A NMR, X-Ray, and DFT combined study on the regio-chemistry of nucleophilic addition to platinum(II) coordinated terminal olefins

The series of platinum complexes [ PtCl( g2- CH2@ CH - C6H4 - X)( tmeda)]( ClO4) ( X= H, 1b; 4- OMe, 1c; 3- OMe, 1d; 4- CF3, 1e; 3- CF3, 1f; 3- NO2, 1g; tmeda = N, N, N0, N0- tetramethyl- 1,2- ethanediamine) has been considered. In the styrene complex ( 1b) both solution ( NMR) and solid state ( X- ray) data indicate a signi. cant difference in the Pt - C bond lengths ( the longer bond being that involving the ole. n carbon atom carrying the phenyl ring). Such a difference increases when X is an electron donor group ( EDG, 1c) and decreases when X is an electron withdrawing group ( EWG, 1d - g). The attack of a nucleophile ( MeO ) to the substituted carbon ( Markovnikov type, M) is by far the most favoured in the case of unsubstituted ( 1b) or EDG- substituted ( 1c) styrenes. The presence of an EWG ( compounds 1d- g) levels off the probability of M and anti- M type of attack. DFT calculations on 1b, c and 1e were also performed. The NLMO analysis reveals the crucial role of the interaction between the. lled p orbital of the ole. n and the empty d orbital of platinum; the carbon with greater electron density becoming less susceptible of nucleophilic attack