1. See e.g. (a) Chatt, J., Pauson, P. L., Venanzi, L. M.: in Organometallic Chemistry, ed. Zeiss, H., Reinhold, N. Y., 1960, p. 468 (general); b) Abel, E. W.: Quart. Rev. Chem. Soc. (London) 17, 133 (1963) (general); c) Wender, I., Pino, P.: (ed.) Organic Synthese via Metal Carbonyls, 1, (1968), Interscience 1968 (general and applications); d) Dobson, G. R., Stotz, I. W., Sheline, R. K.: Advan. Inorg. Chem. Radiochem. 8, 1 (1966) (Group VI carbonyls); e) Abel, E. W., Stone, F. G. A.: Quart. Rev. Chem. Soc. (London) 23, 325 (1969) (structural considerations); f) King, R. B.: Advan. Organometal. Chem. 2, 157 (1964) (carbonyl anions); g) Chini, P.: Inorg. Chim. Acta Reviews 2, 31 (1968) (polynuclear carbonyls); h) Brown, D. A.: Inorg. Chim. Acta Reviews 1, 35 (1967), Strohmeier, W.: Fortschr. Chem. Forsch. 10, 306 (1968), Werner, H.: Angew. Chem. Intern. Ed. 7, 930 (1968) (substitution reactions); i) Hieber, W.: Advan. Organometal. Chem. 8, 1 (1970) (personal survey); j) Abel, E. W., Tyfield, S. P.: Advan. Organometal. Chem. 8, 117 (1970) (carbonyl cations).
2. a) Pauling, L.: Nature of the Chemical Bond, Cornell U. P., 1939; b) Gilliland, W. L., Blanchard, A. A.: J. Amer. Chem. Soc. 48, 410 (1926).
3. a) Graham, W. A. G., Stone, F. G. A.: J. Inorg. Nuclear Chem. 3, 164 (1956); b) Armstrong, D. R., Perkins, P. G.: J. Chem. Soc. (A), 1044 (1969).
4. Ransil, B. J.: Rev. Mod. Phys. 32, 245 (1960).
5. Jaffe, H. H., Doak, G. O.: J. Chem. Phys. 21, 196 (1953).