Experimental Gas-Phase Basicity Scale of Superbasic Phosphazenes

Abstract

Seventeen superbasic phosphazenes and two Verkade's bases were used to supplement and extend the experimental gas-phase basicity scale in the superbasic region. For 19 strong bases the gas-phase basicity values (GB) were determined for the first time. Among them are such well-known bases as BEMP (1071.2 kJ/mol), Verkade's Me-substituted base (1083.8 kJ/mol), Et-N=P(NMe2)2-N=P(NMe2)3 (Et-P2 phosphazene, 1106.9 kJ/mol), and t-Bu-N=P(NMe2)3 (t-Bu-P1 phosphazene, 1058.0 kJ/mol). For the first time experimental GB values were determined for P2 phosphazenes. Together with our previous results self-consistent experimental gas-phase basicity scale between 1020 and 1107 kJ/mol is now established. This way an important region of the gas-phase basicity scale, which was earlier dominated by metal hydroxide bases, is now covered also with organic bases making it more accessible for further studies. The GB values for several superbases were calculated using density functional theory at the B3LYP/6-311+G** level. For the phosphazene family the standard deviation of the correlation between the experimental and theoretical values was 6.5 kJ/mol.

Iminoether Complexes of the Type, fac‐[Re(CO)3L{HNC(CH3)OCH3}]BF4 (L = Bipyridine or a Substituted Bipyridine): Synthesis and Properties

“…Therefore, the methyl acetimidate ligand, which by analogy to the related amidine ligand could be considered a superbase, [7,[28][29][30] has no trans influence. The Re-N ( Figure 2) bond lengths of complexes 2-4 are comparable with typical Re sp 2 nitrogen bond lengths, which range from 2.14 to 2.18 Å.…”

Brønsted Basicities of Diamines in the Gas Phase, Acetonitrile, and Tetrahydrofuran

“…[31] Tripropylamine M7 was chosen as the anchoring point for the results of this work for the following reasons. 1) There is an excellent agreement between the GB value 243.9 kcal mol À1 of R13 (PhP 1 A C H T U N G T R E N N U N G (dma) 2 Me) measured with M7 as the anchor point (see the Supporting Information) and the GB value 243.7 kcal mol À1 of the same compound measured with MTBD (7-Methyl-1,5,7-triazabicycloA C H T U N G T R E N N U N G [4.4.0]dec-5-ene) as the anchor compound in reference [35]. This means that the present GB values are consistent with GB values of many other bases over the range 229.5 to at least 264 kcal mol À1 .…”

Toward extension of the gas-phase basicity scale by novel pyridine containing guanidines

“…The only exception was base 12 for which both approaches significantly overestimated the PA values. We also applied the B3LYP/6-311+G (d,p) method, which was advocated by Koppel and coworkers as the most reliable one for calculating the gas-phase basicity of different types of nitrogen bases [41], as well as phosphazenes [43]; however, no significant improvement was obtained. The same theoretical methods were also applied to calculate the GBs and the PAs of the new bases studied in this work (Table S31 and Fig.…”