Experimental and quantum‐chemical studies of ¹H, ¹³C and ¹⁵N NMR coordination shifts in Pd(II) and Pt(II) chloride complexes with methyl and phenyl derivatives of 2,2′‐bipyridine and 1,10‐phenanthroline

Abstract

1H, 13C and 15N NMR studies of platinide(II) (M=Pd, Pt) chloride complexes with methyl and phenyl derivatives of 2,2'-bipyridine and 1,10-phenanthroline [LL=4,4'-dimethyl-2,2'-bipyridine (dmbpy); 4,4'-diphenyl-2,2'-bipyridine (dpbpy); 4,7-dimethyl-1,10-phenanthroline (dmphen); 4,7-diphenyl-1,10-phenanthroline (dpphen)] having a general [M(LL)Cl2] formula were performed and the respective chemical shifts (delta1H, delta13C, delta15N) reported. 1H high-frequency coordination shifts (Delta1Hcoord=delta1Hcomplex-delta1Hligand) were discussed in relation to the changes of diamagnetic contribution in the relevant 1H shielding constants. The comparison to literature data for similar [M(LL)(XX)], [M(LL)X2] and [M(LL)XY] coordination or organometallic compounds containing various auxiliary ligands revealed a large dependence of delta1H parameters on inductive and anisotropic effects. 15N low-frequency coordination shifts (Delta15Ncoord=delta 15Ncomplex-delta15Nligand) of ca 88-96 ppm for M=Pd and ca 103-111 ppm for M=Pt were attributed to both the decrease of the absolute value of paramagnetic contribution and the increase of the diamagnetic term in the expression for 15N shielding constants. The absolute magnitude of Delta15Ncoord parameter increased by ca 15 ppm upon Pd(II)-->Pt(II) transition and by ca 6-7 ppm following dmbpy-->dmphen or dpbpy-->dpphen ligand replacement; variations between analogous complexes containing methyl and phenyl ligands (dmbpy vs dpbpy; dmphen vs dpphen) did not exceed+/-1.5 ppm. Experimental 1H, 13C, 15N NMR chemical shifts were compared to those quantum-chemically calculated by B3LYP/LanL2DZ+6-31G**//B3LYP/LanL2DZ+6-31G*, both in vacuo and in DMSO or DMF solution.

A functional triazine framework based on N-heterocyclic building blocks

“…S3 †) and likewise, the signal at 70 ppm is char acteristic of the bipyridine unit. 34 Note that in addition to the well defined building blocks present in the material after synthesis, the bipy CTF 400 is highly stable in concentrated acids and bases such as H 2 SO 4 and KOH for several hours without showing any sign of degradation.…”

15N NMR coordination shifts in Pd(II), Pt(II), Au(III), Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes with pyridine, 2,2′-bipyridine, 1,10-phenanthroline, quinoline, isoquinoline, 2,2′-biquinoline, 2,2′:6′, 2′-terpyridine and their alkyl or aryl

“…Surprisingly, there are only three reports on the 15 N NMR of 11 Pt(II) dichloride complexes with the azines concerned [7,14,19] (Table 2); this is in contrast to much more numerous studies for some other coordination compounds (usually containing biologically active ligands or being analogs of cisplatin).…”

“…[15,16] An analogous ca 35 ppm difference between py nitrogens trans to N and trans to CH 3 [11,12] and a relatively high structural similarity of this ligand to the earlier mentioned 2-(3 -methyl-5 -pyrazolyl)-py (δ 15N lig = −84.9 ppm [9] ), one can evaluate | 15N coord | as ca 50-60 ppm. The influence of Cl atoms in the trans position is generally slightly smaller than that caused by N. This is evident for some dichloride complexes described by Pazderski et [7,14,19] Another species fitting to this scheme is the diazide complex trans-[Pd(py) 2 www.interscience.wiley.com/journal/mrc Axial 4-tert-butyl-py −161.4 [25] −92.6 g 1 J 15N -103Rh = 17.9 Hz Equatorial 4-tert-butyl-py (trans to CH 2 C 6 H 5 )…”

“…The number of 15 N NMR studies for Pd(II) complexes with the azines concerned is relatively high (13 papers; 33 compounds + 1 investigated by 14 N NMR) - Table 1. [7 -19] The absolute magnitudes of the Pd(II)-induced 15 N lowfrequency coordination shifts (| 15N coord |, varying within a relatively broad range, ca 30-100 ppm) seem to be primarily determined by two factors: the potential lability of Pd-N bonds (resulting in equilibria of distinct complexes containing variously coordinated azine ligands) and the type of an auxiliary ligand in the trans position (trans effect).…”

“…In this work the published (till May 2008) 15 N NMR data for 47 square-planar Pd(II), Pt(II), and Au(III) and 58 octahedral Co(III), Rh(III), Ir(III), Pd(IV), and Pt(IV) complexes, which are always diamagnetic due to the low-spin electron configuration of their central atoms (d 8 and d 6 , respectively), have been summarized; three other structurally closely related species have been quoted as well although they were investigated by 14 N NMR. Relatively simple azine heterocycles, such as pyridine (py), 2,2 -bipyridine (bpy), 1,10-phenanthroline (phen), quinoline (quin), isoquinoline (isoquin), 2,2 -biquinoline (bquin), 2,2 : 6 , 2 -terpyridine (terpy) and their alkyl or aryl derivatives have been chosen; the auxiliary ligands are generally various, although usually these are rather small inorganic or organic molecules.…”