Novel Coordination Behavior of fac-[ReBr3(CO)3]2- with 1,3,5-Triaza-7-phosphaadamantane (PTA). Systematic Investigation on Stepwise Replacement of the Halides by PTA Ligand. Phase Transfer Studies and X-ray Crystal Structure of [NEt4][ReBr2((PTA)(CO)3], [ReBr(PTA)2(CO)3], and [Re(PTA)3(CO)3]PF6

Starting originally from [NEt 4 ] 2 [ReBr 3 (CO) 3 ] ( 1 ), the three novel complexes [NEt 4 ][ReBr 2 (PTA)(CO) 3 ] ( 2 ), [ReBr(PTA) 2 (CO) 3 ] ( 3a ), and [Re(PTA) 3 (CO) 3 ]PF 6 ( 4 ) (PTA = 1,3,5-triaza-7-phosphaadamantane) were prepared and characterized by IR, 1 H, 13 C, and 31 P NMR spectroscopy and X-ray crystallography. These complexes are the first representatives of mixed carbonyl/PTA complexes of an element of the manganese row. All substitution reactions have been performed under aerobic conditions at ambient temperature and the yields were in all the cases high. The disubstituted complex was isolated as the neutral species 3a and as the dicationic species [ReBr(PTAH) 2 (CO) 3 ]Br 2, 3b, which is protonated at one amine group of each of the two PTA ligands. The substitution reaction leading to the formation of 3a was performed in H 2 O, methanol and DMSO/methanol (4:1) and the reaction was followed using 31 P NMR techniques. These experiments revealed that the number and concentration of intermediate species during the substitution reaction are strongly dependent on the solvent system. Furthermore due to a completely different solubility behavior of 3a and 3b, a fully reversible phase transfer of the disubstituted complex from the organic (THF) to the aqueous layer (2 M NaBr) and back could be induced by simply changing the pH of the aqueous phase. In the 31 P NMR experiment, the existence of the monoprotonated species [ReBr(PTA)(PTAH)(CO) 3 ]Br ( 3c ) could also be detected. X-ray data for complex 2: monoclinic P 2 1 / n, a = 8.6889(4) Å, b = 29.3089(14) Å, c = 9.3017(5) Å, β = 97.1520(10)°, Z = 4, R / R w = 0.048/0.079. X-ray data for complex 3a: monoclinic P 2 1 / c, a = 6.8581(40 Å, b = 21.9499(12) Å, c = 13.9526(8) Å, β = 94.6650(10)°, Z = 4, R / R w = 0.036/0.042. X-ray data for complex 3b: triclinic P 1̄, a = 8.7051(5) Å, b = 11.9307(7) Å, c = 14.7458(8) Å, α = 78.9450(10)°, β = 87.2340(10)°, γ = 76.4770(10)°, Z = 2, R / R w = 0.034/0.042. X-ray data for complex 4: triclinic P 1̄, a = 9.3842(50) Å, b = 13.5797(7) Å, c = 13.9499(7) Å, α = 105.5910(10)°, β = 91.8560(10)°, γ = 107.0190(10)°, Z = 2, R / R w = 0.051/0.062.