Series of two-coordinate and quasi-two-coordinate transition-metal complexes: synthesis, structural, and spectroscopic studies of sterically demanding borylamide ligands -NRBR'2 (R = Ph, R' = Mes, Xyl; R = R' = Mes), their lithium salts, Li(Et2O)2NRBR'2, and their transition-metal derivatives, M(NPhBMes2)2 (M = Cr, Co, Ni), Co(NPhBXyl2)2 and M(NMesBMes2)2 (M = Cr .fwdarw. Ni)

Abstract

ChemInform Abstract Amide ligands (I) (preparation described) and (III), modified by the presence of the diarylboryl substituents, are used to synthesize low-coordinate metal complexes of unusual structure. X-ray analyses are carried out for (IIIa) (P1, Z=2), (VIa) (Pbca, Z = 8), (VIIIb) (P21/c, Z=4), (Xa), (XI) and (XIIa) (all P1, Z=2). The transition-metal complexes are all high-spin with nominally two-coordinate geometries. However, they all display some deviation from linearity, the strongest N-M-N bending is observed in (VIII). In all the complexes the B-N bond lengths are consistent with π-bonds between boron and nitrogen. The neutral ligands are thus B-N analogues of the alkenyls and behave, for the most part, as one-electron donors. Instead of association through bridging at the nitrogen centers, moderate interactions between the metal and the ipso carbons of the B(Mst)2 groups are found for (VIIIb), (Xb) and (XI), leading to pseudo-square-planar coordination in the first and pseudotetrahedral environment in the latter two cases.

Synthesis, Structure, and Magnetic Properties of Sr39Co12N31

“…Table 7 (62). For the molecular compounds, longer Co-N bond distances decrease the overlap of atomic orbitals.…”

A Frustrated and Confused Lewis Pair

“…Careful crystallization of this mixture resulted in the isolation and structural characterization of both major products.W hile product 2 is confirmed to be the isocyanate adduct Ph2tBuAr N/B-FLP( Ph2tBu ArNCO) of the bulky isocyanate/FLP pair (see Figure S9 in the Supporting Information), the unsymmetrical product 3 is the unanticipated, rearranged aminoborane isomer of the targeted Ph2tBuAr N/B-FLP.T he Xray crystal structure of 3 (Scheme 2b)displays an alternative coordination motif for this FLP with ac ovalent BÀNb ond (N1-B1 = 1.4124 (19) )a nd af ree formamide moiety (C1-O1 = 1.2007(17) )t hat conceptually results from hydroboration of the hindered N = Cbond of the isocyanate.This B À N bond is typical of borylamides R 2 B-NR 2 . [20][21][22][23][24] TheB-N-C(H) = Oa toms essentially lie in one plane (B1-N1-C1-O1 = 170.68 8) consistent with adelocalized p system involving the carbonyl C=Od ouble bond in conjugation with the N!B p interaction. TheI Rs pectrum displays ab and at 1647 cm À1 corresponding to the C = Os tretch at ab it lower energy than in unconjugated formamides such as HC(O)NMe 2 (1675 cm À1 ).…”

The Instability of Ni{N(SiMe3)2}2: A Fifty Year Old Transition Metal Silylamide Mystery

“…[2] TheM n, Fe,a nd Co silylamides are thermally stable and have proven to be valuable synthons in diverse applications, [4][5][6][7][8][9][10][11][12][13] but the unstable nature of Ni{N(SiMe 3 ) 2 } 2 has hindered its further use.I ts instability is especially striking because several other stable,h omoleptic Ni II amides are known. These include {Ni(NPh 2 ) 2 } 2 , [14] the borylamides Ni{N(R)BMes 2 } 2 (R = Ph or Mes), [15,16] the primary terphenyl amides Ni{N(H)Ar Me6 } 2 , [17] Ni{N(H)Ar iPr4 } 2 , [18] and Ni{N(H)Ar iPr6 } 2 [17] (Ar Me6 = C 6 H 3 -2,6-(C 6 H 2 -2,4,6-Me 3 ) 2 , Ar iPr4 = C 6 H 3 -2,6(C 6 H 3 -2,6-i Pr 2 ) 2 ,A r iPr6 = C 6 H 3 -2,6(C 6 H 2 -2,4,6-i Pr 3 ) 2 ), and Ni{N(SiMe 3 )Dipp} 2 (Dipp = C 6 H 3 -2,6-i Pr 2 ). [19,20] Computations indicated that the latter and its Fe and Co analogues are probably stabilized by attractive interligand dispersion forces.…”