Markus Richter

Synthese und Struktur von Meldrums Olefin/Synthesis and Structure of Meldrum’s Olefin

Abstract Diisopropylidene ethylenetetracarboxylate, Meldrum’s olefin (4, Mel2) has been prepared from [HNEt3][(Mel)2CSMe] (8) and Meldrum’s acid (1, MelH2) in moderate yield. The X-ray analysis of 4 reveals a centrosymmetrical structure in which the two six-membered rings are folded along their carboxylate carbon axes by 34.9°) and linked by a conventional C-C double bond [1.3501(19) Å ]. The “unsymmetrical” structure of 8 is also discussed.

Synthese und Kristallstruktur von (Ph3PAu)4[AuMn(CO)5]2 und (Ph3PAu)3Re(CO)4/ Synthesis and Crystal Structure of (Ph3PAu)4 [AuMn(CO)5]2 and (Ph3PAu)3Re(CO)4

Abstract The reaction of [Mn(CO)5]- with the cluster cation [(Ph3PAu)8]2+ in thf yields the heterometallic cluster [(Ph3PAu)4 [AuMn(CO)5]2 (1) as the main product besides small amounts of (Ph3PAu)3Mn(CO)4. The former crystallizes as 1-thf in form of red blocks in the triclinic space group P1 with a = 1391,0( 1), b = 1426.7( 1), c = 2308.3(2) pm, α = 92.87(1), β = 97.54( 1), γ = 96.43(1)° and Z = 2. The inner Au6 skeleton of the almost centrosymmetrical cluster consists of two Au4 tetrahedra sharing one edge. Two gold atoms bind a Mn(CO)5 fragment, whereas to the other four gold atoms phosphine ligands are coordinated. The Au-Au distances range from 263.2(1) to 281.9(1) pm, and the Au-Mn distances are 256.6(3) and 256.9(2) pm. By the reaction of [(Ph3PAu)8]2+ with [Re2(CO)9]2- the cluster (Ph3PAu)3Re(CO)4 (2) is obtained in low yield besides the homometallic cluster [(AuPPh3)7]+ as the main product. 2 crystallizes from toluene as 2 C7H8 in the form of yellow blocks with the orthorhombic space group Pna21, and a = 1758.7(3), b = 1648.7(5), c = 2049.3(5) pm. The four metal atoms form a planar lozenge with the Re atom in equatorial position. The Re-Au distances range from 271.2(1) to 273.7(1) pm, and the Au-Au distances are 278.2(1) and 278.4(1) pm