The colorless copper(I) cluster [CuN(Si(CH(3))(3))(2)](4), which contains a square-planar Cu(4)N(4) core, phosphoresces in CH(2)Cl(2) solution (lambda(max), 512 nm; lifetime, 30 &mgr;s) and in the solid state at room temperature. Its electronic absorption spectrum in CH(2)Cl(2) consists of two intense bands at 283 and 246 nm; these transitions, as well as the phosphorescence, are likely to involve population of MOs reflecting substantial Cu.Cu interactions. Solid [CuN(Si(CH(3))(3))(2)](4) luminesces with approximately the same spectrum as that of the CH(2)Cl(2) solutions. At 77 K, the solid-state luminescence red-shifts slightly (lambda(max), 524 nm) and narrows substantially (fwhm, 2400 cm(-)(1); vs 3500 cm(-)(1) at 300 K); the emission lifetime in glassy Et(2)O solution is 690 &mgr;s. X-ray analysis of crystals of [CuN(Si(CH(3))(3))(2)](4) at 130 and 296 K shows that, although the previously reported structure solution (in space group I2/m, with the molecules on 2/m sites; Eur. J. Solid State Inorg. Chem. 1992, 29, 573-583) is approximately correct, the lattice is actually primitive, P2/n, and the only crystallographically required symmetry element for the molecule is a 2-fold axis. C(24)H(72)Cu(4)N(4)Si(8): monoclinic, space group P2/n, Z = 2. At 130 K, a = 9.285(3) Å, b = 13.393(3) Å, c = 17.752(5) Å, and beta = 90.53(2) degrees. [At 296 K, a = 9.3773(4) Å, b = 13.5836(7) Å, c = 17.814(2) Å, and beta = 90.207(7) degrees.] At 130 K, the Cu and N atoms in the cluster are planar within 0.007 Å, and the Cu-N and Cu.Cu distances are 1.917(4)-1.925(4) and 2.6770(7)-2.6937(7) Å, respectively. Despite the low volatility of the compound, it can be used as a precursor for chemical vapor deposition (CVD) of copper metal, under H(2) carrier gas, with both source and substrate at ca. 200 degrees C. Smaller amounts of Cu metal films are also deposited when the substrate temperature is as low as 145 degrees C (in the dark) or 136-138 degrees C (under Pyrex-filtered Xe arc lamp illumination). Thus, Cu CVD with this precursor shows slight photochemical enhancement.

The tetradentate Schiff-base ligand SIXH2 (alpha,alpha-bis(salicylimino)-m-xylene), prepared from salicylaldehyde and m-xylylenediamine, forms cofacial binuclear complexes with Pd and Cu. Of the two isomers possible (trans-syn and trans-anti) for M2(SIX)2, these complexes crystallize exclusively as the trans-anti isomer. In ansolvous Pd2(SIX)2, the metal-containing planes are approximately parallel, with PdPd 4.416(1) A. Pd2(SIX)2 also forms a crystalline solvate, in which the molecules adopt a more open conformation with longer metal-metal distances (5.109(1) and 5.112(1) A). The M...M distance is significantly longer in Cu2(SIX)2 (6.653(1) A), because of conformational changes in the m-xylylene moieties and substantial tetrahedral distortion about Cu.

Key indicators: single-crystal X-ray study; T = 90 K, P = 0.0 kPa; mean (C-C) = 0.003 Å; R factor = 0.032; wR factor = 0.077; data-to-parameter ratio = 24.3.In the title solvate, [Rh 2 (C 22 (2) and 2.090 (2) Å ], and one COD ligand via two 2 -bonds, each directed toward the mid-point of a C C bond (Cg): Rh-Cg = 2.007 (2), 2.013 (2), 2.000 (2) and 2.021 (2) Å . Each Rh I atom has a quasi-square-planar coordination geometry, with average r.m.s. deviations of 0.159 (1) and 0.204 (1) Å from the mean planes defined by Rh and the termini of its four coordinating bonds. The two COD ligands have quasi-C 2 symmetry, twisted from ideal C 2v symmetry by 30.0 (3) and À33.1 (3) , and are quasi-enantiomers of one another. The intramolecular RhÁ Á ÁRh distance of 5.9432 (3) Å suggests that there is no direct metal-metal interaction. Related literature

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CommentThe bond lengths and angles (Table 2) within the aromatic nucleus of the title compound, (I), differ in some respects from those described by Cruickshank (1957) for naphthalene. The largest deviations occur where the ring is the most substituted, at atoms C1 and C2. The C1--C2 bond distance in the title compound is 0.029(6)A, longer than that in naphthalene. The C2--C1--C9 angle is 3.2(4) ° larger, the C2--C3--C4 angle 2.8 (3) ° larger, while the C1--C2--C3 angle is smaller by 4.3 (3) ° than the corresponding angles in naphthalene. The largest deviation from the naphthalene (C1-C10) least-squares plane is observed at atom C12