Hydrotris(pyrazolyl)borato Cycloocta-1,5-diene Complexes of Iridium(I): Synthetic Studies and Equilibria in Solution. X-ray Crystal Structures of a Four- and a Five-Coordinate Iridium(I) Hydrotris(pyrazolyl)borato Complex.
The compounds [Tp(3R,4R,5R)Ir(COD)] (COD = cycloocta-1,5-diene; Tp(3R,4R,5R) = hydrotris(pyrazolyl)borate (1), hydrotris(3-methylpyrazolyl)borate (2), hydrotris(3-isopropylpyrazolyl)borate (3), hydrotris(3,5-dimethylpyrazolyl)borate, hydrotris(3-(trifluoromethyl)-5-methylpyrazolyl)borate, hydrotris(3-phenyl-5-methylpyrazolyl)borate, hydrotris(3,5-diisopropylpyrazolyl)borate, hydrotris(3,4,5-trimethylpyrazolyl)borate, hydrotris(4-chloro-3,5-dimethylpyrazolyl)borate (9), hydrotris(4-bromo-3,5-dimethylpyrazolyl)borate) were prepared and characterized by IR and NMR spectroscopy. The X-ray crystal structure of 9.2MeOH (triclinic, space group P&onemacr; (No. 2); a = 10.044(1) Å, b = 11.186(2) Å, c = 15.499(3) Å; alpha = 77.90(1) degrees, beta = 73.23(1) degrees, gamma = 66.89(1) degrees; Z = 2; R = 0.0276 for 2469 observed reflections) shows that iridium is four-coordinate with an eta(2)-hydrotris(pyrazolyl)borate. The X-ray crystal structure of 1 (triclinic, space group P&onemacr; (No. 2); a = 7.345(1) Å, b = 7.645(1) Å, c = 15.893(5) Å; alpha = 103.17(4) degrees, beta = 90.30(2) degrees, gamma = 93.50(3) degrees; Z = 2; R = 0.0433 for 2606 observed reflections) shows that iridium is five-coordinate with an eta(3)-bonded tris(pyrazolyl)borate. Equilibria between corresponding four- (eta(2)-Tp(3R,4R,5R)) and five-coordinate (eta(3)-Tp(3R,4R,5R)) species of all the complexes are established in solution. The complex containing the ligand HB(Pz(3Me))(3) (Pz = pyrazolyl group) (2) rearranged first to the corresponding complex with HB(Pz(3Me))(2)(Pz(5Me)) and then into that with HB(Pz(3Me))(Pz(5Me))(2). However, 3, which contains HB(Pz(3)()i(Pr))(3), gave only the complex with coordinated HB(Pz(3)()i(Pr))(2)(Pz(5)()i(Pr)).
Albinati
Alberto
A
Istituto di Chimica Farmaceutica, Università di Milano, I-20131 Milano, Italy, and Laboratorium für Anorganische Chemie, ETH Zürich, CH-8092 Zürich, Switzerland.
Bovens
Mike
M
Rüegger
Heinz
H
Venanzi
Luigi M.
LM