Arrested disproportionation in trivalent, mononuclear, and non-metallocene complexes of Zr() and Hf()

Reduction of the group 4 transition metal precursors [(PN) 2 MCl 2 ] (M = Zr ( 1 ), and Hf ( 2 )); PN − = ( N -(2-(diisopropylphosphino)-4-methylphenyl)-2,4,6-trimethylanilide), both readily prepared by transmetallation of 2 LiPN with [MCl 4 (THF) 2 ], with a slight excess of KC 8 , resulted in the isolation of the trivalent complexes [(PN) 2 MCl] (M = Zr ( 3 ), and Hf ( 4 )). Complexes 1-4 were all identified by solid-state X-ray diffraction analysis, whereas in the case of 3 and 4 low temperature X-band EPR spectroscopy allowed for the identification of these metal-centered d 1 radicals. A comparison with the isostructural and isoelectronic but more stable [(PN) 2 TiCl] is also presented. Reduction of [(PN) 2 MCl 2 ] (M = Zr ( 1 ), and Hf ( 2 )) both readily prepared by transmetallation of 2 LiPN with [MCl 4 (THF) 2 ], with a slight excess of KC 8 , resulted in the isolation of the trivalent complexes [(PN) 2 MCl] (M = Zr ( 3 ), and Hf ( 4 )).