Versatile Scorpionates—New Developments in the Coordination Chemistry of Pyrazolylborate Ligands

Abstract

Much more versatile than previously anticipated are the coordination modes of tris(pyrazolyl)borate ligands (scorpionates). Recent contributions in this area not only lead to a new understanding of the electronic effects, but for the first time report unusually high and low hapticities as well as novel coordination modes such as the π coordination of a pyrazolyl ring to potassium (see structure). Potentially useful new ligands have been made available through innovative synthetic routes.

Investigations on the reactivity of arylboronic acid with phenolic pyrazole

“…Organoboron compounds have been an area of active research for several decades now due to the innumerable applications of organoboron compounds in the fields ranging from organic synthesis [1], organometallic and inorganic coordination chemistry [2][3][4][5][6][7][8][9] to materials chemistry [10]. The coordination chemistry of poly(pyrazolyl)borates have been investigated in detail and several reviews have appeared describing the rich coordination chemistry arising out of these systems [2,[11][12][13][14][15][16][17][18].…”

Molybdenum and tungsten complexes of the neutral tripod ligands HC(pz)3 and MeC(CH2PPh2)3

“…Due to its shape, the Tp ligand and analogous systems are often called scorpionates. Since its first synthesis by Trofimenko in the late 1960s, a variety of different organometallic complexes containing Tp have been prepared [1][2][3][4][5][6]. Recently, homoscorpionate ligands with thioether [7,8], thiocarbonyl [9,10] or phosphine [11,12] donors have been reported, as well as NNS and NNO heteroscorpionates [13][14][15].…”

“…This would open a new route to Mo(II) and W(II) as well as Mo(III) complexes. Furthermore, the tripod phosphine ligand 1,1,1-tris(diphenylphosphinomethyl)ethane MeC(CH 2 PPh 2 ) 3 (2) was also employed in this study to compare the different donor atoms nitrogen and phosphorus.…”

Synthesis and Properties of Poly(pyrazolyl)borate and Related Boron-Centered Scorpionate Ligands. Part A: Pyrazole-Based Systems

“…In 2001 a review was given by Edelmann [35] on the coordination chemistry of pyrazolylborate ligands with topics including electronic effects, novel coordination modes and new ligands. Carmona et al described the C-H activation and coordination chemistry of rhodium-and iridium-tris(pyrazolyl)borate complexes [36].…”