Synthesis and Characterization of Calcium Complexes Containing η²-Pyrazolato Ligands

Abstract

Treatment of calcium bromide with 3,5-di-tert-butylpyrazolatopotassium (2 equiv) in tetrahydrofuran afforded Ca(tBu2pz)2(THF)2 (69%). The reaction of this compound with pyridine (3 equiv), tetramethylethylenediamine (TMEDA, 1 equiv), N,N,N',N',N"-pentamethyldiethylenetriamine (PMDETA, 1 equiv), triglyme (1 equiv), and tetraglyme (1 equiv) yielded Ca(tBu2pz)2(py)3 (51%), Ca(tBu2pz)2(TMEDA) (74%), Ca(tBu2pz)2(PMDETA) (50%), Ca(tBu2pz)2(triglyme) (73%), and Ca(tBu2pz)2(tetraglyme) (57%), respectively. Treatment of the tetrahydrofuran adduct of Ca(Me2pz)2, generated in situ, with PMDETA (1 equiv), triglyme (1 equiv), and tetraglyme (1 equiv) afforded Ca(Me2pz)2(PMDETA) (65%), Ca(Me2pz)2(triglyme) (54%), and Ca(Me2pz)2(tetraglyme) (40%), respectively. The X-ray crystal structures of Ca(tBu2pz)2(py)3, Ca(tBu2pz)2(TMEDA), Ca(tBu2pz)2(PMDETA), Ca(tBu2pz)2(triglyme), and Ca(Me2pz)2(PMDETA) revealed six-, seven-, or eight-coordinate calcium centers with eta 2-pyrazolato ligands. Ca(tBu2pz)2(triglyme) sublimes at 160 degrees C (0.1 mmHg). The potential utility of these complexes as source compounds for chemical vapor deposition processes is discussed.

Advances in alkaline earth-nitrogen chemistry

“…Calcium complexes of the Me 2 pz ligand have been reported for a variety of neutral donors, including the monomeric Ca(Me 2 pz) 2 (triglyme), Ca(Me 2 pz) 2 (tetraglyme), and Ca(Me 2 pz) 2 (pmdta) (triglyme = 2, 5, 8, 11-tetraoxadodecane; tetraglyme = 2, 5, 8, 11, 14-pentaoxapentadecane) [147]. Protonated pyrazoles may also act as efficient donors, as shown with the preparation of [M(Me 2 pz) 2 (Me 2 pzH) 4 ], M = Ca (Fig.…”

“…In addition, some mixed-ligand species containing the t Bu 2 pz ligand have also been reported. The THF adducts [Mg 2 ( t Bu 2 pz) 4 (thf) 2 ], [Ca( t Bu 2 pz) 2 (thf) 2 ] and [{M( t Bu 2 pz) 2 (thf)} 2 ] (M = Ca, Sr, Ba), were obtained by a combination of synthetic routes including Route i, M = Mg, Ca, Route ii, M = Sr, Ba (Scheme 2), and by dissolving the homoleptic species in THF (Mg, Ca, Sr, Ba) [147,154,156]. Among the dimeric species, the bridging pyrazolates bind in modes of increasing -contribution as metal size increases with -1 : 1 for [Mg 2 ( t Bu 2 pz) 4 (thf) 2 ], -2 : 2 in [{Ca( t Bu 2 pz) 2 (thf)} 2 ], and -5 : 2 in [{Sr( t Bu 2 pz) 2 (thf)} 2 ] and [{Ba( t Bu 2 pz) 2 (thf) 2 } 2 ] (Table 12).…”

“…Employing the multidentate triglyme and tetraglyme co-ligands affords M( t Bu 2 pz) 2 (triglyme) and M( t Bu 2 pz) 2 (tetraglyme) (M = Ca, Sr, Ba) through Routes i and viii (Scheme 2) [147,157]. Similarly, the nitrogen-based neutral donors afforded the monomeric Mg( t Bu 2 pz) 2 (tmeda), Ca( t Bu 2 pz) 2 (py) 3 , Ca( t Bu 2 pz) 2 (tmeda), Ca( t Bu 2 pz) 2 (pmdta), and Sr( t Bu 2 pz) 2 (pmdta) [147,156,157], each with two terminal 2 -bound pyrazolate ligands.…”

Linear Finite “Mers”—Homoleptic Polynuclear Heavy Alkaline Earth Metal Pyrazolates

“…[2, 3] This structural flexibility, when used in conjunction with donor molecules, enabled the isolation of several families of monomeric alkaline earth metal pyrazolates. [4,5] Studies probing the utility of the pyrazolates as precursor molecules showed that not all compounds sublime intact, [5,6] and frequently loss of donors and consequent reduction in volatility is observed. As an example, Winter and co-workers reported that [Ca(tBu 2 pz) 2 (thf) 2 ] (tBu 2 pz = 3,5-di-tert-butylpyrazolate; thf = tetrahydrofuran) sublimes with partial decomposition (200 8C, 0.1 mm Hg) into a white solid of the composition [Ca(tBu 2 pz) 2 ] n but with an unknown structure.…”

Synthesis and characterization of two new types of oxovanadium complexes with pyrazole as ligand

“…Up to now, four coordination modes of pyrazole are found (see Fig. 1): I, mono-dentate terminal (η 1 -pz) [5][6][7][8][9][10] ; II, endo-bidentate chelating (η 2 -pz) [11][12][13] ; III, all atoms of pyrazolyl ring coordinate center metal (η 5 -pz) [14] ; and IV, exo-bidentate bridging (μ-pz), including a, mono-(μ-pyrazolate) [15] ; b, bis-(μ-pyrazolate) [16 -21] ; c, mixing-dibridges [22][23][24][25] ; and d, tri-(μ-pyrazolate) [8] . Among these coordination modes, I, IVb and IVc are common, while II, III, IVa and IVd are uncommon.…”