Crystallographic Characterization of Stepwise Changes in Ligand Conformations as Their Internal Topology Changes and Two Novel Cross-Bridged Tetraazamacrocyclic Copper(II) Complexes.

The parallel syntheses of two new cross-bridged tetraazamacrocyclic complexes whose ligands are derived from 1,4,8,11-tetraazacyclotetradecane (cyclam = 14N4) and rac-1,4,8,11-tetraaza-5,5,7,12,12,14-hexamethylcyclotetradecane (tetB = 14N4Me(6)) have been characterized through the crystal structure determination of every stepwise intermediate ligand in the multistep ligand syntheses. These structures show that although the final ligand skeletons are nearly identical, the immediate precursors differ greatly because of the six additional methyl groups of the 14N4Me(6) macrocycle. The inversion from one diastereomer to another of the tetracycle derived from rac-14N4Me(6) has been chemically induced through the successive addition of methyl groups to the reactive tertiary nitrogens, and the novel heterocycles produced have been crystallographically characterized with one showing a conformation not previously known for these systems. The structures of the two copper(II) complexes have significant geometrical differences, and accordingly, their electrochemical and spectroscopic properties are compared. The complexes exhibit remarkable kinetic stability under harsh conditions.

Spiral Dinuclear Complexes of Tetradentate N(4) Diazine Ligands with Mn(II), Fe(II), Fe(III), Co(III), and Ni(II) Salts.

A series of dinuclear complexes of the tetradentate dipyridyl-diazine ligand PAHAP with Mn(II), Fe(II), Fe(III), Co(III), and Ni(II) salts is reported in which three ligands wrap themselves around the six-coordinate metal centers in a rare spiral-like fashion. A similar Fe(II) complex is found for the dipyrazinyl-diazine ligand PZHPZ. The ligands are severely twisted with dihedral angles between the metal chelate ring mean planes on each ligand in the range 50-70 degrees, values close to the expected twist angle for orthogonality between the bridging nitrogen atom p orbitals. Full structures are reported for the dinuclear complexes [Mn(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (1), [Fe(2)(PAHAP)(3)](NO(3))(4).3H(2)O (2), [Fe(2)(PZHPZ)(3)](NO(3))(4).5H(2)O (5), [Co(2)(PAHAP)(3)](NO(3))(6).5H(2)O (6), and [Ni(2)(PAHAP)(3)][Ni(H(2)O)(6)](NO(3))(6).4.5H(2)O (7). Other derivatives [Fe(2)(PAHAP)(3)](ClO(4))(4).4H(2)O (3), [Fe(2)(PAHAP)(3)](ClO(4))(6).4.5H(2)O (4), [Ni(2)(PAHAP)(3)](ClO(4))(4).5H(2)O (8), and [Fe(PHAAP-H)(H(2)O)(2)(NO(3))](NO(3))(2) (9) are also reported. Complex 1 crystallized in the monoclinic system, space group C2/c, with a = 13.4086(2) Å, b = 32.0249(1) Å, c = 14.3132(2) Å, alpha = 90 degrees, beta = 115.635(1) degrees, gamma = 90 degrees, and Z = 4. Complex 2 crystallized in the cubic system, space group Pa&thremacr;, with a = b = c = 21.0024(1) Å, alpha = beta = gamma = 90 degrees, and Z = 8. Complex 5 crystallized in the monoclinic system, space group P2/n, with a = 14.039(3) Å, b = 11.335(6) Å, c = 14.6517(15) Å, beta = 96.852(11) degrees, and Z = 1. Complex 6 crystallized in the trigonal system, space group R&thremacr;c(h), with a = b = 17.386(2) Å, c = 32.15(2) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 4. Complex 7 crystallized in the trigonal system, space group R&thremacr;c, with a = b = 17.3737(3) Å, c = 33.235(6) Å, alpha = beta = 90 degrees, gamma = 120 degrees, and Z = 27. Weak ferromagnetic coupling was observed for 1 (2J = 2.1 cm(-)(1)), and no coupling was observed for the dinuclear Ni(II) centers in 7 and 8. 2, 3, and 5 are low-spin Fe(II) systems.

Comparison of the Properties of SnCl(3)(-) and SnBr(3)(-) Complexes of Platinum(II).

The complexes M(3)[Pt(SnX(3))(5)] (M = Bu(4)N(+), PhCH(2)PPh(3)(+); X = Cl, Br), cis-M(2)[PtX(2)(SnX(3))(2)] (M = Bu(4)N(+), PhCH(2)PPh(3)(+), CH(3)PPh(3)(+), Pr(4)N(+); X = Cl, Br), and [PhCH(2)PPh(3)](2)[PtBr(3)(SnBr(3))] have been prepared and characterized by (119)Sn and (195)Pt NMR, far-infrared, and electronic absorption and emission spectroscopies. In acetone solutions the [Pt(SnX(3))(5)](3)(-) ions retain their trigonal bipyramidal structures but are stereochemically nonrigid as evidenced by (119)Sn and (195)Pt NMR spectroscopy. For [Pt(SnCl(3))(5)](3)(-) spin correlation is preserved between 183 and 363 K establishing that the nonrigidity is due to intramolecular tin site exchange, probably via Berry pseudorotation. Whereas, [Pt(SnCl(3))(5)](3)(-) does not undergo loss of SnCl(3)(-) or SnCl(2) to form either [Pt(SnCl(3))(4)](2)(-) or [PtCl(2)(SnCl(3))(2)](2)(-), [Pt(SnBr(3))(5)](3)(-) is not stable in acetone solution in the absence of excess SnBr(2) and forms [PtBr(2)(SnBr(3))(2)](2)(-) and [PtBr(3)(SnBr(3))](2)(-) by loss of SnBr(2). Similarly, [PtCl(2)(SnCl(3))(2)](2)(-) is stable in acetone at ambient temperatures but disproportionates at elevated temperatures and [PtBr(2)(SnBr(3))(2)](2)(-) loses SnBr(2) in acetone to form [PtBr(3)(SnBr(3))](2)(-). The crystal structures of methyltriphenylphosphonium cis-dibromobis(tribromostannyl)platinate(II) and benzyltriphenylphosphonium tribromo(tribromostannyl)platinate(II) have been determined. Both compounds crystallize in the triclinic space group P&onemacr; in unit cells with a = 12.293(16) Å, b = 12.868(6) Å, c = 25.047(8) Å, alpha = 96.11(3) degrees, beta = 91.06(3) degrees, gamma = 116.53(3) degrees, rho(calc) = 2.30 g cm(-)(3), Z = 3 and with a = 11.046(7) Å, b = 14.164(9) Å, c = 22.549(10) Å, alpha = 89.44(4) degrees, beta = 83.32(5) degrees, gamma = 68.31(5) degrees, rho(calc) = 1.893 g cm(-)(3), Z = 2, respectively. Least-squares refinements converged at R = 0.057 and 0.099 for 4048 and 4666 independent observed reflections with I/sigma(I) > 3.0 and I/sigma(I) > 2.0, respectively. For the former, the asymmetric unit contains 1.5 cis-[PtBr(2)(SnBr(3))(2)](2)(-) ions, 0.5 of which is disordered in such a way as to be pseudocentrosymmetric. This disordering involves a half-occupied PtBr(2) unit appearing on either side of the center. Simultaneously, one bromine from each SnBr(3) ligand changes sides while the other two bromines appear in average positions with very small displacements between their positions. The Pt-Sn distance in [PtBr(3)(SnBr(3))](2)(-) (2.486(3) Å) is slightly shorter than that incis-[PtBr(2)(SnBr(3))(2)](2)(-) (2.4955(3) Å, average), and both are significantly longer than that previously found in cis-[PtCl(2)(SnCl(3))(2)](2)(-) (2.3556 Å, average), which is not consistent with the relative magnitudes of the (1)J((195)Pt-(119)Sn) coupling constants (28 487, 25 720, and 27 627 Hz, respectively). From our electronic absorption and emission studies of the Pt-SnX(3)(-) complexes, we conclude that (a) the low-energy transitions are d-d transitions analogous to those found in [PtX(4)](2)(-) systems, (b) the SnCl(3)(-) ligand is a stronger sigma donor than SnBr(3)(-), (c) the triplet state from which the emission occurs is split by spin-orbit coupling into different spin-orbit states, (d) a forbidden spin-orbit state must lie at or near the bottom of the spin-orbit manifold, (e) the solid state crystal environment perturbs the platinum-tin halide electronic states, and (f) dispersion of the samples in solvents changes this perturbation, which can be rationalized in terms of an in-plane distortion of the square planar platinum coordination sphere.