Hardware environment: The program requires at least a 386/387, DOS5, 4 Mbytes of RAM and VGA screen. Availability: The program, together with manual and test files, is available as part of ORTEX2.1c (McArdle, 1994) via ftp or on 1.44 Mbyte floppy disk. (e-mail: P.McArdle @ ucg.ie.)should specify whether the MORGUE or the PARAM version is required.

Sodium, potassium, and cesium salts (iodides, nitrates, acetates, and tetraphenylborates) form 1/1, 1/2 and 2/3 adducts with MLn [M = Co, Ni, Cu, and Zn; n = 1-4; H2L1 = N,N'-(3-methoxysalicyliden)ethane-1,2-diamine; H2L2, H2L3, and H2L4 are the -propane-1,2-diamine, -o-phenylenediamine, and -propane-1,3-diamine analogues of H2L1). Metal salicyladimine, alkali metal, and anion all exert influence on stoichiometry and reactivity. Sodium ions tend to reside within the planes of the salicylaldimine oxygens, as in Na(NO3)(MeOH).NiL4 (1), Na(NO3)(MeOH).CuL1 (2; both with unusual seven-coordinated sodium), and Na.(NiL4)2I.EtOH.H2O (3; with dodecahedral sodium coordination geometry). Potassium and cesium tend to locate between salicylaldimine ligands as in KI.NiL4 (4) and [Cs(NO3).NiL4]3.MeOH (5; structures with infinite sandwich assemblies), CsI.(NiL2)2.H2O (6), CsI3.(NiL4)2 (7; simple sandwich structures), and [K(MeCN)]2.(NiL4)3 (8; a triple-decker sandwich structure). Crystal data for 1 are the following: triclinic, P1, a = 7.3554(6) A, b = 11.2778(10) A, c = 13.562(2) A, alpha = 96.364(10) degrees, beta = 101.924(9) degrees, gamma = 96.809(10) degrees, Z = 2. For 2, triclinic, P1, a = 7.2247(7) A, b = 11.0427(6) A, c = 13.5610(12) A, alpha = 94.804(5) degrees, beta = 98.669(7) degrees, gamma = 99.26(6) Z = 2. For 3, orthorhombic, Pbca, a = 14.4648(19) A, b = 20.968(3) A, c = 28.404(3) A, Z = 8. For 4, triclinic, P1, a = 12.4904(17) A, b = 13.9363(13) A, c = 14.1060(12) A, alpha = 61.033(7) degrees, beta = 89.567(9) degrees, gamma = 71.579(10) degrees, Z = 2. For 5, monoclinic. P2(1)/n, a = 12.5910(2) A, b = 23.4880(2) A, c = 22.6660(2) A, beta = 99.3500(1) degree, Z = 4. For 6, orthorhombic, Pbca, a = 15.752(3) A, b = 23.276(8) A, c = 25.206(6) A, Z = 8. For 7, triclinic, P1, a = 9.6809(11) A, b = 10.0015(13) A, c = 11.2686(13) A, alpha = 101.03 degrees, beta = 90.97 degrees, gamma = 100.55 degrees, Z = 2. For 8, monoclinic, C2/c, a = 29.573(5) A, b = 18.047(3) A, c = 23.184(3) A, beta = 122.860(10) degrees, Z = 8.

The i.r. spectra of [(Ru(r-C5H5) (CO),),], (Ru I), and the new complexes [(RU(T-M~C,H,)(CO),),]. (Ru 11).and [(Ru(x-indenyl)(Ru I l l ) , have been investigated between 1700 and 2100 cm.-l. They are best interpreted in terms of complex equilibria involving cis and trans, bridged (b)-and nonbridged (nb) -tautomers. The b-nb isomer ratio is dependent on substituents on the cyclopentadienyl ring, and variation in solvent, and temperature. The proportion of nb-species increases with increasing temperature, but declines along the series (Ru I) > (Ru 11) > (Ru I l l ) , and heptane > carbon disulphide > xylene > chloroform > tetrahydrofuran > acetonitrile. There is no evidence for the presence of the nb-isomers in solutions of (Ru I l l ) in any solvent at any temperature.The relative intensities of absorption bands due to either b-or nb-isomers do not vary appreciably with changes in ring substituent or temperature, but are affected by solvent for all three complexes. SINCE the original suggestion that [(Fe(x-C5H5) (CO),),], compounds have been prepared. Two have proved to (Fe I), exists in solution primarily as a solvent-dependent be of particular importance : [(Fe(x-indenyl) (CO),),], mixture of cis-and trans-bridged isomers (see Figure 1) (Fe 111) , , and [Fe,(x-C,H,-CHNMe,*CHNMe,*C,H,)rather than solely as the first of t h e ~e , ~. ~ many related (CO),], (Fe IV)., The strong absorption band due to the

The category Computer Program Abstracts provides a rapid means of communicating up-to-date information concerning both new programs or systems and significant updates to existing ones. Following normal submission, a Computer Program Abstract will be reviewed by one or two members of the IUCr Commision on Crystallographic Computing. It should not exceed 500 words in length and should use the standard format given on page 189 of the June 1985

The potent electron‐donating group [(CpFeCO)2(µ‐CO)(µ‐C=CH−)] was combined with different tropylium‐based acceptors yielding the push‐pull complexes [(CpFeCO)2(µ‐CO)(µ‐C=CH−CH=A)][BF4] where =A represents [=CH−(η7‐C7H6)Cr(CO)3]+ (5), [={C10H7}]+ (azulenylium) (7) [={C10H4Me2iPr}]+ (guaiazulenylium) (8). Crystal structures of the precursor complexes [(CpFeCO)2(µ‐CO)(µ‐C=CH−CH=CH−C7H7)] (3), [(CpFeCO)2(µ‐CO){µ‐C=CH−CH=CH−(η6‐C7H7)Cr(CO)3}] (4) and the push‐pull derivative 5 are presented. Whereas complexes 3 and 4 demonstrate localised carbon−carbon double and single bonds in the π‐bridge between the diiron moiety and the seven‐membered ring a small but distinct π‐bond delocalisation can be observed in the π‐linker of the cationic derivative 5. From the NMR spectroscopic results a correlation between the 13C NMR shift of the bridging carbon atom µ‐C of the diiron unit and the coupling constant J(1H‐1H) of the β‐ and γ‐protons of the π‐bridge was found. This correlation indicates an increased π‐bond delocalisation throughout the conjugated bridge with respect to the electron‐accepting capability in the order tricarbonyl(η7‐cycloheptatrienylium)chromium < guaiazulenylium < azulenylium implying a predominantly charge‐delocalised form in the case of the azulenylium complex 7. Considerably large first hyperpolarisabilities β were determined for 5 and 8 by means of hyper‐Rayleigh scattering. Based on the two‐level model β0 values were calculated and related to the bond‐length alternation in the π‐linker. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)