Interatomic distances and angles in four planar systems with adjacent C–O and C–N bonds: structures of pivalamide (I), dipivalamide (II),N‐pivaloylpivalamidinium pyrosulfate (III) and N‐pivaloylpivalamidine (IV)

2,2-Dimethylpropionamide (pivalamide), CsHIINO (I): Mr= 101.15, monoclinic, P21/a, a = 10.303 (1), b = 5.896 (1), c = 10.404 (2)A, f l= 102.65(1) ° , V = 6 1 6 . 7 ( E ) A 3, Z = 4 , D m = l . l ( 1 ) , D x = 1.0894 (3) Mg m -a, Mo Ka, 2 = 0.71069 A for 0108-2701/86/030353-08501.50 graphite-monochromatized radiation, p(Mo Ka) = 0.071 mm -~, T = 140 K, F(000) = 224, R = 0.044 for 1035 unique reflections. Bis(2,2-dimethylpropionyl)amine (dipivalamide), CIoH19NO2 (II): M , = 185.27, orthorhombic, Pcab, a = 10.889 (8), b = 11.545 (15), © 1986 International Union of Crystallography 354 CsHnNO , CloHaaNO2, 2CIoHE1N20+.S20~ AND CIoHEoN20 c =17 . 769 (28) /k, V = 2234 (5) /k 3, Z = 8 , D m= 1.1 (1), Dx= 1.102 (2)Mg m -3, Mo Ktt, 2 = 0.71069A for graphite-monochromatized radiation, #(Mo Ktt) = 0.071 mm -~, T = 140 K, F(000) = 816, R =0 .045 for 1330 unique reflections. Bis[N'-(2,2dimethylpropionyl)-2,2-dimethylpropionamidine] disulfate (N-pivaloylamidinium pyrosulfate), 2CIoH21N20+.S20~ (III): M r = 546.71, triclinic, P1, a = 9.628 (2), b = 10.457 (2), c = 14.964 (3) A, et = 76.25 (2), t = 72.86 (2), y = 86.14 (2) °, V = 1398.3 (5)/k 3, Z = 2, D,n= 1.3 (1), Dx= 1.298 (5) Mg m -3, Mo Kct, 2 = 0.71069/k for graphitemonochromatized radiation, #(Mo Ka) = 0.231 mm1, T = 140 K, F(000)= 588, R = 0.046 for 3128 unique reflections. N~-(2,2-Dimethylpropionyl)-2,2-dimethyl propionamidine (N-pivaloylpivalamidine), CloH20N20 (IV): M r = 184.28, monoclinic, P2Ja, a = 11.603 (6), b = 17.277 (11), e = 12.103 (8)A, f l= 106.35 (5) ° , V = 2 3 2 8 ( 2 ) A 3, z = 8 , Din= !.0(1), Dx= 1.051 (1) Mg m -3, Mo Ka, 2 = 0.71069/k for graphitemonochromatized radiation, #(Mo Ket) = 0.064 mm-1, T = 140 K, F(000)= 816, R = 0.063 for 1914 unique reflections. In these compounds, all of which contain nominally sp2-hybridized C,N,O frameworks, CN bonds span the range 1.281 (4)-1.409 (4)/k. Resonance structures are proposed with unequal weightings that rationalize the observed geometrical variations. Among the eleven different tert-butyl (t-Bu) groups encountered, eight adopt configurations having a methyl C atom nearly coplanar with the adjacent sp 2 centers. The central NH group in (II) and (III), and the central N in (IV) are shielded by the t-Bu groups and are not H-bonded. In (Ill) and (IV) both interand intramolecular NH. . .O hydrogen bonds are formed by the NH 2 groups. Only intermolecular H bonds occur in