The photolysis of CO(NH&~+, CO(NH&(H~O)~+, CO(NH~)~F*+, Co(NH8)sC12+, frans-Co(en)2C12+, and frans-Co(cyclam)Cl2+ in the wavelength region of the ligand field bands is reported, using a continuous wave Argon laser as light source. At 488.0 nm, quantum yields for Co(I1) production by redox decomposition are negligible compared to those for ammonia and X-aquation, which range from For the acidoammines, + N H~ dominates over +x-, and in the case of the chelate complexes, only chloride aquation occurs; frans-Co(en)zC12+ is 72 stereoretentive to give the trans-chloro aquo complex, while Co(cyclam)C12+ photoaquates with 100% stereoretention. It is believed that the low quantum yield values reflect enhanced radiationless deactivation rates, relative to the corresponding Cr(II1) complexes, rather than reduced excited state chemical reactivities. The qualitative photochemistry partly conforms to the photolysis behavior of Cr(II1) complexes but differs in detail ; for example, the stereochemistry of the products indicates that important differences in excited state reaction mechanisms are present.to 5 x he photochemistry of Co(II1) coordination com-

The octacyanotungstate(IV) ion retains a dodecahedral geometry in aqueous solution, with the first spin-allowed d-d transition established as 'E 1 A, from magnetic circular dichroism spectroscopy. The other spin-allowed d-d transitions appear to be nondegenerate and are logically transitions to the ' B, and *A2 excited states. Both dodecahedral and antiprismatic ground states are evident for the octacyanotungstate(V) ion from electron spin resonance measurements, which indicate that the ground-state stereochemistry is both cation and solvent dependent.

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