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Issue 5, 1985
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Alkyl, hydrido, and tetrahydroaluminato complexes of manganese with 1,2-bis(dimethylphosphino)ethane (dmpe). X-Ray crystal structures of Mn2(µ-C6H11)2(C6H11)2(µ-dmpe), (dmpe)2Mn(µ-H)2AlH(µ-H)2AlH(µ-H)2-Mn(dmpe)2, and Li4{MnH(C2H4)[CH2(Me)PCH2CH2PMe2]2}2·2Et2O

Abstract

Alkylation of MnBr2dmpe)2[dmpe = 1,2-bis(dimethylphosphino)ethane] with MgBut2 leads to the t-butyl complex MnBut2(dmpe); alkylation with Mg(C6H11)2 gives the cyclohexyl-bridged dimer Mn2(µ-C6H11)2(C6H11)2(µ-dmpe)(2). By contrast, alkylation with MgEt2 leads to the diamagnetic manganese(I) species, trans-MnH (C2H4)(dmpe)2. Interaction of the latter with LiBut leads to deprotonation of the dmpe ligand and formation of a complex, (4), of stoicheiometry Li2(MnH(C2H4)[CH2(Me)PCH2CH2PMe2]2}·Et2O. A reduction of MnII to MnI also occurs in the interaction of MnBr2(dmpe)2 with LiAlH4 when the tetrahydroaluminate complex [Mn(AlH4)(dmpe)2]2(5) is formed. Hydrolysis of (5) gives the volatile diamagnetic hydride MnH3(dmpe)2. The X-ray crystal structures of the complexes (2), (4), and (5) have been determined. In (2), the molecule, which has two-fold symmetry, has two manganese atoms each bound to one terminal related cyclohexyl group [Mn–C = 2.118(10)Å] and bridged asymmetrically by two symmetry related cyclohexyls [Mn–C = 2.256(9), 2.327(9)Å]. The Mn ⋯ Mn distance is quite short at 2.616(5)Å and the manganese atoms have a distorted tetrahedral co-ordination. In complex (4), two MnH(C2H4)(dmpe)2 units [Mn–H 1.44(4),Mn–C (av.) 2.121(5), Mn–P 2.213(3)–2.274(3)Å] have each lost two hydrogen atoms, one from each of two dmpe methyls, and the resulting four CH2 groups form multicentre alkyl bridges to a central Li4 tetrahedron [C ⋯ Li 2.20–2.36(I), Li ⋯ Li 2.46(1)–2.69(1)Å]. Two of the lithiums are co-ordinated by diethyl ether [ Li–O 2.053(8)Å]. The complex as a whole has C2 symmetry and the manganese(I) centre has a pseudo-octahedral geometry, although pentagonal bipyramidal is an alternative description if the ethylene is considered to occupy two co-ordination sites. Complex (5) is a centrosymmetric dimer in which two cis-octahedral MnH2(dmpe)2 units are bridged by a AlH-(µ-H)2AlH moiety via Al(µ-H)2Mn linkages. The two H atoms in the AlH2Mn bridge are closer to the Mn atoms [Mn–H = 1.61(3), 1.63(3)Å] than to the Al atoms [Al–H = 1.81(3), 1.81(3)Å]. The Al–H distances in the AlH2Al unit are 1.64(3) and 1.80(3)Å, while the terminal Al–H distance is 1.51(3)Å. The aluminium has trigonal bipyramidal co-ordination with one terminal hydrogen in an equatorial position.

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Article information


J. Chem. Soc., Dalton Trans., 1985, 921-929
Article type
Paper

Alkyl, hydrido, and tetrahydroaluminato complexes of manganese with 1,2-bis(dimethylphosphino)ethane (dmpe). X-Ray crystal structures of Mn2(µ-C6H11)2(C6H11)2(µ-dmpe), (dmpe)2Mn(µ-H)2AlH(µ-H)2AlH(µ-H)2-Mn(dmpe)2, and Li4{MnH(C2H4)[CH2(Me)PCH2CH2PMe2]2}2·2Et2O

G. S. Girolami, C. G. Howard, G. Wilkinson, H. M. Dawes, M. Thornton-Pett, M. Motevalli and M. B. Hursthouse, J. Chem. Soc., Dalton Trans., 1985, 921
DOI: 10.1039/DT9850000921

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