CONSECUTIVE INSERTION REACTIONS OF UNSATURATED MOLECULES INTO THE NI-C BONDS OF THE NICKELACYCLE - (ME3P)2NI(CH2CME2-O-C6H4) - FORMATION OFHETEROCYCLES DERIVED FROM 7-MEMBERED CYCLIC ACID ANHYDRIDES

CS2 inserts into the Ni-aryl bond of (Me3P)2Ni(CH2CMe2-o-C6H4) (1a) at very low temperatures (-90-degrees-C) with formation of (Me3P)2Ni(eta 3-S2CC6H4-o-CMe2CH2) (A), which contains a Ni-eta3-S,C,S'-pseudoallyli c moiety. Compound A spontaneously evolves at -70-degrees-C to the dit hiolactone complex (Me3P)2Ni(eta2-S=CSCH2CMe2-o-C6H4) (3a) by means of a reductive elimination process that involves C-S bond formation. Oth er heterocumulenes such as SCO, SCNPh, OCNPh, and C(NC6H4-P-Me)2 also insert into the Ni-aryl bond of 1a, but in these cases the resulting p roducts are 16-electron species of composition (Me3P)2Ni(X-C(=Y)C6H4-o -CMe2CH2). When X not-equal Y, i.e., for unsymmetric heterocumulenes, the Ni center preferentially bonds to the softer heteroatom. All these seven-membered heterometallacycles undergo insertion into the Ni-CH2 linkage by reaction with CO or CNBu(t) to afford products whose nature depends upon the particular, heterocumulene-derived functionality pre sent in the starting complex. For instance, if a C=S group is availabl e, Ni(0) species related to 3a, e.g., (Me3P)2Ni(eta2-S=CSC(=O)CH2CMe2- o-C6H4) (11a), are formed. In the remaining cases, unusual eight-membe red-ring Ni(II) eta2-iminoacyls, such as (Me3P)Ni(eta2-C(=NBu(t))CH2CM e2-o-C6H4C(=O)S) (17), or the free seven-membered heterocycles O=C-X-C (=Y)C6H4-O-CMe2CH2 (along with Ni(CO)2(PMe3)2) are obtained when the e ntering reagent is CNBu(t) or CO, respectively. Related organic hetero cycles, derived from the parent seven-membered cyclic acid anhydride, can be readily obtained by further elaboration of the stable heteronic kelacycles. The interaction Of CS2 with the related nickelacycle (dmpe )Ni(CH2CMe2-o-CrH4) (1b) (dmpe = Me2PCH2CH2PMe2) takes a completely di fferent course and yields the gem-dithiolate complex (dmpe)Ni(S2CCH2CM e2-o-C6H4) (4), which is formally the product of the insertion of CS2 into the two Ni-C bonds of the starting nickelacycle. Compound 4 furth er reacts with CS2 to furnish the Ni(II) trithiocarbonate (dmpe)-Ni(et a2-S2C=S) (5) and the thioketone S=CCH2CMe2-o-C6H4 (6). Complexes 3a, 4, and 5 have been characterized by single-crystal X-ray diffraction a nalyses. Crystallographic data: for 3a, space group P2(1)/n, a = 19.84 7(8) angstrom, b = 9.343(2) angstrom, c = 13.939(3) angstrom, beta = 1 09.79(3)-degrees, Z = 4; for 4, space group Pbca, a = 11.888(4) angstr om, b = 14.073(3) angstrom, c = 25.065(3) angstrom, Z = 8; for 5, spac e group P2(1)/n, a = 14.286(5) angstrom, b = 7.486(1) angstrom, c = 12 .692(1) angstrom, beta = 93.40(2)-degrees, Z = 4.