ADDITION-REACTIONS OF (CO)5(CREPHH2)(E=P,AS) WITH DI(ETHYNYL)PHOSPHANES AND STANNANES - STEPWISE SYNTHESIS OF COMPLEX-BOUND 1,4-DIHETEROCYCLOHEXA-2,5-DIENES

The compounds(CO)5CrEPhH2(E = P, II; E = As,VIII) react with RP(C=CH)2(R = (t)Bu, Ia; R = CH2Ph, Ib)and Me2Sn(C=CPh)2 (V) via insertion into the E-H bonds to give 1,4-dihetero-cyclohexa-2,5-diene complexes of the type [(CO)5Cr[(Ph)P-CH=CH-X-CH=CH (X = RP, III; X = PhAs, IX) and [(CO)5Cr](Ph)P-C(Ph)=CH-SnMe2-CH=C (Ph) (VII) in high yields. The insertion of the dialkynes is stereospecific: trans addition of II to V yields first [(CO)5Cr](Ph)(H)P-C(Ph)=CH-SnMe2-C=CPh (VI) a compound in which the phosphorus group and the Me2Sn(C=CPh) unit are in cis position to each other. Ring closure by insertion of the second phenylethynyl group in VI into the P-H bond affords the six membered cycle of [(CO)5Cr](Ph)P-C(Ph)=CH-SnMe2-CH=C(Ph) (VII). Another way to synthesize complexes of the type VII is given in the reaction of I with H2SnnBu2 (XIII). In the presence of KOH/18-Crown-6, the cycles of RP-CH=CH-SnnBu2-CH=CH (R = (t)Bu, XIVa; R = CH2Ph, XIVb) are formed, which then yields by treatment with (CO)5Cr(Thf) (XV), [(CO)5Cr](R)P-CH=CH-SnnBu2-CH=CH (R = (t)Bu, XVIa; R = CH2Ph, XVIb). A compound, in which both hetero-atoms of the 1-phospha-4-arsacyclohexa-2,5-diene (IXa) are bonded to a 16-electron complex fragment can be synthesized by the reaction of IXa with (CO)5Mo(Thf) (X). [(CO)5Cr](tBu)P-CH--CH-As(Ph)[Mo(CO)5]-CH=CH (XII) can be isolated in high yields. The identity of all new synthesized compounds III, VI, VII, IX, XII, XIV and XVI is confirmed by analytical and spectroscopic (IR, MS, H-1, C-13 and P-31 NMR) data as well as by an X-ray diffraction study of IXa.