Study of the effects on coordination of thioether sites. 1. Complexation study of bromopentacarbonylmanganese(I) with tripodal P3-nSn (n = 0-3) ligands (original) (raw)

Manganese(1) complexes f~c-(11~-P~S,)Mn(CO)sBr (n = 0-3) [P3 W = Z = PPh2; P2S W = PPh2, Z = SPh; PS2 Z = SPh, W = PPhz; S3 W = Z = SPh in CHsC(CH2W)&H2Z)] formed from the corresponding tripodal ligand have been prepared and isolated as pairs of isomers. The reaction of P2S with BrMn(C0)s in chloroform produced a pair of stereoisomers, synfac-(P~-PzS)Mn(CO)sBr (la) and anti-fac-(P~-P2S)Mn(CO)sBr (lb), which were separated and fully characterized. Equilibration (K1= 2/3) between la and lb was established. For PSZ, the equilibrium constant (K2) between syn-fac-(P,S-PSz)Mn(CO)sBr (2a) and anti-fac-(P,S-PS2)Mn(CO)sBr (2b) was unity. Kinetic studies of isomerization of la to lb and 2a to 2b were carried out by using an NMR spectrometer. The activation parameters were obtained A S l a = 30.5 f 0.4 kcal/mol, AS'la = 11 f 1 eu for complex la; AH*% = 24.9 f 0.7 kcal/mol, AS*& = 7 f 2 eu for complex 2a. A mechanistic pathway for these isomerizations is proposed. Crystal structures were determined for three complexes: la, lb, and 2a. X-ray data were collected on a CAD-4 diffractometer at room temperature and were refined by a least-squares treatment. For la: a = 10.669(2) A, b = 17.864(3) A, c = 18.841(12) A, /3 = 105.30(2)', monoclinic, 2 = 4, P21/o R(Fo) = 0.051, R,(F,) = 0.042 for 3043 reflections with Io > 2a(10). For 2 b a = 10.855(3) A, b = 20.322(7) A, c = 17.887(9) A, /3= 104.73(3)', monoclinic, Z = 4,P21/,, R(Fo) = 0.059, R,(Fo) = 0.047 for 3316 reflections withIo > 241,). For 2a: a = 8.670(5) A, b = 9.539(3) A, c = 18.921(9) A, a = 93.09(3)', /3 = 90.27(5)', y = 101.21(4)', triclinic, Z = 2, Pi, R(F,) = 0.052, R,(F,) = 0.054 for 2513 reflections with I, > 2a(10). The conformations of the chelate rings are discussed. (5) Liu, S.-T.; Wang, H.-E.; Cheng, M.-C.; Peng, 5.-M.