STUDY OF THE EFFECTS ON COORDINATION OF THIOETHER SITES .1. COMPLEXATION STUDY OF BROMOPENTACARBONYLMANGANESE(I) WITH TRIPODAL P3-NSN(N=0-3) LIGANDS

Manganese(I) complexes fac-(eta2-P3-nSn)Mn(CO)3Br (n = 0-3) [P3 W = Z = PPh2; P2S W = PPh2, Z = SPh; PS2 Z = SPh, W = PPh2; S3 W = Z = SPh i n CH3C(CH2W)2(CH2Z)] formed from the corresponding tripodal ligand hav e been prepared and isolated as pairs of isomers. The reaction Of P2S with BrMn(CO)5 in chloroform produced a pair of stereoisomers, syn-fac -(P,P'-P2S)Mn(CO)3Br (1a) and anti-fac-(PP'-P2S)Mn(CO)3Br (1b), which were separated and fully characterized. Equilibration (K1 = 2/3) betwe en la and lb was established. For PS2, the equilibrium constant (K2) b etween syn-fac-(P,S-PS2)Mn(CO)3Br (2a) and anti-fac-(P,S-PS2)Mn(CO)3Br (2b) was unity. Kinetic studies of isomerization of la to lb and 2a t o 2b were carried out by using an NMR spectrometer. The activation par ameters were obtained: DELTAH(double dagger)1a = 30.5 +/- 0.4 kcal/mol , DELTAS(double dagger) = 11 +/- 1 eu for complex la; DELTAH(double da gger)2a = 24.9 +/- 0.7 kCal/MOI, AS2a = 7 +/- 2 eu for complex 2a. A mechanistic pathway for these isomerizations is proposed. Crystal stru ctures were determined for three complexes: 1a, 1b, and 2a. X-ray data were collected on a CAD-4 diffractometer at room temperature and were refined by a least-squares treatment. For 1a: a = 10.669(2) angstrom, b = 17.864(3) angstrom, c = 18.841(12) angstrom, beta = 105.30(2)-deg rees, monoclinic, Z = 4, P2(1)/c, R(F(o)) = 0.051, R(w)(F(o)) = 0.042 for 3043 reflections with I(o)) > 2sigma(I(o)). For 2b: a = 10.855(3) angstrom, b = 20.322(7) angstrom, c = 17.887(9) angstrom, beta = 104.7 3(3)-degrees, monoclinic, Z = 4, P2(1)/,=n, R(F(o)) = 0.059, R(w)(F(o) ) = 0.047 for 3316 reflections with I(o) > 2sigma(I(o)). For 2a: a = 8 .670(5) angstrom, b = 9.539(3) angstrom, c = 18.921(9) angstrom, a = 9 3.09(3)-degrees, beta = 90.27(5)-degrees, gamma = 101.21(4)-degrees, t riclinic, Z = 2, P1BAR, R(F(o) = 0.052, R(w)(F(o)) = 0.054 for 2513 re flections with I(o) > 2sigma(I(o)). The conformations of the chelate r ings are discussed.