COMMUNICATIONS spectroscopy. The low g value (2.00374) and the coupling constants (u,,,, = 0.338 mT, uHm = 0.133 mT, aN = 0.802 mT), which are typical of aminyl radicals, enabled the presence of a nitroxyl radical to be ruled out.[''] The diradical 17 ( g = 2.00374) prepared by dehydrogenation of the model compound 11 could be confirmed by ESR spectroscopy. Zero field splitting at 135 K (toluene, glass) was determined to be 1.76 mT. The distance of 1.1 7 nm found from this by point dipole estimation is in good agreement with the calculated distance between the aminyl centers of I .O2 nm. [191 17 The new polymer PPSA has a well-defined structure and a high molecular weight. It is colorless, stable at temperatures up to 380 'C, very soluble in many common organic solvents, and dopable. Continuing investigations into its optical and electronic properties and into the conversion of 1 into the polyradical 15 are in progress.

The synthesis and characterization of four dinuclear V(IV) complexes are described:  1, [LVO(μ-(Ph)2PO2)LVO]; 2, [LVO(μ-(Ph)HPO2)2LVO]; 3, [LVO(μ-OH)2LVO]; and 4, [LVO(μ-OH)(μ-OAc)LVO] (where L = hydrotris(pyrazolyl)borate). X-ray crystal structural analysis of 1−4 gave the following parameters:  1, C46H46B2N14O6P2V2, P1̄, a = 12.249(2) Å, b = 13.951(3) Å, c = 16.391(3) Å, α = 93.95(3)°, β = 100.53(3)°, γ = 110.01(3)°, Z = 2; 2, C47H48B2N19O9P3V3, P1̄, a = 9.927(2) Å, b = 12.307(2) Å, c = 24.878(3) Å, α = 98.12(1)°, β = 100.79(1)°, γ = 91.05(1)°, Z = 2; 3, C22H28B2N14O4V2, Pbca, a = 10.698(1) Å, b = 15.414(3) Å, c = 17.865(3) Å, Z = 4; 4, C24H24B2N12O5V2, C2/c, a = 34.252(4) Å, b = 14.623(2) Å, c = 15.387(2) Å, β = 102.32(1)°, Z = 8. Magnetic measurements indicate that all the compounds except 4 are moderately antiferromagnetically coupled. A rationalization for the magnetic behavior of these and other complexes of this type based on a direct overlap model modulated by the conformation of the eight-membered V(μ-OXO)2V ring is proposed.

Tetranuclear V(III) complexes, [HB(pz)(3)](4)V(4)(&mgr;-C(6)H(5)OPO(3))(4) (I), its acetonitrile solvate (I.4CH(3)CN), and [HB(pz)(3)](4)V(4)(&mgr;-O(2)NC(6)H(4)OPO(3))(4).4C(7)H(8).H(2)O (II), and tetranuclear vanadyl complexes, (t-Bupz)(4)V(4)O(4)(&mgr;-C(6)H(5)PO(3))(4).2H(2)O (III) and (t-Bupz)(5)V(4)O(4)(&mgr;-C(6)H(5)PO(3))(4).4CH(3)CN.0.6 H(2)O (IV), have been prepared and characterized by spectroscopic, magnetic, and electrochemical methods (pz = pyrazole, t-Bupz = tert-butylpyrazole). The use of organic solvents and bulky organic groups as ancillary ligands leads to formation of neutral species instead of the anionic clusters commonly found in the hydrothermal synthesis of vanadium organophosphate/phosphonate systems. Complexes I.4CH(3)CN and IV have also been characterized by single-crystal X-ray diffraction. Crystal data: I.4CH(3)CN, triclinic, P&onemacr;, a = 15.495(3) Å, b = 17.000(3) Å, c = 17.949(4) Å, alpha = 89.17(3) degrees, beta = 86.00(3) degrees, gamma = 78.60(3) degrees, Z = 2; IV, triclinic, P&onemacr;, a = 15.541(3) Å, b = 16.340(2) Å, c = 19.069(5) Å, alpha = 83.58(2) degrees, beta = 79.67(2) degrees, gamma = 63.68(1) degrees, Z = 2. Both are closed clusters, the core structure of the first consisting of a cubane-like arrangement of metal octahedra and phosphate tetrahedra and the core structure of the second consisting of a distorted, collapsed variant of the first. Unlike other vanadium phosphate clusters, these compounds form in the absence of a central, templating agent. As such they represent the simplest form of a closed cluster in which steric forces and cluster connectivity requirements play the primary role in organizing the cluster framework.

1H NMR spectra on the paramagnetic CoII and NiII, ML2 “sandwich” complexes of the “heteroscorpionate” ligands (2-hydroxyphenyl)bis (pyrazolyl)methane and its derivatives revealed the presence of isomeric, cis ↔ trans equilibria of these complexes in solution. The presence of some of the cis isomer in solution at equilibrium has been exploited to synthesize new heterometallic trinuclear species of the type [M1(L1O)2M2(L1O)2M1][BF4], where M1 (octahedral) and M2 (tetrahedral) are Zn2+, Cu2+, Ni2+, and Co2+. Rearrangements during the synthesis of some of these heterometallic species provided an interesting experimental confirmation of the site preferences (octahedral vs tetrahedral) for the first-row transition metals as predicted on the basis of crystal field stabilization energies. X-ray crystallographic characterization of many of the complexes reported in this study gives the following structural parameters:  [Co2(L2O)2Cl2]·MeCN, C36H41N9Cl2Co2O2, monoclinic, a = 10.742(1) Å, b = 21.387(2) Å, c = 16.890(2) Å, β = 95.506(8)°, space group P21/c, Z = 4; [Co3(L2O)4]Cl2·5.2H2O, C68H76N16Cl2Co3O9.2, tetragonal, a = 17.998(1) Å, c = 28.804(3) Å, space group I41/a, Z = 4; [Co(L1O)2Na(L1O)2Co][BF4]·0.5H2O· 0.5 i Pr2O·2MeCN, C59H44N18BCo2F4NaO5, monoclinic, a = 14.377(3) Å, b = 18.712(2) Å, c = 26.732(2) Å, β = 103.30(1)°, space group P21/c, Z = 4; [Co3(L2O)4][BF4]2·2H2O·0.5 i Pr2O, C35.5H41.5N8BCo1.5F4O3.25, orthorhombic, a = 19.076(2) Å, b = 13.872(1) Å, c = 16.363(2) Å, space group P212121, Z = 4; [Co3(L2O)4][BF4]2·MeCN, C70H79N17B2Co3F8O4, monoclinic, a = 22.047(4) Å, b = 16.155(2) Å, c = 21.343(3) Å, β = 92.86(1)°, space group:  C2/c, Z = 4; [Ni(L1O)2Co(L1O)2Ni][BF4]2·2MeCN, C56H50N18B2CoF8Ni2O4, monoclinic, a = 40.782(3) Å, b = 16.511(2) Å, c = 19.891(1) Å, β = 111.508(6)°, space group C2/c, Z = 8; [Ni(L1O)2Zn(L1O)2Ni][BF4]2·MeCN, C54H44N8B2F8Ni2O4Zn, monoclinic, a = 12.374(1) Å, b = 26.481(4) Å, c = 18.651(4) Å, β = 103.69(1)°, space group C2/c, Z = 4; [Co(L1O)2Zn(L1O)2Co][BF4]2, C60H61N17B2Co2F8O5Zn, triclinic, a = 15.071(2) Å, b = 15.331(2) Å, c = 17.148(2) Å, α = 65.120(7)°, β = 68.905(8)°, γ = 71.678(8)°, space group P1̄, Z = 2.