Abstract
The interactions of fac-RhCl3(tht)3, tht = tetrahydrothiophene, with aryl-lithium or -magnesium bromide reagents, aryl = 2,4,6-R3C6H2(R = Me or Pri), 2,6-Me2C6H3, or 2-MeC6H4, and also Mg(PhCH2)Br, have been studied. With Li(2,4,6-Pri3C6H2)(Et2O) only the unique, square, paramagnetic rhodium(II) compound trans-Rh(2,4,6-Pri3C6H2)2(tht)2 is obtained. This reacts with CO reversibly to give labile carbonyl species and with ButNC to give the rhodium(I)σ-bonded iminoacyl Rh(CNBut)3(2,4,6-Pri3C6H2CNBut). A similar mesityl (mes) compound is obtained from Rh(mes)3 and ButNC. Homoleptic rhodium(III) aryls Rh(aryl)3 have been obtained for aryl = 2,6-Me2C6H3 and 2,4,6-Me3C6H2. The mesityl reacts with CO to give a carbonyl species that has a bridged acyl and a bridge in which a mesityl group σ-bonded to one Rh atom is bound η6 to the other. It also reacts with PMe2Ph to give Rh(mes)(PMe2Ph)3. The interaction of RhCl3(tht)3 with Mg(PhCH2)Br gives only the unsymmetric bridged species (tht)(PhCH2)2Rh(µ-Cl)3Rh(CH2Ph)(tht)2. The crystal structures of six compounds have been determined: trans-Rh(2,4,6-Pri3C6H2)2(tht)2 is square with a two-fold axis of symmetry perpendicular to the molecular plane [Rh–C and Rh–S 2.11(1) and 2.291(5)A]. The compounds Rh(CNBut)3(σ-RCNBut), (R = 2,4,6-Me3C6H2 or 2,4,6-Pri3C6H2) have similar structures in which the rhodium(I) centres are square [Rh–C (isocyanide) and Rh–C (imino) 1.88–1.94(2) and 2.08 and 2.06(2)A]. The compound Rh2(2,4,6-Me3C6H2CO)(2,4,6-Me3C6H2(CO)3 contains two rhodium centres with quite different co-ordination: Rh(1) is square with bonds to two carbonyls [Rh–C 1.81(1) and 1.90(1)A], an aryl [Rh–C 2.07(1)A] and an oxygen from the aroyl ligand [Rh–O 2.08(1)A]; Rh(2) is trigonal bipyramidal with the aryl σ-bonded to Rh(1) now η6 bonded over two equatorial [Rh–C 2.33(1) and 2.34(1)A] and one axial [Rh–C 2.44(1)A] Sites, the remaining axial and equatorial sites being occupied by the aroyl carbon [Rh–C 1.94(1)A] and a carbonyl group [Rh–C 1.84(1)A]. The compound Rh(2,4,6-Me3C6H2)(PMe2Ph)3 has square rhodium(I) geometry [Rh–C 2.09(1) and Rh–P 2.304(4)A(trans to the aryl) and 2.276(4) and 2.287(4)Atrans to each other]. The dimer Rh2(PhCH2)3Cl3(tht)3 has a confacial bioctahedral structure with Rh–Cl, Rh–C and Rh–S distances showing considerable variations due to the differing trans influences of the three ligand types.
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