 2 (tBu 2 pzH) 2 ] [54] ) has been reported. The large asymmetry (approximately 0.6 ä) in the NaÀN 2 binding for ligand 1 in 3 La, Er is accompanied by a close Na¥¥¥tBu contact (to Me(133) of the tert-butyl nearest to the shorter NaÀN distance; 2.399(4) (3 La), 2.423(6) ä (3 Er)).…”