Dicyclopentadienyltitanium(IV) pyridine-2,6-dicarboxylate complexes. Synthesis and structural characterization as pentacoordinate titanocene derivatives

Abstract

Reaction of (CsHs)2Ti(CH3)2 or (CH3).C2(C,H4)2Ti(CH3)2 with pyridine-2,6dicarboxylic acid (dipicolinic acid) yields titanocene dipicolinate derivatives. The molecular structure of (C,H,),Ti dipicolinate is that of an axially symmetric, pentacoordinate titanocene derivative with two carboxyl oxygen atoms and the pyridine nitrogen atom as ligating atoms. Two identical chelate bite angles of only 71 0 make the dipicolinate ligand particularly suited to form a remarkably stable titanocene derivative with unprecedented pentacoordinate geometry. '" To whom correspondence should be addressed. ** Cf. ref. 1 and references therein. At the titanium-(II) and-(III) levels, titanocene derivatives with tricoordinate geometry have been reported in a few instances [2-51. *** Whether complexes with '12-coordinated ligands, such as (CsRshTi(CO)C2(C6Hsh [12] or (CsHshTi(CI)OCCH3 [13] should be considered as examples of pseudotetrahedral geometry or as exceptions to this rule is debatable. In a number of instances, pentacoordinate or hexacoordinate dicyc1opentadienyltitanium(lV) species have been proposed without support from crystal structure determinations [14-19}.

Synthesis and Crystal Structure of Bis(.ETA.5-Cyclopentadienyl)-2,6-Pyridinedicarboxylato Titanium(IV) Complex, at 153 K

“…Since the O-Ti-N angle (70.98˚) is within the range of 65 -73˚, these distances and angles are well in agreement with other pentacoordinate metallocene derivatives. 4 The Ti-C distances show a spread of values, from 2.383(2) to 2.414(2)Å; these data are in agreement with previous reports, for example in [(Cp)2Ti(PMe3)2] (2.34(1) -2.42(1)Å). 5 The torsion angles show a deviation of the Cp ring from planarity that is larger than pyridine ring.…”

Crystallochemical formula as a tool for describing metal–ligand complexes – a pyridine-2,6-dicarboxylate example

“…Four complexes exist with tridentate ligands which are 2,6-substituted pyridine derivatives with donor O or N atoms. The pentadentate ligands (except Pydc) were found in the structures of [Ti(Cp) 2 (Pydc)] (FEKHIM; Leik et al, 1986) and [Zr(MeCp) 2 (Pydc)] (HAMSIX; Niemann et al, 1993). The tetradentate ligands are sulfate, 1,4,8,11-tetraazocyclodecan (tacd) and its 2,5,9,12-tetramethyl derivative which are found in the structures of [Pr 2 (Pydc) 2 -(SO 4 )(H 2 O) 5 ]Á2H 2 O (FIPPOK; Zhao et al, 2005), [Mn(tacd)(Pydc)(HPydc)]Á2H 2 O (AQAWEU; Shaikh et al, 2004) and [Ni(Me 4 tacd)(Pydc)]Á 2H 2 O (XUYHEE; Choi et al, 2003).…”

Aqueous-phase synthesis of di-(?5-cyclopentadienyl)salicylato- anddi-(?5-cyclopentadienyl)phthalatotitanium(IV) complexes

“…As a further example of a dicarboxylic acid ligand, dipicolinic acid (2, 6-dicarboxypyridine) (6) was paired with (1) in an aqueous-phase synthesis of the yellow pentacoordinate dipicolinato compound (7) (Scheme 3), which had previously been obtained from dimethyltitanocene and (6) in anhydrous and deoxygenated THF (13). Although (7) precipitated from the aqueous reactant solution in analytical (%N) purity and proved identical in elemental composition and spectroscopic features \ + NIJ \:…”

“…0\:i~ (Table 1) with the product of the previous investigation (13), it tended to become insoluble in all common solvents so rapidly upon isolation that, in all but exceptional cases, controlled recrystallization proved impossible. It is apparent from these results that the synthesis of The entire work-up manipulation was performed efficiently and without any delays so as to avoid product degradation.…”