Paolo Ganis

Allylstannation. II. A total "cis-preference" in the addition of n-Bu2ClSnCH(CH3)CHCH2 to aldehydes

Abstract 1-Buten-3-yldi-n-butylchlorotin, formed by redistribution of ( E Z )-2-butenyltri-n-butyltin and Bu2SnCl2, reacts readily with neat RCHO (R  C2H5, C2H5(CH3)CH, (CH3)2CH, (CH3)3C and C6H5) to give high yields (80–100%) of alcohols of the type RCH(OH)CH2CHCHCH3 only in the Z-configuration. This appears to be the first example of total “cis-preference” in the addition of Grignard-like reagents to carbonyl compounds. The results are discussed in terms of steric requirements around the tin centre which is probably five-coordinate in the transition state.

Synthesis and structure of tricarbonylchromium mono-, bis- and tris-complexes of 10-methyltribenzotriquinacene

Complexation of 10-methyltribenzotriquinacene (MTBT) a bent triarene of C3v symmetry afforded six mono-, bis- and tris-Cr(CO)3complexed isomers which have been isolated and identified. The results of various synthetic experiments indicate that complexation at the convex side of a free benzene ring is favoured, probably for steric reasons. As compared with the isomer complexed at the convex face (anti), that complexed at the concave one (syn) is less stable. The 1H and 13C NMR spectral data together with the X-ray structures of the two bis- and one tris-complexes account for the lower stability of the syn isomers.

The crystal structure of diμ3oxo-bis(μ-monochloroacetato-O,O′)bis(monochloroacetato)tetrakis[dimethyltin(IV)]

Abstract The crystal structure analysis of {[(CH 3 ) 2 SnO 2 CCH 2 Cl] 2 O} 2 is reported. The compound consists of dimeric units located on symmetry centers; the dimers are weakly bonded to form rows oriented in the a direction. The two tin atoms of the structural unit have different environments; but the coordination numbers cannot be assigned.

X-ray and mössbauer studies of tricyclohexyltin(IV) halides. The crystal structures of (cyclo-C6H11)3SnX (X = F, Br and I)

Abstract The structures of tricyclohexyltin fluoride (I), bromide (II) and iodide (III) have been determined by X-ray analysis. Compound I crystallizes in the space group P 2 1 / m with a = 10.422(6), b = 17.238(9), c = 5.769(3) A, β = 104.6(1)° and Z = 2. Compounds II and III crystallize in the space group Pcmn with a = 10.427(6), b = 16.914(9), c = 11.366(6) A, Z = 4; and a = 10.400(6), b = 16.900(10), c = 11.400(4) A, Z = 4, respectively. All three structures consist of discrete tetrahedral ( cyclo -C 6 H 11 ) 3 SnX units. The temperature dependence of the Mossbauer resonance areas has been examined in order to obtain information about the relationship between chemical structure and lattice dynamics.

Crystal structure of tricyclohexyltin chloride

The structure of tricyclohexyltin chloride has been determined by X-ray analysis. The compound crystallizes in the space group P 2 1/ m with a 10.386(6), b 17.195(9), c 5.713(3) A,β 104.26(9)° and Z = 2. It consists of discrete tetrahedral (cyclo-C 6 H 11 ) 3 SnCl units. The departure from the regular tetrahedral geometry is less than that in tricyclohexyltin acetate. The quadrupole splitting value (Δ 3.49 mm s −1 ), so large as to have been attributed to a penta-coordinated geometry, is shown to be consistent with the tetrahedral geometry when distortions are taken into account in the treatment of the point charge model.

X-ray crystal analysis of tricyclohexyltin trifluoroacetate and Mössbauer data for (cyclo-C6H11)3SnO2CR′ (R′ = CH3, CH2CL, CHCL2, CCl3 and CF3)

Abstract The halogenocarboxylates (cyclo-C6H11)3SnO2CR′, (R′ = CH3, CH2Cl, CHCl2, CCl3 and CF3) have been prepared, and characterized by Mossbauer and IR spectroscopy. The crystal structure of (cyclo-C6H11)3SnO2CCF3 has been determined by X-ray analysis. The crystals are orthorhombic, space group Pcmn, with unit cell parameters a 14.390 ± 0.004, b, 13.427 ± 0.004, c 11.516 ± 0.003 A. The structure was resolved by Patterson methods and refined to an R value of 0.147. The coordination about the tin atom can be considered distorted trigonal-pyramidal or distorted tetrahedral. Mossbauer data are explained in terms of distortions of bond angles about the tin atom.

Crystal structure of 1,10-phenanthrolinedichlorodi-n-butyltin

Abstract The structure of 1,10-phenanthrolinedichlorodi-n-butyltin has been determined by X-ray analysis. The compound crystallizes in the space group P 2 1 2 1 2 1 with a 10.785(5), b 11.017(5), c 18.163(12) A and Z = 4. It consists of distorted octahedral units of (C 12 H 8 )(C 4 H 9 ) 2 SnCl 2 with trans configuration. The structure and the Mossbauer behaviour are compared with those of similar compounds.

Synthesis, structure and reactivity of homobimetallic Rh(I) and Ir(I) complexes of s- and as-indacene-diide

Abstract The Rh(COD) and Ir(COD) homobimetallic complexes of s-indacene-diide, 2,6-dimethyl-s-indacene-diide, as-indacene-diide, and 2,7-dimethyl-as-indacene-diide have been synthesized from the di-lithium salts of the dianions and metal dimers [M(μ-Cl)L2]2 (M = Rh, Ir; L2 = COD, NBD, (ethylene)2, (CO)2 as mixtures of syn and anti isomers. The syn/anti ratio depends on the nature of the ancillary ligands at the metal and on the s or as geometry of the bridging ligand. In the reaction of the 2,7-dimethyl-as-indacene-diide-[M(COD)]2 species with CO, the higher reactivity of the syn isomers has been justified on the basis of a greater instability of the ground state due to steric interactions between the COD groups. Bis-η1 metal-bonded intermediates have been identified in the carbonylation of iridium derivatives; on the other hand, the formation of the bis-η5 mixed complexes syn and anti-{2,7-dimethyl-as-indacene-diide-[Rh(COD)][Rh(CO)2]} and their reactivity strongly support the existence of metalmetal interaction in the rhodium derivatives.

Indenyl and indacenyl ligands in homo and heterobimetallic complexes

Abstract Metal atoms that are held in close proximity exhibit unique properties and many ligands have been tested for their ability to coordinate two or more transition metals in an effort to search for new chemical and physical properties. During the last decade, extensive studies have been conducted on a series of heterobimetallic indenyl complexes of Cr(0) and Rh(I). The mutual effect of the two metal units, viz. Cr(CO) 3 and RhL 2 [L 2 =COD, NBD, (CO) 2 ], anti coordinated to the same planar bridging ligand influences both the reactivity and the catalytic activity of the two metals. Some insight into the dependence of the mutual effects on the stereochemistry of the bimetallic complexes may be provided by the availability of pairs of pure syn and anti bimetallic stereoisomers of rigid bridging ligands. Reported here are the preliminary results concerning the synthesis of syn and anti homobimetallic s -indacene-diide-[RhL 2 ] 2 complexes.

Metal complexes of 2-(o-hydroxyphenyl)pyridine

Abstract Complexes of 2-(o-hydroxyphenyl)pyridine (PhOHpy) with group VIIIB metal ions were synthesized and characterized by elemental analysis and spectroscopic measurements. The crystal and molecular structures of Co(PhOpy)3 and Pd(PhOpy)2 were determined. The Co complex crystallizes in the orthorhombic space group Fdd2, with a = 28.185- (14), b = 36.639(18), c = 12.639(18) A; Z = 16. The molecule has a mer-octahedral structure. Crystals of the Pd complex are orthorhombic, space group Pbca, with a = 17.140(3), b = 11.143(2), c = 9.488(2) A, Z = 4. The molecule is square-planar.