Crystal structure of metal polycyclopentadienyl compounds

Abstract

Ni II and Zn II complexes of the hexa-dentate macrocyclic ligand cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetra-decane-6,13-diamine The title pendent-arm macrocyclic hexaamine ligand binds stereospeci®cally in a hexadentate manner, and we report here its isomorphous Ni II and Zn II complexes (both as perchlorate salts), namely (cis-6,13-dimethyl-1,4,8,11-tetraazacyclotetra-decane-6,13-diamine-6 N)nickel(II) diperchlorate, [Ni-(C 12 H 30 N 6)](ClO 4) 2 , and (cis-6,13-dimethyl-1,4,8,11-tetraaza-cyclotetradecane-6,13-diamine-6 N)zinc(II) diperchlorate, [Zn(C 12 H 30 N 6)](ClO 4) 2. Distortion of the NÐMÐN valence angles from their ideal octahedral values becomes more pronounced with increasing metal-ion size and the present results are compared with other structures of this ligand. Comment The coordination chemistry of the isomeric pendent-arm macrocycles trans-and cis-6,13-dimethyl-1,4,8,11-tetraaza-cyclotetradecane-6,13-diamine (L 1 and L 2 , respectively) has revealed a number of interesting variations in the structural and physical properties of their complexes. Complexes of the hexadentate-coordinated trans isomer (Curtis et al., 1987; Bernhardt et al., 1989, 1990, 1991; Borzel et al., 1998) are more common than the corresponding cis complexes (Bernhardt et al., 1992, 1993, 1997; Lye et al., 1994). It is an interesting feature that L 1 and L 2 can only bind in one con®guration when coordinated as hexadentates, so the structure of the organic ligand determines the isomerism of the resulting complexes. The hexadentate trans isomers coordinate such that the metal is coplanar with the four secondary amines, and the pendent amines bind in trans coordination sites. By contrast, in the corresponding cis isomers, the macrocycle adopts a folded conformation and the pendent amines coordinate in cis sites. Molecular-mechanics calculations (Bernhardt & Comba, 1991) predicted that the cis isomer L 2 , bound as a hexadentate, would be able to complex both small and large metal ions, whereas the hexadentate-coordinated trans isomer could only accommodate metals up to a certain size, until one or both axial MÐN bonds were broken as a consequence of strain in the complex. These computational results have been borne out by subsequent experimental data. The two complexes [NiL 2 ](ClO 4) 2 , (I), and [ZnL 2 ](ClO 4) 2 , (II), are isomorphous and the absolute con®guration was determined in each case. The Ni II and Zn II crystals studied here, both grown from racemic solutions, were found to be enantiomorphs. Views of the two complex cations are shown in Figs. 1 and 2. The folded conformation of the macrocycle is evident, with the coordinated four secondary amines having the same absolute con®guration i.e. RRRR (SSSS). Each complex cation has (non-crystallographic) C 2 symmetry; the principal axis bisects the N5ÐMÐN6 angle, and the MÐN bond lengths separate into three distinct pairs (Tables 1 and 3). Both macrocyclic ®ve-membered chelate rings adopt the same conformation (or !!), where the CÐC bond in each ring is oblique to the C ...

Borabenzene Derivatives. 24.1From Lithium 1-Methylboratabenzene to 2-Mono- and 2,2-Disubstituted 1-Methyl-1,2-dihydroborinines with Me3Si, Me3Ge, Me3Sn, and Me3Pb Substituents. Degenerate Sigmatropic Rearrangements with Exceptionally Low Barriers and the Structure of 2-(Me3Sn)C5H5BMe

“…The chemistry of these compounds has been reviewed in depth by Jutzi . Most of the older structural work in this area, including e.g. the structures of CpSnMe 3 17b or SnCp 4 ,17c is of low accuracy and does not allow meaningful comparisons.…”

“…Most of the older structural work in this area, including e.g. the structures of CpSnMe 3 17b or SnCp 4 ,17c is of low accuracy and does not allow meaningful comparisons. However, the structure of (Me 5 C 5 )SnI 3 is similar to that of 4 in that it also shows a long Sn−C bond [224.7(5) pm] and an angle of 98.4(3)° of the Sn−C vector to the best ring plane …”

Tin-119 Mössbauer and nuclear magnetic resonance studies of organotin compounds. Part 1. Sterically crowded tetraorganotin derivatives

“…of 0.76 mm s '. Such a site is what may be expected for a distorted tetrahedral environment (being less than 1.66 mm s ') 1 3 -1 4 where one Sn-C bond is much longer than the others. Such a tetrahedral tin geometry would be expected if some of the Sn atoms still had enough energy to move closer to the tetrahedral holes.…”

Tin Organometallic Compounds: Classification and Analysis of Crystallographic and Structural Data: Part Ii. Dimeric Derivatives

“…Seven different donor atoms serve as bridges. Nine derivatives [41][42][43][44][45][46][47] utilize the carbon donor atom of a ligand to bridge tin moieties. The Sn-O-Sn bridge angle ranges from 125.0(5)° to 180°. Five examples with tetrahedral SnC 3 N chromphores are linked by a nitrogen donor atom of a ligand.…”

“…An oxygen atom links tin atoms in seven derivatives, tetrahedral SnC 3 0 chromophores [31,32,34,35], SnC 2 CIO [33a], and SnC 2 0 2 chromophores [30,33b]. Here there is more variation in the stereochemistry about tin; tetrahedral [41,43,44] and trigonal-bipyramidal [42,46,47], The other three examples have non equivalent tin atoms, SnC 2 CI 2 with SnN 2 C 2 CI 2 [42], SnC 3 CI with SnC 3 NCI [42] and SnCI 3 C with SnCI 3 OC [45]. The Sn-N-Sn bridge angle varies from 114.9(3)° to 125.2(1)°.…”