_P.-Powell-auth.-Principles-of-Organometallic-Chemistry-Springer-Netherlands-1988

Transition metal carbonyls
Niobium and tantalum hali des yield salts of the 18 electron anions Nb( CO); and
Ta(CO);, but no neutra! binary carbonyls have been isolated.
Some metal halides such as ruthenium trichloride afford carbonyl halides ifthe
carbonylation is carried out in the absence of a halide acceptor.
Zn.l'O . lOatm
~----+ Ru,(C0) 12
2RuCl, · 3H 2 0 + 7CO ~ Ru(CO),Cl 2 + 2HCI + C0 2 + SH,O
latm
2RhCI, · 3H 2 0 + 3CO ~ [Rh(CO)Cl 2 ], + 2HCI + C0 2 + SH 2 0
1 atm
1
Cu/MeOH
CO,<l atm
Rh,(C0), 2
Further reduction to binary cluster carbonyls can be effected as shown.
Many metal carbonyls including M(C0) 6 (M = Cr, Ma, W), Mn 2 (C0) 10 • Fe(CO),,
Co 2 (C0) 8 and Ni(C0) 4 are commercially available at reasonable cost, sa it is now
seldom necessary to prepare them in the laboratory.
(c) PREPARATION OF POLYN!JCLEAR CARBONYLS. Usually polynuclear carbonyls
are prepared starting from the simpler derivatives. Fe 2 (C0) 9 is obtained as
insoluble orange plates by photolysis of a cooled solution of Fe(C0) 5 in acetic
anhydride:
hv
Fe(COJ, _______, Fe(C0) 4 + CO
Fe(C0) 4 + Fe(CO), ---> Fe 2 (C0), 1
Co 4 (C0) 12 results when Co 2 (C0) 8 is heated in an inert atmosphere:
5tY'
2Co,(CO), ---'=-> Co 4 (C0Ju + 4CO
Similarly higher osmium carbonyl clusters are obtained from the pyrolysis of
Os,(C0) 12 (p. 3 51 ). Other syntheses involve carbonyl anions as intermediates
(p. 171).
5.2.8 Reactions of metal carbonyls
The chemistry of metal carbonyls is sa vast that only a few examples of their
reactions can be mentioned here.
(a) SUBSTITUTION OF CARBON MONOXIDE. Lewis bases, in particular phosphorus,
arsenic and antimony donors, can substitute carbon monoxide in metal
carbonyls. Two mechanisms can be envisaged for such reactions. In the first (a)
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