Hydrotris(indazolyl)borates:  Homoscorpionates with Tunable Regiochemistry

A series of hydrotris(indazolyl)borates containing diverse substituents on the indazole ring and representing two types of regiochemistries have been synthesized. Indazoles with a 7-alkyl substituent or a 6,7-fused benzo ring formed ligands with boron bonded to the less hindered N-2 (=Tp3Bo), while those with alkyl or aryl substituents in any other position yielded ligands with boron bonded to the more hindered N-1 (=Tp4Bo), thus being the first example of homoscorpionates with 4,5-substituents. Octahedral homo- and heteroleptic complexes of Co, Fe, and Zn have been prepared and characterized, as well as complexes of the types [M(L)(NCS)], [Mo(L)(CO)2(η3-CH2CMeCH2)], [Rh(L)(COD)], and [Rh(L)(CO)2]. X-ray crystallography provided structures of the complexes [Rh(HB{3-methylindazol-1-yl}3)(COD)], 1 (space group P21/n; a = 11.766(2), b = 16.189(2), c = 15.149(2) Å; β = 92.51(1)°; Z = 4; R = 0.0306 for 4318 independent reflections), [Co(HB{7-methylinazol-2-yl}3)(HB{3-neopentylpyrazol-1-yl}3)], 2 (space group P1̄; a = 13.368(4), b = 13.652(4), c = 16.203(9) Å; α = 73.73(4), β = 71.26(3), γ = 63.54(2)°; Z = 2; R = 0.0761 for 7721 independent reflections), and [Co(hydrotris{3-methyl-2H-benz[g]indazol-2-yl}borate)(hydrotris{3-neopentylpyrazol-1-yl}borate)]·C6H5CN, 3 (space group P1̄; a = 13.216(6), b = 13.706(4), c = 17.881(6) Å; α = 73.79(2), β = 86.71(3), γ = 85.61(3)°; Z = 2; R = 0.1138 for 6698 independent reflections).