Ligand structures tris complexes

The first copper(I) complex of tris(hydroxymethyl)phosphine ((760) tetrahedral) has been reported by Samuelson and co-workers. This group addressed the question of anion-controlled nuclearity and metal-metal distances in copper(I)-bis(diphenylphosphino)methane complexes, and in this endeavor they reported the structures of complexes (761) (Cu-Cu separation 3.005-3.128 A), (762) (Cu-Cu separation 3.165 A) and (763) (tetrahedral Cu-Cu 3.293 A). 6 They synthesized and provided structural evidence of oxy anion- encapsulated copper(I) complexes of this ligand. The complexes (764) (distorted tetrahedral Cu-Cu 3.143 A), (765) (distorted tetrahedral Cu-Cu 3.424A), (766) (distorted trigonal Cu-Cu 3.170A), and (767) (Cu-Cu 3.032-3.077A) were reported. They studied solid-state emission spectra of these complexes.567 During this pursuit they... 

About twenty years ago we reported on the di-isothiocyanato iron(II) complex of the tetradentate ligand tpa (tris(2-pyridylmethyl)amine) [7] (6). It was shown that this complex exhibits the spin crossover phenomenon with a critical temperature Tm of about 170 K. Several different solvated phases of the same system have since been characterized by Chansou et al. [8]. The unsolvated phase which can be isolated from an aqueous solution has been investigated by nuclear forward scattering (NFS), nuclear inelastic scattering (NIS) [9], extended x-ray absorption fine structure (EXAFS) spectroscopy, conventional Mossbauer spectroscopy, and by measurements of the magnetic susceptibility (SQUID) [10-13]. The various measurements consistently show that the transition is complete and abrupt and it exhibits a hysteresis loop between 102 and 110 K. 

Structures of l-hydroxy-2-pyridinonate and 3-hydroxy-2-p5rridino-nate complexes may be compared with those of the more extensively studied 3-hydroxy-4-pyridinonates through the published crystal structures of their tris-ligand iron(III) complexes. The iron(III) tris-ligand complex of l-n-butyl-3-hydroxy-2-pyridinone has fac geometry it crystallizes as a trihydrate 135). 

The structures of the bis-ligand iron(II) complexes of the tripodal ligands tiis(pyiidin-2-yl)methane and tris(pyridin-2-yl)phosphine oxide have been determined." " The tetradentate tripodal ligand... 

Pyrrole units form part of the coordinating entities of Schiff base ligands derived from pyrrole 2-carboxaldehyde, for example in the iron(II) complex of the ligand derived from pyrrole 2-carboxaldehyde and trien, which is low-spin despite the feeble coordinating properties of the pyrrole—CH=N— units. The synthesis, structure, and spectroscopic and electrochemical properties of tris-ligand iron(III) complexes of phenyldipyrromethenate (dipyrrin, (129)), and its... 

The structures of the bis-ligand iron(II) complexes of the tripodal ligands tris(pyrazol-l-yl)methane and bis(pyrazol-l-yl)(pyridin-2-yl)methane have been determined the former is a spin cross-over complex." " Polybis(pyrazolateiiron(II) has a ID chain structure with the Fe " " ions doubly bridged by pyrazolates the Fe + ions (-S = 2) are weakly antiferromagnetically coupled. ... 

Attempts to prepare adducts directly from [VO(oxme)2] (138) were unsuccessful and a trigonal bipyramidal structure was suggested for this compound as for [VO(2-Me-oxine)2] (139).825 The [VO(oxine)2X] compounds were prepared by addition of V0S04 to an aqueous solution containing 8-hydroxyquinoline and the base X. For the adducts [VO(oxine)2X], a correlation was found between v(V=0) and the pK of the X ligand, except with bases with substituents where steric hindrance may be operating, and no evidence was obtained for the existence of both cis and trans isomers, unlike the case of [VO(acac)2] adducts (Section 33.5.5.4.ii). For the tris complexes [VO(oxine)3] , an octahedral structure in which one oxine ligand is unidentate and bonded to V was proposed.825... 

The thermodynamic stability of the binuclear site has been demonstrated by the spontaneous assembly of [Fe20(02CR)2L2] (13) from ferric salts in the presence of water, an alkyl carboxylate salt, and a tridentate nitrogen donor ligand L that can cap an octahedral face on iron (8). Suitable ligands include tris(pyrazolyl)borates and 1,4,7-triazacyclononanes. Structure (13) is in essence a portion of the basic ferric acetate structure. The complexes are excellent physical and structural models of the diiron sites and model some aspects of reactivity including redox activity and interconversion of the oxo and hydroxo bridge. 

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