Syntheses and crystal structures at -35.degree.C of bis(.eta.3-2-allyl)-1,2-ethanobis(tricarbonylcobalt) and bis(.eta.3-2-allyl)-1,3-propanonobis((trimethyl phosphite)dicarbonylcobalt)

Abstract

The two T73-allyl complexes {(CO)3Co[(CH2)2CCH2]j2 and |(CO)3Co[(CH2)2CCH2](2CO have been prepared by reaction of (chloromethyl)allyl chloride and NaCo(CO)4 in refluxing THF. Both species are formed during this reaction and may be converted to the trimethyl phosphite derivatives by replacement of one CO ligand per Co atom. The structures of |(CO)3Co[(CH2)2CCH2]|2 and j[(CH30)3P](CO)2Co[(CH2)2CCH2]j2CO have been determined by single-crystal x-ray diffraction techniques with three-dimensional data gathered at -35 °C by counter methods. Bulky yellow crystals of ((CO)3Co[(CH2)2CCH2])2 form in monoclinic space group C2/m, with unit cell constants (at -35 °C) a = 11.570 (3) Á, b = 10.910 (2) Á, c = 6.568 (1) Á, and ß = 99.95 (1)°. The calculated density of 1.583 g cm™3, assuming two molecules of {(CO)3Co[(CH2)2CCH2]}2 per unit cell, agrees with the measured value of 1.57 g cm™3. |[(CH30)3P](CO)2Co[(C-H2)2CCH2]}2CO crystallizes as thin yellow prisms in orthorhombic space group P2{2{2, with unit cell constants (at -35 °C) a = 19.688 (4), b = 20.843 (10), and c = 6.532 (2) Á. The calculated density of 1.528 g cm™3 for four molecules of phosphite complex per unit cell agrees with the measured value of 1.50 g cm™3. Full-matrix least-squares refinements of the structures have converged with R indices (on |E|) of 0.021 and 0.062 for the j(CO)3Co[(CH2)2CCH2]j2 and j[(CH30)3P](CO)2Co[(CH2)2CCH2]j2CO complexes, respectively, using the 1168 and 2134 symmetry-independent reflections with /" > 2.0 (/0). Molecules of ¡(CO)3Co[(CH2)2CCH2]|2 possess rigorous Cy, symmetry and display the significant differences in Co-C(carbonyl) distances which have previously been attributed to the nature of the Co-t;3-allyl interaction. Although molecules of |[(CH30)3P](CO)2Co[(CH2)2CCH2]|2CO have no rigorous crystallographic symmetry, they do exhibit approximate-C2 symmetry. In addition to the Co-C(carbonyl) bond asymmetry noted in |(CO)3Co[(CH2)2CCH2]|2, the substitution of P(OCH3)3 for CO has produced differences in the Co-C(allyl, terminal) bond lengths of |[(CH30)3-P] (CO)2Co[(CH2)2CCH2] |2CO.

Tetramethyleneethane as a Bis(allylic) Ligand: 16-Electron Cobalt Configurations in Preference to Cobalt–Cobalt Bonding

“…The structures of the mononuclear (C 3 H 5 )­Co­(CO) n ( n = 3, 2, 1) were optimized by the same DFT methods (Figure ). The only low-lying structure predicted for C 3 H 5 Co­(CO) 3 is the singlet C s structure (η 3 -C 3 H 5 )­Co­(CO) 3 known experimentally. ,− The predicted Co–C distances and the ν­(CO) frequencies are comparable to the experimental values. The only structure obtained for C 3 H 5 Co­(CO) 2 is also a C s singlet (η 3 -C 3 H 5 )­Co­(CO) 2 structure.…”

“…All of the low-energy binuclear TMECo 2 (CO) n ( n = 6, 5, 4, 3) structures have the TME moiety functioning as a bis­(trihapto) ligand, thus bonding to each cobalt atom in a similar manner to the allyl–cobalt bond in the well-known ,,− (η 3 -C 3 H 5 )­Co­(CO) 3 . For the two low-energy structures 2S-1 and 2S-2 of the more highly unsaturated TMECo 2 (CO) 2 , the TME moiety functions as a bis­(tetrahapto)­ligand with the two “central” TME carbons bonded to both cobalt atoms (Figure ).…”

“…The two low-energy TMECo 2 (CO) 6 structures are a cis / trans pair of (η 3 ,η 3 -TME)­Co 2 (CO) 6 structures 6S-1 and 6S-2 (Figure ). These structures may simply be regarded as two (η 3 -allyl)­Co­(CO) 3 units related to the well-known ,,− (η 3 -C 3 H 5 )­Co­(CO) 3 joined together by a C–C bond between the two central carbon atoms of each trihapto­(allyl) unit. The trans isomer 6S-1 is the lower energy of these two isomers by ∼3 kcal/mol and has been synthesized and characterized structurally by X-ray crystallography …”

A Well-Defined Isocyano Analogue of HCo(CO)4. 3: Hydride Migration to Olefins, H-Atom Transfer and Reactivity toward Protic Sources

“…As shown in Scheme , HCo­(CNAr Mes2 ) 4 ( 1 ) reacts with 1,3-cyclohexadiene (1,3-CHD), 1,4-cyclohexadiene (1,4-CHD), 1,3-cyclooctadiene (1,3-COD), and cyclooctatetraene (COT) to exclusively form cobalt tris­(isocyanide) η 3 -π-allyl complexes (i.e., (η 3 -allyl)­Co­(CNAr Mes2 ) 3 ; 4 R , R = CDH, COD, COT) with loss of a single CNAr Mes2 ligand. Crystallographic structure determinations of complexes 4 R (Figure ) revealed that they possess a pyramidalized tris­(isocyanide) cobalt core capped by an η 3 -π-allyl interaction and overall are structurally similar to other (η 3 -allyl)­CoL 3 complexes reported in the Cambridge Structural Database (CSD; L = CO, PR 3 ). − Of this series of η 3 -allyl complexes, the molecular structure of 4 COT is the most notable, as a saturated methylene group (i.e., CH 2 ) is located at the apical position of the newly formed C 8 H 9 cyclooctatrienyl ring. An a nalysis of the bond distances in 4 COT indicate that it is best described as a conjugated η 3 -allyl diene, rather than a coordinated pentadienyl fragment.…”

Intermediate Complexes in the Octacarbonyl Dicobalt-Initiated Living Polymerization of 3-Methyl-1,2-butadiene

“…The composition of 1 − 3 deduced from the stoichiometry of their formation according to eqs 1−3 could be verified by osmometric molecular weight determination of the isolated complexes. The 13 C NMR spectra of the complexes show carbon resonances which are in the chemical shift range of known η 3 -allyl-type complexes 3 An ORTEP (50% probability ellipsoids) view of Co 2 (CO) 7 (Me 2 CCCH 2 ) 2 ( 1 ) as determined by X-ray diffraction.…”