Hydrotris(methimazolyl)borate, a soft analogue of hydrotris(pyrazolyl)borate. Preparation and crystal structure of a novel zinc complex

Abstract

The synthesis of a new ligand, hydrotris(methimazolyl)borate, a soft analogue of hydrotris(pyrazolyl)borate, is reported; to demonstrate the coordination chemistry of this novel ligand, complexes of CuI and ZnII are prepared and characterised

Chemistry of the p-block elements with anionic scorpionate ligands

“…Since the S-donor atom is exo-to the heterocycle ring, the methimazolylborates form eight-membered chelates, whereas the pyrazole borates form six-membered chelates. Thus, while the M(Tp) fragment has local C3v symmetry, the larger chelate rings in M(Tm) lead to a propeller-like C3 motif [2]. This geometry also results in the N-substituents being more distant from the metal centre than the 3-substituents in Tp complexes, resulting in a significantly lesser steric demand.…”

“…Substitution at boron, and use of alternative N-donor heterocycles has further expanded the family, while our group was instrumental in introducing heterocycles which give rise to ligands with a S3 donor set (Chart 1) [2,3].…”

The Stability of Mercaptobenzothiazole Based Soft Scorpionate Complexes

“…A schematic representation of the developments in scorpionate chemistry. From left to right: hydrotris(pyrazolyl)borate (Tp) (far left) [1,2]; the soft scorpionates hydrotris(methimazolyl)borate (Tm R ; R = Me, Ph, t Bu, etc)(centre left, top) [4,5] and hydrotris(mercaptobenzothiazolyl)borate (Tbz)(centre left, below) [9]; selenium and oxygen donor systems (centre right) [6,14,15]; and the poly(alkylthioalkyl)borates (right) [3,16]. The tetrakis(thioalky)borate anion (top right) was the first alternative soft donor system to be reported [3].…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13] Not only has there been an increase in the range of heterocycles employed (benzoimidazole-2-thione, 6 1,3,4-thiadiazole-2-thione, 7,8 benzothiazole-2-thione, 9 thiazolidine-2-thione, 9,10 1,2,4-triazole-5-thione, 11 pyridine-2-thione, 12 pyridazine-2-thione 13 ) but the range of donor atoms has also expanded, with systems containing nitrogen, 1,2,6 , sulfur, [3][4][5][6][7][8][9][10][11][12][13] selenium, 14,15 oxygen 6 and phosphorus 16 donors (Figure 1) having all been reported. The chemistry being generated using these species is diverse, but within the reports on the complexes of soft scorpionates are results which suggest that in some circumstances these ligands may be prone to decomposition.…”

“…The chemistry being generated using these species is diverse, but within the reports on the complexes of soft scorpionates are results which suggest that in some circumstances these ligands may be prone to decomposition. 4 The hydrotris(mercaptobenzothiazolyl)borate anion (Tbz, Figure 1) was first reported in 2001, 9 yet, apart from the single thallium(I) complex in the original paper, no further metal complexes were reported until 2012. 17 Given the widespread use of these soft scorpionate ligands, this lack of utilisation hints at an underlying problem.…”