Carbene complexes: XXII. Preparation, properties and structures of the N,N-functionalized bis(amino)carbenemolybdenum(O) carbonyls [ [formula omitted] { [formula omitted]CH 2)}] and [formula omitted]Ph 2] (CH 2) 2N {(CH 2) 3PPh 2}] n

Abstract

Treatment of 1,2-bis(γ-diphenylphosphinopropylamino)ethane [obtained from 1,2-bis(allylamino)ethane and 2PPh 2H and CH(NMe 2)(OMe) 2] yielded the electron-rich enetetramine ▪CN(R)(CH 2) 2NR] 2 [R  CH 2) 3PPh 2] [abbreviated as L 2 (CH 2) 3PPh 2 ]. Although L 2 All, the analogue in which R  CH 2CH:CH 2, is unknown, the carbenemolybdenum title compounds [Mo(CO) 4(L All] ( 3) and ▪ Mo(CO) 3 {L (CH 2) 3 PPh 2 ] n ( 4) have been prepared from [Mo(CO) 6]: for 3 from CH(NMe 2)(OMe) 2 + [All(H)N(CH 2)] 2 and for 4 from L 2 (CH 2) 3PPh 2 . In 3 only one of the R groups behaves in a ligating mode. L All being a chelating ligand, 3 is thus a rare example of a metal complex having both carbene- and η 2 -alkene-ligation and the first for molybdenum. The presumed polymeric structure of 4 is believed to arise from one of the P III sites behaving in a chelating fashion with the other in a bridging mode. Treatment of 3 with 13CO stereoselectively gave the isotopomer in which a CO trans to a CO was displaced, the trans effect thus being parallel to the trans influence (X-ray data); a coproduct was cis-[Mo(CO) 4( 13CO)(L All)]. Similarly, cis-[Mo(CO) 4(L All)(PEt 3)] was the sole product of reaction between 3 and PEt 3, which upon irradiation yielded fac- together with mer-[Mo CO) 3(L All)(PEt 3)]. Thermolysis of 3 afforded AllC: N(CH 2) 2NAll as the only organic product. The X-ray structure of 3 showed that the mutually trans Mo CO bonds are significantly longer [av. 2.037(5) Å] than MoCO trans to carbene [1.984(4) Å] or alkene [1.975(5) Å], with Mo C carb at 2.229(4) Å.