Eight new cobalt(III) complexes of the type, [CoX3(mmtp)]n+ (mmtp= 1,1,1-tris(dimethylphosphino-methyl)ethane, X3=(Cl)3, (Br)3, (CN)3, (NH3)3 mmtp, 3-azapentane-1,5-diamine (dien), 1,4,7-triazacyclononane (tacn), and 1,4,7-trithiacyclononane (ttcn)), were prepared and characterized. All of the complexes are stable in the solid state, but the halogeno complexes aquate rapidly in water, and the ammonia complex liberates NH3 slowly in 1 mol dm-3 HCl to give [CoCl2(NH3)(mmtp)]+, other complexes including [Co(mmtp)2]3+ being stable in solution. The crystal structure of [Co(mmtp)2][Co(CN)e] · 2.25H2O was determined by X-ray analysis. Crystal data: orthorhombic, space group Pca21, a=31.579(5), b=10.521(1), c=23.458(3) Å, V=7794(2) Å3, Z=8, R=0.084 for 4196 reflections. The Co-P bond distances are 2.291(9)-2.357(7) Å (av 2.331 Å), which are appreciably longer than those usually found in Co(III)-phosphine complexes. The absorption spectra of the complexes were compared with one another and with those of the related complexes.
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