REACTIVITY OF ALPHA-PHOSPHINO ENOLATE COMPLEXES OF NICKEL(II) AND PALLADIUM(II) TOWARD ELECTROPHILIC METAL CENTERS - SYNTHESIS AND CRYSTAL-STRUCTURES OF THE BIMETALLIC PALLADIUM(II)-GOLD(I) COMPLEX [(DMBA)PD(PH(2)PCH(AUPPH(3))C(O)PH)](BF4) AND OF THE NICKEL(II)-COBALT(II) PARAMAGNETIC COMPLEX CIS-[NI(PH(2)PCH-C(-O)P-C6H4CH3)(2)]COI2

The chemoselective reactivity of metal-coordinated phosphino enolates has been studied by the reactions of cis-[Ni{R'(2)PCHsic)C((sic)O)R}(2 )] (R = Ph, p-C(6)H(4)Me, Me; R' = Ph, Pr-i, not all combinations) and [(C N)Pd{Ph(2)PCH(sic)C((sic)O)Ph}] (C N = o-C(6)H(4)CH(2)NMe(2), dmb a or C10H8N, 8-mq) with different metal electrophiles. In the reaction of cis-[Ni{Ph(2)PCH(sic)C((sic)O)Ph}(2)] (1a) with [PtCl2(COD)] (COD = 1,5-cyclooctadiene), a transmetalation of the P,O ligands was observ ed, yielding the known complex cis-[Pt{Ph(2)PCH(sic)C((sic)O)Ph}(2)] ( 3). However, reaction of cis-[Ni(R'2PCH(sic)C((sic)O)R}(2)] with anhyd rous CoI2 afforded the heterobinuclear complexes cis-[Ni{R'2PCH(sic)C( (sic)O)R}(2)]CoI2 (5a, R = Ph, R' = Ph; 5b, R = p-C(6)H(4)Me, R' = Ph; 5c, R = Me, R' = Ph; 7, R = Ph, R' = Pr-i) which contain the phosphin o enolate ligand in an unusual chelating-bridging mu-eta(1)(O):eta(2)( P,O) coordination mode in a nonplanar NiO2Co unit. The magnetic proper ties of these complexes are discussed. The SHOP-type catalyst [Ni(Ph){ Ph(2)PCH(sic)C((sic)O)Ph}(PPh(3))] also behaved as an oxygen-donor met alloligand toward CoI2 to give a paramagnetic Co(II) complex. In contr ast, reaction of [(C N)Pd{Ph(2)PCH(sic)C((sic)O)Ph}] with [Au(PPh(3))] (+) occurred with formation of [(dmba) Pd{Ph(2)PCH(AuPPh(3))C(O)Ph}](B F4) (4a) in which a C-enolate-Au bond has been formed while the P,O ch elate has remained coordinated to palladium. This reaction generates a new stereogenic center, as also evidenced by H-1 NMR spectroscopy. Th e solid state structures of complexes 4a . 1/2C(7)H(8) and 5b . CH2Cl2 have been determined by single-crystal X-ray diffraction: 4a . 1/2C(7 )H(8) crystallizes in the triclinic space group P (1) over bar with Z = 2 in a unit cell of dimensions a = 16.778(4) Angstrom, b = 14.269(5) Angstrom, c = 10.838(6) Angstrom, alpha = 79.27(4)degrees, beta = 71. 59(3)degrees, and gamma = 72.68(2)degrees; 5 . CH2Cl2 crystallizes in the monoclinic space group P2(1)/n with Z = 4 in a unit cell of dimens ions a = 12.940(1) Angstrom, b = 18.329(2) Angstrom, c = 18.495(2) Ang strom, and beta = 91.627(8)degrees. The structures have been solved fr om diffractometer data by direct and Fourier methods and refined by fu ll-matrix least-squares methods on the basis of 7240 (4a . 1/2C(7)H(8) ) and 3644 (5b . CH2Cl2) observed reflections to R and R(w) values of 0.0363 and 0.0406 (4a . 1/2C(7)H(8)) and 0.040 and 0.038 (5b . CH2Cl2) , respectively.