5974
X 'AA,,a 'E, and b 'A, Electronic States of Methylnitrene David R. Yarkony,*aacHenry F. Schaefer HI,* Ihmc and Stephen RothenbergId
Contribution f r o m the Department o f Chemistry, University of California, Berkeley, California 94720, and In-formation Systems Design, Oakland, California 94621. Received April 1, 1974 Abstract: An a priori theoretical study of the electronic structure of methylnitrene has been carried out. Using a double < basis set, the geometries of the lowest 3A1, 'E, and 'A1 states have been predicted at the self-consistentfield level of theory. The three states, all of which arise from the same electron configuration la122a123a121al~~le45al22e2, are pdedicted to have very similar geometries. For the ground 3A, state, we predict r(CH) = 1.09 A, R(CN) = 1.47 A, B(NCH) = 110". At the predicted equilibrium geometry, several molecular properties were calculated using a larger basis set including d functions on C and N and p functions on hydrogen. The predicted 2.23 D (]E), and 2.36 D ('Al). The ' E and ] A l states are predicted dipole moments are substantial: 2.11 D ("?), to lie 14,200 and 27,700 cm-I above the 3A.!ground state. Comparisons are made with the properties of the simplest nitrene, NH.
N
itrenes, molecules of the type R-N, are short-lived intermediates of increasing importance in organic a n d inorganic chemistry.?-: This interest has in part been motivated by certain similarities between nitrenes and another class of free radicals, the carbenes.'j Both nitrenes and carbenes usually have small energy separations between their lowest singlet and triplet electronic states. In addition, both classes of molecules seem to conform to the idea of Skell' that singlet states should insert into double bonds in a stereospecific manner, while triplets insert nonstereospecifically. The simplest nitrene, NH, is perhaps the most thoroughly studied, both from a n experimental and theoretical point of view. The X 32-state is known to be the ground state, but the precise position of the first excited a lA state has not been established experimen tall^.^ The b lZ+ state is known t o lie 8650 cm-' above a 'A, and all three of these states arise from the electron configuration (1)
lU*2fJ*3U~lX~
As might be expected, the three states have rather similar the bond distances varying by only 0.004 A . Although the triplet-singlet separation is not known from experiment, several theoretical studies"-" suggest a value of 1.5 eV o r 12,000 cm- '. Huo'O has predicted the values of a number of molecular properties of NH, including the dipole moment: 1.63 D (:jZ-), 1.64 D ('A), and 1.66 D ('Z+). The experimental value is known" (1.49 D) for the lA state
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( I ) (a) Charles Fish Fellow; (b) Alfred P. Sloan F c l l o ~ ;(c) University of California; (d) Information Systems Design. ( 2 ) W. I. Lwowski, Ed., "Nitrcnes," Interscience, New York, N. Y . , 1970. (3) (a) Y . Hayashi and D. Swcrn, J . Amer. Chem. SOC.,95, 5205 (1973); (b) P. F. Alcwood, P. M. I
