Synthesis, structure and reactivity of bromo- and aquatricarbonylrhenium(I) phosphinite and phosphonite derivatives

Abstract

[ReBr(CO) 5] reacted with phosphinite or phosphonite ligands in benzene or toluene to yield fac-( 1) or mer, trans-( 2) complexes, ([ReBr(CO) 3(L) 2] L=PPh 2(OMe), a; PPh 2(OEt), b; PPh(OMe) 2, c; PPh(OEt) 2, d) characterized by elemental analysis, mass spectrometry, IR and NMR ( 1H, 13C and 31P) spectroscopies, and for complexes 1b, 2c and 2d, X-ray diffractometry was used. Complexes 2a– 2d reacted with Ag[BF 4] in wet acetone to form moderate yield of mer, trans-[Re(H 2O)(CO) 3(L) 2][BF 4] ( 3). Comparison of the spectra of compounds 3 with those of precursors 2 together with the diffractometric results for compounds 3a– 3c, show that all the complexes have the same configuration around the rhenium atom. Crystals of compounds 3 consist of centrosymmetric dimers formed by hydrogen bonds between the water molecules and the BF 4 − anions. The lability of compounds 3 was explored by 19F and 31P NMR, and in the case of 3c the complex [Re(η 1-BF 4)(CO) 3{PPh(OMe) 2} 2] ( 4c) was isolated from the mother liquor. Spectroscopic and diffractometric studies of 4c show monodentate coordination of the tetrafluorborato ligand to the rhenium atom.