ELECTRONIC ABSORPTION-SPECTRA OF METAL TETRACARBONYLS

The electronic absorption spectra of approximately tetrahedral M(CO)4 (M = Ni, Pd, Pt, Co, Rh, Ir) molecules have been measured. The closed-shell molecules (M = Ni, Pd, Pt) exhibit ²* CO bands in the ultraviolet region of the spectrum. The band at 36 630 cm-1 in the spectrum of Ni(CO)4 is assigned to t2(d) t2(²*), and the broad system at 41 670 cm-1probably represents several other d-²* transitions. Similar bands are observed at slightly higher energies in the spectrum of Pd(CO)4. The spectrum of Pt(CO)4 shows a single band at 48310 cm-1, which is attributed to a d-p or d-²* transition. Relatively low-energy a ³ t2(d) transitions are observed in the spectra of the open-shell molecules (28 190, 28 900, 31 720 cm-1 in Co(CO)4; 29 850 cm-1 in Rh(CO)4; 32 570 cm-1 in Ir(CO)4). Transitions with d -²* character are observed at 37 180, 39060, and 44 840 cm-1 in Co(CO)4, 41 670 and 46510 cm-1 in Rh(CO)4, and 40650 and 48080 cm-1 in Ir(CO)4. © 1979, American Chemical Society. All rights reserved.