MO‐π‐Bindungsordnung‐Bindungslängen‐Beziehungen für Hetero‐π‐Systeme, I. π‐Systeme mit CN‐Bindungen

Abstract

rn Mit Hilfe einer fur ungesattigte Kohlenwasserstoffe erhaltenen HMO-n-Bindungsordnung-Bindungslangen-Beziehung werden fur CN-Hetero-r-Bindungssysteme die emprrischen Resonanzintegral-Heteroparameter / L -i i und ~C -N zu 1.10 bzw. 1 .OO bestimmt. Die mit diesen Parametern berechneten HMO-n-Bindungsordnungen ergeben mit experimentellen Bindungsabstanden, die mit einer Standardabweichung von hochstens 0.01 5 8, bestimmt wurden, eine lineare Beziehung, deren Gleichung nach der Methode der kleinsten Fehlerquadrate zu R z M O [A] 1.474 0.225 prs mit einer Standardabweichung van 0.019 A und einem Korrelationskoeffizienten von 0 865 fur 114 Punkte bestjmmt wurde. Fur PPP-SCF-n-Bindungsordnungen betragt die Ausgleichsgerade mit einer Standardabweichung von 0.022 A und einem Korrelat~onskoeffizienten von 0.801 fur 168 Werte. RP,PP [A] = 1 443 0.167 prs MO-x-Bond Order-Bond Lengths Relations for Hetero-rr-Systems, 1 x-Systems with CN-Bonds A HMO-n-bond order-bond lengths relation obtained for unsaturated hydrocarbons allows the empirical determination of the HMO resonance integral parameters for CN-n-bonds as kC=N = 1 , l O and kC-N = 1,OO. HMO-x-Bond orders calculated with these parameters give a linear relation with bond lengths determined experimentally with a standard deviation of less than 0,015 A. The equation determined by linear least squares methods is R Z M O [A] ~~ 1,474 -0,225 p n with a standard deviation of 0,019 A and a correlation coefficient of 0,865 for 114 points. For PPP-SCF-x-bond orders the least squares equation yields RgpP [A] = 1,443 --0,167 prs with a standard deviation of 0,022 A and a correlation coefficient of 0,801 for 168 points.Zwischen der MO-x-Bindungsordnung 1) und dem entsprechenden Bindungsabstand in ungesattigten Verbindungen besteht ein Zusammenhang, der theoretisch begriindet HafeelingerJdhrg. 103

Structural studies of organoboron compounds. XLIII. 4-[(1-Hydroxycyclohexyl)methyl]-2,2,5-triphenyl-1,3-dioxa-4-azonia-2-borata-4-cyclopentene

“…The T-bond order of the C=O bond (1.293(2) A)., estimated to be about 0 . 5 from a plot of C-0 distance vs. MO-T-bond order (13), is considerably less than that expected for a C=O double bond. Comparison of the C=O distance in 4 with those in 8 (8) (1.337 A) and 9 (9) (1.288 A) shows the influence of the adjacent (conjugated) aryl substituent on the C=O bond: there is obviously more double bond character in the C-0 groups of 4 and 9 than there is in the aliphatic substituted hydroxamate 8.…”

“…From plots of T-bond order vs. bond length for C-N bonds (12,13), these distances have T-bond orders between 0.70 and 0.85. The T-bond order of the C=O bond (1.293(2) A)., estimated to be about 0 .…”

Synthesis and reactivity of organolanthanide complexes containing phenothiazine ligand toward carbodiimide and isothiocyanate

“…116.6(7) N(1)-C (14) (1) 58.2(4) N(2)-C(14)-Yb (1) 58.4(4) N(3)-C(14)-Yb (1) 177.2(6) C(29)-N(3)-C (18) 124.7(8) C(29)-N(3)-C (14) 117.0(8) (14) 117.2(7) 1.725 (6) Å , are in intermediate values between the corresponding C-N and C-S single-and double-bond distances [13]. These bond parameters indicate substantial electronic delocalization over the S-C-N unit [14].…”

“…Significantly, the distance of N(2)-C(17) (1.395 (7) Å ) in 9 is shorter than the corresponding value found in 5 (N(3)-C (14) 1.454(10) Å ), which maybe indicted that the lone pair electrons of the N(2) atom partially delocalized on the S-C-N unit. The Yb-C(Cp) distances in complex 9 are the normal ranges observed for yetterbocene complexes [13].…”

Synthesis, Spectral and Structural Study of N-[1-(N,N,N?,N?-Tetramethylphosphoramidoyl)- 1H-Benzimidazol-2-yl]-Propionimidic Ethyl Ether

“…The P N4 (1.6304(10)Å) and P N5 (1.6245(9)Å) bond lengths are shorter than P N1 (1.7248(9)Å) and are thus shorter than a standard single P N bond (1.73Å) [19]. The C N bond length (1.2777(13)Å) of the imidic group is the same as in pure unconjugated C N (1.27Å) [20] and approximately the same as for C N imidate bond (1.265Å) [14,15,21]. This may be explained by the absence of conjugation between the n and π electrons inside the imidate function (O C N).…”