The rate of phosphine substitution of PPh3 by PMePh2 in CpRu(PPh3)2X (1,  X = Cl, 2 ,X =Br, 3 , X =I, 4 , X =N3, 5 ,X =NCO, 6 , X =NCS) was measured in CDCl3 under pseudo-first order conditions over the temperature range 25-70�C. The relative rates of reaction are observed to be: 1  > 4 > 2  > 5  > 3  > 6 .  No reaction is observed for X=F, SnCl3 and H under these conditions.  The activation parameters are similar (DH� ,= 24-30 kcal/mol, DS� = 21-38 cal/mol-K) and consistent with an Id mechanism. The observed order of the rates does not correlate with the size, the electronegativity of X but correlates reasonably well with the electrochemical potentials of 1-6  and may reflect differences in p-donor ability of the X group with the best p-donors having the fastest rate.

Kinetics of phosphine substitution in CpRu(PPh3-)2X (X =Cl, Br, I, N3, NCO, and SCN)

247th National Meeting (2014)

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