Michael J. Sgro

Frustrated Lewis Pair Inspired Carbon Dioxide Reduction by a Ruthenium Tris(aminophosphine) Complex

Frustrating ruthenium: the ruthenium complex 1 is shown to bind carbon dioxide or aldehyde in a manner similar to a frustrated Lewis pair. Compound 2 catalyzes the reduction of CO(2) in the presence of pinacolborane (HBpin), yielding MeOBpin and O(Bpin)(2) (Ru red, P orange, N green, O light red, C black).

Synthesis and exchange reactions of Ni-dimine-COD, acetylene and olefin complexes

The complexes MesDADNi(COD) (1), DippDADNi(COD) (2), DippDABNiCOD (3) and DippBIANNi(COD) (5) were readily prepared from Ni(COD)(2). The analogous reaction of the ligand MesBIAN afforded (MesBIAN)(2)Ni (4). The related Ni alkyne complexes DADNi(PhC[triple bond]CPh) (6), DippDABNi(PhC[triple bond]CPh) (7) and DippBIANNi(PhC[triple bond]CPh) (8) are readily prepared by addition of alkyne to solutions of the COD species. The analogous reactions employing tBuDAD ligand with either Ni(COD)(2) alone or Ni(COD)(2) and PhC[triple bond]CPh led only to the known bis-ligand Ni complex, although tBuDADNi(MeCO(2)C[triple bond]CCO(2)Me) (9) is readily prepared. In a similar fashion, the species DippDADNi(MeCO(2)C[triple bond]CCO(2)Me) (10), DippDABNi(Me(3)SiC[triple bond]CSiMe(3)) (11), DippDABNi(MeCO(2)C[triple bond]CCO(2)Me) (12) and DippBIANNi(MeCO(2)C[triple bond]CCO(2)Me) (13) were prepared. Reactions with olefins afforded DippDABNi(MeCO(2)CH=CHCO(2)Me) (14), DippDABNi(MeCO(2)CH=CHPh) (15). Employing isolated (3) or (15) in exchange reactions afforded (7), (11) (14) and (15). Similarly (6) served as a precursor to (10) while (11) reacts with PhC[triple bond]CPh to give (7). The solid state structures of (1), (3)-(7), (9), (11) and (15) are reported.

Bronsted acid-catalyzed skeletal rearrangements in polycyclic conjugated boracycles: a thermal route to a ladder diborole

The dibenzodiboracyclobutylidene 1 was recently shown to undergo photochemical rearrangement to the more thermodynamically stable dibenzodiborapentalene 2. In order to discover a more efficient thermal route for this isomerization, the redox chemistry of both 1 and 2 was explored. Radical anions can be formed and characterized by EPR spectroscopy by one electron reduction using potassium graphite. The [Cp*2Co]+ salt of the radical anion of 2 was characterized by X-ray crystallography. The dipotassium salts 1K2 and 2K2 can be prepared by using two equivalents of potassium naphthalenide; both were fully characterized. It was found that smooth rearrangement of 1K2 to 2K2 is mediated by weak Bronsted acids such as tert-butanol or 2,6-dimethylphenol; a mechanism based on similar rearrangements in the isoelectronic neutral all-carbon framework is proposed.

Ni(II), Pd(II) and Pt(II) complexes of PNP and PSP tridentate amino–phosphine ligands

The ligands D((CH(2))(2)NHPiPr(2))(2) (D = NH 1, S 2) react with (dme)NiCl(2) or (PhCN)(2)MCl(2) (M = Pd, Pt) to give complexes of the form [D((CH(2))(2)NHPiPr(2))(2)MX]X (X = Cl, I; M = Ni, Pd, Pt) which were converted to corresponding iodide derivatives by reaction with Me(3)SiI. Reaction of 1 or 2 with (COD)PdMeCl affords facile routes to [κ(3)P,N,P-NH((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (8a) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)PdMe]Cl (9a) in high yields. An alternative synthetic approach involves oxidative addition of MeI to a M(0) precursor yielding [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)NiMe]I (10), [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 8b Pt 11) and [κ(3)P,S,P-S(CH(2)CH(2)NHPiPr(2))(2)MMe]I (M = Pd 9b, Pt 12). Alternatively, use of NEt(3)HCl in place of MeI produces the species [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MH]X (X = Cl, M = Ni 13a, Pd 14a, Pt 16a). The analogs containing 2; [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)MH]X (M = Pd, X = PF(6)15: M = Pt, X = Br, 17a, PF(6)17b) were also prepared in yields ranging from 74-93%. In addition, aryl halide oxidative addition was also employed to prepare [κ(3)P,N,P-HN(CH(2)CH(2)NHPiPr(2))(2)MC(6)H(4)F]Cl (M = Ni 18, Pd 19) and [κ(3)P,S,P-S((CH(2))(2)NHPiPr(2))(2)Pd(C(6)H(4)F)]Cl (20). Crystal structures of 3a, 4a, 5a, 6a, 8a, 9a, 14b and 16b are reported.